SQLite

struct SessionBuffer {
  u8 *aBuf;                       /* Pointer to changeset buffer */
  int nBuf;                       /* Size of buffer aBuf */
  int nAlloc;                     /* Size of allocation containing aBuf */
};

/*
** An object of this type is used internally as an abstraction for 
** input data. Input data may be supplied either as a single large buffer
** (e.g. sqlite3changeset_start()) or using a stream function (e.g.
**  sqlite3changeset_start_str()).
*/
struct SessionInput {
  int iNext;                      /* Offset in aData[] of next change */
  u8 *aData;                      /* Pointer to buffer containing changeset */
  int nData;                      /* Number of bytes in aData */

  SessionBuffer buf;              /* Current read buffer */

*/
static int sessionValueSetStr(
  sqlite3_value *pVal,            /* Set the value of this object */
  u8 *aData,                      /* Buffer containing string or blob data */
  int nData,                      /* Size of buffer aData[] in bytes */
  u8 enc                          /* String encoding (0 for blobs) */
){
  /* In theory this code could just pass SQLITE_TRANSIENT as the final
  ** argument to sqlite3ValueSetStr() and have the copy created 
  ** automatically. But doing so makes it difficult to detect any OOM
  ** error. Hence the code to create the copy externally. */
  u8 *aCopy = sqlite3_malloc(nData);
  if( aCopy==0 ) return SQLITE_NOMEM;
  memcpy(aCopy, aData, nData);
  sqlite3ValueSetStr(pVal, nData, (char*)aCopy, enc, sqlite3_free);
  return SQLITE_OK;
}

  if( pnByte ) *pnByte = nRead+1;
  return rc;
}

/*
** The input pointer currently points to the first byte of the first field
** of a record consisting of nCol columns. This function ensures the entire
** record is buffered. It does not move the input pointer.
**
** If successful, SQLITE_OK is returned and *pnByte is set to the size of
** the record in bytes. Otherwise, an SQLite error code is returned. The
** final value of *pnByte is undefined in this case.
*/
static int sessionChangesetBufferRecord(
  SessionInput *pIn,              /* Input data */
  int nCol,                       /* Number of columns in record */
  int *pnByte                     /* OUT: Size of record in bytes */
){
  int rc = SQLITE_OK;
  int nByte = 0;
  int i;
  for(i=0; rc==SQLITE_OK && i<nCol; i++){
    int eType;
    rc = sessionInputBuffer(pIn, nByte + 10);

/*
** The input pointer currently points to the second byte of a table-header.
** Specifically, to the following:
**
**   + number of columns in table (varint)
**   + array of PK flags (1 byte per column),
**   + table name (nul terminated).
**
** This function decodes the table-header and populates the p->nCol, 
** p->zTab and p->abPK[] variables accordingly. The p->apValue[] array is 
** also allocated or resized according to the new value of p->nCol. The
** input pointer is left pointing to the byte following the table header.
**
** If successful, SQLITE_OK is returned. Otherwise, an SQLite error code
** is returned and the final values of the various fields enumerated above
** are undefined.
*/
static int sessionChangesetReadTblhdr(sqlite3_changeset_iter *p){
  int rc;
  int nCopy;
  assert( p->rc==SQLITE_OK );

  rc = sessionChangesetBufferTblhdr(&p->in, &nCopy);

  return SQLITE_OK;
}

/*
** Add all changes in the changeset passed via the first two arguments to
** hash tables.
*/
static int sessionChangesetToHash(
  sqlite3_changeset_iter *pIter,   /* Iterator to read from */
  SessionTable **ppTabList        /* IN/OUT: List of table objects */
){
  u8 *aRec;
  int nRec;
  int rc = SQLITE_OK;
  SessionTable *pTab = 0;

  while( SQLITE_ROW==sessionChangesetNext(pIter, &aRec, &nRec) ){
    const char *zNew;
    int nCol;
    int op;
    int iHash;
    int bIndirect;
    SessionChange *pChange;
    SessionChange *pExist = 0;
    SessionChange **pp;










    sqlite3changeset_op(pIter, &zNew, &nCol, &op, &bIndirect);
    if( !pTab || sqlite3_stricmp(zNew, pTab->zName) ){
      /* Search the list for a matching table */
      int nNew = (int)strlen(zNew);
      u8 *abPK;

      sqlite3changeset_pk(pIter, &abPK, 0);

){
  SessionTable *pList = 0;        /* List of SessionTable objects */
  int rc;                         /* Return code */
  int bPatch;                     /* True for a patchset */

  assert( xOutput==0 || (ppOut==0 && pnOut==0) );

  rc = sessionChangesetToHash(pLeft, &pList);
  if( rc==SQLITE_OK ){
    rc = sessionChangesetToHash(pRight, &pList);
  }
  bPatch = pLeft->bPatchset || pRight->bPatchset;

  /* Create the serialized output changeset based on the contents of the
  ** hash tables attached to the SessionTable objects in list pList. 
  */
  if( rc==SQLITE_OK ){

*/
int sqlite3session_changeset(
  sqlite3_session *pSession,      /* Session object */
  int *pnChangeset,               /* OUT: Size of buffer at *ppChangeset */
  void **ppChangeset              /* OUT: Buffer containing changeset */
);


























