resources: Prevent including the same resource in multiple pack files.

ui/base/resource/data_pack.cc

 // Copyright (c) 2012 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 "ui/base/resource/data_pack.h"
 
 #include <errno.h>
 
+#include <algorithm>
+
 #include "base/files/file_util.h"
 #include "base/files/memory_mapped_file.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/string_piece.h"
 
 // For details of the file layout, see
 // http://dev.chromium.org/developers/design-documents/linuxresourcesandlocalizedstrings
 
@@ skipping 205 matching lines @@
 }
 
 ResourceHandle::TextEncodingType DataPack::GetTextEncodingType() const {
   return text_encoding_type_;
 }
 
 ui::ScaleFactor DataPack::GetScaleFactor() const {
   return scale_factor_;
 }
 
+#if DCHECK_IS_ON()
+void DataPack::CheckForDuplicateResources(
+    const ScopedVector<ResourceHandle>& packs) {
+  for (size_t i = 0; i < resource_count_ + 1; ++i) {

[Nico, 2015/05/02 00:50:48]

why + 1?

[sadrul, 2015/05/02 04:17:09]

I am following the code from DataPack::LoadImpl() above (lines 157+). I
considered introducing a
DataPack::ForEachDataPackEntry(void(*func)(DataPackEntry*)), and use that from
both places, since this looks a bit subtle, but decided against it. WDYT?

+    const DataPackEntry* entry = reinterpret_cast<const DataPackEntry*>(
+        mmap_->data() + kHeaderLength + (i * sizeof(DataPackEntry)));
+    const uint16 resource_id = entry->resource_id;
+    const float resource_scale = GetScaleForScaleFactor(scale_factor_);
+    std::for_each(packs.begin(), packs.end(),
+                  [resource_id, resource_scale](const ResourceHandle* handle) {
+                    DCHECK(GetScaleForScaleFactor(handle->GetScaleFactor()) !=
+                               resource_scale ||
+                           !handle->HasResource(resource_id));
+                  });

[Nico, 2015/05/02 00:50:48]

nit: Writing this as

    for (const ResourceHandle* handle : packs) {
      DCHECK(GetScaleForScaleFactor(handle->GetScaleFactor()) !=
                 resource_scale ||
             !handle->HasResource(resource_id));
    }

is both shorter and more readable

[sadrul, 2015/05/02 04:17:09]

Heh, yeah. Totally. Done.

+  }
+}
+#endif  // DCHECK_IS_ON()
+
 // static
 bool DataPack::WritePack(const base::FilePath& path,
                          const std::map<uint16, base::StringPiece>& resources,
                          TextEncodingType textEncodingType) {
   FILE* file = base::OpenFile(path, "wb");
   if (!file)
     return false;
 
   if (fwrite(&kFileFormatVersion, sizeof(kFileFormatVersion), 1, file) != 1) {
     LOG(ERROR) << "Failed to write file version";
@@ skipping 72 matching lines @@
       return false;
     }
   }
 
   base::CloseFile(file);
 
   return true;
 }
 
 }  // namespace ui