vdbemem.c

sqlite-3.4.1,嵌入式数据库.是一个功能强大的开源数据库,给学习和研发以及小型公司的发展带来了全所未有的好处.

/*
** 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 <math.h>
#include <ctype.h>
#include "vdbeInt.h"

/*
** Call sqlite3VdbeMemExpandBlob() on the supplied value (type Mem*)
** P if required.
*/
#define expandBlob(P) (((P)->flags&MEM_Zero)?sqlite3VdbeMemExpandBlob(P):0)

/*
** 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


  /* MemTranslate() may return SQLITE_OK or SQLITE_NOMEM. If NOMEM is returned,
  ** then the encoding of the value may not have changed.
  */
  rc = sqlite3VdbeMemTranslate(pMem, desiredEnc);
  assert(rc==SQLITE_OK    || rc==SQLITE_NOMEM);
  assert(rc==SQLITE_OK    || pMem->enc!=desiredEnc);
  assert(rc==SQLITE_NOMEM || pMem->enc==desiredEnc);
  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;
  u8 *z;
  expandBlob(pMem);
  if( (pMem->flags & (MEM_Ephem|MEM_Static|MEM_Short))==0 ){
    return SQLITE_OK;
  }
  assert( (pMem->flags & MEM_Dyn)==0 );
  n = pMem->n;
  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 = (char*)z;
  pMem->flags &= ~(MEM_Ephem|MEM_Static|MEM_Short);
  return SQLITE_OK;
}

/*
** If the given Mem* has a zero-filled tail, turn it into an ordinary
** blob stored in dynamically allocated space.
*/
#ifndef SQLITE_OMIT_INCRBLOB
int sqlite3VdbeMemExpandBlob(Mem *pMem){
  if( pMem->flags & MEM_Zero ){
    char *pNew;
    int nByte;
    assert( (pMem->flags & MEM_Blob)!=0 );
    nByte = pMem->n + pMem->u.i;
    if( nByte<=0 ) nByte = 1;
    pNew = sqliteMalloc(nByte);
    if( pNew==0 ){ 
      return SQLITE_NOMEM;
    }
    memcpy(pNew, pMem->z, pMem->n);
    memset(&pNew[pMem->n], 0, pMem->u.i);
    sqlite3VdbeMemRelease(pMem);
    pMem->z = pNew;
    pMem->n += pMem->u.i;
    pMem->u.i = 0;
    pMem->flags &= ~(MEM_Zero|MEM_Static|MEM_Ephem|MEM_Short|MEM_Term);
    pMem->flags |= MEM_Dyn;
  }
  return SQLITE_OK;
}
#endif


/*
** 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;
  expandBlob(pMem);
  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 = (u8*)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 = (char*)z;
  pMem->flags &= ~(MEM_Ephem|MEM_Static);
  assert(0==(1&(int)pMem->z));
  return SQLITE_OK;
}

/*
** Make sure the given Mem is \u0000 terminated.
*/
int sqlite3VdbeMemNulTerminate(Mem *pMem){
  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; 
    sqlite3VdbeMemExpandBlob(pMem);
    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;
    if( pMem->xDel ){
      pMem->xDel(pMem->z);
    }else{
      sqliteFree(pMem->z);
    }
    pMem->xDel = 0;
    pMem->z = z;
    pMem->flags |= MEM_Term;
  }
  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;
  char *z = pMem->zShort;

  assert( !(fg&MEM_Zero) );
  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_Int ){
    sqlite3_snprintf(NBFS, z, "%lld", pMem->u.i);
  }else{
    assert( fg & MEM_Real );
    sqlite3_snprintf(NBFS, z, "%!.15g", pMem->r);
  }
  pMem->n = strlen(z);
  pMem->z = z;
  pMem->enc = SQLITE_UTF8;
  pMem->flags |= MEM_Str | MEM_Short | MEM_Term;
  sqlite3VdbeChangeEncoding(pMem, enc);
  return rc;
}