/*
** CAPI3REF: Generate A Patchset From A Session Object
**
** The differences between a patchset and a changeset are that:
**
** <ul>

*/
int sqlite3session_patchset(
  sqlite3_session *pSession,      /* Session object */
  int *pnPatchset,                /* OUT: Size of buffer at *ppChangeset */
  void **ppPatchset               /* OUT: Buffer containing changeset */
);










/*
** CAPI3REF: Test if a changeset has recorded any changes.
**
** Return non-zero if no changes to attached tables have been recorded by 
** the session object passed as the first argument. Otherwise, if one or 
** more changes have been recorded, return zero.
**

int sqlite3changeset_start(
  sqlite3_changeset_iter **pp,    /* OUT: New changeset iterator handle */
  int nChangeset,                 /* Size of changeset blob in bytes */
  void *pChangeset                /* Pointer to blob containing changeset */
);

























/*
** CAPI3REF: Advance A Changeset Iterator
**
** This function may only be used with iterators created by function
** [sqlite3changeset_start()]. If it is called on an iterator passed to
** a conflict-handler callback by [sqlite3changeset_apply()], SQLITE_MISUSE
** is returned and the call has no effect.

** changeset. If it is not, the results are undefined.
*/
int sqlite3changeset_invert(
  int nIn, const void *pIn,       /* Input changeset */
  int *pnOut, void **ppOut        /* OUT: Inverse of input */
);











/*
** CAPI3REF: Concatenate Two Changeset Objects
**
** This function is used to concatenate two changesets, A and B, into a 
** single changeset. The result is a changeset equivalent to applying
** changeset A followed by changeset B. 
**

  void *pA,                       /* Pointer to buffer containing changeset A */
  int nB,                         /* Number of bytes in buffer pB */
  void *pB,                       /* Pointer to buffer containing changeset B */
  int *pnOut,                     /* OUT: Number of bytes in output changeset */
  void **ppOut                    /* OUT: Buffer containing output changeset */
);













/*
** CAPI3REF: Apply A Changeset To A Database
**
** Apply a changeset to a database. This function attempts to update the
** "main" database attached to handle db with the changes found in the
** changeset passed via the second and third arguments.
**

    void *pCtx,                   /* Copy of sixth arg to _apply() */
    int eConflict,                /* DATA, MISSING, CONFLICT, CONSTRAINT */
    sqlite3_changeset_iter *p     /* Handle describing change and conflict */
  ),
  void *pCtx                      /* First argument passed to xConflict */
);

























/* 
** CAPI3REF: Constants Passed To The Conflict Handler
**
** Values that may be passed as the second argument to a conflict-handler.
**
** <dl>
** <dt>SQLITE_CHANGESET_DATA<dd>

**   If this value is returned, any changes applied so far are rolled back 
**   and the call to sqlite3changeset_apply() returns SQLITE_ABORT.
** </dl>
*/
#define SQLITE_CHANGESET_OMIT       0
#define SQLITE_CHANGESET_REPLACE    1
#define SQLITE_CHANGESET_ABORT      2

/*
** CAPI3REF: Streaming Versions of API functions.
**
** The six streaming API xxx_str() 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
**
**  <pre>
**  &nbsp;     int nChangeset,
**  &nbsp;     void *pChangeset,
**  </pre>
**
** Is replaced by:
**
**  <pre>
**  &nbsp;     int (*xInput)(void *pIn, void *pData, int *pnData),
**  &nbsp;     void *pIn,
**  </pre>
**
** 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_str(), 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:
**
**  <pre>
**  &nbsp;     int *pnChangeset,
**  &nbsp;     void **ppChangeset,
**  </pre>
**
** Is replaced by:
**
**  <pre>
**  &nbsp;     int (*xOutput)(void *pOut, const void *pData, int nData),
**  &nbsp;     void *pOut
**  </pre>
**
** 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.
*/
int sqlite3changeset_apply_str(
  sqlite3 *db,                    /* Apply change to "main" db of this handle */
  int (*xInput)(void *pIn, void *pData, int *pnData), /* Input function */
  void *pIn,                                          /* First arg for xInput */
  int(*xFilter)(
    void *pCtx,                   /* Copy of sixth arg to _apply() */
    const char *zTab              /* Table name */
  ),
  int(*xConflict)(
    void *pCtx,                   /* Copy of sixth arg to _apply() */
    int eConflict,                /* DATA, MISSING, CONFLICT, CONSTRAINT */
    sqlite3_changeset_iter *p     /* Handle describing change and conflict */
  ),
  void *pCtx                      /* First argument passed to xConflict */
);
int sqlite3changeset_concat_str(
  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_str(
  int (*xInput)(void *pIn, void *pData, int *pnData),
  void *pIn,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
);
int sqlite3changeset_start_str(
  sqlite3_changeset_iter **pp,
  int (*xInput)(void *pIn, void *pData, int *pnData),
  void *pIn
);
int sqlite3session_changeset_str(
  sqlite3_session *pSession,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
);
int sqlite3session_patchset_str(
  sqlite3_session *pSession,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
);


/*
** Make sure we can call this stuff from C++.
*/
#ifdef __cplusplus
}
#endif

#endif  /* SQLITE_ENABLE_SESSION && SQLITE_ENABLE_PREUPDATE_HOOK */