vdbemem.c

sqlite最新源码

** negative, zero or positive if pMem1 is less than, equal to, or greater
** than pMem2. Sorting order is NULL's first, followed by numbers (integers
** and reals) sorted numerically, followed by text ordered by the collating
** sequence pColl and finally blob's ordered by memcmp().
**
** Two NULL values are considered equal by this function.
*/
int sqlite3MemCompare(const Mem *pMem1, const Mem *pMem2, const CollSeq *pColl){
  int rc;
  int f1, f2;
  int combined_flags;

  /* Interchange pMem1 and pMem2 if the collating sequence specifies
  ** DESC order.
  */
  f1 = pMem1->flags;
  f2 = pMem2->flags;
  combined_flags = f1|f2;
  assert( (combined_flags & MEM_RowSet)==0 );
 
  /* If one value is NULL, it is less than the other. If both values
  ** are NULL, return 0.
  */
  if( combined_flags&MEM_Null ){
    return (f2&MEM_Null) - (f1&MEM_Null);
  }

  /* If one value is a number and the other is not, the number is less.
  ** If both are numbers, compare as reals if one is a real, or as integers
  ** if both values are integers.
  */
  if( combined_flags&(MEM_Int|MEM_Real) ){
    if( !(f1&(MEM_Int|MEM_Real)) ){
      return 1;
    }
    if( !(f2&(MEM_Int|MEM_Real)) ){
      return -1;
    }
    if( (f1 & f2 & MEM_Int)==0 ){
      double r1, r2;
      if( (f1&MEM_Real)==0 ){
        r1 = (double)pMem1->u.i;
      }else{
        r1 = pMem1->r;
      }
      if( (f2&MEM_Real)==0 ){
        r2 = (double)pMem2->u.i;
      }else{
        r2 = pMem2->r;
      }
      if( r1<r2 ) return -1;
      if( r1>r2 ) return 1;
      return 0;
    }else{
      assert( f1&MEM_Int );
      assert( f2&MEM_Int );
      if( pMem1->u.i < pMem2->u.i ) return -1;
      if( pMem1->u.i > pMem2->u.i ) return 1;
      return 0;
    }
  }

  /* If one value is a string and the other is a blob, the string is less.
  ** If both are strings, compare using the collating functions.
  */
  if( combined_flags&MEM_Str ){
    if( (f1 & MEM_Str)==0 ){
      return 1;
    }
    if( (f2 & MEM_Str)==0 ){
      return -1;
    }

    assert( pMem1->enc==pMem2->enc );
    assert( pMem1->enc==SQLITE_UTF8 || 
            pMem1->enc==SQLITE_UTF16LE || pMem1->enc==SQLITE_UTF16BE );

    /* The collation sequence must be defined at this point, even if
    ** the user deletes the collation sequence after the vdbe program is
    ** compiled (this was not always the case).
    */
    assert( !pColl || pColl->xCmp );

    if( pColl ){
      if( pMem1->enc==pColl->enc ){
        /* The strings are already in the correct encoding.  Call the
        ** comparison function directly */
        return pColl->xCmp(pColl->pUser,pMem1->n,pMem1->z,pMem2->n,pMem2->z);
      }else{
        const void *v1, *v2;
        int n1, n2;
        Mem c1;
        Mem c2;
        memset(&c1, 0, sizeof(c1));
        memset(&c2, 0, sizeof(c2));
        sqlite3VdbeMemShallowCopy(&c1, pMem1, MEM_Ephem);
        sqlite3VdbeMemShallowCopy(&c2, pMem2, MEM_Ephem);
        v1 = sqlite3ValueText((sqlite3_value*)&c1, pColl->enc);
        n1 = v1==0 ? 0 : c1.n;
        v2 = sqlite3ValueText((sqlite3_value*)&c2, pColl->enc);
        n2 = v2==0 ? 0 : c2.n;
        rc = pColl->xCmp(pColl->pUser, n1, v1, n2, v2);
        sqlite3VdbeMemRelease(&c1);
        sqlite3VdbeMemRelease(&c2);
        return rc;
      }
    }
    /* If a NULL pointer was passed as the collate function, fall through
    ** to the blob case and use memcmp().  */
  }
 
  /* Both values must be blobs.  Compare using memcmp().  */
  rc = memcmp(pMem1->z, pMem2->z, (pMem1->n>pMem2->n)?pMem2->n:pMem1->n);
  if( rc==0 ){
    rc = pMem1->n - pMem2->n;
  }
  return rc;
}

