vdbemem.c

sqlite 嵌入式数据库的源码

/*
** 2004 May 26
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains code use to manipulate "Mem" structure.  A "Mem"
** stores a single value in the VDBE.  Mem is an opaque structure visible
** only within the VDBE.  Interface routines refer to a Mem using the
** name sqlite_value
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*
** If pMem is an object with a valid string representation, this routine
** ensures the internal encoding for the string representation is
** 'desiredEnc', one of SQLITE_UTF8, SQLITE_UTF16LE or SQLITE_UTF16BE.
**
** If pMem is not a string object, or the encoding of the string
** representation is already stored using the requested encoding, then this
** routine is a no-op.
**
** SQLITE_OK is returned if the conversion is successful (or not required).
** SQLITE_NOMEM may be returned if a malloc() fails during conversion
** between formats.
*/
int sqlite3VdbeChangeEncoding(Mem *pMem, int desiredEnc){
  int rc;
  if( !(pMem->flags&MEM_Str) || pMem->enc==desiredEnc ){
    return SQLITE_OK;
  }
#ifdef SQLITE_OMIT_UTF16
  return SQLITE_ERROR;
#else
  rc = sqlite3VdbeMemTranslate(pMem, desiredEnc);
  if( rc==SQLITE_NOMEM ){
    sqlite3VdbeMemRelease(pMem);
    pMem->flags = MEM_Null;
    pMem->z = 0;
  }
  return rc;
#endif
}

/*
** Make the given Mem object MEM_Dyn.
**
** Return SQLITE_OK on success or SQLITE_NOMEM if malloc fails.
*/
int sqlite3VdbeMemDynamicify(Mem *pMem){
  int n = pMem->n;
  u8 *z;
  if( (pMem->flags & (MEM_Ephem|MEM_Static|MEM_Short))==0 ){
    return SQLITE_OK;
  }
  assert( (pMem->flags & MEM_Dyn)==0 );
  assert( pMem->flags & (MEM_Str|MEM_Blob) );
  z = sqliteMallocRaw( n+2 );
  if( z==0 ){
    return SQLITE_NOMEM;
  }
  pMem->flags |= MEM_Dyn|MEM_Term;
  pMem->xDel = 0;
  memcpy(z, pMem->z, n );
  z[n] = 0;
  z[n+1] = 0;
  pMem->z = z;
  pMem->flags &= ~(MEM_Ephem|MEM_Static|MEM_Short);
  return SQLITE_OK;
}

/*
** Make the given Mem object either MEM_Short or MEM_Dyn so that bytes
** of the Mem.z[] array can be modified.
**
** Return SQLITE_OK on success or SQLITE_NOMEM if malloc fails.
*/
int sqlite3VdbeMemMakeWriteable(Mem *pMem){
  int n;
  u8 *z;
  if( (pMem->flags & (MEM_Ephem|MEM_Static))==0 ){
    return SQLITE_OK;
  }
  assert( (pMem->flags & MEM_Dyn)==0 );
  assert( pMem->flags & (MEM_Str|MEM_Blob) );
  if( (n = pMem->n)+2<sizeof(pMem->zShort) ){
    z = pMem->zShort;
    pMem->flags |= MEM_Short|MEM_Term;
  }else{
    z = sqliteMallocRaw( n+2 );
    if( z==0 ){
      return SQLITE_NOMEM;
    }
    pMem->flags |= MEM_Dyn|MEM_Term;
    pMem->xDel = 0;
  }
  memcpy(z, pMem->z, n );
  z[n] = 0;
  z[n+1] = 0;
  pMem->z = z;
  pMem->flags &= ~(MEM_Ephem|MEM_Static);
  return SQLITE_OK;
}

/*
** Make sure the given Mem is \u0000 terminated.
*/
int sqlite3VdbeMemNulTerminate(Mem *pMem){
  /* In SQLite, a string without a nul terminator occurs when a string
  ** is loaded from disk (in this case the memory management is ephemeral),
  ** or when it is supplied by the user as a bound variable or function
  ** return value. Therefore, the memory management of the string must be
  ** either ephemeral, static or controlled by a user-supplied destructor.
  */
  assert(                         
    !(pMem->flags&MEM_Str) ||                /* it's not a string, or      */
    (pMem->flags&MEM_Term) ||                /* it's nul term. already, or */
    (pMem->flags&(MEM_Ephem|MEM_Static)) ||  /* it's static or ephem, or   */
    (pMem->flags&MEM_Dyn && pMem->xDel)      /* external management        */
  );
  if( (pMem->flags & MEM_Term)!=0 || (pMem->flags & MEM_Str)==0 ){
    return SQLITE_OK;   /* Nothing to do */
  }

  if( pMem->flags & (MEM_Static|MEM_Ephem) ){
    return sqlite3VdbeMemMakeWriteable(pMem);
  }else{
    char *z = sqliteMalloc(pMem->n+2);
    if( !z ) return SQLITE_NOMEM;
    memcpy(z, pMem->z, pMem->n);
    z[pMem->n] = 0;
    z[pMem->n+1] = 0;
    pMem->xDel(pMem->z);
    pMem->xDel = 0;
    pMem->z = z;
  }
  return SQLITE_OK;
}

