Struct odbc_api::parameter::VarChar

pub struct VarChar<B> { /* fields omitted */ }

Binds a byte array as Variadic sized character data. It can not be used for columnar bulk fetches, but if the buffer type is stack allocated it can be utilized in row wise bulk fetches.

Meaningful instantiations of this type are:

• self::VarCharSlice - immutable borrowed parameter.
• self::VarCharSliceMut - mutable borrowed input / output parameter
• self::VarCharArray - stack allocated owned input / output parameter
• self::VarCharBox - heap allocated owned input /output parameter

Implementations

impl VarChar<Box<[u8], Global>>

pub fn null() -> Self

Constructs a ‘missing’ value.

pub fn from_string(val: String) -> Self

Create an owned parameter containing the character data from the passed string.

pub fn from_vec(val: Vec<u8>) -> Self

Create a VarChar box from a Vec.

impl<B> VarChar<B> where
    B: Borrow<[u8]>, 

pub fn from_buffer(buffer: B, indicator: Indicator) -> Self

Creates a new instance from an existing buffer. Should the indicator be NoTotal or indicate a length longer than buffer, the last element in the buffer must be nul (\0).

pub fn as_bytes(&self) -> Option<&[u8]>

Returns the binary representation of the string, excluding the terminating zero or None in case the indicator is NULL_DATA.

pub fn is_complete(&self) -> bool

Call this method to ensure that the entire field content did fit into the buffer. If you retrieve a field using crate::CursorRow::get_data, you can repeat the call until this method is false to read all the data.

use odbc_api::{CursorRow, parameter::VarCharArray, Error, handles::Statement};

fn process_large_text<S: Statement>(
    col_index: u16,
    row: &mut CursorRow<S>
) -> Result<(), Error>{
    let mut buf = VarCharArray::<512>::NULL;
    row.get_data(col_index, &mut buf)?;
    while !buf.is_complete() {
        // Process bytes in stream without allocation. We can assume repeated calls to
        // get_data do not return `None` since it would have done so on the first call.
        process_text_slice(buf.as_bytes().unwrap());
    }
    Ok(())
}

fn process_text_slice(text: &[u8]) { /*...*/}

pub fn indicator(&self) -> Indicator

Read access to the underlying ODBC indicator. After data has been fetched the indicator value is set to the length the buffer should have had, excluding the terminating zero. It may also be NULL_DATA to indicate NULL or NO_TOTAL which tells us the data source does not know how big the buffer must be to hold the complete value. NO_TOTAL implies that the content of the current buffer is valid up to its maximum capacity.

impl<B> VarChar<B> where
    B: Borrow<[u8]>, 

pub fn hide_truncation(&mut self)

Call this method to reset the indicator to a value which matches the length returned by the Self::as_bytes method. This is useful if you want to insert values into the database despite the fact, that they might have been truncated. Otherwise the behaviour of databases in this situation is driver specific. Some drivers insert up to the terminating zero, others detect the truncation and throw an error.

impl<'a> VarChar<&'a [u8]>

pub const NULL: Self

Indicates missing data

pub fn new(value: &'a [u8]) -> Self

Constructs a new VarChar containing the text in the specified buffer.

Caveat: This constructor is going to create a truncated value in case the input slice ends with nul. Should you want to insert an actual string those payload ends with nul into the database you need a buffer one byte longer than the string. You can instantiate such a value using Self::from_buffer.

impl<const LENGTH: usize> VarChar<[u8; LENGTH]>

pub const NULL: Self

Indicates a missing value.

pub fn new(text: &[u8]) -> Self

Construct from a slice. If value is longer than LENGTH it will be truncated. In that case the last byte will be set to 0.

Trait Implementations

impl<B> CData for VarChar<B> where
    B: Borrow<[u8]>, 

fn cdata_type(&self) -> CDataType

The identifier of the C data type of the value buffer. When it is retrieving data from the data source with fetch, the driver converts the data to this type. When it sends data to the source, the driver converts the data from this type.

fn indicator_ptr(&self) -> *const isize

Indicates the length of variable sized types. May be zero for fixed sized types. Used to determine the size or existence of input parameters.

fn value_ptr(&self) -> *const c_void

Pointer to a value corresponding to the one described by cdata_type.

fn buffer_length(&self) -> isize

Maximum length of the type in bytes (not characters). It is required to index values in bound buffers, if more than one parameter is bound. Can be set to zero for types not bound as parameter arrays, i.e. CStr.

impl<B> CDataMut for VarChar<B> where
    B: BorrowMut<[u8]>, 

fn mut_indicator_ptr(&mut self) -> *mut isize

Indicates the length of variable sized types. May be zero for fixed sized types.

fn mut_value_ptr(&mut self) -> *mut c_void

Pointer to a value corresponding to the one described by cdata_type.

impl<B: Clone> Clone for VarChar<B>

fn clone(&self) -> VarChar<B>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<B: Debug> Debug for VarChar<B>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<B> HasDataType for VarChar<B> where
    B: Borrow<[u8]>, 

fn data_type(&self) -> DataType

The SQL data as which the parameter is bound to ODBC.

impl<B: Copy> Copy for VarChar<B>