Data pack file reader and unit test, used for resources on Linux.

See http://dev.chromium.org/developers/design-documents/linuxresourcesandlocalizedstrings for more details.

Review URL: http://codereview.chromium.org/17253


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@7751 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 109 insertions, 0 deletions

diff --git a/base/data_pack.cc b/base/data_pack.cc
new file mode 100644
index 0000000..17db8c4
--- /dev/null
+++ b/base/data_pack.cc
@@ -0,0 +1,109 @@
+// Copyright (c) 2008 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/data_pack.h"
+
+#include "base/file_util.h"
+#include "base/logging.h"
+#include "base/string_piece.h"
+
+// For details of the file layout, see
+// http://dev.chromium.org/developers/design-documents/linuxresourcesandlocalizedstrings
+
+namespace {
+static const uint32_t kFileFormatVersion = 1;
+// Length of file header: version and entry count.
+static const size_t kHeaderLength = 2 * sizeof(uint32_t);
+
+struct DataPackEntry {
+  uint32_t resource_id;
+  uint32_t file_offset;
+  uint32_t length;
+
+  static int CompareById(const void* void_key, const void* void_entry) {
+    uint32_t key = *reinterpret_cast<const uint32_t*>(void_key);
+    const DataPackEntry* entry =
+        reinterpret_cast<const DataPackEntry*>(void_entry);
+    if (key < entry->resource_id) {
+      return -1;
+    } else if (key > entry->resource_id) {
+      return 1;
+    } else {
+      return 0;
+    }
+  }
+}  __attribute((packed));
+
+}  // anonymous namespace
+
+namespace base {
+
+// In .cc for MemoryMappedFile dtor.
+DataPack::DataPack() : resource_count_(0) {
+}
+DataPack::~DataPack() {
+}
+
+bool DataPack::Load(const FilePath& path) {
+  mmap_.reset(new file_util::MemoryMappedFile);
+  if (!mmap_->Initialize(path)) {
+    mmap_.reset();
+    return false;
+  }
+
+  // Parse the header of the file.
+  // First uint32_t: version; second: resource count.
+  const uint32* ptr = reinterpret_cast<const uint32_t*>(mmap_->data());
+  uint32 version = ptr[0];
+  if (version != kFileFormatVersion) {
+    LOG(ERROR) << "Bad data pack version: got " << version << ", expected "
+               << kFileFormatVersion;
+    mmap_.reset();
+    return false;
+  }
+  resource_count_ = ptr[1];
+
+  // Sanity check the file.
+  // 1) Check we have enough entries.
+  if (kHeaderLength + resource_count_ * sizeof(DataPackEntry) >
+      mmap_->length()) {
+    LOG(ERROR) << "Data pack file corruption: too short for number of "
+                  "entries specified.";
+    mmap_.reset();
+    return false;
+  }
+  // 2) Verify the entries are within the appropriate bounds.
+  for (size_t i = 0; i < resource_count_; ++i) {
+    const DataPackEntry* entry = reinterpret_cast<const DataPackEntry*>(
+        mmap_->data() + kHeaderLength + (i * sizeof(DataPackEntry)));
+    if (entry->file_offset + entry->length > mmap_->length()) {
+      LOG(ERROR) << "Entry #" << i << " in data pack points off end of file. "
+                 << "Was the file corrupted?";
+      mmap_.reset();
+      return false;
+    }
+  }
+
+  return true;
+}
+
+bool DataPack::Get(uint32_t resource_id, StringPiece* data) {
+  // It won't be hard to make this endian-agnostic, but it's not worth
+  // bothering to do right now.
+  COMPILE_ASSERT(__BYTE_ORDER == __LITTLE_ENDIAN,
+                 datapack_assumes_little_endian);
+
+  DataPackEntry* target = reinterpret_cast<DataPackEntry*>(
+      bsearch(&resource_id, mmap_->data() + kHeaderLength, resource_count_,
+              sizeof(DataPackEntry), DataPackEntry::CompareById));
+  if (!target) {
+    LOG(ERROR) << "No resource found with id: " << resource_id;
+    return false;
+  }
+
+  data->set(mmap_->data() + target->file_offset, target->length);
+  return true;
+}
+
+}  // namespace base