/*
** Add MEM_Str to the set of representations for the given Mem.  Numbers
** are converted using sqlite3_snprintf().  Converting a BLOB to a string
** is a no-op.
**
** Existing representations MEM_Int and MEM_Real are *not* invalidated.
**
** A MEM_Null value will never be passed to this function. This function is
** used for converting values to text for returning to the user (i.e. via
** sqlite3_value_text()), or for ensuring that values to be used as btree
** keys are strings. In the former case a NULL pointer is returned the
** user and the later is an internal programming error.
*/
int sqlite3VdbeMemStringify(Mem *pMem, int enc){
  int rc = SQLITE_OK;
  int fg = pMem->flags;
  u8 *z = pMem->zShort;

  assert( !(fg&(MEM_Str|MEM_Blob)) );
  assert( fg&(MEM_Int|MEM_Real) );

  /* For a Real or Integer, use sqlite3_snprintf() to produce the UTF-8
  ** string representation of the value. Then, if the required encoding
  ** is UTF-16le or UTF-16be do a translation.
  ** 
  ** FIX ME: It would be better if sqlite3_snprintf() could do UTF-16.
  */
  if( fg & MEM_Real ){
    sqlite3_snprintf(NBFS, z, "%.15g", pMem->r);
  }else{
    assert( fg & MEM_Int );
    sqlite3_snprintf(NBFS, z, "%lld", pMem->i);
  }
  pMem->n = strlen(z);
  pMem->z = z;
  pMem->enc = SQLITE_UTF8;
  pMem->flags |= MEM_Str | MEM_Short | MEM_Term;
  sqlite3VdbeChangeEncoding(pMem, enc);
  return rc;
}

/*
** Release any memory held by the Mem. This may leave the Mem in an
** inconsistent state, for example with (Mem.z==0) and
** (Mem.type==SQLITE_TEXT).
*/
void sqlite3VdbeMemRelease(Mem *p){
  if( p->flags & MEM_Dyn ){
    if( p->xDel ){
      p->xDel((void *)p->z);
    }else{
      sqliteFree(p->z);
    }
    p->z = 0;
    p->xDel = 0;
  }
}

/*
** Return some kind of integer value which is the best we can do
** at representing the value that *pMem describes as an integer.
** If pMem is an integer, then the value is exact.  If pMem is
** a floating-point then the value returned is the integer part.
** If pMem is a string or blob, then we make an attempt to convert
** it into a integer and return that.  If pMem is NULL, return 0.
**
** If pMem is a string, its encoding might be changed.
*/
i64 sqlite3VdbeIntValue(Mem *pMem){
  int flags = pMem->flags;
  if( flags & MEM_Int ){
    return pMem->i;
  }else if( flags & MEM_Real ){
    return (i64)pMem->r;
  }else if( flags & (MEM_Str|MEM_Blob) ){
    i64 value;
    if( sqlite3VdbeChangeEncoding(pMem, SQLITE_UTF8)
       || sqlite3VdbeMemNulTerminate(pMem) ){
      return SQLITE_NOMEM;
    }
    assert( pMem->z );
    sqlite3atoi64(pMem->z, &value);
    return value;
  }else{
    return 0;
  }
}

/*
** Convert pMem to type integer.  Invalidate any prior representations.
*/
int sqlite3VdbeMemIntegerify(Mem *pMem){
  pMem->i = sqlite3VdbeIntValue(pMem);
  sqlite3VdbeMemRelease(pMem);
  pMem->flags = MEM_Int;
  return SQLITE_OK;
}

/*
** Return the best representation of pMem that we can get into a
** double.  If pMem is already a double or an integer, return its
** value.  If it is a string or blob, try to convert it to a double.
** If it is a NULL, return 0.0.
*/
double sqlite3VdbeRealValue(Mem *pMem){
  if( pMem->flags & MEM_Real ){
    return pMem->r;
  }else if( pMem->flags & MEM_Int ){
    return (double)pMem->i;
  }else if( pMem->flags & (MEM_Str|MEM_Blob) ){
    if( sqlite3VdbeChangeEncoding(pMem, SQLITE_UTF8)
       || sqlite3VdbeMemNulTerminate(pMem) ){
      return SQLITE_NOMEM;
    }
    assert( pMem->z );
    return sqlite3AtoF(pMem->z, 0);
  }else{
    return 0.0;
  }
}