/*
** Move data out of a btree key or data field and into a Mem structure.
** The data or key is taken from the entry that pCur is currently pointing
** to.  offset and amt determine what portion of the data or key to retrieve.
** key is true to get the key or false to get data.  The result is written
** into the pMem element.
**
** The pMem structure is assumed to be uninitialized.  Any prior content
** is overwritten without being freed.
**
** If this routine fails for any reason (malloc returns NULL or unable
** to read from the disk) then the pMem is left in an inconsistent state.
*/
int sqlite3VdbeMemFromBtree(
  BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
  int offset,       /* Offset from the start of data to return bytes from. */
  int amt,          /* Number of bytes to return. */
  int key,          /* If true, retrieve from the btree key, not data. */
  Mem *pMem         /* OUT: Return data in this Mem structure. */
){
  char *zData;       /* Data from the btree layer */
  int available = 0; /* Number of bytes available on the local btree page */
  sqlite3 *db;       /* Database connection */
  int rc = SQLITE_OK;

  db = sqlite3BtreeCursorDb(pCur);
  assert( sqlite3_mutex_held(db->mutex) );
  assert( (pMem->flags & MEM_RowSet)==0 );
  if( key ){
    zData = (char *)sqlite3BtreeKeyFetch(pCur, &available);
  }else{
    zData = (char *)sqlite3BtreeDataFetch(pCur, &available);
  }
  assert( zData!=0 );

  if( offset+amt<=available && ((pMem->flags&MEM_Dyn)==0 || pMem->xDel) ){
    sqlite3VdbeMemRelease(pMem);
    pMem->z = &zData[offset];
    pMem->flags = MEM_Blob|MEM_Ephem;
  }else if( SQLITE_OK==(rc = sqlite3VdbeMemGrow(pMem, amt+2, 0)) ){
    pMem->flags = MEM_Blob|MEM_Dyn|MEM_Term;
    pMem->enc = 0;
    pMem->type = SQLITE_BLOB;
    if( key ){
      rc = sqlite3BtreeKey(pCur, offset, amt, pMem->z);
    }else{
      rc = sqlite3BtreeData(pCur, offset, amt, pMem->z);
    }
    pMem->z[amt] = 0;
    pMem->z[amt+1] = 0;
    if( rc!=SQLITE_OK ){
      sqlite3VdbeMemRelease(pMem);
    }
  }
  pMem->n = amt;

  return rc;
}

/* This function is only available internally, it is not part of the
** external API. It works in a similar way to sqlite3_value_text(),
** except the data returned is in the encoding specified by the second
** parameter, which must be one of SQLITE_UTF16BE, SQLITE_UTF16LE or
** SQLITE_UTF8.
**
** (2006-02-16:)  The enc value can be or-ed with SQLITE_UTF16_ALIGNED.
** If that is the case, then the result must be aligned on an even byte
** boundary.
*/
const void *sqlite3ValueText(sqlite3_value* pVal, u8 enc){
  if( !pVal ) return 0;

  assert( pVal->db==0 || sqlite3_mutex_held(pVal->db->mutex) );
  assert( (enc&3)==(enc&~SQLITE_UTF16_ALIGNED) );
  assert( (pVal->flags & MEM_RowSet)==0 );

  if( pVal->flags&MEM_Null ){
    return 0;
  }
  assert( (MEM_Blob>>3) == MEM_Str );
  pVal->flags |= (pVal->flags & MEM_Blob)>>3;
  expandBlob(pVal);
  if( pVal->flags&MEM_Str ){
    sqlite3VdbeChangeEncoding(pVal, enc & ~SQLITE_UTF16_ALIGNED);
    if( (enc & SQLITE_UTF16_ALIGNED)!=0 && 1==(1&SQLITE_PTR_TO_INT(pVal->z)) ){
      assert( (pVal->flags & (MEM_Ephem|MEM_Static))!=0 );
      if( sqlite3VdbeMemMakeWriteable(pVal)!=SQLITE_OK ){
        return 0;
      }
    }
    sqlite3VdbeMemNulTerminate(pVal);
  }else{
    assert( (pVal->flags&MEM_Blob)==0 );
    sqlite3VdbeMemStringify(pVal, enc);
    assert( 0==(1&SQLITE_PTR_TO_INT(pVal->z)) );
  }
  assert(pVal->enc==(enc & ~SQLITE_UTF16_ALIGNED) || pVal->db==0
              || pVal->db->mallocFailed );
  if( pVal->enc==(enc & ~SQLITE_UTF16_ALIGNED) ){
    return pVal->z;
  }else{
    return 0;
  }
}

