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Overview
Comment:All mutexing and locking appears to be in place. Now we just have to test it and make it all work. (CVS 4264)
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 0f7941aef976aa4f3be3e0046edd1ae042e5d9a3
User & Date: drh 2007-08-21 20:25:40
Context
2007-08-22
00:39
Reenable the memory management logic. The quick.test script now runs with SQLITE_MEMDEBUG and SQLITE_ENABLE_MEMORY_MANAGEMENT. 7 minor errors. (CVS 4265) check-in: 1914044b user: drh tags: trunk
2007-08-21
20:25
All mutexing and locking appears to be in place. Now we just have to test it and make it all work. (CVS 4264) check-in: 0f7941ae user: drh tags: trunk
19:33
The sqlite3_value object now carries an sqlite3* pointer to use for recording malloc failures. This eliminates the need to pass sqlite3* pointers into many internal interfaces. Also added more mutexing. (CVS 4263) check-in: 92872761 user: drh tags: trunk
Changes
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Changes to src/sqlite.h.in.

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** on how SQLite interfaces are suppose to operate.
**
** The name of this file under configuration management is "sqlite.h.in".
** The makefile makes some minor changes to this file (such as inserting
** the version number) and changes its name to "sqlite3.h" as
** part of the build process.
**
** @(#) $Id: sqlite.h.in,v 1.234 2007/08/21 19:33:56 drh Exp $
*/
#ifndef _SQLITE3_H_
#define _SQLITE3_H_
#include <stdarg.h>     /* Needed for the definition of va_list */

/*
** Make sure we can call this stuff from C++.
................................................................................
** column was extracted from.
**
** As with all other SQLite APIs, those postfixed with "16" return UTF-16
** encoded strings, the other functions return UTF-8.
**
** These APIs are only available if the library was compiled with the 
** SQLITE_ENABLE_COLUMN_METADATA preprocessor symbol defined.




*/
const char *sqlite3_column_database_name(sqlite3_stmt*,int);
const void *sqlite3_column_database_name16(sqlite3_stmt*,int);
const char *sqlite3_column_table_name(sqlite3_stmt*,int);
const void *sqlite3_column_table_name16(sqlite3_stmt*,int);
const char *sqlite3_column_origin_name(sqlite3_stmt*,int);
const void *sqlite3_column_origin_name16(sqlite3_stmt*,int);
................................................................................
# define SQLITE_TEXT     3
#endif
#define SQLITE3_TEXT     3

/*
** CAPI3REF: Results Values From A Query
**
** These routines return information about the information
** in a single column of the current result row of a query.  In every
** case the first argument is a pointer to the 
** [sqlite3_stmt | SQL statement] that is being
** evaluate (the [sqlite3_stmt*] that was returned from 
** [sqlite3_prepare_v2()] or one of its variants) and
** the second argument is the index of the column for which information 
** should be returned.  The left-most column has an index of 0.

**
** If the SQL statement is not currently point to a valid row, or if the
** the column index is out of range, the result is undefined.









**
** The sqlite3_column_type() routine returns 
** [SQLITE_INTEGER | datatype code] for the initial data type
** of the result column.  The returned value is one of [SQLITE_INTEGER],
** [SQLITE_FLOAT], [SQLITE_TEXT], [SQLITE_BLOB], or [SQLITE_NULL].  The value
** returned by sqlite3_column_type() is only meaningful if no type
** conversions have occurred as described below.  After a type conversion,
................................................................................
**
** In other words, you should call sqlite3_column_text(), sqlite3_column_blob(),
** or sqlite3_column_text16() first to force the result into the desired
** format, then invoke sqlite3_column_bytes() or sqlite3_column_bytes16() to
** find the size of the result.  Do not mix call to sqlite3_column_text() or
** sqlite3_column_blob() with calls to sqlite3_column_bytes16().  And do not
** mix calls to sqlite3_column_text16() with calls to sqlite3_column_bytes().







*/
const void *sqlite3_column_blob(sqlite3_stmt*, int iCol);
int sqlite3_column_bytes(sqlite3_stmt*, int iCol);
int sqlite3_column_bytes16(sqlite3_stmt*, int iCol);
double sqlite3_column_double(sqlite3_stmt*, int iCol);
int sqlite3_column_int(sqlite3_stmt*, int iCol);
sqlite3_int64 sqlite3_column_int64(sqlite3_stmt*, int iCol);
................................................................................
** is returned from [sqlite3_value_blob()], [sqlite3_value_text()], or
** [sqlite3_value_text16()] can be invalidated by a subsequent call to
** [sqlite3_value_bytes()], [sqlite3_value_bytes16()], [sqlite3_value_text()],
** or [sqlite3_value_text16()].  
**
** These routines must be called from the same thread as
** the SQL function that supplied the sqlite3_value* parameters.



