1 files changed, 261 insertions, 0 deletions
diff --git a/js/src/vm/Compression.cpp b/js/src/vm/Compression.cpp
new file mode 100644
index 0000000000..cc6903eaae
--- /dev/null
+++ b/js/src/vm/Compression.cpp
@@ -0,0 +1,261 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * 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 "vm/Compression.h"
+
+#include "mozilla/DebugOnly.h"
+#include "mozilla/MemoryChecking.h"
+#include "mozilla/PodOperations.h"
+#include "mozilla/ScopeExit.h"
+
+#include "js/Utility.h"
+#include "util/Memory.h"
+
+using namespace js;
+
+static void* zlib_alloc(void* cx, uInt items, uInt size) {
+  return js_calloc(items, size);
+}
+
+static void zlib_free(void* cx, void* addr) { js_free(addr); }
+
+Compressor::Compressor(const unsigned char* inp, size_t inplen)
+    : inp(inp),
+      inplen(inplen),
+      initialized(false),
+      finished(false),
+      currentChunkSize(0) {
+  MOZ_ASSERT(inplen > 0, "data to compress can't be empty");
+
+  zs.opaque = nullptr;
+  zs.next_in = (Bytef*)inp;
+  zs.avail_in = 0;
+  zs.next_out = nullptr;
+  zs.avail_out = 0;
+  zs.zalloc = zlib_alloc;
+  zs.zfree = zlib_free;
+  zs.total_in = 0;
+  zs.total_out = 0;
+  zs.msg = nullptr;
+  zs.state = nullptr;
+  zs.data_type = 0;
+  zs.adler = 0;
+  zs.reserved = 0;
+
+  // Reserve space for the CompressedDataHeader.
+  outbytes = sizeof(CompressedDataHeader);
+}
+
+Compressor::~Compressor() {
+  if (initialized) {
+    int ret = deflateEnd(&zs);
+    if (ret != Z_OK) {
+      // If we finished early, we can get a Z_DATA_ERROR.
+      MOZ_ASSERT(ret == Z_DATA_ERROR);
+      MOZ_ASSERT(!finished);
+    }
+  }
+}
+
+// According to the zlib docs, the default value for windowBits is 15. Passing
+// -15 is treated the same, but it also forces 'raw deflate' (no zlib header or
+// trailer). Raw deflate is necessary for chunked decompression.
+static const int WindowBits = -15;
+
+bool Compressor::init() {
+  if (inplen >= UINT32_MAX) {
+    return false;
+  }
+  // zlib is slow and we'd rather be done compression sooner
+  // even if it means decompression is slower which penalizes
+  // Function.toString()
+  int ret = deflateInit2(&zs, Z_BEST_SPEED, Z_DEFLATED, WindowBits, 8,
+                         Z_DEFAULT_STRATEGY);
+  if (ret != Z_OK) {
+    MOZ_ASSERT(ret == Z_MEM_ERROR);
+    return false;
+  }
+  initialized = true;
+  return true;
+}
+
+void Compressor::setOutput(unsigned char* out, size_t outlen) {
+  MOZ_ASSERT(outlen > outbytes);
+  zs.next_out = out + outbytes;
+  zs.avail_out = outlen - outbytes;
+}
+
+Compressor::Status Compressor::compressMore() {
+  MOZ_ASSERT(zs.next_out);
+  uInt left = inplen - (zs.next_in - inp);
+  if (left <= MAX_INPUT_SIZE) {
+    zs.avail_in = left;
+  } else if (zs.avail_in == 0) {
+    zs.avail_in = MAX_INPUT_SIZE;
+  }
+
+  // Finish the current chunk if needed.
+  bool flush = false;
+  MOZ_ASSERT(currentChunkSize <= CHUNK_SIZE);
+  if (currentChunkSize + zs.avail_in >= CHUNK_SIZE) {
+    // Adjust avail_in, so we don't get chunks that are larger than
+    // CHUNK_SIZE.
+    zs.avail_in = CHUNK_SIZE - currentChunkSize;
+    MOZ_ASSERT(currentChunkSize + zs.avail_in == CHUNK_SIZE);
+    flush = true;
+  }
+
+  MOZ_ASSERT(zs.avail_in <= left);
+  bool done = zs.avail_in == left;
+
+  Bytef* oldin = zs.next_in;
+  Bytef* oldout = zs.next_out;
+  int ret = deflate(&zs, done ? Z_FINISH : (flush ? Z_FULL_FLUSH : Z_NO_FLUSH));
+  outbytes += zs.next_out - oldout;
+  currentChunkSize += zs.next_in - oldin;
+  MOZ_ASSERT(currentChunkSize <= CHUNK_SIZE);
+
+  if (ret == Z_MEM_ERROR) {
+    zs.avail_out = 0;
+    return OOM;
+  }
+  if (ret == Z_BUF_ERROR || (ret == Z_OK && zs.avail_out == 0)) {
+    // We have to resize the output buffer. Note that we're not done yet
+    // because ret != Z_STREAM_END.
