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 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this file,

  * You can obtain one at http://mozilla.org/MPL/2.0/. */

 #include <algorithm>

 #include "SeekableZStream.h"

 #include "Logging.h"

 bool

 SeekableZStream::Init(const void *buf, size_t length)

 {

   const SeekableZStreamHeader *header = SeekableZStreamHeader::validate(buf);

   if (!header) {

     LOG("Not a seekable zstream");

     return false;

   }

   buffer = reinterpret_cast<const unsigned char *>(buf);

   totalSize = header->totalSize;

   chunkSize = header->chunkSize;

   lastChunkSize = header->lastChunkSize;

   windowBits = header->windowBits;

   dictionary.Init(buffer + sizeof(SeekableZStreamHeader), header->dictSize);

   offsetTable.Init(buffer + sizeof(SeekableZStreamHeader) + header->dictSize,

                    header->nChunks);

   filter = GetFilter(header->filter);

   /* Sanity check */

   if ((chunkSize == 0) ||

       (!IsPageAlignedSize(chunkSize)) ||

       (chunkSize > 8 * PageSize()) ||

       (offsetTable.numElements() < 1) ||

       (lastChunkSize == 0) ||

       (lastChunkSize > chunkSize) ||

       (length < totalSize)) {

     LOG("Malformed or broken seekable zstream");

     return false;

   }

   return true;

 }

 bool

 SeekableZStream::Decompress(void *where, size_t chunk, size_t length)

 {

   while (length) {

     size_t len = std::min(length, static_cast<size_t>(chunkSize));

     if (!DecompressChunk(where, chunk, len))

       return false;

     where = reinterpret_cast<unsigned char *>(where) + len;

     length -= len;

     chunk++;

   }

   return true;

 }

 bool

 SeekableZStream::DecompressChunk(void *where, size_t chunk, size_t length)

 {

   if (chunk >= offsetTable.numElements()) {

     LOG("DecompressChunk: chunk #%" PRIdSize " out of range [0-%" PRIdSize ")",

         chunk, offsetTable.numElements());

     return false;

   }

   bool isLastChunk = (chunk == offsetTable.numElements() - 1);

   size_t chunkLen = isLastChunk ? lastChunkSize : chunkSize;

   if (length == 0 || length > chunkLen)

     length = chunkLen;

   DEBUG_LOG("DecompressChunk #%" PRIdSize " @%p (%" PRIdSize "/% " PRIdSize ")",

         chunk, where, length, chunkLen);

   z_stream zStream;

   memset(&zStream, 0, sizeof(zStream));

   zStream.avail_in = (isLastChunk ? totalSize : uint32_t(offsetTable[chunk + 1]))

                      - uint32_t(offsetTable[chunk]);

   zStream.next_in = const_cast<Bytef *>(buffer + uint32_t(offsetTable[chunk]));

   zStream.avail_out = length;

   zStream.next_out = reinterpret_cast<Bytef *>(where);

   /* Decompress chunk */

   if (inflateInit2(&zStream, windowBits) != Z_OK) {

     LOG("inflateInit failed: %s", zStream.msg);

     return false;

   }

   if (dictionary && inflateSetDictionary(&zStream, dictionary,

                                          dictionary.numElements()) != Z_OK) {

     LOG("inflateSetDictionary failed: %s", zStream.msg);

     return false;

   }

   if (inflate(&zStream, (length == chunkLen) ? Z_FINISH : Z_SYNC_FLUSH)

       != (length == chunkLen) ? Z_STREAM_END : Z_OK) {

     LOG("inflate failed: %s", zStream.msg);

     return false;

   }

   if (inflateEnd(&zStream) != Z_OK) {

     LOG("inflateEnd failed: %s", zStream.msg);

     return false;

   }

   if (filter)

     filter(chunk * chunkSize, UNFILTER, (unsigned char *)where, chunkLen);

   return true;

 }

 /* Branch/Call/Jump conversion filter for Thumb, derived from xz-utils

  * by Igor Pavlov and Lasse Collin, published in the public domain */

 static void

 BCJ_Thumb_filter(off_t offset, SeekableZStream::FilterDirection dir,

                  unsigned char *buf, size_t size)

