Struct odbc_api::handles::SqlText

source ·
pub struct SqlText<'a> { /* private fields */ }
Expand description

Handles conversion from UTF-8 string slices to ODBC SQL char encoding. Depending on the conditional compiliation due to feature flags, the UTF-8 strings are either passed without conversion to narrow method calls, or they are converted to UTF-16, before passed to the wide methods.

Implementations§

Create an SqlText buffer from an UTF-8 string slice

Examples found in repository?
src/preallocated.rs (line 90)
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    pub fn execute(
        &mut self,
        query: &str,
        params: impl ParameterCollectionRef,
    ) -> Result<Option<CursorImpl<&mut StatementImpl<'o>>>, Error> {
        let query = SqlText::new(query);
        execute_with_parameters(move || Ok(&mut self.statement), Some(&query), params)
    }

    /// Transfer ownership to the underlying statement handle.
    ///
    /// The resulting type is one level of indirection away from the raw pointer of the ODBC API. It
    /// no longer has any guarantees about bound buffers, but is still guaranteed to be a valid
    /// allocated statement handle. This serves together with
    /// [`crate::handles::StatementImpl::into_sys`] or [`crate::handles::Statement::as_sys`] this
    /// serves as an escape hatch to access the functionality provided by `crate::sys` not yet
    /// accessible through safe abstractions.
    pub fn into_statement(self) -> StatementImpl<'o> {
        self.statement
    }

    /// List tables, schemas, views and catalogs of a datasource.
    ///
    /// # Parameters
    ///
    /// * `catalog_name`: Filter result by catalog name. Accept search patterns. Use `%` to match
    ///   any number of characters. Use `_` to match exactly on character. Use `\` to escape
    ///   characeters.
    /// * `schema_name`: Filter result by schema. Accepts patterns in the same way as
    ///   `catalog_name`.
    /// * `table_name`: Filter result by table. Accepts patterns in the same way as `catalog_name`.
    /// * `table_type`: Filters results by table type. E.g: 'TABLE', 'VIEW'. This argument accepts a
    ///   comma separeted list of table types. Omit it to not filter the result by table type at
    ///   all.
    pub fn tables(
        &mut self,
        catalog_name: &str,
        schema_name: &str,
        table_name: &str,
        table_type: &str,
    ) -> Result<CursorImpl<&mut StatementImpl<'o>>, Error> {
        execute_tables(
            &mut self.statement,
            &SqlText::new(catalog_name),
            &SqlText::new(schema_name),
            &SqlText::new(table_name),
            &SqlText::new(table_type),
        )
    }

    /// A cursor describing columns of all tables matching the patterns. Patterns support as
    /// placeholder `%` for multiple characters or `_` for a single character. Use `\` to escape.The
    /// returned cursor has the columns:
    /// `TABLE_CAT`, `TABLE_SCHEM`, `TABLE_NAME`, `COLUMN_NAME`, `DATA_TYPE`, `TYPE_NAME`,
    /// `COLUMN_SIZE`, `BUFFER_LENGTH`, `DECIMAL_DIGITS`, `NUM_PREC_RADIX`, `NULLABLE`,
    /// `REMARKS`, `COLUMN_DEF`, `SQL_DATA_TYPE`, `SQL_DATETIME_SUB`, `CHAR_OCTET_LENGTH`,
    /// `ORDINAL_POSITION`, `IS_NULLABLE`.
    ///
    /// In addition to that there may be a number of columns specific to the data source.
    pub fn columns(
        &mut self,
        catalog_name: &str,
        schema_name: &str,
        table_name: &str,
        column_name: &str,
    ) -> Result<CursorImpl<&mut StatementImpl<'o>>, Error> {
        execute_columns(
            &mut self.statement,
            &SqlText::new(catalog_name),
            &SqlText::new(schema_name),
            &SqlText::new(table_name),
            &SqlText::new(column_name),
        )
    }

    /// Number of rows affected by the last `INSERT`, `UPDATE` or `DELETE` statment. May return
    /// `None` if row count is not available. Some drivers may also allow to use this to determine
    /// how many rows have been fetched using `SELECT`. Most drivers however only know how many rows
    /// have been fetched after they have been fetched.
    ///
    /// ```
    /// use odbc_api::{Connection, Error};
    ///
    /// /// Make everyone rich and return how many colleagues are happy now.
    /// fn raise_minimum_salary(
    ///     conn: &Connection<'_>,
    ///     new_min_salary: i32
    /// ) -> Result<usize, Error> {
    ///     // We won't use conn.execute directly, because we need a handle to ask about the number
    ///     // of changed rows. So let's allocate the statement explicitly.
    ///     let mut stmt = conn.preallocate()?;
    ///     stmt.execute(
    ///         "UPDATE Employees SET salary = ? WHERE salary < ?",
    ///         (&new_min_salary, &new_min_salary),
    ///     )?;
    ///     let number_of_updated_rows = stmt
    ///         .row_count()?
    ///         .expect("For UPDATE statements row count must always be available.");
    ///     Ok(number_of_updated_rows)
    /// }
    /// ```
    pub fn row_count(&mut self) -> Result<Option<usize>, Error> {
        self.statement
            .row_count()
            .into_result(&self.statement)
            .map(|count| {
                // ODBC returns -1 in case a row count is not available
                if count == -1 {
                    None
                } else {
                    Some(count.try_into().unwrap())
                }
            })
    }

    /// Call this method to enable asynchronous polling mode on the statement
    pub fn into_polling(mut self) -> Result<PreallocatedPolling<'o>, Error> {
        self.statement
            .set_async_enable(true)
            .into_result(&self.statement)?;
        Ok(PreallocatedPolling::new(self.statement))
    }
}

impl<'o> AsStatementRef for Preallocated<'o> {
    fn as_stmt_ref(&mut self) -> StatementRef<'_> {
        self.statement.as_stmt_ref()
    }
}

/// Asynchronous sibling of [`Preallocated`] using polling mode for execution. Can be obtained using
/// [`Preallocated::into_polling`].
pub struct PreallocatedPolling<'open_connection> {
    /// A valid statement handle in polling mode
    statement: StatementImpl<'open_connection>,
}

impl<'o> PreallocatedPolling<'o> {
    fn new(statement: StatementImpl<'o>) -> Self {
        Self { statement }
    }

    /// Executes a statement. This is the fastest way to sequentially execute different SQL
    /// Statements asynchronously.
    ///
    /// # Parameters
    ///
    /// * `query`: The text representation of the SQL statement. E.g. "SELECT * FROM my_table;".
    /// * `params`: `?` may be used as a placeholder in the statement text. You can use `()` to
    ///   represent no parameters. Check the [`crate::parameter`] module level documentation for
    ///   more information on how to pass parameters.
    /// * `sleep`: Governs the polling intervals
    ///
    /// # Return
    ///
    /// Returns `Some` if a cursor is created. If `None` is returned no cursor has been created (
    /// e.g. the query came back empty). Note that an empty query may also create a cursor with zero
    /// rows. Since we want to reuse the statement handle a returned cursor will not take ownership
    /// of it and instead burrow it.
    ///
    /// # Example
    ///
    /// ```
    /// use odbc_api::{Connection, Error};
    /// use std::{io::{self, stdin, Read}, time::Duration};
    ///
    /// /// Execute many different queries sequentially.
    /// async fn execute_all(conn: &Connection<'_>, queries: &[&str]) -> Result<(), Error>{
    ///     let mut statement = conn.preallocate()?.into_polling()?;
    ///     let sleep = || tokio::time::sleep(Duration::from_millis(20));
    ///     for query in queries {
    ///         println!("Executing {query}");
    ///         match statement.execute(&query, (), sleep).await {
    ///             Err(e) => println!("{}", e),
    ///             Ok(None) => println!("No results set generated."),
    ///             Ok(Some(cursor)) => {
    ///                 // ...print cursor contents...
    ///             },
    ///         }
    ///     }
    ///     Ok(())
    /// }
    /// ```
    pub async fn execute(
        &mut self,
        query: &str,
        params: impl ParameterCollectionRef,
        sleep: impl Sleep,
    ) -> Result<Option<CursorPolling<&mut StatementImpl<'o>>>, Error> {
        let query = SqlText::new(query);
        execute_with_parameters_polling(
            move || Ok(&mut self.statement),
            Some(&query),
            params,
            sleep,
        )
        .await
    }
More examples
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src/connection.rs (line 118)
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    pub fn execute(
        &self,
        query: &str,
        params: impl ParameterCollectionRef,
    ) -> Result<Option<CursorImpl<StatementImpl<'_>>>, Error> {
        let query = SqlText::new(query);
        let lazy_statement = move || self.allocate_statement();
        execute_with_parameters(lazy_statement, Some(&query), params)
    }

    /// Asynchronous sibling of [`Self::execute`]. Uses polling mode to be asynchronous. `sleep`
    /// does govern the behaviour of polling, by waiting for the future in between polling. Sleep
    /// should not be implemented using a sleep which blocks the system thread, but rather utilize
    /// the methods provided by your async runtime. E.g.:
    ///
    /// ```
    /// use odbc_api::{Connection, IntoParameter, Error};
    /// use std::time::Duration;
    ///
    /// async fn insert_post<'a>(
    ///     connection: &'a Connection<'a>,
    ///     user: &str,
    ///     post: &str,
    /// ) -> Result<(), Error> {
    ///     // Poll every 50 ms.
    ///     let sleep = || tokio::time::sleep(Duration::from_millis(50));
    ///     let sql = "INSERT INTO POSTS (user, post) VALUES (?, ?)";
    ///     // Execute query using ODBC polling method
    ///     let params = (&user.into_parameter(), &post.into_parameter());
    ///     connection.execute_polling(&sql, params, sleep).await?;
    ///     Ok(())
    /// }
    /// ```
    pub async fn execute_polling(
        &self,
        query: &str,
        params: impl ParameterCollectionRef,
        sleep: impl Sleep,
    ) -> Result<Option<CursorPolling<StatementImpl<'_>>>, Error> {
        let query = SqlText::new(query);
        let lazy_statement = move || self.allocate_statement();
        execute_with_parameters_polling(lazy_statement, Some(&query), params, sleep).await
    }