*/
const void *sqlite3_value_blob(sqlite3_value*);
int sqlite3_value_bytes(sqlite3_value*);
int sqlite3_value_bytes16(sqlite3_value*);
double sqlite3_value_double(sqlite3_value*);
int sqlite3_value_int(sqlite3_value*);
sqlite3_int64 sqlite3_value_int64(sqlite3_value*);
................................................................................
sqlite3_mutex *sqlite3_mutex_alloc(int);
void sqlite3_mutex_free(sqlite3_mutex*);
void sqlite3_mutex_enter(sqlite3_mutex*);
int sqlite3_mutex_try(sqlite3_mutex*);
void sqlite3_mutex_leave(sqlite3_mutex*);
int sqlite3_mutex_held(sqlite3_mutex*);
int sqlite3_mutex_notheld(sqlite3_mutex*);







#define SQLITE_MUTEX_FAST             0
#define SQLITE_MUTEX_RECURSIVE        1
#define SQLITE_MUTEX_STATIC_MASTER    2
#define SQLITE_MUTEX_STATIC_MEM       3
#define SQLITE_MUTEX_STATIC_PRNG      4









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** on how SQLite interfaces are suppose to operate.
**
** The name of this file under configuration management is "sqlite.h.in".
** The makefile makes some minor changes to this file (such as inserting
** the version number) and changes its name to "sqlite3.h" as
** part of the build process.
**
** @(#) $Id: sqlite.h.in,v 1.235 2007/08/21 20:25:40 drh Exp $
*/
#ifndef _SQLITE3_H_
#define _SQLITE3_H_
#include <stdarg.h>     /* Needed for the definition of va_list */

/*
** Make sure we can call this stuff from C++.
................................................................................
** column was extracted from.
**
** As with all other SQLite APIs, those postfixed with "16" return UTF-16
** encoded strings, the other functions return UTF-8.
**
** These APIs are only available if the library was compiled with the 
** SQLITE_ENABLE_COLUMN_METADATA preprocessor symbol defined.
**
** If two or more threads call one or more of these routines against the same
** prepared statement and column at the same time then the results are
** undefined.
*/
const char *sqlite3_column_database_name(sqlite3_stmt*,int);
const void *sqlite3_column_database_name16(sqlite3_stmt*,int);
const char *sqlite3_column_table_name(sqlite3_stmt*,int);
const void *sqlite3_column_table_name16(sqlite3_stmt*,int);
const char *sqlite3_column_origin_name(sqlite3_stmt*,int);
const void *sqlite3_column_origin_name16(sqlite3_stmt*,int);
................................................................................
# define SQLITE_TEXT     3
#endif
#define SQLITE3_TEXT     3

/*
** CAPI3REF: Results Values From A Query
**
** These routines return information about
** a single column of the current result row of a query.  In every
** case the first argument is a pointer to the 
** [sqlite3_stmt | SQL statement] that is being
** evaluated (the [sqlite3_stmt*] that was returned from 
** [sqlite3_prepare_v2()] or one of its variants) and
** the second argument is the index of the column for which information 
** should be returned.  The left-most column of the result set
** has an index of 0.
**
** If the SQL statement is not currently point to a valid row, or if the
** the column index is out of range, the result is undefined. 
** These routines may only be called when the most recent call to
** [sqlite3_step()] has returned [SQLITE_ROW] and neither
** [sqlite3_reset()] nor [sqlite3_finalize()] has been call subsequently.
** If any of these routines are called after [sqlite3_reset()] or
** [sqlite3_finalize()] or after [sqlite3_step()] has returned
** something other than [SQLITE_ROW], the results are undefined.
** If [sqlite3_step()] or [sqlite3_reset()] or [sqlite3_finalize()]
** are called from a different thread while any of these routines
** are pending, then the results are undefined.  
**
** The sqlite3_column_type() routine returns 
** [SQLITE_INTEGER | datatype code] for the initial data type
** of the result column.  The returned value is one of [SQLITE_INTEGER],
** [SQLITE_FLOAT], [SQLITE_TEXT], [SQLITE_BLOB], or [SQLITE_NULL].  The value
** returned by sqlite3_column_type() is only meaningful if no type
** conversions have occurred as described below.  After a type conversion,
................................................................................
**
** In other words, you should call sqlite3_column_text(), sqlite3_column_blob(),
** or sqlite3_column_text16() first to force the result into the desired
** format, then invoke sqlite3_column_bytes() or sqlite3_column_bytes16() to
** find the size of the result.  Do not mix call to sqlite3_column_text() or
** sqlite3_column_blob() with calls to sqlite3_column_bytes16().  And do not
** mix calls to sqlite3_column_text16() with calls to sqlite3_column_bytes().
**
** The pointers returned are valid until a type conversion occurs as
** described above, or until [sqlite3_step()] or [sqlite3_reset()] or
** [sqlite3_finalize()] is called.  The memory space used to hold strings
** and blobs is freed automatically.  Do <b>not</b> pass the pointers returned
** [sqlite3_column_blob()], [sqlite_column_text()], etc. into 
** [sqlite3_free()].
*/
const void *sqlite3_column_blob(sqlite3_stmt*, int iCol);
int sqlite3_column_bytes(sqlite3_stmt*, int iCol);
int sqlite3_column_bytes16(sqlite3_stmt*, int iCol);
double sqlite3_column_double(sqlite3_stmt*, int iCol);
int sqlite3_column_int(sqlite3_stmt*, int iCol);
sqlite3_int64 sqlite3_column_int64(sqlite3_stmt*, int iCol);
................................................................................
** is returned from [sqlite3_value_blob()], [sqlite3_value_text()], or
** [sqlite3_value_text16()] can be invalidated by a subsequent call to
** [sqlite3_value_bytes()], [sqlite3_value_bytes16()], [sqlite3_value_text()],
** or [sqlite3_value_text16()].  
**
** These routines must be called from the same thread as
** the SQL function that supplied the sqlite3_value* parameters.
** Or, if the sqlite3_value* argument comes from the [sqlite3_column_value()]
** interface, then these routines should be called from the same thread
** that ran [sqlite3_column_value()].
*/
const void *sqlite3_value_blob(sqlite3_value*);
int sqlite3_value_bytes(sqlite3_value*);
int sqlite3_value_bytes16(sqlite3_value*);
double sqlite3_value_double(sqlite3_value*);
int sqlite3_value_int(sqlite3_value*);
sqlite3_int64 sqlite3_value_int64(sqlite3_value*);
................................................................................
sqlite3_mutex *sqlite3_mutex_alloc(int);
void sqlite3_mutex_free(sqlite3_mutex*);
void sqlite3_mutex_enter(sqlite3_mutex*);
int sqlite3_mutex_try(sqlite3_mutex*);
void sqlite3_mutex_leave(sqlite3_mutex*);
int sqlite3_mutex_held(sqlite3_mutex*);
int sqlite3_mutex_notheld(sqlite3_mutex*);

/*
** CAPI3REF: Mutex Types
**
** The [sqlite3_mutex_alloc()] interface takes a single argument
** which is one of these integer constants.
*/
#define SQLITE_MUTEX_FAST             0
#define SQLITE_MUTEX_RECURSIVE        1
#define SQLITE_MUTEX_STATIC_MASTER    2
#define SQLITE_MUTEX_STATIC_MEM       3
#define SQLITE_MUTEX_STATIC_PRNG      4


Changes to src/vdbeapi.c.

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const void *sqlite3_value_text16le(sqlite3_value *pVal){
  return sqlite3ValueText(pVal, SQLITE_UTF16LE);
}
#endif /* SQLITE_OMIT_UTF16 */
int sqlite3_value_type(sqlite3_value* pVal){
  return pVal->type;
}
/* sqlite3_value_numeric_type() defined in vdbe.c */

/**************************** sqlite3_result_  *******************************
** The following routines are used by user-defined functions to specify
** the function result.
*/
void sqlite3_result_blob(
  sqlite3_context *pCtx, 
  const void *z, 
  int n, 
  void (*xDel)(void *)
){
  assert( n>=0 );

  sqlite3VdbeMemSetStr(&pCtx->s, z, n, 0, xDel);
}
void sqlite3_result_double(sqlite3_context *pCtx, double rVal){

  sqlite3VdbeMemSetDouble(&pCtx->s, rVal);
}
void sqlite3_result_error(sqlite3_context *pCtx, const char *z, int n){

  pCtx->isError = 1;
  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF8, SQLITE_TRANSIENT);
}
#ifndef SQLITE_OMIT_UTF16
void sqlite3_result_error16(sqlite3_context *pCtx, const void *z, int n){

  pCtx->isError = 1;
  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16NATIVE, SQLITE_TRANSIENT);
}
#endif
void sqlite3_result_int(sqlite3_context *pCtx, int iVal){

  sqlite3VdbeMemSetInt64(&pCtx->s, (i64)iVal);
}
void sqlite3_result_int64(sqlite3_context *pCtx, i64 iVal){

  sqlite3VdbeMemSetInt64(&pCtx->s, iVal);
}
void sqlite3_result_null(sqlite3_context *pCtx){

  sqlite3VdbeMemSetNull(&pCtx->s);
}
void sqlite3_result_text(
  sqlite3_context *pCtx, 
  const char *z, 
  int n,
  void (*xDel)(void *)
){

  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF8, xDel);
}
#ifndef SQLITE_OMIT_UTF16
void sqlite3_result_text16(
  sqlite3_context *pCtx, 
  const void *z, 
  int n, 
  void (*xDel)(void *)
){

  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16NATIVE, xDel);
}
void sqlite3_result_text16be(
  sqlite3_context *pCtx, 
  const void *z, 
  int n, 
  void (*xDel)(void *)
){

  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16BE, xDel);
}
void sqlite3_result_text16le(
  sqlite3_context *pCtx, 
  const void *z, 
  int n, 
  void (*xDel)(void *)
){

  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16LE, xDel);
}
#endif /* SQLITE_OMIT_UTF16 */
void sqlite3_result_value(sqlite3_context *pCtx, sqlite3_value *pValue){

  sqlite3VdbeMemCopy(&pCtx->s, pValue);
}
void sqlite3_result_zeroblob(sqlite3_context *pCtx, int n){

  sqlite3VdbeMemSetZeroBlob(&pCtx->s, n);
}

/* Force an SQLITE_TOOBIG error. */
void sqlite3_result_error_toobig(sqlite3_context *pCtx){

  sqlite3VdbeMemSetZeroBlob(&pCtx->s, SQLITE_MAX_LENGTH+1);
}


/*
** Execute the statement pStmt, either until a row of data is ready, the
** statement is completely executed or an error occurs.
................................................................................
/*
** Check to see if column iCol of the given statement is valid.  If
** it is, return a pointer to the Mem for the value of that column.
** If iCol is not valid, return a pointer to a Mem which has a value
** of NULL.
*/
static Mem *columnMem(sqlite3_stmt *pStmt, int i){




  Vdbe *pVm = (Vdbe *)pStmt;


  int vals = sqlite3_data_count(pStmt);
  if( pVm==0 || pVm->resOnStack==0 || i>=pVm->nResColumn || i<0 ){


    static const Mem nullMem = {{0}, 0.0, 0, "", 0, MEM_Null, SQLITE_NULL };
    sqlite3Error(pVm->db, SQLITE_RANGE, 0);
    return (Mem*)&nullMem;
  }
  return &pVm->pTos[(1-vals)+i];

}

/*
** This function is called after invoking an sqlite3_value_XXX function on a 
** column value (i.e. a value returned by evaluating an SQL expression in the
** select list of a SELECT statement) that may cause a malloc() failure. If 
** malloc() has failed, the threads mallocFailed flag is cleared and the result
** code of statement pStmt set to SQLITE_NOMEM.
**
** Specificly, this is called from within:
**
**     sqlite3_column_int()
**     sqlite3_column_int64()
**     sqlite3_column_text()
**     sqlite3_column_text16()
**     sqlite3_column_real()
**     sqlite3_column_bytes()
................................................................................
{
  /* If malloc() failed during an encoding conversion within an
  ** sqlite3_column_XXX API, then set the return code of the statement to
  ** SQLITE_NOMEM. The next call to _step() (if any) will return SQLITE_ERROR
  ** and _finalize() will return NOMEM.
  */
  Vdbe *p = (Vdbe *)pStmt;

  p->rc = sqlite3ApiExit(0, p->rc);


}

/**************************** sqlite3_column_  *******************************
** The following routines are used to access elements of the current row
** in the result set.
*/
const void *sqlite3_column_blob(sqlite3_stmt *pStmt, int i){
................................................................................
}
const unsigned char *sqlite3_column_text(sqlite3_stmt *pStmt, int i){
  const unsigned char *val = sqlite3_value_text( columnMem(pStmt,i) );
  columnMallocFailure(pStmt);
  return val;
}
sqlite3_value *sqlite3_column_value(sqlite3_stmt *pStmt, int i){
  return columnMem(pStmt, i);


}
#ifndef SQLITE_OMIT_UTF16
const void *sqlite3_column_text16(sqlite3_stmt *pStmt, int i){
  const void *val = sqlite3_value_text16( columnMem(pStmt,i) );
  columnMallocFailure(pStmt);
  return val;
}
#endif /* SQLITE_OMIT_UTF16 */
int sqlite3_column_type(sqlite3_stmt *pStmt, int i){
  return sqlite3_value_type( columnMem(pStmt,i) );


}

/* The following function is experimental and subject to change or
** removal */
/*int sqlite3_column_numeric_type(sqlite3_stmt *pStmt, int i){
**  return sqlite3_value_numeric_type( columnMem(pStmt,i) );
**}
................................................................................
*/
static const void *columnName(
  sqlite3_stmt *pStmt,
  int N,
  const void *(*xFunc)(Mem*),
  int useType
){
  const void *ret;
  Vdbe *p = (Vdbe *)pStmt;
  int n = sqlite3_column_count(pStmt);

  if( p==0 || N>=n || N<0 ){
    return 0;
  }



  N += useType*n;
  ret = xFunc(&p->aColName[N]);


  /* A malloc may have failed inside of the xFunc() call. If this is the case,
  ** clear the mallocFailed flag and return NULL.
  */
  sqlite3ApiExit(0, 0);







  return ret;
}

/*
** Return the name of the Nth column of the result set returned by SQL
** statement pStmt.
*/







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const void *sqlite3_value_text16le(sqlite3_value *pVal){
  return sqlite3ValueText(pVal, SQLITE_UTF16LE);
}
#endif /* SQLITE_OMIT_UTF16 */
int sqlite3_value_type(sqlite3_value* pVal){
  return pVal->type;
}


/**************************** sqlite3_result_  *******************************
** The following routines are used by user-defined functions to specify
** the function result.
*/
void sqlite3_result_blob(
  sqlite3_context *pCtx, 
  const void *z, 
  int n, 
  void (*xDel)(void *)
){
  assert( n>=0 );
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetStr(&pCtx->s, z, n, 0, xDel);
}
void sqlite3_result_double(sqlite3_context *pCtx, double rVal){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetDouble(&pCtx->s, rVal);
}
void sqlite3_result_error(sqlite3_context *pCtx, const char *z, int n){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  pCtx->isError = 1;
  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF8, SQLITE_TRANSIENT);
}
#ifndef SQLITE_OMIT_UTF16
void sqlite3_result_error16(sqlite3_context *pCtx, const void *z, int n){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  pCtx->isError = 1;
  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16NATIVE, SQLITE_TRANSIENT);
}
#endif
void sqlite3_result_int(sqlite3_context *pCtx, int iVal){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetInt64(&pCtx->s, (i64)iVal);
}
void sqlite3_result_int64(sqlite3_context *pCtx, i64 iVal){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetInt64(&pCtx->s, iVal);
}
void sqlite3_result_null(sqlite3_context *pCtx){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetNull(&pCtx->s);
}
void sqlite3_result_text(
  sqlite3_context *pCtx, 
  const char *z, 
  int n,
  void (*xDel)(void *)
){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF8, xDel);
}
#ifndef SQLITE_OMIT_UTF16
void sqlite3_result_text16(
  sqlite3_context *pCtx, 
  const void *z, 
  int n, 
  void (*xDel)(void *)
){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16NATIVE, xDel);
}
void sqlite3_result_text16be(
  sqlite3_context *pCtx, 
  const void *z, 
  int n, 
  void (*xDel)(void *)
){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16BE, xDel);
}
void sqlite3_result_text16le(
  sqlite3_context *pCtx, 
  const void *z, 
  int n, 
  void (*xDel)(void *)
){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16LE, xDel);
}
#endif /* SQLITE_OMIT_UTF16 */
void sqlite3_result_value(sqlite3_context *pCtx, sqlite3_value *pValue){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemCopy(&pCtx->s, pValue);
}
void sqlite3_result_zeroblob(sqlite3_context *pCtx, int n){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetZeroBlob(&pCtx->s, n);
}

/* Force an SQLITE_TOOBIG error. */
void sqlite3_result_error_toobig(sqlite3_context *pCtx){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetZeroBlob(&pCtx->s, SQLITE_MAX_LENGTH+1);
}


/*
** Execute the statement pStmt, either until a row of data is ready, the
** statement is completely executed or an error occurs.
................................................................................
/*
** Check to see if column iCol of the given statement is valid.  If
** it is, return a pointer to the Mem for the value of that column.
** If iCol is not valid, return a pointer to a Mem which has a value
** of NULL.
*/
static Mem *columnMem(sqlite3_stmt *pStmt, int i){
  Vdbe *pVm;
  int vals;
  Mem *pOut;

  pVm = (Vdbe *)pStmt;
  if( pVm && pVm->resOnStack && i<pVm->nResColumn && i>=0 ){
    sqlite3_mutex_enter(pVm->db->mutex);
    vals = sqlite3_data_count(pStmt);

    pOut = &pVm->pTos[(1-vals)+i];
  }else{
    static const Mem nullMem = {{0}, 0.0, 0, "", 0, MEM_Null, SQLITE_NULL };
    sqlite3Error(pVm->db, SQLITE_RANGE, 0);
    pOut = (Mem*)&nullMem;
  }

  return pOut;
}

/*
** This function is called after invoking an sqlite3_value_XXX function on a 
** column value (i.e. a value returned by evaluating an SQL expression in the
** select list of a SELECT statement) that may cause a malloc() failure. If 
** malloc() has failed, the threads mallocFailed flag is cleared and the result
** code of statement pStmt set to SQLITE_NOMEM.
**
** Specifically, this is called from within:
**
**     sqlite3_column_int()
**     sqlite3_column_int64()
**     sqlite3_column_text()
**     sqlite3_column_text16()
**     sqlite3_column_real()
**     sqlite3_column_bytes()
................................................................................
{
  /* If malloc() failed during an encoding conversion within an
  ** sqlite3_column_XXX API, then set the return code of the statement to
  ** SQLITE_NOMEM. The next call to _step() (if any) will return SQLITE_ERROR
  ** and _finalize() will return NOMEM.
  */
  Vdbe *p = (Vdbe *)pStmt;
  if( p ){
    p->rc = sqlite3ApiExit(p->db, p->rc);
    sqlite3_mutex_leave(p->db->mutex);
  }
}

/**************************** sqlite3_column_  *******************************
** The following routines are used to access elements of the current row
** in the result set.
*/
const void *sqlite3_column_blob(sqlite3_stmt *pStmt, int i){
................................................................................
}
const unsigned char *sqlite3_column_text(sqlite3_stmt *pStmt, int i){
  const unsigned char *val = sqlite3_value_text( columnMem(pStmt,i) );
  columnMallocFailure(pStmt);
  return val;
}
sqlite3_value *sqlite3_column_value(sqlite3_stmt *pStmt, int i){
  sqlite3_value *pOut = columnMem(pStmt, i);
  columnMallocFailure(pStmt);
  return pOut;
}
#ifndef SQLITE_OMIT_UTF16
const void *sqlite3_column_text16(sqlite3_stmt *pStmt, int i){
  const void *val = sqlite3_value_text16( columnMem(pStmt,i) );
  columnMallocFailure(pStmt);
  return val;
}
#endif /* SQLITE_OMIT_UTF16 */
int sqlite3_column_type(sqlite3_stmt *pStmt, int i){
  int iType = sqlite3_value_type( columnMem(pStmt,i) );
  columnMallocFailure(pStmt);
  return iType;
}

/* The following function is experimental and subject to change or
** removal */
/*int sqlite3_column_numeric_type(sqlite3_stmt *pStmt, int i){
**  return sqlite3_value_numeric_type( columnMem(pStmt,i) );
**}
................................................................................
*/
static const void *columnName(
  sqlite3_stmt *pStmt,
  int N,
  const void *(*xFunc)(Mem*),
  int useType
){
  const void *ret = 0;
  Vdbe *p = (Vdbe *)pStmt;
  int n;
  



  if( p!=0 ){
    n = sqlite3_column_count(pStmt);
    if( N<n && N>=0 ){
      N += useType*n;
      ret = xFunc(&p->aColName[N]);

#if 0
      /* A malloc may have failed inside of the xFunc() call. If this
      ** is the case, clear the mallocFailed flag and return NULL.
      */

      if( p->db && p->db->mallocFailed ){
        p->db->mallocFailed = 0;
        ret = 0;
      }
#endif
    }
  }
  return ret;
}

/*
** Return the name of the Nth column of the result set returned by SQL
** statement pStmt.
*/