HI_Bufsize

Cogent API and Utilities: Version 4.1
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# `HI_Bufsize`

`HI_Bufsize` -- sets the history buffer size.

## Syntax

    #include <cogent/cogent.h>

``ST_STATUS HI_Bufsize`(IP_hTASK historian, char* retbuf, int buflen, char* histname, int numvalues, int size);`

## Arguments

`historian`

  The task pointer to the Cascade Historian program.

`retbuf`

  An optional buffer containing an error message.

`buflen`

  The length in bytes of `retbuf`. If `retbuf` is non-NULL, this must be a valid non-zero length. If `retbuf` is NULL, this parameter is ignored.

`histname`

  The name of a history.

`numvalues`

  The new maximum number of value/time (or y/x) pairs that can be buffered for this history. If `0` is specified, then the function is treated as a query, the buffer size is not modified, and the current value is returned in `size`.

`size`

  A pointer to an integer variable that is set to the current maximum number of value/time (or y/x) pairs that can be buffered for this history.

## Returns

`ST_OK` on success. Otherwise `ST_ERROR`, and the `retbuf` will contain a NULL-terminated character string with an error message. If the return value is `ST_OK`, the `retbuf` may not contain useful information.

## Description

This function sets the number of data values that will be buffered for the specified history. (There are actually up to twice this number stored at any time, as the Cascade Historian double-buffers its data storage.) When a buffer is full, the data is flushed to disk, as long as an associated file has been assigned (with filebase or `HI_FileBase`). A larger buffer will retain more data in memory and increase the speed of queries on that data if it is within the range of the data in the buffer.

The history data is flushed to disk whenever this function is called. Until this function is used, the history buffer size is set to the initial default value (`100`).

This function corresponds to the Cascade Historian bufsize command and the `hist_bufsize` dynamic library function.

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