    /// In some use cases there you only execute a single statement, or the time to open a
    /// connection does not matter users may wish to choose to not keep a connection alive seperatly
    /// from the cursor, in order to have an easier time withe the borrow checker.
    ///
    /// ```no_run
    /// use lazy_static::lazy_static;
    /// use odbc_api::{Environment, Error, Cursor};
    ///
    /// lazy_static! {
    ///     static ref ENV: Environment = unsafe { Environment::new().unwrap() };
    /// }
    ///
    /// const CONNECTION_STRING: &str =
    ///     "Driver={ODBC Driver 17 for SQL Server};\
    ///     Server=localhost;UID=SA;\
    ///     PWD=My@Test@Password1;";
    ///
    /// fn execute_query(query: &str) -> Result<Option<impl Cursor>, Error> {
    ///     let conn = ENV.connect_with_connection_string(CONNECTION_STRING)?;
    ///
    ///     // connect.execute(&query, ()) // Compiler error: Would return local ref to `conn`.
    ///
    ///     conn.into_cursor(&query, ())
    /// }
    /// ```
    pub fn into_cursor(
        self,
        query: &str,
        params: impl ParameterCollectionRef,
    ) -> Result<Option<CursorImpl<StatementConnection<'c>>>, Error> {
        let cursor = match self.execute(query, params) {
            Ok(Some(cursor)) => cursor,
            Ok(None) => return Ok(None),
            Err(e) => return Err(e),
        };
        // The rust compiler needs some help here. It assumes otherwise that the lifetime of the
        // resulting cursor would depend on the lifetime of `params`.
        let mut cursor = ManuallyDrop::new(cursor);
        let handle = cursor.as_sys();
        // Safe: `handle` is a valid statement, and we are giving up ownership of `self`.
        let statement = unsafe { StatementConnection::new(handle, self) };
        // Safe: `statement is in the cursor state`.
        let cursor = unsafe { CursorImpl::new(statement) };
        Ok(Some(cursor))
    }

    /// Prepares an SQL statement. This is recommended for repeated execution of similar queries.
    ///
    /// Should your use case require you to execute the same query several times with different
    /// parameters, prepared queries are the way to go. These gives the database a chance to cache
    /// the access plan associated with your SQL statement. It is not unlike compiling your program
    /// once and executing it several times.
    ///
    /// ```
    /// use odbc_api::{Connection, Error, IntoParameter};
    /// use std::io::{self, stdin, Read};
    ///
    /// fn interactive(conn: &Connection) -> io::Result<()>{
    ///     let mut prepared = conn.prepare("SELECT * FROM Movies WHERE title=?;").unwrap();
    ///     let mut title = String::new();
    ///     stdin().read_line(&mut title)?;
    ///     while !title.is_empty() {
    ///         match prepared.execute(&title.as_str().into_parameter()) {
    ///             Err(e) => println!("{}", e),
    ///             // Most drivers would return a result set even if no Movie with the title is found,
    ///             // the result set would just be empty. Well, most drivers.
    ///             Ok(None) => println!("No result set generated."),
    ///             Ok(Some(cursor)) => {
    ///                 // ...print cursor contents...
    ///             }
    ///         }
    ///         stdin().read_line(&mut title)?;
    ///     }
    ///     Ok(())
    /// }
    /// ```
    ///
    /// # Parameters
    ///
    /// * `query`: The text representation of the SQL statement. E.g. "SELECT * FROM my_table;". `?`
    ///   may be used as a placeholder in the statement text, to be replaced with parameters during
    ///   execution.
    pub fn prepare(&self, query: &str) -> Result<Prepared<StatementImpl<'_>>, Error> {
        let query = SqlText::new(query);
        let mut stmt = self.allocate_statement()?;
        stmt.prepare(&query).into_result(&stmt)?;
        Ok(Prepared::new(stmt))
    }

    /// Prepares an SQL statement which takes ownership of the connection. The advantage over
    /// [`Self::prepare`] is, that you do not need to keep track of the lifetime of the connection
    /// seperatly and can create types which do own the prepared query and only depend on the
    /// lifetime of the environment. The downside is that you can not use the connection for
    /// anything else anymore.
    ///
    /// # Parameters
    ///
    /// * `query`: The text representation of the SQL statement. E.g. "SELECT * FROM my_table;". `?`
    ///   may be used as a placeholder in the statement text, to be replaced with parameters during
    ///   execution.
    ///
    /// ```no_run
    /// use lazy_static::lazy_static;
    /// use odbc_api::{
    ///     Environment, Error, ColumnarBulkInserter, StatementConnection,
    ///     buffers::{BufferDesc, AnyBuffer},
    /// };
    ///
    /// lazy_static! {
    ///     static ref ENV: Environment = unsafe { Environment::new().unwrap() };
    /// }
    ///
    /// const CONNECTION_STRING: &str =
    ///     "Driver={ODBC Driver 17 for SQL Server};\
    ///     Server=localhost;UID=SA;\
    ///     PWD=My@Test@Password1;";
    ///
    /// /// Supports columnar bulk inserts on a heterogenous schema (columns have different types),
    /// /// takes ownership of a connection created using an environment with static lifetime.
    /// type Inserter = ColumnarBulkInserter<StatementConnection<'static>, AnyBuffer>;
    ///
    /// /// Creates an inserter which can be reused to bulk insert birthyears with static lifetime.
    /// fn make_inserter(query: &str) -> Result<Inserter, Error> {
    ///     let conn = ENV.connect_with_connection_string(CONNECTION_STRING)?;
    ///     let prepared = conn.into_prepared("INSERT INTO Birthyear (name, year) VALUES (?, ?)")?;
    ///     let buffers = [
    ///         BufferDesc::Text { max_str_len: 255},
    ///         BufferDesc::I16 { nullable: false },
    ///     ];
    ///     let capacity = 400;
    ///     prepared.into_column_inserter(capacity, buffers)
    /// }
    /// ```
    pub fn into_prepared(self, query: &str) -> Result<Prepared<StatementConnection<'c>>, Error> {
        let query = SqlText::new(query);
        let mut stmt = self.allocate_statement()?;
        stmt.prepare(&query).into_result(&stmt)?;
        // Safe: `handle` is a valid statement, and we are giving up ownership of `self`.
        let stmt = unsafe { StatementConnection::new(stmt.into_sys(), self) };
        Ok(Prepared::new(stmt))
    }

    /// Allocates an SQL statement handle. This is recommended if you want to sequentially execute
    /// different queries over the same connection, as you avoid the overhead of allocating a
    /// statement handle for each query.
    ///
    /// Should you want to repeatedly execute the same query with different parameters try
    /// [`Self::prepare`] instead.
    ///
    /// # Example
    ///
    /// ```
    /// use odbc_api::{Connection, Error};
    /// use std::io::{self, stdin, Read};
    ///
    /// fn interactive(conn: &Connection) -> io::Result<()>{
    ///     let mut statement = conn.preallocate().unwrap();
    ///     let mut query = String::new();
    ///     stdin().read_line(&mut query)?;
    ///     while !query.is_empty() {
    ///         match statement.execute(&query, ()) {
    ///             Err(e) => println!("{}", e),
    ///             Ok(None) => println!("No results set generated."),
    ///             Ok(Some(cursor)) => {
    ///                 // ...print cursor contents...
    ///             },
    ///         }
    ///         stdin().read_line(&mut query)?;
    ///     }
    ///     Ok(())
    /// }
    /// ```
    pub fn preallocate(&self) -> Result<Preallocated<'_>, Error> {
        let stmt = self.allocate_statement()?;
        Ok(Preallocated::new(stmt))
    }

    /// Specify the transaction mode. By default, ODBC transactions are in auto-commit mode.
    /// Switching from manual-commit mode to auto-commit mode automatically commits any open
    /// transaction on the connection. There is no open or begin transaction method. Each statement
    /// execution automatically starts a new transaction or adds to the existing one.
    ///
    /// In manual commit mode you can use [`Connection::commit`] or [`Connection::rollback`]. Keep
    /// in mind, that even `SELECT` statements can open new transactions. This library will rollback
    /// open transactions if a connection goes out of SCOPE. This however will log an error, since
    /// the transaction state is only discovered during a failed disconnect. It is preferable that
    /// the application makes sure all transactions are closed if in manual commit mode.
    pub fn set_autocommit(&self, enabled: bool) -> Result<(), Error> {
        self.connection
            .set_autocommit(enabled)
            .into_result(&self.connection)
    }

    /// To commit a transaction in manual-commit mode.
    pub fn commit(&self) -> Result<(), Error> {
        self.connection.commit().into_result(&self.connection)
    }

    /// To rollback a transaction in manual-commit mode.
    pub fn rollback(&self) -> Result<(), Error> {
        self.connection.rollback().into_result(&self.connection)
    }

