vdbeaux.c

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**      3                     3            signed integer
**      4                     4            signed integer
**      5                     6            signed integer
**      6                     8            signed integer
**      7                     8            IEEE float
**      8                     0            Integer constant 0
**      9                     0            Integer constant 1
**     10,11                               reserved for expansion
**    N>=12 and even       (N-12)/2        BLOB
**    N>=13 and odd        (N-13)/2        text
**
** The 8 and 9 types were added in 3.3.0, file format 4.  Prior versions
** of SQLite will not understand those serial types.
*/

/*
** Return the serial-type for the value stored in pMem.
*/
u32 sqlite3VdbeSerialType(Mem *pMem, int file_format){
  int flags = pMem->flags;
  int n;

  if( flags&MEM_Null ){
    return 0;
  }
  if( flags&MEM_Int ){
    /* Figure out whether to use 1, 2, 4, 6 or 8 bytes. */
#   define MAX_6BYTE ((((i64)0x00001000)<<32)-1)
    i64 i = pMem->u.i;
    u64 u;
    if( file_format>=4 && (i&1)==i ){
      return 8+i;
    }
    u = i<0 ? -i : i;
    if( u<=127 ) return 1;
    if( u<=32767 ) return 2;
    if( u<=8388607 ) return 3;
    if( u<=2147483647 ) return 4;
    if( u<=MAX_6BYTE ) return 5;
    return 6;
  }
  if( flags&MEM_Real ){
    return 7;
  }
  assert( flags&(MEM_Str|MEM_Blob) );
  n = pMem->n;
  if( flags & MEM_Zero ){
    n += pMem->u.i;
  }
  assert( n>=0 );
  return ((n*2) + 12 + ((flags&MEM_Str)!=0));
}

/*
** Return the length of the data corresponding to the supplied serial-type.
*/
int sqlite3VdbeSerialTypeLen(u32 serial_type){
  if( serial_type>=12 ){
    return (serial_type-12)/2;
  }else{
    static const u8 aSize[] = { 0, 1, 2, 3, 4, 6, 8, 8, 0, 0, 0, 0 };
    return aSize[serial_type];
  }
}

/*
** If we are on an architecture with mixed-endian floating 
** points (ex: ARM7) then swap the lower 4 bytes with the 
** upper 4 bytes.  Return the result.
**
** For most architectures, this is a no-op.
**
** (later):  It is reported to me that the mixed-endian problem
** on ARM7 is an issue with GCC, not with the ARM7 chip.  It seems
** that early versions of GCC stored the two words of a 64-bit
** float in the wrong order.  And that error has been propagated
** ever since.  The blame is not necessarily with GCC, though.
** GCC might have just copying the problem from a prior compiler.
** I am also told that newer versions of GCC that follow a different
** ABI get the byte order right.
**
** Developers using SQLite on an ARM7 should compile and run their
** application using -DSQLITE_DEBUG=1 at least once.  With DEBUG
** enabled, some asserts below will ensure that the byte order of
** floating point values is correct.
**
** (2007-08-30)  Frank van Vugt has studied this problem closely
** and has send his findings to the SQLite developers.  Frank
** writes that some Linux kernels offer floating point hardware
** emulation that uses only 32-bit mantissas instead of a full 
** 48-bits as required by the IEEE standard.  (This is the
** CONFIG_FPE_FASTFPE option.)  On such systems, floating point
** byte swapping becomes very complicated.  To avoid problems,
** the necessary byte swapping is carried out using a 64-bit integer
** rather than a 64-bit float.  Frank assures us that the code here
** works for him.  We, the developers, have no way to independently
** verify this, but Frank seems to know what he is talking about
** so we trust him.
*/
#ifdef SQLITE_MIXED_ENDIAN_64BIT_FLOAT
static u64 floatSwap(u64 in){
  union {
    u64 r;
    u32 i[2];
  } u;
  u32 t;

  u.r = in;
  t = u.i[0];
  u.i[0] = u.i[1];
  u.i[1] = t;
  return u.r;
}
# define swapMixedEndianFloat(X)  X = floatSwap(X)
#else
# define swapMixedEndianFloat(X)
#endif

/*
** Write the serialized data blob for the value stored in pMem into 
** buf. It is assumed that the caller has allocated sufficient space.
** Return the number of bytes written.
**
** nBuf is the amount of space left in buf[].  nBuf must always be
** large enough to hold the entire field.  Except, if the field is
** a blob with a zero-filled tail, then buf[] might be just the right
** size to hold everything except for the zero-filled tail.  If buf[]
** is only big enough to hold the non-zero prefix, then only write that
** prefix into buf[].  But if buf[] is large enough to hold both the
** prefix and the tail then write the prefix and set the tail to all
** zeros.
**
** Return the number of bytes actually written into buf[].  The number
** of bytes in the zero-filled tail is included in the return value only
** if those bytes were zeroed in buf[].
*/ 
int sqlite3VdbeSerialPut(u8 *buf, int nBuf, Mem *pMem, int file_format){
  u32 serial_type = sqlite3VdbeSerialType(pMem, file_format);
  int len;

  /* Integer and Real */
  if( serial_type<=7 && serial_type>0 ){
    u64 v;
    int i;
    if( serial_type==7 ){
      assert( sizeof(v)==sizeof(pMem->r) );
      memcpy(&v, &pMem->r, sizeof(v));
      swapMixedEndianFloat(v);
    }else{
      v = pMem->u.i;
    }
    len = i = sqlite3VdbeSerialTypeLen(serial_type);
    assert( len<=nBuf );
    while( i-- ){
      buf[i] = (v&0xFF);
      v >>= 8;
    }
    return len;
  }

  /* String or blob */
  if( serial_type>=12 ){
    assert( pMem->n + ((pMem->flags & MEM_Zero)?pMem->u.i:0)
             == sqlite3VdbeSerialTypeLen(serial_type) );
    assert( pMem->n<=nBuf );
    len = pMem->n;
    memcpy(buf, pMem->z, len);
    if( pMem->flags & MEM_Zero ){
      len += pMem->u.i;
      if( len>nBuf ){
        len = nBuf;
      }
      memset(&buf[pMem->n], 0, len-pMem->n);
    }
    return len;
  }

  /* NULL or constants 0 or 1 */
  return 0;
}

/*
** Deserialize the data blob pointed to by buf as serial type serial_type
** and store the result in pMem.  Return the number of bytes read.
*/ 
int sqlite3VdbeSerialGet(
  const unsigned char *buf,     /* Buffer to deserialize from */
  u32 serial_type,              /* Serial type to deserialize */
  Mem *pMem                     /* Memory cell to write value into */
){
  switch( serial_type ){
    case 10:   /* Reserved for future use */
    case 11:   /* Reserved for future use */
    case 0: {  /* NULL */
      pMem->flags = MEM_Null;
      break;
    }
    case 1: { /* 1-byte signed integer */
      pMem->u.i = (signed char)buf[0];
      pMem->flags = MEM_Int;
      return 1;
    }
    case 2: { /* 2-byte signed integer */
      pMem->u.i = (((signed char)buf[0])<<8) | buf[1];
      pMem->flags = MEM_Int;
      return 2;
    }
    case 3: { /* 3-byte signed integer */
      pMem->u.i = (((signed char)buf[0])<<16) | (buf[1]<<8) | buf[2];
      pMem->flags = MEM_Int;
      return 3;
    }
    case 4: { /* 4-byte signed integer */
      pMem->u.i = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
      pMem->flags = MEM_Int;
      return 4;
    }
    case 5: { /* 6-byte signed integer */
      u64 x = (((signed char)buf[0])<<8) | buf[1];
      u32 y = (buf[2]<<24) | (buf[3]<<16) | (buf[4]<<8) | buf[5];
      x = (x<<32) | y;
      pMem->u.i = *(i64*)&x;
      pMem->flags = MEM_Int;
      return 6;
    }
    case 6:   /* 8-byte signed integer */
    case 7: { /* IEEE floating point */
      u64 x;
      u32 y;
#if !defined(NDEBUG) && !defined(SQLITE_OMIT_FLOATING_POINT)
      /* Verify that integers and floating point values use the same
      ** byte order.  Or, that if SQLITE_MIXED_ENDIAN_64BIT_FLOAT is
      ** defined that 64-bit floating point values really are mixed
      ** endian.
      */
      static const u64 t1 = ((u64)0x3ff00000)<<32;
      static const double r1 = 1.0;
      u64 t2 = t1;
      swapMixedEndianFloat(t2);
      assert( sizeof(r1)==sizeof(t2) && memcmp(&r1, &t2, sizeof(r1))==0 );
#endif

      x = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
      y = (buf[4]<<24) | (buf[5]<<16) | (buf[6]<<8) | buf[7];
      x = (x<<32) | y;
      if( serial_type==6 ){
        pMem->u.i = *(i64*)&x;
        pMem->flags = MEM_Int;
      }else{
        assert( sizeof(x)==8 && sizeof(pMem->r)==8 );
        swapMixedEndianFloat(x);
        memcpy(&pMem->r, &x, sizeof(x));
        pMem->flags = MEM_Real;
      }
      return 8;
    }
    case 8:    /* Integer 0 */
    case 9: {  /* Integer 1 */
      pMem->u.i = serial_type-8;
      pMem->flags = MEM_Int;
      return 0;
    }
    default: {
      int len = (serial_type-12)/2;
      pMem->z = (char *)buf;
      pMem->n = len;
      pMem->xDel = 0;
      if( serial_type&0x01 ){
        pMem->flags = MEM_Str | MEM_Ephem;
      }else{
        pMem->flags = MEM_Blob | MEM_Ephem;
      }
      return len;
    }
  }
  return 0;
}

/*
** The header of a record consists of a sequence variable-length integers.
** These integers are almost always small and are encoded as a single byte.
** The following macro takes advantage this fact to provide a fast decode
** of the integers in a record header.  It is faster for the common case
** where the integer is a single byte.  It is a little slower when the
** integer is two or more bytes.  But overall it is faster.
**
** The following expressions are equivalent:
**
**     x = sqlite3GetVarint32( A, &B );
**
**     x = GetVarint( A, B );
**
*/
#define GetVarint(A,B)  ((B = *(A))<=0x7f ? 1 : sqlite3GetVarint32(A, &B))

/*
** This function compares the two table rows or index records specified by 
** {nKey1, pKey1} and {nKey2, pKey2}, returning a negative, zero
** or positive integer if {nKey1, pKey1} is less than, equal to or 
** greater than {nKey2, pKey2}.  Both Key1 and Key2 must be byte strings
** composed by the OP_MakeRecord opcode of the VDBE.
*/
int sqlite3VdbeRecordCompare(
  void *userData,
  int nKey1, const void *pKey1, 
  int nKey2, const void *pKey2
){
  KeyInfo *pKeyInfo = (KeyInfo*)userData;
  u32 d1, d2;          /* Offset into aKey[] of next data element */
  u32 idx1, idx2;      /* Offset into aKey[] of next header element */
  u32 szHdr1, szHdr2;  /* Number of bytes in header */
  int i = 0;
  int nField;
  int rc = 0;
  const unsigned char *aKey1 = (const unsigned char *)pKey1;
  const unsigned char *aKey2 = (const unsigned char *)pKey2;

  Mem mem1;
  Mem mem2;
  mem1.enc = pKeyInfo->enc;
  mem1.db = pKeyInfo->db;
  mem2.enc = pKeyInfo->enc;
  mem2.db = pKeyInfo->db;
  
  idx1 = GetVarint(aKey1, szHdr1);
  d1 = szHdr1;
  idx2 = GetVarint(aKey2, szHdr2);
  d2 = szHdr2;
  nField = pKeyInfo->nField;
  while( idx1<szHdr1 && idx2<szHdr2 ){
    u32 serial_type1;
    u32 serial_type2;

    /* Read the serial types for the next element in each key. */
    idx1 += GetVarint( aKey1+idx1, serial_type1 );
    if( d1>=nKey1 && sqlite3VdbeSerialTypeLen(serial_type1)>0 ) break;
    idx2 += GetVarint( aKey2+idx2, serial_type2 );
    if( d2>=nKey2 && sqlite3VdbeSerialTypeLen(serial_type2)>0 ) break;

    /* Extract the values to be compared.
    */
    d1 += sqlite3VdbeSerialGet(&aKey1[d1], serial_type1, &mem1);
    d2 += sqlite3VdbeSerialGet(&aKey2[d2], serial_type2, &mem2);

    /* Do the comparison
    */
    rc = sqlite3MemCompare(&mem1, &mem2, i<nField ? pKeyInfo->aColl[i] : 0);
    if( mem1.flags & MEM_Dyn ) sqlite3VdbeMemRelease(&mem1);
    if( mem2.flags & MEM_Dyn ) sqlite3VdbeMemRelease(&mem2);
    if( rc!=0 ){
      break;
    }
    i++;
  }

  /* One of the keys ran out of fields, but all the fields up to that point
  ** were equal. If the incrKey flag is true, then the second key is
  ** treated as larger.
  */
  if( rc==0 ){
    if( pKeyInfo->incrKey ){
      rc = -1;
    }else if( !pKeyInfo->prefixIsEqual ){
      if( d1<nKey1 ){
        rc = 1;
      }else if( d2<nKey2 ){
        rc = -1;
      }
    }
  }else if( pKeyInfo->aSortOrder && i<pKeyInfo->nField
               && pKeyInfo->aSortOrder[i] ){
    rc = -rc;
  }

  return rc;
}

/*
** The argument is an index entry composed using the OP_MakeRecord opcode.
** The last entry in this record should be an integer (specifically
** an integer rowid).  This routine returns the number of bytes in
** that integer.
*/
int sqlite3VdbeIdxRowidLen(const u8 *aKey){
  u32 szHdr;        /* Size of the header */
  u32 typeRowid;    /* Serial type of the rowid */

  sqlite3GetVarint32(aKey, &szHdr);
  sqlite3GetVarint32(&aKey[szHdr-1], &typeRowid);
  return sqlite3VdbeSerialTypeLen(typeRowid);
}
  

/*
** pCur points at an index entry created using the OP_MakeRecord opcode.
** Read the rowid (the last field in the record) and store it in *rowid.
** Return SQLITE_OK if everything works, or an error code otherwise.
*/
int sqlite3VdbeIdxRowid(BtCursor *pCur, i64 *rowid){
  i64 nCellKey = 0;
  int rc;
  u32 szHdr;        /* Size of the header */
  u32 typeRowid;    /* Serial type of the rowid */
  u32 lenRowid;     /* Size of the rowid */
  Mem m, v;

  sqlite3BtreeKeySize(pCur, &nCellKey);
  if( nCellKey<=0 ){
    return SQLITE_CORRUPT_BKPT;
  }
  rc = sqlite3VdbeMemFromBtree(pCur, 0, nCellKey, 1, &m);
  if( rc ){
    return rc;
  }
  sqlite3GetVarint32((u8*)m.z, &szHdr);
  sqlite3GetVarint32((u8*)&m.z[szHdr-1], &typeRowid);
  lenRowid = sqlite3VdbeSerialTypeLen(typeRowid);
  sqlite3VdbeSerialGet((u8*)&m.z[m.n-lenRowid], typeRowid, &v);
  *rowid = v.u.i;
  sqlite3VdbeMemRelease(&m);
  return SQLITE_OK;
}

/*
** Compare the key of the index entry that cursor pC is point to against
** the key string in pKey (of length nKey).  Write into *pRes a number
** that is negative, zero, or positive if pC is less than, equal to,
** or greater than pKey.  Return SQLITE_OK on success.
**
** pKey is either created without a rowid or is truncated so that it
** omits the rowid at the end.  The rowid at the end of the index entry
** is ignored as well.
*/
int sqlite3VdbeIdxKeyCompare(
  Cursor *pC,                 /* The cursor to compare against */
  int nKey, const u8 *pKey,   /* The key to compare */
  int *res                    /* Write the comparison result here */
){
  i64 nCellKey = 0;
  int r