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SQLITE3CHANGESET_APPLY_STRM(3)                        Library Functions Manual

NAME
     sqlite3changeset_apply_strm, sqlite3changeset_concat_strm,
     sqlite3changeset_invert_strm, sqlite3changeset_start_strm,
     sqlite3session_changeset_strm, sqlite3session_patchset_strm,
     sqlite3changegroup_add_strm, sqlite3changegroup_output_strm - Streaming
     Versions of API functions.

SYNOPSIS
     int
     sqlite3changeset_apply_strm(sqlite3 *db,
         int (*xInput)(void *pIn, void *pData, int *pnData), void *pIn,
         int(*xFilter)( void *pCtx,                   const char *zTab              ),
         int(*xConflict)( void *pCtx,                   int eConflict,                sqlite3_changeset_iter *p     ),
         void *pCtx                      );

     int
     sqlite3changeset_concat_strm(int (*xInputA)(void *pIn, void *pData, int *pnData),
         void *pInA, int (*xInputB)(void *pIn, void *pData, int *pnData),
         void *pInB, int (*xOutput)(void *pOut, const void *pData, int nData),
         void *pOut );

     int
     sqlite3changeset_invert_strm(int (*xInput)(void *pIn, void *pData, int *pnData),
         void *pIn, int (*xOutput)(void *pOut, const void *pData, int nData),
         void *pOut );

     int
     sqlite3changeset_start_strm(sqlite3_changeset_iter **pp,
         int (*xInput)(void *pIn, void *pData, int *pnData), void *pIn );

     int
     sqlite3session_changeset_strm(sqlite3_session *pSession,
         int (*xOutput)(void *pOut, const void *pData, int nData),
         void *pOut );

     int
     sqlite3session_patchset_strm(sqlite3_session *pSession,
         int (*xOutput)(void *pOut, const void *pData, int nData),
         void *pOut );

     int
     sqlite3changegroup_add_strm(sqlite3_changegroup*,
         int (*xInput)(void *pIn, void *pData, int *pnData), void *pIn );

     int
     sqlite3changegroup_output_strm(sqlite3_changegroup*,
         int (*xOutput)(void *pOut, const void *pData, int nData),
         void *pOut );

DESCRIPTION
     The six streaming API xxx_strm() functions serve similar purposes to the
     corresponding non-streaming API functions:

     <table border=1 style="margin-left:8ex;margin-right:8ex">
     <tr><th>Streaming function<th>Non-streaming equivalent</th>
     <tr><td>sqlite3changeset_apply_str<td>sqlite3changeset_apply
     <tr><td>sqlite3changeset_concat_str<td>sqlite3changeset_concat
     <tr><td>sqlite3changeset_invert_str<td>sqlite3changeset_invert
     <tr><td>sqlite3changeset_start_str<td>sqlite3changeset_start
     <tr><td>sqlite3session_changeset_str<td>sqlite3session_changeset
     <tr><td>sqlite3session_patchset_str<td>sqlite3session_patchset </table>

     Non-streaming functions that accept changesets (or patchsets) as input
     require that the entire changeset be stored in a single buffer in memory.
     Similarly, those that return a changeset or patchset do so by returning a
     pointer to a single large buffer allocated using sqlite3_malloc().
     Normally this is convenient.  However, if an application running in a
     low-memory environment is required to handle very large changesets, the
     large contiguous memory allocations required can become onerous.

     In order to avoid this problem, instead of a single large buffer, input
     is passed to a streaming API functions by way of a callback function that
     the sessions module invokes to incrementally request input data as it is
     required.  In all cases, a pair of API function parameters such as

           int nChangeset,       void *pChangeset,

     Is replaced by:

           int (*xInput)(void *pIn, void *pData, int *pnData),       void
     *pIn,

     Each time the xInput callback is invoked by the sessions module, the
     first argument passed is a copy of the supplied pIn context pointer.  The
     second argument, pData, points to a buffer (*pnData) bytes in size.
     Assuming no error occurs the xInput method should copy up to (*pnData)
     bytes of data into the buffer and set (*pnData) to the actual number of
     bytes copied before returning SQLITE_OK.  If the input is completely
     exhausted, (*pnData) should be set to zero to indicate this.  Or, if an
     error occurs, an SQLite error code should be returned.  In all cases, if
     an xInput callback returns an error, all processing is abandoned and the
     streaming API function returns a copy of the error code to the caller.

     In the case of sqlite3changeset_start_strm(), the xInput callback may be
     invoked by the sessions module at any point during the lifetime of the
     iterator.  If such an xInput callback returns an error, the iterator
     enters an error state, whereby all subsequent calls to iterator functions
     immediately fail with the same error code as returned by xInput.

     Similarly, streaming API functions that return changesets (or patchsets)
     return them in chunks by way of a callback function instead of via a
     pointer to a single large buffer.  In this case, a pair of parameters
     such as:

           int *pnChangeset,       void **ppChangeset,

     Is replaced by:

           int (*xOutput)(void *pOut, const void *pData, int nData),
     void *pOut

     The xOutput callback is invoked zero or more times to return data to the
     application.  The first parameter passed to each call is a copy of the
     pOut pointer supplied by the application.  The second parameter, pData,
     points to a buffer nData bytes in size containing the chunk of output
     data being returned.  If the xOutput callback successfully processes the
     supplied data, it should return SQLITE_OK to indicate success.
     Otherwise, it should return some other SQLite error code.  In this case
     processing is immediately abandoned and the streaming API function
     returns a copy of the xOutput error code to the application.

     The sessions module never invokes an xOutput callback with the third
     parameter set to a value less than or equal to zero.  Other than this, no
     guarantees are made as to the size of the chunks of data returned.

SEE ALSO
     sqlite3changeset_apply(3), sqlite3changeset_concat(3),
     sqlite3changeset_invert(3), sqlite3changeset_start(3),
     sqlite3session_changeset(3), sqlite3session_patchset(3)

NetBSD 8.0                      March 11, 2017                      NetBSD 8.0