    /// Indicates the state of the connection. If `true` the connection has been lost. If `false`,
    /// the connection is still active.
    pub fn is_dead(&self) -> Result<bool, Error> {
        self.connection.is_dead().into_result(&self.connection)
    }

    /// Allows sending this connection to different threads. This Connection will still be only be
    /// used by one thread at a time, but it may be a different thread each time.
    ///
    /// # Example
    ///
    /// ```no_run
    /// use std::thread;
    /// use lazy_static::lazy_static;
    /// use odbc_api::Environment;
    /// lazy_static! {
    ///     static ref ENV: Environment = unsafe { Environment::new().unwrap() };
    /// }
    /// const MSSQL: &str =
    ///     "Driver={ODBC Driver 17 for SQL Server};\
    ///     Server=localhost;\
    ///     UID=SA;\
    ///     PWD=My@Test@Password1;\
    /// ";
    ///
    /// let conn = ENV.connect_with_connection_string("MSSQL").unwrap();
    /// let conn = unsafe { conn.promote_to_send() };
    /// let handle = thread::spawn(move || {
    ///     if let Some(cursor) = conn.execute("SELECT title FROM Movies ORDER BY year",())? {
    ///         // Use cursor to process results
    ///     }
    ///     Ok::<(), odbc_api::Error>(())
    /// });
    /// handle.join().unwrap()?;
    /// # Ok::<(), odbc_api::Error>(())
    /// ```
    ///
    /// # Safety
    ///
    /// According to the ODBC standard this should be safe. By calling this function you express your
    /// trust in the implementation of the ODBC driver your application is using.
    ///
    /// See: <https://docs.microsoft.com/en-us/sql/odbc/reference/develop-app/multithreading?view=sql-server-ver15>
    ///
    /// This function may be removed in future versions of this crate and connections would be
    /// `Send` out of the Box. This will require sufficient testing in which a wide variety of
    /// database drivers prove to be thread safe. For now this API tries to error on the side of
    /// caution, and leaves the amount of trust you want to put in the driver implementation to the
    /// user. I have seen this go wrong in the past, but time certainly improved the situation. At
    /// one point this will be cargo cult and Connection can be `Send` by default (hopefully).
    ///
    /// Note to users of `unixodbc`: You may configure the threading level to make unixodbc
    /// synchronize access to the driver (and thereby making them thread safe if they are not thread
    /// safe by themself. This may however hurt your performance if the driver would actually be
    /// able to perform operations in parallel.
    ///
    /// See: <https://stackoverflow.com/questions/4207458/using-unixodbc-in-a-multithreaded-concurrent-setting>
    pub unsafe fn promote_to_send(self) -> force_send_sync::Send<Self> {
        force_send_sync::Send::new(self)
    }

    /// Get the name of the database management system used by the connection.
    pub fn database_management_system_name(&self) -> Result<String, Error> {
        let mut buf = Vec::new();
        self.connection
            .fetch_database_management_system_name(&mut buf)
            .into_result(&self.connection)?;
        let name = slice_to_utf8(&buf).unwrap();
        Ok(name)
    }

    /// Maximum length of catalog names.
    pub fn max_catalog_name_len(&self) -> Result<u16, Error> {
        self.connection
            .max_catalog_name_len()
            .into_result(&self.connection)
    }

    /// Maximum length of schema names.
    pub fn max_schema_name_len(&self) -> Result<u16, Error> {
        self.connection
            .max_schema_name_len()
            .into_result(&self.connection)
    }

    /// Maximum length of table names.
    pub fn max_table_name_len(&self) -> Result<u16, Error> {
        self.connection
            .max_table_name_len()
            .into_result(&self.connection)
    }

    /// Maximum length of column names.
    pub fn max_column_name_len(&self) -> Result<u16, Error> {
        self.connection
            .max_column_name_len()
            .into_result(&self.connection)
    }

    /// Get the name of the current catalog being used by the connection.
    pub fn current_catalog(&self) -> Result<String, Error> {
        let mut buf = Vec::new();
        self.connection
            .fetch_current_catalog(&mut buf)
            .into_result(&self.connection)?;
        let name = slice_to_utf8(&buf).expect("Return catalog must be correctly encoded");
        Ok(name)
    }

    /// A cursor describing columns of all tables matching the patterns. Patterns support as
    /// placeholder `%` for multiple characters or `_` for a single character. Use `\` to escape.The
    /// returned cursor has the columns:
    /// `TABLE_CAT`, `TABLE_SCHEM`, `TABLE_NAME`, `COLUMN_NAME`, `DATA_TYPE`, `TYPE_NAME`,
    /// `COLUMN_SIZE`, `BUFFER_LENGTH`, `DECIMAL_DIGITS`, `NUM_PREC_RADIX`, `NULLABLE`,
    /// `REMARKS`, `COLUMN_DEF`, `SQL_DATA_TYPE`, `SQL_DATETIME_SUB`, `CHAR_OCTET_LENGTH`,
    /// `ORDINAL_POSITION`, `IS_NULLABLE`.
    ///
    /// In addition to that there may be a number of columns specific to the data source.
    pub fn columns(
        &self,
        catalog_name: &str,
        schema_name: &str,
        table_name: &str,
        column_name: &str,
    ) -> Result<CursorImpl<StatementImpl<'_>>, Error> {
        execute_columns(
            self.allocate_statement()?,
            &SqlText::new(catalog_name),
            &SqlText::new(schema_name),
            &SqlText::new(table_name),
            &SqlText::new(column_name),
        )
    }

    /// List tables, schemas, views and catalogs of a datasource.
    ///
    /// # Parameters
    ///
    /// * `catalog_name`: Filter result by catalog name. Accept search patterns. Use `%` to match
    ///   any number of characters. Use `_` to match exactly on character. Use `\` to escape
    ///   characeters.
    /// * `schema_name`: Filter result by schema. Accepts patterns in the same way as
    ///   `catalog_name`.
    /// * `table_name`: Filter result by table. Accepts patterns in the same way as `catalog_name`.
    /// * `table_type`: Filters results by table type. E.g: 'TABLE', 'VIEW'. This argument accepts a
    ///   comma separeted list of table types. Omit it to not filter the result by table type at
    ///   all.
    ///
    /// # Example
    ///
    /// ```
    /// use odbc_api::{Connection, Cursor, Error, ResultSetMetadata, buffers::TextRowSet};
    ///
    /// fn print_all_tables(conn: &Connection<'_>) -> Result<(), Error> {
    ///     // Set all filters to an empty string, to really print all tables
    ///     let mut cursor = conn.tables("", "", "", "")?;
    ///
    ///     // The column are gonna be TABLE_CAT,TABLE_SCHEM,TABLE_NAME,TABLE_TYPE,REMARKS, but may
    ///     // also contain additional driver specific columns.
    ///     for (index, name) in cursor.column_names()?.enumerate() {
    ///         if index != 0 {
    ///             print!(",")
    ///         }
    ///         print!("{}", name?);
    ///     }
    ///
    ///     let batch_size = 100;
    ///     let mut buffer = TextRowSet::for_cursor(batch_size, &mut cursor, Some(4096))?;
    ///     let mut row_set_cursor = cursor.bind_buffer(&mut buffer)?;
    ///
    ///     while let Some(row_set) = row_set_cursor.fetch()? {
    ///         for row_index in 0..row_set.num_rows() {
    ///             if row_index != 0 {
    ///                 print!("\n");
    ///             }
    ///             for col_index in 0..row_set.num_cols() {
    ///                 if col_index != 0 {
    ///                     print!(",");
    ///                 }
    ///                 let value = row_set
    ///                     .at_as_str(col_index, row_index)
    ///                     .unwrap()
    ///                     .unwrap_or("NULL");
    ///                 print!("{}", value);
    ///             }
    ///         }
    ///     }
    ///
    ///     Ok(())
    /// }
    /// ```
    pub fn tables(
        &self,
        catalog_name: &str,
        schema_name: &str,
        table_name: &str,
        table_type: &str,
    ) -> Result<CursorImpl<StatementImpl<'_>>, Error> {
        let statement = self.allocate_statement()?;

        execute_tables(
            statement,
            &SqlText::new(catalog_name),
            &SqlText::new(schema_name),
            &SqlText::new(table_name),
            &SqlText::new(table_type),
        )
    }
src/environment.rs (line 208)
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    pub fn connect(
        &self,
        data_source_name: &str,
        user: &str,
        pwd: &str,
    ) -> Result<Connection<'_>, Error> {
        let data_source_name = SqlText::new(data_source_name);
        let user = SqlText::new(user);
        let pwd = SqlText::new(pwd);

        let mut connection = self.allocate_connection()?;
        connection
            .connect(&data_source_name, &user, &pwd)
            .into_result(&connection)?;
        Ok(Connection::new(connection))
    }

    /// Allocates a connection handle and establishes connections to a driver and a data source.
    ///
    /// An alternative to `connect`. It supports data sources that require more connection
    /// information than the three arguments in `connect` and data sources that are not defined in
    /// the system information.
    ///
    /// To find out your connection string try: <https://www.connectionstrings.com/>
    ///
    /// # Example
    ///
    /// ```no_run
    /// use odbc_api::Environment;
    ///
    /// let env = Environment::new()?;
    ///
    /// let connection_string = "
    ///     Driver={ODBC Driver 17 for SQL Server};\
    ///     Server=localhost;\
    ///     UID=SA;\
    ///     PWD=My@Test@Password1;\
    /// ";
    ///
    /// let mut conn = env.connect_with_connection_string(connection_string)?;
    /// # Ok::<(), odbc_api::Error>(())
    /// ```
    pub fn connect_with_connection_string(
        &self,
        connection_string: &str,
    ) -> Result<Connection<'_>, Error> {
        let connection_string = SqlText::new(connection_string);
        let mut connection = self.allocate_connection()?;
        connection
            .connect_with_connection_string(&connection_string)
            .into_result(&connection)?;
        Ok(Connection::new(connection))
    }

