baseuefidecompresslib.c

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    if (Index == Special) {
      CharC = (UINT16) GetBits (Sd, 2);
      while ((INT16) (--CharC) >= 0) {
        Sd->mPTLen[Index++] = 0;
      }
    }
  }

  while (Index < nn) {
    Sd->mPTLen[Index++] = 0;
  }
  
  return MakeTable (Sd, nn, Sd->mPTLen, 8, Sd->mPTTable);
}

/**
  Reads code lengths for Char&Len Set.
  
  Read in and decode the Char&Len Set Code Length Array, then
  generate the Huffman Code mapping table for the Char&Len Set.

  @param  Sd the global scratch data

**/
VOID
GlueReadCLen (
  SCRATCH_DATA  *Sd
  )
{
  UINT16           Number;
  UINT16           CharC;
  volatile UINT16  Index;
  UINT32           Mask;

  Number = (UINT16) GetBits (Sd, CBIT);

  if (Number == 0) {
    //
    // This represents only Huffman code used
    //
    CharC = (UINT16) GetBits (Sd, CBIT);

    for (Index = 0; Index < NC; Index++) {
      Sd->mCLen[Index] = 0;
    }

    for (Index = 0; Index < 4096; Index++) {
      Sd->mCTable[Index] = CharC;
    }

    return ;
  }

  Index = 0;
  while (Index < Number) {
    CharC = Sd->mPTTable[Sd->mBitBuf >> (BITBUFSIZ - 8)];
    if (CharC >= NT) {
      Mask = 1U << (BITBUFSIZ - 1 - 8);

      do {

        if (Mask & Sd->mBitBuf) {
          CharC = Sd->mRight[CharC];
        } else {
          CharC = Sd->mLeft[CharC];
        }

        Mask >>= 1;

      } while (CharC >= NT);
    }
    //
    // Advance what we have read
    //
    FillBuf (Sd, Sd->mPTLen[CharC]);

    if (CharC <= 2) {

      if (CharC == 0) {
        CharC = 1;
      } else if (CharC == 1) {
        CharC = (UINT16) (GetBits (Sd, 4) + 3);
      } else if (CharC == 2) {
        CharC = (UINT16) (GetBits (Sd, CBIT) + 20);
      }

      while ((INT16) (--CharC) >= 0) {
        Sd->mCLen[Index++] = 0;
      }

    } else {

      Sd->mCLen[Index++] = (UINT8) (CharC - 2);

    }
  }

  while (Index < NC) {
    Sd->mCLen[Index++] = 0;
  }

  MakeTable (Sd, NC, Sd->mCLen, 12, Sd->mCTable);

  return ;
}

/**
  Decode a character/length value.
  
  Read one value from mBitBuf, Get one code from mBitBuf. If it is at block boundary, generates
  Huffman code mapping table for Extra Set, Code&Len Set and
  Position Set.

  @param  Sd The global scratch data.

  @return The value decoded.

**/
UINT16
GlueDecodeC (
  SCRATCH_DATA  *Sd
  )
{
  UINT16  Index2;
  UINT32  Mask;

  if (Sd->mBlockSize == 0) {
    //
    // Starting a new block
    // Read BlockSize from block header
    // 
    Sd->mBlockSize    = (UINT16) GetBits (Sd, 16);

    //
    // Read in the Extra Set Code Length Arrary,
    // Generate the Huffman code mapping table for Extra Set.
    //
    Sd->mBadTableFlag = ReadPTLen (Sd, NT, TBIT, 3);
    if (Sd->mBadTableFlag != 0) {
      return 0;
    }

    //
    // Read in and decode the Char&Len Set Code Length Arrary,
    // Generate the Huffman code mapping table for Char&Len Set.
    //
    ReadCLen (Sd);

    //
    // Read in the Position Set Code Length Arrary, 
    // Generate the Huffman code mapping table for the Position Set.
    //
    Sd->mBadTableFlag = ReadPTLen (Sd, MAXNP, Sd->mPBit, (UINT16) (-1));
    if (Sd->mBadTableFlag != 0) {
      return 0;
    }
  }