/*
** Create a new sqlite3_value object.
*/
sqlite3_value *sqlite3ValueNew(sqlite3 *db){
  Mem *p = sqlite3DbMallocZero(db, sizeof(*p));
  if( p ){
    p->flags = MEM_Null;
    p->type = SQLITE_NULL;
    p->db = db;
  }
  return p;
}

/*
** Create a new sqlite3_value object, containing the value of pExpr.
**
** This only works for very simple expressions that consist of one constant
** token (i.e. "5", "5.1", "'a string'"). If the expression can
** be converted directly into a value, then the value is allocated and
** a pointer written to *ppVal. The caller is responsible for deallocating
** the value by passing it to sqlite3ValueFree() later on. If the expression
** cannot be converted to a value, then *ppVal is set to NULL.
*/
int sqlite3ValueFromExpr(
  sqlite3 *db,              /* The database connection */
  Expr *pExpr,              /* The expression to evaluate */
  u8 enc,                   /* Encoding to use */
  u8 affinity,              /* Affinity to use */
  sqlite3_value **ppVal     /* Write the new value here */
){
  int op;
  char *zVal = 0;
  sqlite3_value *pVal = 0;

  if( !pExpr ){
    *ppVal = 0;
    return SQLITE_OK;
  }
  op = pExpr->op;

  if( op==TK_STRING || op==TK_FLOAT || op==TK_INTEGER ){
    zVal = sqlite3DbStrNDup(db, (char*)pExpr->token.z, pExpr->token.n);
    pVal = sqlite3ValueNew(db);
    if( !zVal || !pVal ) goto no_mem;
    sqlite3Dequote(zVal);
    sqlite3ValueSetStr(pVal, -1, zVal, SQLITE_UTF8, SQLITE_DYNAMIC);
    if( (op==TK_INTEGER || op==TK_FLOAT ) && affinity==SQLITE_AFF_NONE ){
      sqlite3ValueApplyAffinity(pVal, SQLITE_AFF_NUMERIC, enc);
    }else{
      sqlite3ValueApplyAffinity(pVal, affinity, enc);
    }
  }else if( op==TK_UMINUS ) {
    if( SQLITE_OK==sqlite3ValueFromExpr(db,pExpr->pLeft,enc,affinity,&pVal) ){
      pVal->u.i = -1 * pVal->u.i;
      /* (double)-1 In case of SQLITE_OMIT_FLOATING_POINT... */
      pVal->r = (double)-1 * pVal->r;
    }
  }
#ifndef SQLITE_OMIT_BLOB_LITERAL
  else if( op==TK_BLOB ){
    int nVal;
    assert( pExpr->token.n>=3 );
    assert( pExpr->token.z[0]=='x' || pExpr->token.z[0]=='X' );
    assert( pExpr->token.z[1]=='\'' );
    assert( pExpr->token.z[pExpr->token.n-1]=='\'' );
    pVal = sqlite3ValueNew(db);
    if( !pVal ) goto no_mem;
    nVal = pExpr->token.n - 3;
    zVal = (char*)pExpr->token.z + 2;
    sqlite3VdbeMemSetStr(pVal, sqlite3HexToBlob(db, zVal, nVal), nVal/2,
                         0, SQLITE_DYNAMIC);
  }
#endif

  *ppVal = pVal;
  return SQLITE_OK;

no_mem:
  db->mallocFailed = 1;
  sqlite3DbFree(db, zVal);
  sqlite3ValueFree(pVal);
  *ppVal = 0;
  return SQLITE_NOMEM;
}

/*
** Change the string value of an sqlite3_value object
*/
void sqlite3ValueSetStr(
  sqlite3_value *v,     /* Value to be set */
  int n,                /* Length of string z */
  const void *z,        /* Text of the new string */
  u8 enc,               /* Encoding to use */
  void (*xDel)(void*)   /* Destructor for the string */
){
  if( v ) sqlite3VdbeMemSetStr((Mem *)v, z, n, enc, xDel);
}

/*
** Free an sqlite3_value object
*/
void sqlite3ValueFree(sqlite3_value *v){
  if( !v ) return;
  sqlite3VdbeMemRelease((Mem *)v);
  sqlite3DbFree(((Mem*)v)->db, v);
}

/*
** Return the number of bytes in the sqlite3_value object assuming
** that it uses the encoding "enc"
*/
int sqlite3ValueBytes(sqlite3_value *pVal, u8 enc){
  Mem *p = (Mem*)pVal;
  if( (p->flags & MEM_Blob)!=0 || sqlite3ValueText(pVal, enc) ){
    if( p->flags & MEM_Zero ){
      return p->n + p->u.nZero;
    }else{
      return p->n;
    }
  }
  return 0;
}