/*
** Memory cell pMem contains the context of an aggregate function.
** This routine calls the finalize method for that function.  The
** result of the aggregate is stored back into pMem.
**
** Return SQLITE_ERROR if the finalizer reports an error.  SQLITE_OK
** otherwise.
*/
int sqlite3VdbeMemFinalize(Mem *pMem, FuncDef *pFunc){
  int rc = SQLITE_OK;
  if( pFunc && pFunc->xFinalize ){
    sqlite3_context ctx;
    assert( (pMem->flags & MEM_Null)!=0 || pFunc==pMem->u.pDef );
    ctx.s.flags = MEM_Null;
    ctx.s.z = pMem->zShort;
    ctx.pMem = pMem;
    ctx.pFunc = pFunc;
    ctx.isError = 0;
    pFunc->xFinalize(&ctx);
    if( pMem->z && pMem->z!=pMem->zShort ){
      sqliteFree( pMem->z );
    }
    *pMem = ctx.s;
    if( pMem->flags & MEM_Short ){
      pMem->z = pMem->zShort;
    }
    if( ctx.isError ){
      rc = SQLITE_ERROR;
    }
  }
  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|MEM_Agg) ){
    if( p->xDel ){
      if( p->flags & MEM_Agg ){
        sqlite3VdbeMemFinalize(p, p->u.pDef);
        assert( (p->flags & MEM_Agg)==0 );
        sqlite3VdbeMemRelease(p);
      }else{
        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->u.i;
  }else if( flags & MEM_Real ){
    return (i64)pMem->r;
  }else if( flags & (MEM_Str|MEM_Blob) ){
    i64 value;
    pMem->flags |= MEM_Str;
    if( sqlite3VdbeChangeEncoding(pMem, SQLITE_UTF8)
       || sqlite3VdbeMemNulTerminate(pMem) ){
      return 0;
    }
    assert( pMem->z );
    sqlite3Atoi64(pMem->z, &value);
    return value;
  }else{
    return 0;
  }
}

/*
** 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->u.i;
  }else if( pMem->flags & (MEM_Str|MEM_Blob) ){
    double val = 0.0;
    pMem->flags |= MEM_Str;
    if( sqlite3VdbeChangeEncoding(pMem, SQLITE_UTF8)
       || sqlite3VdbeMemNulTerminate(pMem) ){
      return 0.0;
    }
    assert( pMem->z );
    sqlite3AtoF(pMem->z, &val);
    return val;
  }else{
    return 0.0;
  }
}

/*
** The MEM structure is already a MEM_Real.  Try to also make it a
** MEM_Int if we can.
*/
void sqlite3VdbeIntegerAffinity(Mem *pMem){
  assert( pMem->flags & MEM_Real );
  pMem->u.i = pMem->r;
  if( ((double)pMem->u.i)==pMem->r ){
    pMem->flags |= MEM_Int;
  }
}

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

/*
** 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;
}

/*
** Convert pMem so that it has types MEM_Real or MEM_Int or both.
** Invalidate any prior representations.
*/
int sqlite3VdbeMemNumerify(Mem *pMem){
  double r1, r2;
  i64 i;
  assert( (pMem->flags & (MEM_Int|MEM_Real|MEM_Null))==0 );
  assert( (pMem->flags & (MEM_Blob|MEM_Str))!=0 );
  r1 = sqlite3VdbeRealValue(pMem);
  i = (i64)r1;
  r2 = (double)i;
  if( r1==r2 ){
    sqlite3VdbeMemIntegerify(pMem);
  }else{
    pMem->r = r1;
    pMem->flags = MEM_Real;
    sqlite3VdbeMemRelease(pMem);
  }
  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;
  pMem->n = 0;
}

/*
** Delete any previous value and set the value to be a BLOB of length
** n containing all zeros.
*/
void sqlite3VdbeMemSetZeroBlob(Mem *pMem, int n){
  sqlite3VdbeMemRelease(pMem);
  pMem->flags = MEM_Blob|MEM_Zero|MEM_Short;
  pMem->type = SQLITE_BLOB;
  pMem->n = 0;
  if( n<0 ) n = 0;
  pMem->u.i = n;
  pMem->z = pMem->zShort;
  pMem->enc = SQLITE_UTF8;
}

/*
** 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->u.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){
  if( sqlite3_isnan(val) ){
    sqlite3VdbeMemSetNull(pMem);
  }else{
    sqlite3VdbeMemRelease(pMem);
    pMem->r = val;
    pMem->flags = MEM_Real;
    pMem->type = SQLITE_FLOAT;
  }
}

/*
** Return true if the Mem object contains a TEXT or BLOB that is
** too large - whose size exceeds SQLITE_MAX_LENGTH.
*/
int sqlite3VdbeMemTooBig(Mem *p){
  if( p->flags & (MEM_Str|MEM_Blob) ){
    int n = p->n;
    if( p->flags & MEM_Zero ){
      n += p->u.i;
    }
    return n>SQLITE_MAX_LENGTH;
  }
  return 0; 
}

/*
** 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;
}