  //
  // Get one code according to Code&Set Huffman Table
  //
  Sd->mBlockSize--;
  Index2 = Sd->mCTable[Sd->mBitBuf >> (BITBUFSIZ - 12)];

  if (Index2 >= NC) {
    Mask = 1U << (BITBUFSIZ - 1 - 12);

    do {
      if (Sd->mBitBuf & Mask) {
        Index2 = Sd->mRight[Index2];
      } else {
        Index2 = Sd->mLeft[Index2];
      }

      Mask >>= 1;
    } while (Index2 >= NC);
  }
  //
  // Advance what we have read
  //
  FillBuf (Sd, Sd->mCLen[Index2]);

  return Index2;
}

/**
  Decode the source data and put the resulting data into the destination buffer.

  Decode the source data and put the resulting data into the destination buffer.
  
  @param  Sd The global scratch data

**/
VOID
GlueDecode (
  SCRATCH_DATA  *Sd
  )
{
  UINT16  BytesRemain;
  UINT32  DataIdx;
  UINT16  CharC;

  BytesRemain = (UINT16) (-1);

  DataIdx     = 0;

  for (;;) {
    //
    // Get one code from mBitBuf
    // 
    CharC = DecodeC (Sd);
    if (Sd->mBadTableFlag != 0) {
      return ;
    }

    if (CharC < 256) {
      //
      // Process an Original character
      //
      if (Sd->mOutBuf >= Sd->mOrigSize) {
        return ;
      } else {
        //
        // Write orignal character into mDstBase
        //
        Sd->mDstBase[Sd->mOutBuf++] = (UINT8) CharC;
      }

    } else {
      //
      // Process a Pointer
      //
      CharC       = (UINT16) (CharC - (UINT8_MAX + 1 - THRESHOLD));
 
      //
      // Get string length
      //
      BytesRemain = CharC;

      //
      // Locate string position
      //
      DataIdx     = Sd->mOutBuf - DecodeP (Sd) - 1;

      //
      // Write BytesRemain of bytes into mDstBase
      //
      BytesRemain--;
      while ((INT16) (BytesRemain) >= 0) {
        Sd->mDstBase[Sd->mOutBuf++] = Sd->mDstBase[DataIdx++];
        if (Sd->mOutBuf >= Sd->mOrigSize) {
          return ;
        }

        BytesRemain--;
      }
    }
  }

  return ;
}

/**
  Retrieves the size of the uncompressed buffer and the size of the scratch buffer.

  Retrieves the size of the uncompressed buffer and the temporary scratch buffer 
  required to decompress the buffer specified by Source and SourceSize.
  If the size of the uncompressed buffer or the size of the scratch buffer cannot
  be determined from the compressed data specified by Source and SourceData, 
  then RETURN_INVALID_PARAMETER is returned.  Otherwise, the size of the uncompressed
  buffer is returned in DestinationSize, the size of the scratch buffer is returned
  in ScratchSize, and RETURN_SUCCESS is returned.
  This function does not have scratch buffer available to perform a thorough 
  checking of the validity of the source data.  It just retrieves the "Original Size"
  field from the beginning bytes of the source data and output it as DestinationSize.
  And ScratchSize is specific to the decompression implementation.

  If Source is NULL, then ASSERT().
  If DestinationSize is NULL, then ASSERT().
  If ScratchSize is NULL, then ASSERT().

  @param  Source          The source buffer containing the compressed data.
  @param  SourceSize      The size, in bytes, of the source buffer.
  @param  DestinationSize A pointer to the size, in bytes, of the uncompressed buffer
                          that will be generated when the compressed buffer specified
                          by Source and SourceSize is decompressed..
  @param  ScratchSize     A pointer to the size, in bytes, of the scratch buffer that
                          is required to decompress the compressed buffer specified 
                          by Source and SourceSize.