    /// Allocates a connection handle and establishes connections to a driver and a data source.
    ///
    /// An alternative to `connect` and `connect_with_connection_string`. This method can be
    /// provided with an incomplete or even empty connection string. If any additional information
    /// is required, the driver manager/driver will attempt to create a prompt to allow the user to
    /// provide the additional information.
    ///
    /// If the connection is successful, the complete connection string (including any information
    /// provided by the user through a prompt) is returned.
    ///
    /// # Parameters
    ///
    /// * `connection_string`: Connection string.
    /// * `completed_connection_string`: Output buffer with the complete connection string. It is
    ///   recommended to choose a buffer with at least `1024` bytes length. **Note**: Some driver
    ///   implementation have poor error handling in case the provided buffer is too small. At the
    ///   time of this writing:
    ///   * Maria DB crashes with STATUS_TACK_BUFFER_OVERRUN
    ///   * SQLite does not change the output buffer at all and does not indicate truncation.
    /// * `driver_completion`: Specifies how and if the driver manager uses a prompt to complete
    ///   the provided connection string. For arguments other than
    ///   [`crate::DriverCompleteOption::NoPrompt`] this method is going to create a message only
    ///   parent window for you on windows. On other platform this method is going to panic. In case
    ///   you want to provide your own parent window please use [`Self::driver_connect_with_hwnd`].
    ///
    /// # Examples
    ///
    /// In the first example, we intentionally provide a blank connection string so the user will be
    /// prompted to select a data source to use. Note that this functionality is only available on
    /// windows.
    ///
    /// ```no_run
    /// use odbc_api::{Environment, handles::OutputStringBuffer, DriverCompleteOption};
    ///
    /// let env = Environment::new()?;
    ///
    /// let mut output_buffer = OutputStringBuffer::with_buffer_size(1024);
    /// let connection = env.driver_connect(
    ///     "",
    ///     &mut output_buffer,
    ///     DriverCompleteOption::Prompt,
    /// )?;
    ///
    /// // Check that the output buffer has been large enough to hold the entire connection string.
    /// assert!(!output_buffer.is_truncated());
    ///
    /// // Now `connection_string` will contain the data source selected by the user.
    /// let connection_string = output_buffer.to_utf8();
    /// # Ok::<_,odbc_api::Error>(())
    /// ```
    ///
    /// In the following examples we specify a DSN that requires login credentials, but the DSN does
    /// not provide those credentials. Instead, the user will be prompted for a UID and PWD. The
    /// returned `connection_string` will contain the `UID` and `PWD` provided by the user. Note
    /// that this functionality is currently only available on windows targets.
    ///
    /// ```
    /// # use odbc_api::DriverCompleteOption;
    /// # #[cfg(target_os = "windows")]
    /// # fn f(
    /// #    mut output_buffer: odbc_api::handles::OutputStringBuffer,
    /// #    env: odbc_api::Environment,
    /// # ) -> Result<(), odbc_api::Error> {
    /// let without_uid_or_pwd = "DSN=SomeSharedDatabase;";
    /// let connection = env.driver_connect(
    ///     &without_uid_or_pwd,
    ///     &mut output_buffer,
    ///     DriverCompleteOption::Complete,
    /// )?;
    /// let connection_string = output_buffer.to_utf8();
    ///
    /// // Now `connection_string` might be something like
    /// // `DSN=SomeSharedDatabase;UID=SA;PWD=My@Test@Password1;`
    /// # Ok(()) }
    /// ```
    ///
    /// In this case, we use a DSN that is already sufficient and does not require a prompt. Because
    /// a prompt is not needed, `window` is also not required. The returned `connection_string` will
    /// be mostly the same as `already_sufficient` but the driver may append some extra attributes.
    ///
    /// ```
    /// # use odbc_api::DriverCompleteOption;
    /// # fn f(
    /// #    mut output_buffer: odbc_api::handles::OutputStringBuffer,
    /// #    env: odbc_api::Environment,
    /// # ) -> Result<(), odbc_api::Error> {
    /// let already_sufficient = "DSN=MicrosoftAccessFile;";
    /// let connection = env.driver_connect(
    ///    &already_sufficient,
    ///    &mut output_buffer,
    ///    DriverCompleteOption::NoPrompt,
    /// )?;
    /// let connection_string = output_buffer.to_utf8();
    ///
    /// // Now `connection_string` might be something like
    /// // `DSN=MicrosoftAccessFile;DBQ=C:\Db\Example.accdb;DriverId=25;FIL=MS Access;MaxBufferSize=2048;`
    /// # Ok(()) }
    /// ```
    pub fn driver_connect(
        &self,
        connection_string: &str,
        completed_connection_string: &mut OutputStringBuffer,
        driver_completion: DriverCompleteOption,
    ) -> Result<Connection<'_>, Error> {
        #[cfg(target_os = "windows")]
        let parent_window = match driver_completion {
            DriverCompleteOption::NoPrompt => None,
            _ => {
                if !cfg!(target_os = "windows") {
                    panic!("Prompt is not supported on non windows platforms. Use `NoPrompt`.")
                }
                // We need a parent window, let's provide a message only window.
                Some(
                    WindowBuilder::new()
                        .with_visible(false)
                        .build(&EventLoop::new())
                        .unwrap(),
                )
            }
        };
        #[cfg(target_os = "windows")]
        let hwnd = parent_window
            .as_ref()
            .map(|window| window.hwnd() as HWnd)
            .unwrap_or(null_mut());
        #[cfg(not(target_os = "windows"))]
        let hwnd = null_mut();
        unsafe {
            self.driver_connect_with_hwnd(
                connection_string,
                completed_connection_string,
                driver_completion,
                hwnd,
            )
        }
    }

    /// Allows to call driver connect with a user supplied HWnd. Same as [`Self::driver_connect`],
    /// but with the possibility to provide your own parent window handle in case you want to show
    /// a prompt to the user.
    ///
    /// # Safety
    ///
    /// `parent_window` must be a valid window handle, to a window type supported by the ODBC driver
    /// manager. On windows this is a plain window handle, which is of course understood by the
    /// windows built in ODBC driver manager. Other working combinations are unknown to the author.
    pub unsafe fn driver_connect_with_hwnd(
        &self,
        connection_string: &str,
        completed_connection_string: &mut OutputStringBuffer,
        driver_completion: DriverCompleteOption,
        parent_window: HWnd,
    ) -> Result<Connection<'_>, Error> {
        let mut connection = self.allocate_connection()?;
        let connection_string = SqlText::new(connection_string);

        let connection_string_is_complete = connection
            .driver_connect(
                &connection_string,
                parent_window,
                completed_connection_string,
                driver_completion.as_sys(),
            )
            .into_result_bool(&connection)?;
        if !connection_string_is_complete {
            return Err(Error::AbortedConnectionStringCompletion);
        }
        Ok(Connection::new(connection))
    }
Examples found in repository?
src/handles/statement.rs (line 316)
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    unsafe fn exec_direct(&mut self, statement: &SqlText) -> SqlResult<()> {
        sql_exec_direc(
            self.as_sys(),
            statement.ptr(),
            statement.len_char().try_into().unwrap(),
        )
        .into_sql_result("SQLExecDirect")
    }

    /// Close an open cursor.
    fn close_cursor(&mut self) -> SqlResult<()> {
        unsafe { SQLCloseCursor(self.as_sys()) }.into_sql_result("SQLCloseCursor")
    }

    /// Send an SQL statement to the data source for preparation. The application can include one or
    /// more parameter markers in the SQL statement. To include a parameter marker, the application
    /// embeds a question mark (?) into the SQL string at the appropriate position.
    fn prepare(&mut self, statement: &SqlText) -> SqlResult<()> {
        unsafe {
            sql_prepare(
                self.as_sys(),
                statement.ptr(),
                statement.len_char().try_into().unwrap(),
            )
        }
        .into_sql_result("SQLPrepare")
    }

    /// Executes a statement prepared by `prepare`. After the application processes or discards the
    /// results from a call to `execute`, the application can call SQLExecute again with new
    /// parameter values.
    ///
    /// # Safety
    ///
    /// While `self` as always guaranteed to be a valid allocated handle, this function may
    /// dereference bound parameters. It is the callers responsibility to ensure these are still
    /// valid. One strategy is to reset potentially invalid parameters right before the call using
    /// `reset_parameters`.
    ///
    /// # Return
    ///
    /// * [`SqlResult::NeedData`] if execution requires additional data from delayed parameters.
    /// * [`SqlResult::NoData`] if a searched update or delete statement did not affect any rows at
    ///   the data source.
    unsafe fn execute(&mut self) -> SqlResult<()> {
        SQLExecute(self.as_sys()).into_sql_result("SQLExecute")
    }

    /// Number of columns in result set.
    ///
    /// Can also be used to check, whether or not a result set has been created at all.
    fn num_result_cols(&self) -> SqlResult<i16> {
        let mut out: i16 = 0;
        unsafe { SQLNumResultCols(self.as_sys(), &mut out) }
            .into_sql_result("SQLNumResultCols")
            .on_success(|| out)
    }