/*
** Convert pMem so that it is of type MEM_Real.  Invalidate any
** prior representations.
*/
int sqlite3VdbeMemRealify(Mem *pMem){
  pMem->r = sqlite3VdbeRealValue(pMem);
  sqlite3VdbeMemRelease(pMem);
  pMem->flags = MEM_Real;
  return SQLITE_OK;
}

/*
** Delete any previous value and set the value stored in *pMem to NULL.
*/
void sqlite3VdbeMemSetNull(Mem *pMem){
  sqlite3VdbeMemRelease(pMem);
  pMem->flags = MEM_Null;
  pMem->type = SQLITE_NULL;
}

/*
** Delete any previous value and set the value stored in *pMem to val,
** manifest type INTEGER.
*/
void sqlite3VdbeMemSetInt64(Mem *pMem, i64 val){
  sqlite3VdbeMemRelease(pMem);
  pMem->i = val;
  pMem->flags = MEM_Int;
  pMem->type = SQLITE_INTEGER;
}

/*
** Delete any previous value and set the value stored in *pMem to val,
** manifest type REAL.
*/
void sqlite3VdbeMemSetDouble(Mem *pMem, double val){
  sqlite3VdbeMemRelease(pMem);
  pMem->r = val;
  pMem->flags = MEM_Real;
  pMem->type = SQLITE_FLOAT;
}

/*
** Make an shallow copy of pFrom into pTo.  Prior contents of
** pTo are overwritten.  The pFrom->z field is not duplicated.  If
** pFrom->z is used, then pTo->z points to the same thing as pFrom->z
** and flags gets srcType (either MEM_Ephem or MEM_Static).
*/
void sqlite3VdbeMemShallowCopy(Mem *pTo, const Mem *pFrom, int srcType){
  memcpy(pTo, pFrom, sizeof(*pFrom)-sizeof(pFrom->zShort));
  pTo->xDel = 0;
  if( pTo->flags & (MEM_Str|MEM_Blob) ){
    pTo->flags &= ~(MEM_Dyn|MEM_Static|MEM_Short|MEM_Ephem);
    assert( srcType==MEM_Ephem || srcType==MEM_Static );
    pTo->flags |= srcType;
  }
}

/*
** Make a full copy of pFrom into pTo.  Prior contents of pTo are
** freed before the copy is made.
*/
int sqlite3VdbeMemCopy(Mem *pTo, const Mem *pFrom){
  int rc;
  if( pTo->flags & MEM_Dyn ){
    sqlite3VdbeMemRelease(pTo);
  }
  sqlite3VdbeMemShallowCopy(pTo, pFrom, MEM_Ephem);
  if( pTo->flags & MEM_Ephem ){
    rc = sqlite3VdbeMemMakeWriteable(pTo);
  }else{
    rc = SQLITE_OK;
  }
  return rc;
}

/*
** Transfer the contents of pFrom to pTo. Any existing value in pTo is
** freed. If pFrom contains ephemeral data, a copy is made.
**
** pFrom contains an SQL NULL when this routine returns.  SQLITE_NOMEM
** might be returned if pFrom held ephemeral data and we were unable
** to allocate enough space to make a copy.
*/
int sqlite3VdbeMemMove(Mem *pTo, Mem *pFrom){
  int rc;
  if( pTo->flags & MEM_Dyn ){
    sqlite3VdbeMemRelease(pTo);
  }
  memcpy(pTo, pFrom, sizeof(Mem));
  if( pFrom->flags & MEM_Short ){
    pTo->z = pTo->zShort;
  }
  pFrom->flags = MEM_Null;
  pFrom->xDel = 0;
  if( pTo->flags & MEM_Ephem ){
    rc = sqlite3VdbeMemMakeWriteable(pTo);
  }else{
    rc = SQLITE_OK;
  }
  return rc;
}

/*
** Change the value of a Mem to be a string or a BLOB.
*/
int sqlite3VdbeMemSetStr(
  Mem *pMem,          /* Memory cell to set to string value */
  const char *z,      /* String pointer */
  int n,              /* Bytes in string, or negative */
  u8 enc,             /* Encoding of z.  0 for BLOBs */
  void (*xDel)(void*) /* Destructor function */
){
  sqlite3VdbeMemRelease(pMem);
  if( !z ){
    pMem->flags = MEM_Null;
    pMem->type = SQLITE_NULL;
    return SQLITE_OK;
  }

  pMem->z = (char *)z;
  if( xDel==SQLITE_STATIC ){
    pMem->flags = MEM_Static;
  }else if( xDel==SQLITE_TRANSIENT ){
    pMem->flags = MEM_Ephem;
  }else{
    pMem->flags = MEM_Dyn;
    pMem->xDel = xDel;
  }

  pMem->enc = enc;
  pMem->type = enc==0 ? SQLITE_BLOB : SQLITE_TEXT;
  pMem->n = n;

  assert( enc==0 || enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE