static MagickBooleanType EncodeImage(const ImageInfo *image_info,Image *image,
  const size_t data_size)
{
#define MaxCode(number_bits)  ((one << (number_bits))-1)
#define MaxHashTable  5003
#define MaxGIFBits  12UL
#define MaxGIFTable  (1UL << MaxGIFBits)
#define GIFOutputCode(code) \
{ \
  /*  \
    Emit a code. \
  */ \
  if (bits > 0) \
    datum|=(code) << bits; \
  else \
    datum=code; \
  bits+=number_bits; \
  while (bits >= 8) \
  { \
    /*  \
      Add a character to current packet. \
    */ \
    packet[length++]=(unsigned char) (datum & 0xff); \
    if (length >= 254) \
      { \
        (void) WriteBlobByte(image,(unsigned char) length); \
        (void) WriteBlob(image,length,packet); \
        length=0; \
      } \
    datum>>=8; \
    bits-=8; \
  } \
  if (free_code > max_code)  \
    { \
      number_bits++; \
      if (number_bits == MaxGIFBits) \
        max_code=MaxGIFTable; \
      else \
        max_code=MaxCode(number_bits); \
    } \
}

  IndexPacket
    index;

  register ssize_t
    i;

  short
    *hash_code,
    *hash_prefix,
    waiting_code;

  size_t
    bits,
    clear_code,
    datum,
    end_of_information_code,
    free_code,
    length,
    max_code,
    next_pixel,
    number_bits,
    one,
    pass;

  ssize_t
    displacement,
    offset,
    k,
    y;

  unsigned char
    *packet,
    *hash_suffix;

  /*
    Allocate encoder tables.
  */
  assert(image != (Image *) NULL);
  one=1;
  packet=(unsigned char *) AcquireQuantumMemory(256,sizeof(*packet));
  hash_code=(short *) AcquireQuantumMemory(MaxHashTable,sizeof(*hash_code));
  hash_prefix=(short *) AcquireQuantumMemory(MaxHashTable,sizeof(*hash_prefix));
  hash_suffix=(unsigned char *) AcquireQuantumMemory(MaxHashTable,
    sizeof(*hash_suffix));
  if ((packet == (unsigned char *) NULL) || (hash_code == (short *) NULL) ||
      (hash_prefix == (short *) NULL) ||
      (hash_suffix == (unsigned char *) NULL))
    {
      if (packet != (unsigned char *) NULL)
        packet=(unsigned char *) RelinquishMagickMemory(packet);
      if (hash_code != (short *) NULL)
        hash_code=(short *) RelinquishMagickMemory(hash_code);
      if (hash_prefix != (short *) NULL)
        hash_prefix=(short *) RelinquishMagickMemory(hash_prefix);
      if (hash_suffix != (unsigned char *) NULL)
        hash_suffix=(unsigned char *) RelinquishMagickMemory(hash_suffix);
      return(MagickFalse);
    }
  /*
    Initialize GIF encoder.
  */
  number_bits=data_size;
  max_code=MaxCode(number_bits);
  clear_code=((short) one << (data_size-1));
  end_of_information_code=clear_code+1;
  free_code=clear_code+2;
  length=0;
  datum=0;
  bits=0;
  for (i=0; i < MaxHashTable; i++)
    hash_code[i]=0;
  GIFOutputCode(clear_code);
  /*
    Encode pixels.
  */
  offset=0;
  pass=0;
  waiting_code=0;
  for (y=0; y < (ssize_t) image->rows; y++)
  {
    register const IndexPacket
      *restrict indexes;

    register const PixelPacket
      *restrict p;

    register ssize_t
      x;

    p=GetVirtualPixels(image,0,offset,image->columns,1,&image->exception);
    if (p == (const PixelPacket *) NULL)
      break;
    indexes=GetVirtualIndexQueue(image);
    if (y == 0)
      waiting_code=(short) (*indexes);
    for (x=(ssize_t) (y == 0 ? 1 : 0); x < (ssize_t) image->columns; x++)
    {
      /*
        Probe hash table.
      */
      index=(IndexPacket) ((size_t) GetPixelIndex(indexes+x) & 0xff);
      p++;
      k=(ssize_t) (((size_t) index << (MaxGIFBits-8))+waiting_code);
      if (k >= MaxHashTable)
        k-=MaxHashTable;
      next_pixel=MagickFalse;
      displacement=1;
      if (hash_code[k] > 0)
        {
          if ((hash_prefix[k] == waiting_code) &&
              (hash_suffix[k] == (unsigned char) index))
            {
              waiting_code=hash_code[k];
              continue;
            }
          if (k != 0)
            displacement=MaxHashTable-k;
          for ( ; ; )
          {
            k-=displacement;
            if (k < 0)
              k+=MaxHashTable;
            if (hash_code[k] == 0)
              break;
            if ((hash_prefix[k] == waiting_code) &&
                (hash_suffix[k] == (unsigned char) index))
              {
                waiting_code=hash_code[k];
                next_pixel=MagickTrue;
                break;
              }
          }
          if (next_pixel != MagickFalse)
            continue;
        }
      GIFOutputCode((size_t) waiting_code);
      if (free_code < MaxGIFTable)
        {
          hash_code[k]=(short) free_code++;
          hash_prefix[k]=waiting_code;
          hash_suffix[k]=(unsigned char) index;
        }
      else
        {
          /*
            Fill the hash table with empty entries.
          */
          for (k=0; k < MaxHashTable; k++)
            hash_code[k]=0;
          /*
            Reset compressor and issue a clear code.
          */
          free_code=clear_code+2;
          GIFOutputCode(clear_code);
          number_bits=data_size;
          max_code=MaxCode(number_bits);
        }
      waiting_code=(short) index;
    }
    if (image_info->interlace == NoInterlace)
      offset++;
    else
      switch (pass)
      {
        case 0:
        default:
        {
          offset+=8;
          if (offset >= (ssize_t) image->rows)
            {
              pass++;
              offset=4;
            }
          break;
        }
        case 1:
        {
          offset+=8;
          if (offset >= (ssize_t) image->rows)
            {
              pass++;
              offset=2;
            }
          break;
        }
        case 2:
        {
          offset+=4;
          if (offset >= (ssize_t) image->rows)
            {
              pass++;
              offset=1;
            }
          break;
        }
        case 3:
        {
          offset+=2;
          break;
        }
      }
  }
  /*
    Flush out the buffered code.
  */
  GIFOutputCode((size_t) waiting_code);
  GIFOutputCode(end_of_information_code);
  if (bits > 0)
    {
      /*
        Add a character to current packet.
      */
      packet[length++]=(unsigned char) (datum & 0xff);
      if (length >= 254)
        {
          (void) WriteBlobByte(image,(unsigned char) length);
          (void) WriteBlob(image,length,packet);
          length=0;
        }
    }
  /*
    Flush accumulated data.
  */
  if (length > 0)
    {
      (void) WriteBlobByte(image,(unsigned char) length);
      (void) WriteBlob(image,length,packet);
    }
  /*
    Free encoder memory.
  */
  hash_suffix=(unsigned char *) RelinquishMagickMemory(hash_suffix);
  hash_prefix=(short *) RelinquishMagickMemory(hash_prefix);
  hash_code=(short *) RelinquishMagickMemory(hash_code);
  packet=(unsigned char *) RelinquishMagickMemory(packet);
  return(MagickTrue);
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.