    /// Number of placeholders of a prepared query.
    fn num_params(&self) -> SqlResult<u16> {
        let mut out: i16 = 0;
        unsafe { SQLNumParams(self.as_sys(), &mut out) }
            .into_sql_result("SQLNumParams")
            .on_success(|| out.try_into().unwrap())
    }

    /// Sets the batch size for bulk cursors, if retrieving many rows at once.
    ///
    /// # Safety
    ///
    /// It is the callers responsibility to ensure that buffers bound using `bind_col` can hold the
    /// specified amount of rows.
    unsafe fn set_row_array_size(&mut self, size: usize) -> SqlResult<()> {
        assert!(size > 0);
        sql_set_stmt_attr(
            self.as_sys(),
            StatementAttribute::RowArraySize,
            size as Pointer,
            0,
        )
        .into_sql_result("SQLSetStmtAttr")
    }

    /// Specifies the number of values for each parameter. If it is greater than 1, the data and
    /// indicator buffers of the statement point to arrays. The cardinality of each array is equal
    /// to the value of this field.
    ///
    /// # Safety
    ///
    /// The bound buffers must at least hold the number of elements specified in this call then the
    /// statement is executed.
    unsafe fn set_paramset_size(&mut self, size: usize) -> SqlResult<()> {
        assert!(size > 0);
        sql_set_stmt_attr(
            self.as_sys(),
            StatementAttribute::ParamsetSize,
            size as Pointer,
            0,
        )
        .into_sql_result("SQLSetStmtAttr")
    }

    /// Sets the binding type to columnar binding for batch cursors.
    ///
    /// Any Positive number indicates a row wise binding with that row length. `0` indicates a
    /// columnar binding.
    ///
    /// # Safety
    ///
    /// It is the callers responsibility to ensure that the bound buffers match the memory layout
    /// specified by this function.
    unsafe fn set_row_bind_type(&mut self, row_size: usize) -> SqlResult<()> {
        sql_set_stmt_attr(
            self.as_sys(),
            StatementAttribute::RowBindType,
            row_size as Pointer,
            0,
        )
        .into_sql_result("SQLSetStmtAttr")
    }

    fn set_metadata_id(&mut self, metadata_id: bool) -> SqlResult<()> {
        unsafe {
            sql_set_stmt_attr(
                self.as_sys(),
                StatementAttribute::MetadataId,
                metadata_id as usize as Pointer,
                0,
            )
            .into_sql_result("SQLSetStmtAttr")
        }
    }

    /// Enables or disables asynchronous execution for this statement handle. If asynchronous
    /// execution is not enabled on connection level it is disabled by default and everything is
    /// executed synchronously.
    ///
    /// This is equivalent to stetting `SQL_ATTR_ASYNC_ENABLE` in the bare C API.
    ///
    /// See
    /// <https://docs.microsoft.com/en-us/sql/odbc/reference/develop-app/executing-statements-odbc>
    fn set_async_enable(&mut self, on: bool) -> SqlResult<()> {
        unsafe {
            sql_set_stmt_attr(
                self.as_sys(),
                StatementAttribute::AsyncEnable,
                on as usize as Pointer,
                0,
            )
            .into_sql_result("SQLSetStmtAttr")
        }
    }

    /// Binds a buffer holding an input parameter to a parameter marker in an SQL statement. This
    /// specialized version takes a constant reference to parameter, but is therefore limited to
    /// binding input parameters. See [`Statement::bind_parameter`] for the version which can bind
    /// input and output parameters.
    ///
    /// See <https://docs.microsoft.com/en-us/sql/odbc/reference/syntax/sqlbindparameter-function>.
    ///
    /// # Safety
    ///
    /// * It is up to the caller to ensure the lifetimes of the bound parameters.
    /// * Calling this function may influence other statements that share the APD.
    unsafe fn bind_input_parameter(
        &mut self,
        parameter_number: u16,
        parameter: &(impl HasDataType + CData + ?Sized),
    ) -> SqlResult<()> {
        let parameter_type = parameter.data_type();
        SQLBindParameter(
            self.as_sys(),
            parameter_number,
            ParamType::Input,
            parameter.cdata_type(),
            parameter_type.data_type(),
            parameter_type.column_size(),
            parameter_type.decimal_digits(),
            // We cast const to mut here, but we specify the input_output_type as input.
            parameter.value_ptr() as *mut c_void,
            parameter.buffer_length(),
            // We cast const to mut here, but we specify the input_output_type as input.
            parameter.indicator_ptr() as *mut isize,
        )
        .into_sql_result("SQLBindParameter")
    }

    /// Binds a buffer holding a single parameter to a parameter marker in an SQL statement. To bind
    /// input parameters using constant references see [`Statement::bind_input_parameter`].
    ///
    /// See <https://docs.microsoft.com/en-us/sql/odbc/reference/syntax/sqlbindparameter-function>.
    ///
    /// # Safety
    ///
    /// * It is up to the caller to ensure the lifetimes of the bound parameters.
    /// * Calling this function may influence other statements that share the APD.
    unsafe fn bind_parameter(
        &mut self,
        parameter_number: u16,
        input_output_type: ParamType,
        parameter: &mut (impl CDataMut + HasDataType),
    ) -> SqlResult<()> {
        let parameter_type = parameter.data_type();
        SQLBindParameter(
            self.as_sys(),
            parameter_number,
            input_output_type,
            parameter.cdata_type(),
            parameter_type.data_type(),
            parameter_type.column_size(),
            parameter_type.decimal_digits(),
            parameter.value_ptr() as *mut c_void,
            parameter.buffer_length(),
            parameter.mut_indicator_ptr(),
        )
        .into_sql_result("SQLBindParameter")
    }

    /// Binds an input stream to a parameter marker in an SQL statement. Use this to stream large
    /// values at statement execution time. To bind preallocated constant buffers see
    /// [`Statement::bind_input_parameter`].
    ///
    /// See <https://docs.microsoft.com/en-us/sql/odbc/reference/syntax/sqlbindparameter-function>.
    ///
    /// # Safety
    ///
    /// * It is up to the caller to ensure the lifetimes of the bound parameters.
    /// * Calling this function may influence other statements that share the APD.
    unsafe fn bind_delayed_input_parameter(
        &mut self,
        parameter_number: u16,
        parameter: &mut (impl DelayedInput + HasDataType),
    ) -> SqlResult<()> {
        let paramater_type = parameter.data_type();
        SQLBindParameter(
            self.as_sys(),
            parameter_number,
            ParamType::Input,
            parameter.cdata_type(),
            paramater_type.data_type(),
            paramater_type.column_size(),
            paramater_type.decimal_digits(),
            parameter.stream_ptr(),
            0,
            // We cast const to mut here, but we specify the input_output_type as input.
            parameter.indicator_ptr() as *mut isize,
        )
        .into_sql_result("SQLBindParameter")
    }

    /// `true` if a given column in a result set is unsigned or not a numeric type, `false`
    /// otherwise.
    ///
    /// `column_number`: Index of the column, starting at 1.
    fn is_unsigned_column(&self, column_number: u16) -> SqlResult<bool> {
        unsafe { self.numeric_col_attribute(Desc::Unsigned, column_number) }.map(|out| match out {
            0 => false,
            1 => true,
            _ => panic!("Unsigned column attribute must be either 0 or 1."),
        })
    }

    /// Returns a number identifying the SQL type of the column in the result set.
    ///
    /// `column_number`: Index of the column, starting at 1.
    fn col_type(&self, column_number: u16) -> SqlResult<SqlDataType> {
        unsafe { self.numeric_col_attribute(Desc::Type, column_number) }
            .map(|ret| SqlDataType(ret.try_into().unwrap()))
    }

    /// The concise data type. For the datetime and interval data types, this field returns the
    /// concise data type; for example, `TIME` or `INTERVAL_YEAR`.
    ///
    /// `column_number`: Index of the column, starting at 1.
    fn col_concise_type(&self, column_number: u16) -> SqlResult<SqlDataType> {
        unsafe { self.numeric_col_attribute(Desc::ConciseType, column_number) }
            .map(|ret| SqlDataType(ret.try_into().unwrap()))
    }

    /// Returns the size in bytes of the columns. For variable sized types the maximum size is
    /// returned, excluding a terminating zero.
    ///
    /// `column_number`: Index of the column, starting at 1.
    fn col_octet_length(&self, column_number: u16) -> SqlResult<isize> {
        unsafe { self.numeric_col_attribute(Desc::OctetLength, column_number) }
    }

    /// Maximum number of characters required to display data from the column.
    ///
    /// `column_number`: Index of the column, starting at 1.
    fn col_display_size(&self, column_number: u16) -> SqlResult<isize> {
        unsafe { self.numeric_col_attribute(Desc::DisplaySize, column_number) }
    }

    /// Precision of the column.
    ///
    /// Denotes the applicable precision. For data types SQL_TYPE_TIME, SQL_TYPE_TIMESTAMP, and all
    /// the interval data types that represent a time interval, its value is the applicable
    /// precision of the fractional seconds component.
    fn col_precision(&self, column_number: u16) -> SqlResult<isize> {
        unsafe { self.numeric_col_attribute(Desc::Precision, column_number) }
    }

    /// The applicable scale for a numeric data type. For DECIMAL and NUMERIC data types, this is
    /// the defined scale. It is undefined for all other data types.
    fn col_scale(&self, column_number: u16) -> SqlResult<Len> {
        unsafe { self.numeric_col_attribute(Desc::Scale, column_number) }
    }

