mozglue/linker/SeekableZStream.cpp
author Jim Blandy <jimb@mozilla.com>
Tue, 24 Jun 2014 22:12:07 -0700
changeset 199513 69d61e42d5dfbf4588b72449249ff3e7f2125304
parent 197506 79eab42e54839fef24c3e1604466e64a1c082277
child 213895 3554e60ef779185b7a5725bbed120e8b47c755c2
permissions -rw-r--r--
Bug 914753: Make Emacs file variable header lines correct, or at least consistent. DONTBUILD r=ehsan The -*- file variable lines -*- establish per-file settings that Emacs will pick up. This patch makes the following changes to those lines (and touches nothing else): - Never set the buffer's mode. Years ago, Emacs did not have a good JavaScript mode, so it made sense to use Java or C++ mode in .js files. However, Emacs has had js-mode for years now; it's perfectly serviceable, and is available and enabled by default in all major Emacs packagings. Selecting a mode in the -*- file variable line -*- is almost always the wrong thing to do anyway. It overrides Emacs's default choice, which is (now) reasonable; and even worse, it overrides settings the user might have made in their '.emacs' file for that file extension. It's only useful when there's something specific about that particular file that makes a particular mode appropriate. - Correctly propagate settings that establish the correct indentation level for this file: c-basic-offset and js2-basic-offset should be js-indent-level. Whatever value they're given should be preserved; different parts of our tree use different indentation styles. - We don't use tabs in Mozilla JS code. Always set indent-tabs-mode: nil. Remove tab-width: settings, at least in files that don't contain tab characters. - Remove js2-mode settings that belong in the user's .emacs file, like js2-skip-preprocessor-directives.

/* 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) {
    ERROR("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)) {
    ERROR("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()) {
    ERROR("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) {
    ERROR("inflateInit failed: %s", zStream.msg);
    return false;
  }
  if (dictionary && inflateSetDictionary(&zStream, dictionary,
                                         dictionary.numElements()) != Z_OK) {
    ERROR("inflateSetDictionary failed: %s", zStream.msg);
    return false;
  }
  if (inflate(&zStream, (length == chunkLen) ? Z_FINISH : Z_SYNC_FLUSH)
      != (length == chunkLen) ? Z_STREAM_END : Z_OK) {
    ERROR("inflate failed: %s", zStream.msg);
    return false;
  }
  if (inflateEnd(&zStream) != Z_OK) {
    ERROR("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;
}