  @retval  RETURN_SUCCESS The size of destination buffer and the size of scratch 
                          buffer are successull retrieved.
  @retval  RETURN_INVALID_PARAMETER The source data is corrupted

**/
RETURN_STATUS
EFIAPI
UefiDecompressGetInfo (
  IN  CONST VOID  *Source,
  IN  UINT32      SourceSize,
  OUT UINT32      *DestinationSize,
  OUT UINT32      *ScratchSize
  )
{
  UINT32  CompressedSize;

  ASSERT (Source != NULL);
  ASSERT (DestinationSize != NULL);
  ASSERT (ScratchSize != NULL);

  *ScratchSize  = sizeof (SCRATCH_DATA);

  if (SourceSize < 8) {
    return RETURN_INVALID_PARAMETER;
  }

  CopyMem (&CompressedSize, Source, sizeof (UINT32));
  CopyMem (DestinationSize, (VOID *)((UINT8 *)Source + 4), sizeof (UINT32));

  if (SourceSize < (CompressedSize + 8)) {
    return RETURN_INVALID_PARAMETER;
  }

  return RETURN_SUCCESS;
}

/**
  Decompresses a compressed source buffer.

  This function is designed so that the decompression algorithm can be implemented
  without using any memory services.  As a result, this function is not allowed to
  call any memory allocation services in its implementation.  It is the caller’s r
  esponsibility to allocate and free the Destination and Scratch buffers.
  If the compressed source data specified by Source is sucessfully decompressed 
  into Destination, then RETURN_SUCCESS is returned.  If the compressed source data 
  specified by Source is not in a valid compressed data format,
  then RETURN_INVALID_PARAMETER is returned.

  If Source is NULL, then ASSERT().
  If Destination is NULL, then ASSERT().
  If the required scratch buffer size > 0 and Scratch is NULL, then ASSERT().

  @param  Source      The source buffer containing the compressed data.
  @param  Destination The destination buffer to store the decompressed data
  @param  Scratch     A temporary scratch buffer that is used to perform the decompression.
                      This is an optional parameter that may be NULL if the 
                      required scratch buffer size is 0.
                     
  @retval  RETURN_SUCCESS Decompression is successfull
  @retval  RETURN_INVALID_PARAMETER The source data is corrupted

**/
RETURN_STATUS
EFIAPI
UefiDecompress (
  IN CONST VOID  *Source,
  IN OUT VOID    *Destination,
  IN OUT VOID    *Scratch
  )
{
  volatile UINT32  Index;
  UINT32           CompSize;
  UINT32           OrigSize;
  SCRATCH_DATA     *Sd;
  CONST UINT8      *Src;
  UINT8            *Dst;

  ASSERT (Source != NULL);
  ASSERT (Destination != NULL);
  ASSERT (Scratch != NULL);

  Src     = Source;
  Dst     = Destination;

  Sd = (SCRATCH_DATA *) Scratch;

  CompSize  = Src[0] + (Src[1] << 8) + (Src[2] << 16) + (Src[3] << 24);
  OrigSize  = Src[4] + (Src[5] << 8) + (Src[6] << 16) + (Src[7] << 24);

  //
  // If compressed file size is 0, return
  //
  if (OrigSize == 0) {
    return RETURN_SUCCESS;
  }

  Src = Src + 8;

  for (Index = 0; Index < sizeof (SCRATCH_DATA); Index++) {
    ((UINT8 *) Sd)[Index] = 0;
  }
  //
  // The length of the field 'Position Set Code Length Array Size' in Block Header.
  // For EFI 1.1 de/compression algorithm(Version 1), mPBit = 4
  // For Tiano de/compression algorithm(Version 2), mPBit = 5
  //
  Sd->mPBit     = 4;
  Sd->mSrcBase  = (UINT8 *)Src;
  Sd->mDstBase  = Dst;
  //
  // CompSize and OrigSize are caculated in bytes
  //
  Sd->mCompSize = CompSize;
  Sd->mOrigSize = OrigSize;

  //
  // Fill the first BITBUFSIZ bits
  //
  FillBuf (Sd, BITBUFSIZ);

  //
  // Decompress it
  //
  Decode (Sd);

  if (Sd->mBadTableFlag != 0) {
    //
    // Something wrong with the source
    //
    return RETURN_INVALID_PARAMETER;
  }

  return RETURN_SUCCESS;
}