    /// The column alias, if it applies. If the column alias does not apply, the column name is
    /// returned. If there is no column name or a column alias, an empty string is returned.
    fn col_name(&self, column_number: u16, buffer: &mut Vec<SqlChar>) -> SqlResult<()> {
        // String length in bytes, not characters. Terminating zero is excluded.
        let mut string_length_in_bytes: i16 = 0;
        // Let's utilize all of `buf`s capacity.
        buffer.resize(buffer.capacity(), 0);
        unsafe {
            let mut res = sql_col_attribute(
                self.as_sys(),
                column_number,
                Desc::Name,
                mut_buf_ptr(buffer) as Pointer,
                binary_length(buffer).try_into().unwrap(),
                &mut string_length_in_bytes as *mut i16,
                null_mut(),
            )
            .into_sql_result("SQLColAttribute");

            if res.is_err() {
                return res;
            }

            if is_truncated_bin(buffer, string_length_in_bytes.try_into().unwrap()) {
                // If we could rely on every ODBC driver sticking to the specifcation it would
                // probably best to resize by `string_length_in_bytes / 2 + 1`. Yet e.g. SQLite
                // seems to report the length in characters, so to work with a wide range of DB
                // systems, and since buffers for names are not expected to become super large we
                // ommit the division by two here.
                buffer.resize((string_length_in_bytes + 1).try_into().unwrap(), 0);

                res = sql_col_attribute(
                    self.as_sys(),
                    column_number,
                    Desc::Name,
                    mut_buf_ptr(buffer) as Pointer,
                    binary_length(buffer).try_into().unwrap(),
                    &mut string_length_in_bytes as *mut i16,
                    null_mut(),
                )
                .into_sql_result("SQLColAttribute");
            }
            // Resize buffer to exact string length without terminal zero
            resize_to_fit_without_tz(buffer, string_length_in_bytes.try_into().unwrap());

            res
        }
    }

    /// # Safety
    ///
    /// It is the callers responsibility to ensure that `attribute` refers to a numeric attribute.
    unsafe fn numeric_col_attribute(&self, attribute: Desc, column_number: u16) -> SqlResult<Len> {
        let mut out: Len = 0;
        sql_col_attribute(
            self.as_sys(),
            column_number,
            attribute,
            null_mut(),
            0,
            null_mut(),
            &mut out as *mut Len,
        )
        .into_sql_result("SQLColAttribute")
        .on_success(|| out)
    }

    /// Sets the SQL_DESC_COUNT field of the APD to 0, releasing all parameter buffers set for the
    /// given StatementHandle.
    fn reset_parameters(&mut self) -> SqlResult<()> {
        unsafe {
            SQLFreeStmt(self.as_sys(), FreeStmtOption::ResetParams).into_sql_result("SQLFreeStmt")
        }
    }

    /// Describes parameter marker associated with a prepared SQL statement.
    ///
    /// # Parameters
    ///
    /// * `parameter_number`: Parameter marker number ordered sequentially in increasing parameter
    ///   order, starting at 1.
    fn describe_param(&self, parameter_number: u16) -> SqlResult<ParameterDescription> {
        let mut data_type = SqlDataType::UNKNOWN_TYPE;
        let mut parameter_size = 0;
        let mut decimal_digits = 0;
        let mut nullable = odbc_sys::Nullability::UNKNOWN;
        unsafe {
            SQLDescribeParam(
                self.as_sys(),
                parameter_number,
                &mut data_type,
                &mut parameter_size,
                &mut decimal_digits,
                &mut nullable,
            )
        }
        .into_sql_result("SQLDescribeParam")
        .on_success(|| ParameterDescription {
            data_type: DataType::new(data_type, parameter_size, decimal_digits),
            nullable: Nullability::new(nullable),
        })
    }

    /// Use to check if which additional parameters need data. Should be called after binding
    /// parameters with an indicator set to [`crate::sys::DATA_AT_EXEC`] or a value created with
    /// [`crate::sys::len_data_at_exec`].
    ///
    /// Return value contains a parameter identifier passed to bind parameter as a value pointer.
    fn param_data(&mut self) -> SqlResult<Option<Pointer>> {
        unsafe {
            let mut param_id: Pointer = null_mut();
            // Use cases for `PARAM_DATA_AVAILABLE` and `NO_DATA` not implemented yet.
            match SQLParamData(self.as_sys(), &mut param_id as *mut Pointer) {
                SqlReturn::NEED_DATA => SqlResult::Success(Some(param_id)),
                other => other.into_sql_result("SQLParamData").on_success(|| None),
            }
        }
    }

    /// Executes a columns query using this statement handle.
    fn columns(
        &mut self,
        catalog_name: &SqlText,
        schema_name: &SqlText,
        table_name: &SqlText,
        column_name: &SqlText,
    ) -> SqlResult<()> {
        unsafe {
            sql_columns(
                self.as_sys(),
                catalog_name.ptr(),
                catalog_name.len_char().try_into().unwrap(),
                schema_name.ptr(),
                schema_name.len_char().try_into().unwrap(),
                table_name.ptr(),
                table_name.len_char().try_into().unwrap(),
                column_name.ptr(),
                column_name.len_char().try_into().unwrap(),
            )
            .into_sql_result("SQLColumns")
        }
    }

    /// Returns the list of table, catalog, or schema names, and table types, stored in a specific
    /// data source. The driver returns the information as a result set.
    ///
    /// The catalog, schema and table parameters are search patterns by default unless
    /// [`Self::set_metadata_id`] is called with `true`. In that case they must also not be `None` since
    /// otherwise a NulPointer error is emitted.
    fn tables(
        &mut self,
        catalog_name: &SqlText,
        schema_name: &SqlText,
        table_name: &SqlText,
        table_type: &SqlText,
    ) -> SqlResult<()> {
        unsafe {
            sql_tables(
                self.as_sys(),
                catalog_name.ptr(),
                catalog_name.len_char().try_into().unwrap(),
                schema_name.ptr(),
                schema_name.len_char().try_into().unwrap(),
                table_name.ptr(),
                table_name.len_char().try_into().unwrap(),
                table_type.ptr(),
                table_type.len_char().try_into().unwrap(),
            )
            .into_sql_result("SQLTables")
        }
    }
More examples
Hide additional examples
src/handles/connection.rs (line 97)
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    pub fn connect(
        &mut self,
        data_source_name: &SqlText,
        user: &SqlText,
        pwd: &SqlText,
    ) -> SqlResult<()> {
        unsafe {
            sql_connect(
                self.handle,
                data_source_name.ptr(),
                data_source_name.len_char().try_into().unwrap(),
                user.ptr(),
                user.len_char().try_into().unwrap(),
                pwd.ptr(),
                pwd.len_char().try_into().unwrap(),
            )
            .into_sql_result("SQLConnect")
        }
    }

    /// An alternative to `connect`. It supports data sources that require more connection
    /// information than the three arguments in `connect` and data sources that are not defined in
    /// the system information.
    pub fn connect_with_connection_string(&mut self, connection_string: &SqlText) -> SqlResult<()> {
        unsafe {
            let parent_window = null_mut();
            let mut completed_connection_string = OutputStringBuffer::empty();

            self.driver_connect(
                connection_string,
                parent_window,
                &mut completed_connection_string,
                DriverConnectOption::NoPrompt,
            )
            // Since we did pass NoPrompt we know the user can not abort the prompt.
            .map(|_connection_string_is_complete| ())
        }
    }

    /// An alternative to `connect` for connecting with a connection string. Allows for completing
    /// a connection string with a GUI prompt on windows.
    ///
    /// # Return
    ///
    /// [`SqlResult::NoData`] in case the prompt completing the connection string has been aborted.
    ///
    /// # Safety
    ///
    /// `parent_window` must either be a valid window handle or `NULL`.
    pub unsafe fn driver_connect(
        &mut self,
        connection_string: &SqlText,
        parent_window: HWnd,
        completed_connection_string: &mut OutputStringBuffer,
        driver_completion: DriverConnectOption,
    ) -> SqlResult<()> {
        sql_driver_connect(
            self.handle,
            parent_window,
            connection_string.ptr(),
            connection_string.len_char().try_into().unwrap(),
            completed_connection_string.mut_buf_ptr(),
            completed_connection_string.buf_len(),
            completed_connection_string.mut_actual_len_ptr(),
            driver_completion,
        )
        .into_sql_result("SQLDriverConnect")
    }

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src/handles/statement.rs (line 317)
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    unsafe fn exec_direct(&mut self, statement: &SqlText) -> SqlResult<()> {
        sql_exec_direc(
            self.as_sys(),
            statement.ptr(),
            statement.len_char().try_into().unwrap(),
        )
        .into_sql_result("SQLExecDirect")
    }

    /// Close an open cursor.
    fn close_cursor(&mut self) -> SqlResult<()> {
        unsafe { SQLCloseCursor(self.as_sys()) }.into_sql_result("SQLCloseCursor")
    }

    /// Send an SQL statement to the data source for preparation. The application can include one or
    /// more parameter markers in the SQL statement. To include a parameter marker, the application
    /// embeds a question mark (?) into the SQL string at the appropriate position.
    fn prepare(&mut self, statement: &SqlText) -> SqlResult<()> {
        unsafe {
            sql_prepare(
                self.as_sys(),
                statement.ptr(),
                statement.len_char().try_into().unwrap(),
            )
        }
        .into_sql_result("SQLPrepare")
    }