 {

   size_t i;

   for (i = 0; i + 4 <= size; i += 2) {

     if ((buf[i + 1] & 0xf8) == 0xf0 && (buf[i + 3] & 0xf8) == 0xf8) {

       uint32_t src = (buf[i] << 11)

                      | ((buf[i + 1] & 0x07) << 19)

                      | buf[i + 2]

                      | ((buf[i + 3] & 0x07) << 8);

       src <<= 1;

       uint32_t dest;

       if (dir == SeekableZStream::FILTER)

         dest = offset + (uint32_t)(i) + 4 + src;

       else

         dest = src - (offset + (uint32_t)(i) + 4);

       dest >>= 1;

       buf[i] = dest >> 11;

       buf[i + 1] = 0xf0 | ((dest >> 19) & 0x07);

       buf[i + 2] = dest;

       buf[i + 3] = 0xf8 | ((dest >> 8) & 0x07);

       i += 2;

     }

   }

 }

 /* Branch/Call/Jump conversion filter for ARM, derived from xz-utils

  * by Igor Pavlov and Lasse Collin, published in the public domain */

 static void

 BCJ_ARM_filter(off_t offset, SeekableZStream::FilterDirection dir,

                unsigned char *buf, size_t size)

 {

   size_t i;

   for (i = 0; i + 4 <= size; i += 4) {

     if (buf[i + 3] == 0xeb) {

       uint32_t src = buf[i]

                      | (buf[i + 1] << 8)

                      | (buf[i + 2] << 16);

       src <<= 2;

       uint32_t dest;

       if (dir == SeekableZStream::FILTER)

         dest = offset + (uint32_t)(i) + 8 + src;

       else

         dest = src - (offset + (uint32_t)(i) + 8);

       dest >>= 2;

       buf[i] = dest;

       buf[i + 1] = dest >> 8;

       buf[i + 2] = dest >> 16;

     }

   }

 }

 /* Branch/Call/Jump conversion filter for x86, derived from xz-utils

  * by Igor Pavlov and Lasse Collin, published in the public domain */

 #define Test86MSByte(b) ((b) == 0 || (b) == 0xff)

 static void

 BCJ_X86_filter(off_t offset, SeekableZStream::FilterDirection dir,

                unsigned char *buf, size_t size)

 {

   static const bool MASK_TO_ALLOWED_STATUS[8] =

     { true, true, true, false, true, false, false, false };

   static const uint32_t MASK_TO_BIT_NUMBER[8] =

     { 0, 1, 2, 2, 3, 3, 3, 3 };

   uint32_t prev_mask = 0;

   uint32_t prev_pos = 0;

   for (size_t i = 0; i + 5 <= size;) {

     uint8_t b = buf[i];

     if (b != 0xe8 && b != 0xe9) {

       ++i;

       continue;

     }

     const uint32_t off = offset + (uint32_t)(i) - prev_pos;

     prev_pos = offset + (uint32_t)(i);

     if (off > 5) {

       prev_mask = 0;

     } else {

       for (uint32_t i = 0; i < off; ++i) {

         prev_mask &= 0x77;

         prev_mask <<= 1;

       }

     }

     b = buf[i + 4];

     if (Test86MSByte(b) && MASK_TO_ALLOWED_STATUS[(prev_mask >> 1) & 0x7]

         && (prev_mask >> 1) < 0x10) {

       uint32_t src = ((uint32_t)(b) << 24)

                      | ((uint32_t)(buf[i + 3]) << 16)

                      | ((uint32_t)(buf[i + 2]) << 8)

                      | (buf[i + 1]);

       uint32_t dest;

       while (true) {

         if (dir == SeekableZStream::FILTER)

           dest = src + (offset + (uint32_t)(i) + 5);

         else

           dest = src - (offset + (uint32_t)(i) + 5);

         if (prev_mask == 0)

           break;

         const uint32_t i = MASK_TO_BIT_NUMBER[prev_mask >> 1];

         b = (uint8_t)(dest >> (24 - i * 8));

         if (!Test86MSByte(b))

           break;

         src = dest ^ ((1 << (32 - i * 8)) - 1);

       }

       buf[i + 4] = (uint8_t)(~(((dest >> 24) & 1) - 1));

       buf[i + 3] = (uint8_t)(dest >> 16);

       buf[i + 2] = (uint8_t)(dest >> 8);

       buf[i + 1] = (uint8_t)(dest);

       i += 5;

       prev_mask = 0;

     } else {

       ++i;

       prev_mask |= 1;

       if (Test86MSByte(b))

         prev_mask |= 0x10;

     }

   }

 }

 SeekableZStream::ZStreamFilter

 SeekableZStream::GetFilter(SeekableZStream::FilterId id)

 {

   switch (id) {

   case BCJ_THUMB:

     return BCJ_Thumb_filter;

   case BCJ_ARM:

     return BCJ_ARM_filter;

   case BCJ_X86:

     return BCJ_X86_filter;

   default:

     return nullptr;

   }

   return nullptr;

 }