[ON HOLD] Implement pull-based design for content decoding

net/filter/stream_source_util.cc

+// Copyright 2016 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 "net/filter/stream_source_util.h"
+
+#include "base/strings/string_util.h"
+#include "net/filter/brotli_stream_source.h"
+#include "net/filter/gzip_stream_source.h"
+#include "net/filter/sdch_stream_source.h"
+#include "net/filter/stream_source.h"
+#include "net/http/http_response_headers.h"
+
+namespace net {
+
+namespace {
+
+const char kDeflate[] = "deflate";
+const char kGZip[] = "gzip";
+const char kSdch[] = "sdch";
+const char kXGZip[] = "x-gzip";
+const char kBrotli[] = "br";
+
+std::unique_ptr<StreamSource> BuildSource(
+    std::unique_ptr<StreamSource> previous,
+    StreamSource::SourceType type) {
+  std::unique_ptr<FilterStreamSource> next = nullptr;
+  if (type == StreamSource::TYPE_BROTLI) {
+    next = CreateBrotliStreamSource(std::move(previous));
+  } else if (type == StreamSource::TYPE_SDCH) {
+    next.reset(new SdchStreamSource(std::move(previous), nullptr));
+  } else if (type == StreamSource::TYPE_GZIP ||
+             type == StreamSource::TYPE_DEFLATE ||
+             type == StreamSource::TYPE_GZIP_FALLBACK) {
+    GzipStreamSource::GzipStreamSourceMode mode;
+    if (type == StreamSource::TYPE_DEFLATE) {
+      mode = GzipStreamSource::GZIP_STREAM_SOURCE_DEFLATE;
+    } else if (type == StreamSource::TYPE_GZIP) {
+      mode = GzipStreamSource::GZIP_STREAM_SOURCE_GZIP;
+    } else {
+      mode = GzipStreamSource::GZIP_STREAM_SOURCE_GZIP_WITH_FALLBACK;
+    }
+    next.reset(new GzipStreamSource(std::move(previous), mode));
+  }
+  if (!next->Init())
+    return nullptr;
+  return std::move(next);
+}
+
+}  // namespace
+
+std::unique_ptr<StreamSource> StreamSourceUtil::BuildSourceChain(
+    std::unique_ptr<StreamSource> previous,
+    HttpResponseHeaders* headers) {
+  std::string type;
+  std::vector<StreamSource::SourceType> types;
+  size_t iter = 0;
+  while (headers->EnumerateHeader(&iter, "Content-Encoding", &type)) {
+    if (base::LowerCaseEqualsASCII(type, kBrotli)) {
+      types.push_back(StreamSource::TYPE_BROTLI);
+    } else if (base::LowerCaseEqualsASCII(type, kDeflate)) {
+      types.push_back(StreamSource::TYPE_DEFLATE);
+    } else if (base::LowerCaseEqualsASCII(type, kGZip) ||
+               base::LowerCaseEqualsASCII(type, kXGZip)) {
+      types.push_back(StreamSource::TYPE_GZIP);
+    } else if (base::LowerCaseEqualsASCII(type, kSdch)) {
+      types.push_back(StreamSource::TYPE_SDCH);
+    }
+  }
+
+  // SDCH-specific hack: if the first filter is SDCH, add a gzip filter in front
+  // of it in fallback mode.
+  if (!types.empty() && types.at(0) == StreamSource::TYPE_SDCH)
+    types.insert(types.begin(), StreamSource::TYPE_GZIP_FALLBACK);
+
+  for (const auto& type : types) {
+    previous = BuildSource(std::move(previous), type);
+    if (previous == nullptr)
+      return nullptr;
+  }
+
+  return previous;
+}
+
+std::string StreamSourceUtil::SourceTypeAsString(
+    StreamSource::SourceType type) {
+  switch (type) {
+#define STREAM_SOURCE_TYPE(label)  \
+  case StreamSource::TYPE_##label: \
+    return #label;
+#include "net/filter/stream_source_type_list.h"
+#undef STREAM_SOURCE_TYPE
+    default:
+      NOTREACHED();
+      return nullptr;
+  }
+}
+
+std::string StreamSourceUtil::OrderedStreamSourceList(StreamSource* source) {
+  if (source->previous()) {
+    return SourceTypeAsString(source->type()) + "," +
+           OrderedStreamSourceList(source->previous());
+  } else {
+    return SourceTypeAsString(source->type());
+  }
+}
+
+}  // namespace net