    /// Executes a statement prepared by `prepare`. After the application processes or discards the
    /// results from a call to `execute`, the application can call SQLExecute again with new
    /// parameter values.
    ///
    /// # Safety
    ///
    /// While `self` as always guaranteed to be a valid allocated handle, this function may
    /// dereference bound parameters. It is the callers responsibility to ensure these are still
    /// valid. One strategy is to reset potentially invalid parameters right before the call using
    /// `reset_parameters`.
    ///
    /// # Return
    ///
    /// * [`SqlResult::NeedData`] if execution requires additional data from delayed parameters.
    /// * [`SqlResult::NoData`] if a searched update or delete statement did not affect any rows at
    ///   the data source.
    unsafe fn execute(&mut self) -> SqlResult<()> {
        SQLExecute(self.as_sys()).into_sql_result("SQLExecute")
    }

    /// Number of columns in result set.
    ///
    /// Can also be used to check, whether or not a result set has been created at all.
    fn num_result_cols(&self) -> SqlResult<i16> {
        let mut out: i16 = 0;
        unsafe { SQLNumResultCols(self.as_sys(), &mut out) }
            .into_sql_result("SQLNumResultCols")
            .on_success(|| out)
    }

    /// Number of placeholders of a prepared query.
    fn num_params(&self) -> SqlResult<u16> {
        let mut out: i16 = 0;
        unsafe { SQLNumParams(self.as_sys(), &mut out) }
            .into_sql_result("SQLNumParams")
            .on_success(|| out.try_into().unwrap())
    }

    /// Sets the batch size for bulk cursors, if retrieving many rows at once.
    ///
    /// # Safety
    ///
    /// It is the callers responsibility to ensure that buffers bound using `bind_col` can hold the
    /// specified amount of rows.
    unsafe fn set_row_array_size(&mut self, size: usize) -> SqlResult<()> {
        assert!(size > 0);
        sql_set_stmt_attr(
            self.as_sys(),
            StatementAttribute::RowArraySize,
            size as Pointer,
            0,
        )
        .into_sql_result("SQLSetStmtAttr")
    }

    /// Specifies the number of values for each parameter. If it is greater than 1, the data and
    /// indicator buffers of the statement point to arrays. The cardinality of each array is equal
    /// to the value of this field.
    ///
    /// # Safety
    ///
    /// The bound buffers must at least hold the number of elements specified in this call then the
    /// statement is executed.
    unsafe fn set_paramset_size(&mut self, size: usize) -> SqlResult<()> {
        assert!(size > 0);
        sql_set_stmt_attr(
            self.as_sys(),
            StatementAttribute::ParamsetSize,
            size as Pointer,
            0,
        )
        .into_sql_result("SQLSetStmtAttr")
    }

    /// Sets the binding type to columnar binding for batch cursors.
    ///
    /// Any Positive number indicates a row wise binding with that row length. `0` indicates a
    /// columnar binding.
    ///
    /// # Safety
    ///
    /// It is the callers responsibility to ensure that the bound buffers match the memory layout
    /// specified by this function.
    unsafe fn set_row_bind_type(&mut self, row_size: usize) -> SqlResult<()> {
        sql_set_stmt_attr(
            self.as_sys(),
            StatementAttribute::RowBindType,
            row_size as Pointer,
            0,
        )
        .into_sql_result("SQLSetStmtAttr")
    }

    fn set_metadata_id(&mut self, metadata_id: bool) -> SqlResult<()> {
        unsafe {
            sql_set_stmt_attr(
                self.as_sys(),
                StatementAttribute::MetadataId,
                metadata_id as usize as Pointer,
                0,
            )
            .into_sql_result("SQLSetStmtAttr")
        }
    }

    /// Enables or disables asynchronous execution for this statement handle. If asynchronous
    /// execution is not enabled on connection level it is disabled by default and everything is
    /// executed synchronously.
    ///
    /// This is equivalent to stetting `SQL_ATTR_ASYNC_ENABLE` in the bare C API.
    ///
    /// See
    /// <https://docs.microsoft.com/en-us/sql/odbc/reference/develop-app/executing-statements-odbc>
    fn set_async_enable(&mut self, on: bool) -> SqlResult<()> {
        unsafe {
            sql_set_stmt_attr(
                self.as_sys(),
                StatementAttribute::AsyncEnable,
                on as usize as Pointer,
                0,
            )
            .into_sql_result("SQLSetStmtAttr")
        }
    }

    /// Binds a buffer holding an input parameter to a parameter marker in an SQL statement. This
    /// specialized version takes a constant reference to parameter, but is therefore limited to
    /// binding input parameters. See [`Statement::bind_parameter`] for the version which can bind
    /// input and output parameters.
    ///
    /// See <https://docs.microsoft.com/en-us/sql/odbc/reference/syntax/sqlbindparameter-function>.
    ///
    /// # Safety
    ///
    /// * It is up to the caller to ensure the lifetimes of the bound parameters.
    /// * Calling this function may influence other statements that share the APD.
    unsafe fn bind_input_parameter(
        &mut self,
        parameter_number: u16,
        parameter: &(impl HasDataType + CData + ?Sized),
    ) -> SqlResult<()> {
        let parameter_type = parameter.data_type();
        SQLBindParameter(
            self.as_sys(),
            parameter_number,
            ParamType::Input,
            parameter.cdata_type(),
            parameter_type.data_type(),
            parameter_type.column_size(),
            parameter_type.decimal_digits(),
            // We cast const to mut here, but we specify the input_output_type as input.
            parameter.value_ptr() as *mut c_void,
            parameter.buffer_length(),
            // We cast const to mut here, but we specify the input_output_type as input.
            parameter.indicator_ptr() as *mut isize,
        )
        .into_sql_result("SQLBindParameter")
    }

    /// Binds a buffer holding a single parameter to a parameter marker in an SQL statement. To bind
    /// input parameters using constant references see [`Statement::bind_input_parameter`].
    ///
    /// See <https://docs.microsoft.com/en-us/sql/odbc/reference/syntax/sqlbindparameter-function>.
    ///
    /// # Safety
    ///
    /// * It is up to the caller to ensure the lifetimes of the bound parameters.
    /// * Calling this function may influence other statements that share the APD.
    unsafe fn bind_parameter(
        &mut self,
        parameter_number: u16,
        input_output_type: ParamType,
        parameter: &mut (impl CDataMut + HasDataType),
    ) -> SqlResult<()> {
        let parameter_type = parameter.data_type();
        SQLBindParameter(
            self.as_sys(),
            parameter_number,
            input_output_type,
            parameter.cdata_type(),
            parameter_type.data_type(),
            parameter_type.column_size(),
            parameter_type.decimal_digits(),
            parameter.value_ptr() as *mut c_void,
            parameter.buffer_length(),
            parameter.mut_indicator_ptr(),
        )
        .into_sql_result("SQLBindParameter")
    }

    /// Binds an input stream to a parameter marker in an SQL statement. Use this to stream large
    /// values at statement execution time. To bind preallocated constant buffers see
    /// [`Statement::bind_input_parameter`].
    ///
    /// See <https://docs.microsoft.com/en-us/sql/odbc/reference/syntax/sqlbindparameter-function>.
    ///
    /// # Safety
    ///
    /// * It is up to the caller to ensure the lifetimes of the bound parameters.
    /// * Calling this function may influence other statements that share the APD.
    unsafe fn bind_delayed_input_parameter(
        &mut self,
        parameter_number: u16,
        parameter: &mut (impl DelayedInput + HasDataType),
    ) -> SqlResult<()> {
        let paramater_type = parameter.data_type();
        SQLBindParameter(
            self.as_sys(),
            parameter_number,
            ParamType::Input,
            parameter.cdata_type(),
            paramater_type.data_type(),
            paramater_type.column_size(),
            paramater_type.decimal_digits(),
            parameter.stream_ptr(),
            0,
            // We cast const to mut here, but we specify the input_output_type as input.
            parameter.indicator_ptr() as *mut isize,
        )
        .into_sql_result("SQLBindParameter")
    }

    /// `true` if a given column in a result set is unsigned or not a numeric type, `false`
    /// otherwise.
    ///
    /// `column_number`: Index of the column, starting at 1.
    fn is_unsigned_column(&self, column_number: u16) -> SqlResult<bool> {
        unsafe { self.numeric_col_attribute(Desc::Unsigned, column_number) }.map(|out| match out {
            0 => false,
            1 => true,
            _ => panic!("Unsigned column attribute must be either 0 or 1."),
        })
    }

    /// Returns a number identifying the SQL type of the column in the result set.
    ///
    /// `column_number`: Index of the column, starting at 1.
    fn col_type(&self, column_number: u16) -> SqlResult<SqlDataType> {
        unsafe { self.numeric_col_attribute(Desc::Type, column_number) }
            .map(|ret| SqlDataType(ret.try_into().unwrap()))
    }

    /// The concise data type. For the datetime and interval data types, this field returns the
    /// concise data type; for example, `TIME` or `INTERVAL_YEAR`.
    ///
    /// `column_number`: Index of the column, starting at 1.
    fn col_concise_type(&self, column_number: u16) -> SqlResult<SqlDataType> {
        unsafe { self.numeric_col_attribute(Desc::ConciseType, column_number) }
            .map(|ret| SqlDataType(ret.try_into().unwrap()))
    }

    /// Returns the size in bytes of the columns. For variable sized types the maximum size is
    /// returned, excluding a terminating zero.
    ///
    /// `column_number`: Index of the column, starting at 1.
    fn col_octet_length(&self, column_number: u16) -> SqlResult<isize> {
        unsafe { self.numeric_col_attribute(Desc::OctetLength, column_number) }
    }