+    MOZ_ASSERT(zs.avail_out == 0);
+    return MOREOUTPUT;
+  }
+
+  if (done || currentChunkSize == CHUNK_SIZE) {
+    MOZ_ASSERT_IF(!done, flush);
+    MOZ_ASSERT(chunkSize(inplen, chunkOffsets.length()) == currentChunkSize);
+    if (!chunkOffsets.append(outbytes)) {
+      return OOM;
+    }
+    currentChunkSize = 0;
+    MOZ_ASSERT_IF(done, chunkOffsets.length() == (inplen - 1) / CHUNK_SIZE + 1);
+  }
+
+  MOZ_ASSERT_IF(!done, ret == Z_OK);
+  MOZ_ASSERT_IF(done, ret == Z_STREAM_END);
+  return done ? DONE : CONTINUE;
+}
+
+size_t Compressor::totalBytesNeeded() const {
+  return AlignBytes(outbytes, sizeof(uint32_t)) + sizeOfChunkOffsets();
+}
+
+void Compressor::finish(char* dest, size_t destBytes) {
+  MOZ_ASSERT(!chunkOffsets.empty());
+
+  CompressedDataHeader* compressedHeader =
+      reinterpret_cast<CompressedDataHeader*>(dest);
+  compressedHeader->compressedBytes = outbytes;
+
+  size_t outbytesAligned = AlignBytes(outbytes, sizeof(uint32_t));
+
+  // Zero the padding bytes, the ImmutableStringsCache will hash them.
+  mozilla::PodZero(dest + outbytes, outbytesAligned - outbytes);
+
+  uint32_t* destArr = reinterpret_cast<uint32_t*>(dest + outbytesAligned);
+
+  MOZ_ASSERT(uintptr_t(dest + destBytes) ==
+             uintptr_t(destArr + chunkOffsets.length()));
+  mozilla::PodCopy(destArr, chunkOffsets.begin(), chunkOffsets.length());
+
+  finished = true;
+}
+
+bool js::DecompressString(const unsigned char* inp, size_t inplen,
+                          unsigned char* out, size_t outlen) {
+  MOZ_ASSERT(inplen <= UINT32_MAX);
+
+  // Mark the memory we pass to zlib as initialized for MSan.
+  MOZ_MAKE_MEM_DEFINED(out, outlen);
+
+  z_stream zs;
+  zs.zalloc = zlib_alloc;
+  zs.zfree = zlib_free;
+  zs.opaque = nullptr;
+  zs.next_in = (Bytef*)inp;
+  zs.avail_in = inplen;
+  zs.next_out = out;
+  MOZ_ASSERT(outlen);
+  zs.avail_out = outlen;
+  int ret = inflateInit(&zs);
+  if (ret != Z_OK) {
+    MOZ_ASSERT(ret == Z_MEM_ERROR);
+    return false;
+  }
+  ret = inflate(&zs, Z_FINISH);
+  MOZ_ASSERT(ret == Z_STREAM_END);
+  ret = inflateEnd(&zs);
+  MOZ_ASSERT(ret == Z_OK);
+  return true;
+}
+
+bool js::DecompressStringChunk(const unsigned char* inp, size_t chunk,
+                               unsigned char* out, size_t outlen) {
+  MOZ_ASSERT(outlen <= Compressor::CHUNK_SIZE);
+
+  const CompressedDataHeader* header =
+      reinterpret_cast<const CompressedDataHeader*>(inp);
+
+  size_t compressedBytes = header->compressedBytes;
+  size_t compressedBytesAligned = AlignBytes(compressedBytes, sizeof(uint32_t));
+
+  const unsigned char* offsetBytes = inp + compressedBytesAligned;
+  const uint32_t* offsets = reinterpret_cast<const uint32_t*>(offsetBytes);
+
+  uint32_t compressedStart =
+      chunk > 0 ? offsets[chunk - 1] : sizeof(CompressedDataHeader);
+  uint32_t compressedEnd = offsets[chunk];
+
+  MOZ_ASSERT(compressedStart < compressedEnd);
+  MOZ_ASSERT(compressedEnd <= compressedBytes);
+
+  bool lastChunk = compressedEnd == compressedBytes;
+
+  // Mark the memory we pass to zlib as initialized for MSan.
+  MOZ_MAKE_MEM_DEFINED(out, outlen);
+
+  z_stream zs;
+  zs.zalloc = zlib_alloc;
+  zs.zfree = zlib_free;
+  zs.opaque = nullptr;
+  zs.next_in = (Bytef*)(inp + compressedStart);
+  zs.avail_in = compressedEnd - compressedStart;
+  zs.next_out = out;
+  MOZ_ASSERT(outlen);
+  zs.avail_out = outlen;
+
+  // Bug 1505857 - Use 'volatile' so variable is preserved in crashdump
+  // when release-asserts below are tripped.
+  volatile int ret = inflateInit2(&zs, WindowBits);
+  if (ret != Z_OK) {
+    MOZ_ASSERT(ret == Z_MEM_ERROR);
+    return false;
+  }
+
+  auto autoCleanup = mozilla::MakeScopeExit([&] {
+    mozilla::DebugOnly<int> ret = inflateEnd(&zs);
+    MOZ_ASSERT(ret == Z_OK);
+  });
+
+  if (lastChunk) {
+    ret = inflate(&zs, Z_FINISH);
+    MOZ_RELEASE_ASSERT(ret == Z_STREAM_END);
+  } else {
+    ret = inflate(&zs, Z_NO_FLUSH);
+    if (ret == Z_MEM_ERROR) {
+      return false;
+    }
+    MOZ_RELEASE_ASSERT(ret == Z_OK);
+  }
+  MOZ_ASSERT(zs.avail_in == 0);
+  MOZ_ASSERT(zs.avail_out == 0);
+  return true;
+}