Struct odbc_api::buffers::TextColumn

pub struct TextColumn { /* fields omitted */ }

A buffer intended to be bound to a column of a cursor. Elements of the buffer will contain a variable amount of characters up to a maximum string length. Since most SQL types have a string representation this buffer can be bound to a column of almost any type, ODBC driver and driver manager should take care of the conversion. Since elements of this type have variable length an indicator buffer needs to be bound, whether the column is nullable or not, and therefore does not matter for this buffer.

Implementations

impl TextColumn

pub fn new(batch_size: usize, max_str_len: usize) -> Self

This will allocate a value and indicator buffer for batch_size elements. Each value may have a maximum length of max_str_len. This implies that max_str_len is increased by one in order to make space for the null terminating zero at the end of strings.

pub unsafe fn value_at(&self, row_index: usize) -> Option<&[u8]>

Return the value for the given row index.

Safety

The column buffer does not know how many elements were in the last row group, and therefore can not guarantee the accessed element to be valid and in a defined state. It also can not panic on accessing an undefined element. It will panic however if row_index is larger or equal to the maximum number of elements in the buffer.

pub fn rebind(&mut self, new_max_str_len: usize, num_rows: usize)

Changes the max_str_len of the buffer. This operation is useful if you find an unexpected large input string during insertion.

This is however costly, as not only does the new buffer have to be allocated, but all values have to copied from the old to the new buffer.

This method could also be used to reduce the maximum string length, which would truncate strings in the process.

Parameters

• new_max_str_len: New maximum string length without terminating zero.
• num_rows: Number of valid rows currently stored in this buffer.

pub fn append(&mut self, index: usize, text: Option<&[u8]>)

Appends a new element to the column buffer. Rebinds the buffer to increase maximum string length should text be to large.

Parameters

• index: Zero based index of the new row position. Must be equal to the number of rows currently in the buffer.
• text: Text to store without terminating zero.

Trait Implementations

impl CData for TextColumn

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.

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. 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 CDataMut for TextColumn

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 Input for TextColumn

fn data_type(&self) -> DataType

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