    /// Maximum number of characters required to display data from the column.
    ///
    /// `column_number`: Index of the column, starting at 1.
    fn col_display_size(&self, column_number: u16) -> SqlResult<isize> {
        unsafe { self.numeric_col_attribute(Desc::DisplaySize, column_number) }
    }

    /// Precision of the column.
    ///
    /// Denotes the applicable precision. For data types SQL_TYPE_TIME, SQL_TYPE_TIMESTAMP, and all
    /// the interval data types that represent a time interval, its value is the applicable
    /// precision of the fractional seconds component.
    fn col_precision(&self, column_number: u16) -> SqlResult<isize> {
        unsafe { self.numeric_col_attribute(Desc::Precision, column_number) }
    }

    /// The applicable scale for a numeric data type. For DECIMAL and NUMERIC data types, this is
    /// the defined scale. It is undefined for all other data types.
    fn col_scale(&self, column_number: u16) -> SqlResult<Len> {
        unsafe { self.numeric_col_attribute(Desc::Scale, column_number) }
    }

    /// The column alias, if it applies. If the column alias does not apply, the column name is
    /// returned. If there is no column name or a column alias, an empty string is returned.
    fn col_name(&self, column_number: u16, buffer: &mut Vec<SqlChar>) -> SqlResult<()> {
        // String length in bytes, not characters. Terminating zero is excluded.
        let mut string_length_in_bytes: i16 = 0;
        // Let's utilize all of `buf`s capacity.
        buffer.resize(buffer.capacity(), 0);
        unsafe {
            let mut res = sql_col_attribute(
                self.as_sys(),
                column_number,
                Desc::Name,
                mut_buf_ptr(buffer) as Pointer,
                binary_length(buffer).try_into().unwrap(),
                &mut string_length_in_bytes as *mut i16,
                null_mut(),
            )
            .into_sql_result("SQLColAttribute");

            if res.is_err() {
                return res;
            }

            if is_truncated_bin(buffer, string_length_in_bytes.try_into().unwrap()) {
                // If we could rely on every ODBC driver sticking to the specifcation it would
                // probably best to resize by `string_length_in_bytes / 2 + 1`. Yet e.g. SQLite
                // seems to report the length in characters, so to work with a wide range of DB
                // systems, and since buffers for names are not expected to become super large we
                // ommit the division by two here.
                buffer.resize((string_length_in_bytes + 1).try_into().unwrap(), 0);

                res = sql_col_attribute(
                    self.as_sys(),
                    column_number,
                    Desc::Name,
                    mut_buf_ptr(buffer) as Pointer,
                    binary_length(buffer).try_into().unwrap(),
                    &mut string_length_in_bytes as *mut i16,
                    null_mut(),
                )
                .into_sql_result("SQLColAttribute");
            }
            // Resize buffer to exact string length without terminal zero
            resize_to_fit_without_tz(buffer, string_length_in_bytes.try_into().unwrap());

            res
        }
    }

    /// # Safety
    ///
    /// It is the callers responsibility to ensure that `attribute` refers to a numeric attribute.
    unsafe fn numeric_col_attribute(&self, attribute: Desc, column_number: u16) -> SqlResult<Len> {
        let mut out: Len = 0;
        sql_col_attribute(
            self.as_sys(),
            column_number,
            attribute,
            null_mut(),
            0,
            null_mut(),
            &mut out as *mut Len,
        )
        .into_sql_result("SQLColAttribute")
        .on_success(|| out)
    }

    /// Sets the SQL_DESC_COUNT field of the APD to 0, releasing all parameter buffers set for the
    /// given StatementHandle.
    fn reset_parameters(&mut self) -> SqlResult<()> {
        unsafe {
            SQLFreeStmt(self.as_sys(), FreeStmtOption::ResetParams).into_sql_result("SQLFreeStmt")
        }
    }

    /// Describes parameter marker associated with a prepared SQL statement.
    ///
    /// # Parameters
    ///
    /// * `parameter_number`: Parameter marker number ordered sequentially in increasing parameter
    ///   order, starting at 1.
    fn describe_param(&self, parameter_number: u16) -> SqlResult<ParameterDescription> {
        let mut data_type = SqlDataType::UNKNOWN_TYPE;
        let mut parameter_size = 0;
        let mut decimal_digits = 0;
        let mut nullable = odbc_sys::Nullability::UNKNOWN;
        unsafe {
            SQLDescribeParam(
                self.as_sys(),
                parameter_number,
                &mut data_type,
                &mut parameter_size,
                &mut decimal_digits,
                &mut nullable,
            )
        }
        .into_sql_result("SQLDescribeParam")
        .on_success(|| ParameterDescription {
            data_type: DataType::new(data_type, parameter_size, decimal_digits),
            nullable: Nullability::new(nullable),
        })
    }

    /// Use to check if which additional parameters need data. Should be called after binding
    /// parameters with an indicator set to [`crate::sys::DATA_AT_EXEC`] or a value created with
    /// [`crate::sys::len_data_at_exec`].
    ///
    /// Return value contains a parameter identifier passed to bind parameter as a value pointer.
    fn param_data(&mut self) -> SqlResult<Option<Pointer>> {
        unsafe {
            let mut param_id: Pointer = null_mut();
            // Use cases for `PARAM_DATA_AVAILABLE` and `NO_DATA` not implemented yet.
            match SQLParamData(self.as_sys(), &mut param_id as *mut Pointer) {
                SqlReturn::NEED_DATA => SqlResult::Success(Some(param_id)),
                other => other.into_sql_result("SQLParamData").on_success(|| None),
            }
        }
    }

    /// Executes a columns query using this statement handle.
    fn columns(
        &mut self,
        catalog_name: &SqlText,
        schema_name: &SqlText,
        table_name: &SqlText,
        column_name: &SqlText,
    ) -> SqlResult<()> {
        unsafe {
            sql_columns(
                self.as_sys(),
                catalog_name.ptr(),
                catalog_name.len_char().try_into().unwrap(),
                schema_name.ptr(),
                schema_name.len_char().try_into().unwrap(),
                table_name.ptr(),
                table_name.len_char().try_into().unwrap(),
                column_name.ptr(),
                column_name.len_char().try_into().unwrap(),
            )
            .into_sql_result("SQLColumns")
        }
    }

    /// Returns the list of table, catalog, or schema names, and table types, stored in a specific
    /// data source. The driver returns the information as a result set.
    ///
    /// The catalog, schema and table parameters are search patterns by default unless
    /// [`Self::set_metadata_id`] is called with `true`. In that case they must also not be `None` since
    /// otherwise a NulPointer error is emitted.
    fn tables(
        &mut self,
        catalog_name: &SqlText,
        schema_name: &SqlText,
        table_name: &SqlText,
        table_type: &SqlText,
    ) -> SqlResult<()> {
        unsafe {
            sql_tables(
                self.as_sys(),
                catalog_name.ptr(),
                catalog_name.len_char().try_into().unwrap(),
                schema_name.ptr(),
                schema_name.len_char().try_into().unwrap(),
                table_name.ptr(),
                table_name.len_char().try_into().unwrap(),
                table_type.ptr(),
                table_type.len_char().try_into().unwrap(),
            )
            .into_sql_result("SQLTables")
        }
    }
More examples
Hide additional examples
src/handles/connection.rs (line 98)
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    pub fn connect(
        &mut self,
        data_source_name: &SqlText,
        user: &SqlText,
        pwd: &SqlText,
    ) -> SqlResult<()> {
        unsafe {
            sql_connect(
                self.handle,
                data_source_name.ptr(),
                data_source_name.len_char().try_into().unwrap(),
                user.ptr(),
                user.len_char().try_into().unwrap(),
                pwd.ptr(),
                pwd.len_char().try_into().unwrap(),
            )
            .into_sql_result("SQLConnect")
        }
    }

    /// An alternative to `connect`. It supports data sources that require more connection
    /// information than the three arguments in `connect` and data sources that are not defined in
    /// the system information.
    pub fn connect_with_connection_string(&mut self, connection_string: &SqlText) -> SqlResult<()> {
        unsafe {
            let parent_window = null_mut();
            let mut completed_connection_string = OutputStringBuffer::empty();

            self.driver_connect(
                connection_string,
                parent_window,
                &mut completed_connection_string,
                DriverConnectOption::NoPrompt,
            )
            // Since we did pass NoPrompt we know the user can not abort the prompt.
            .map(|_connection_string_is_complete| ())
        }
    }

    /// An alternative to `connect` for connecting with a connection string. Allows for completing
    /// a connection string with a GUI prompt on windows.
    ///
    /// # Return
    ///
    /// [`SqlResult::NoData`] in case the prompt completing the connection string has been aborted.
    ///
    /// # Safety
    ///
    /// `parent_window` must either be a valid window handle or `NULL`.
    pub unsafe fn driver_connect(
        &mut self,
        connection_string: &SqlText,
        parent_window: HWnd,
        completed_connection_string: &mut OutputStringBuffer,
        driver_completion: DriverConnectOption,
    ) -> SqlResult<()> {
        sql_driver_connect(
            self.handle,
            parent_window,
            connection_string.ptr(),
            connection_string.len_char().try_into().unwrap(),
            completed_connection_string.mut_buf_ptr(),
            completed_connection_string.buf_len(),
            completed_connection_string.mut_actual_len_ptr(),
            driver_completion,
        )
        .into_sql_result("SQLDriverConnect")
    }

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Gets the TypeId of self. Read more
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Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.