[MD settings] i18n source stream filtering

content/browser/webui/i18n_source_stream.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 "content/browser/webui/i18n_source_stream.h"
+
+#include <algorithm>
+#include <utility>
+
+#include "base/logging.h"
+#include "base/strings/string_piece.h"
+#include "net/base/io_buffer.h"
+
+namespace content {
+
+I18nSourceStream::~I18nSourceStream() {}
+
+std::unique_ptr<I18nSourceStream> I18nSourceStream::Create(
+    std::unique_ptr<SourceStream> upstream,
+    SourceStream::SourceType type,
+    const ui::TemplateReplacements* replacements) {
+  DCHECK(replacements);
+  std::unique_ptr<I18nSourceStream> source(
+      new I18nSourceStream(std::move(upstream), type, replacements));
+  return source;
+}
+
+I18nSourceStream::I18nSourceStream(std::unique_ptr<SourceStream> upstream,
+                                   SourceStream::SourceType type,
+                                   const ui::TemplateReplacements* replacements)
+    : FilterSourceStream(type, std::move(upstream)),
+      drain_offset_(0),
+      replacements_(replacements) {}
+
+std::string I18nSourceStream::GetTypeAsString() const {
+  return "i18n";
+}
+
+int I18nSourceStream::FilterData(net::IOBuffer* output_buffer,
+                                 int output_buffer_size,
+                                 net::IOBuffer* input_buffer,
+                                 int input_buffer_size,
+                                 int* consumed_bytes,
+                                 bool upstream_end_reached) {

[mmenke, 2016/12/14 16:10:45]

optional:  Suggest DCHECK(output_.empty() || (upstream_end_reached &&
input_buffer_size == 0));

To document the invariant this code depends on.

[dschuyler, 2016/12/15 00:17:08]

Done.

+  *consumed_bytes = input_buffer_size;
+  int bytes_out = 0;

[mmenke, 2016/12/14 16:10:45]

If you decide not to go with my suggestion below, you should at least move this
down to just above the last if statement.  Google style is to declare variables
just before first use, to reduce their scope.

[dschuyler, 2016/12/15 00:17:09]

Done.

+  // TODO(dschuyler): Perform replacements without accumulation.
+  // Accumulate.
+  input_.append(input_buffer->data(), input_buffer_size);
+  if (upstream_end_reached && !drain_offset_ && output_.empty()) {
+    // Process.
+    output_ = ui::ReplaceTemplateExpressions(input_, *replacements_);
+  }
+
+  if (drain_offset_ < output_.size()) {

[mmenke, 2016/12/14 16:10:45]

optional nit:  When there's nothing else to do, early return is often preferred
(Though in cases where if more code were added, you'd want it to be done in both
cases, early return may not be a good idea).

Anyhow, suggest going with:

if (drain_offset_ == output_.size())
  return;

(== is a bit clearer than >=)

And then you can also declare bytes_read down here, too.

[dschuyler, 2016/12/15 00:17:09]

Done.

+    // Drain.
+    bytes_out = std::min(output_.size() - drain_offset_,
+                         static_cast<size_t>(output_buffer_size));
+    output_.copy(output_buffer->data(), bytes_out, drain_offset_);
+    drain_offset_ += bytes_out;
+  }
+
+  return bytes_out;
+}
+
+}  // namespace content