Implement content_decoder_tool.cc to decode offline any resources.

net/tools/contentdecodertool/contentdecodertool.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 <iostream>
+
+#include "base/command_line.h"
+#include "net/base/io_buffer.h"
+#include "net/filter/filter.h"
+#include "net/filter/mock_filter_context.h"
+
+using net::Filter;
+
+namespace {
+
+// Print the command line help.
+void PrintHelp() {
+  std::cout << "contentdecodertool encoding_type [encoding_type]*" << std::endl

[pasko, 2016/03/16 12:05:53]

let's name it content_encoding (instead of encoding_type), seems less ambiguous
and more widely recognizable by people

not necessary, but somewhat neat:
PrintHelp(argv[0]) could print the exact name of the command that was used to
run the command (including the path), no need to maintain consistency with the
way we name the build target.

another very minor nit: the star ('*') is slightly harder to notice than '...',
so various *nix manuals use the syntax like:

tail [OPTION]... [FILE]...

[gabadie, 2016/03/16 18:09:16]

Done.

[pasko, 2016/03/16 18:30:59]

OK, the 2 out of 3 suggestions were not necessary, but your thoughts about why
not taking them would have been appreciated :)

[gabadie, 2016/03/17 18:13:17]

My bad. I have just completely forgotten them. 

+            << std::endl;
+  std::cout << "Decodes the stdin into the stdout using an encoding_type list "
+            << "given in arguments. This list is expected to be the Content-"
+            << "Encoding HTTP response header's value splitted by `,`."
+            << std::endl;
+}
+
+}  // namespace
+
+int main(int argc, char* argv[]) {
+  base::CommandLine::Init(argc, argv);
+  const base::CommandLine& command_line =
+      *base::CommandLine::ForCurrentProcess();
+
+  std::vector<std::string> encoding_type_names;
+#if defined(OS_WIN)
+  base::CommandLine::StringVector wide_args = command_line.GetArgs();
+  for (const auto& arg : wide_args) {
+    encoding_type_names.push_back(base::WideToUTF8(arg));
+  }
+#else
+  encoding_type_names = command_line.GetArgs();
+#endif
+
+  if (encoding_type_names.size() == 0) {
+    PrintHelp();
+    return 1;
+  }
+
+  std::vector<Filter::FilterType> encoding_types;
+  for (const auto& encoding_type_name : encoding_type_names) {
+    Filter::FilterType encode_type =

[pasko, 2016/03/16 12:05:53]

I think |filter_type| suits better as a name

[gabadie, 2016/03/16 18:09:17]

Done.

+        Filter::ConvertEncodingToType(encoding_type_name);
+    if (encode_type == Filter::FILTER_TYPE_UNSUPPORTED) {
+      std::cerr << "Unsupported decoder `" << encoding_type_name << "`."
+                << std::endl;
+      return 1;
+    }
+    encoding_types.push_back(encode_type);
+  }
+
+  net::MockFilterContext filter_context;
+  scoped_ptr<Filter> filter(Filter::Factory(encoding_types, filter_context));
+  if (!filter) {
+    std::cerr << "Couldn't create the decoder." << std::endl;
+    return 1;
+  }
+
+  net::IOBuffer* encode_buffer = filter->stream_buffer();
+  int encode_buffer_size = filter->stream_buffer_size();

[pasko, 2016/03/16 12:05:53]

I do not understand why the word 'encode' is used. There is no 'encode'
operation used here. So a more readable name would be 'encoded_buffer_size'.

I would actually prefer to name variables as suggested in documentation for
net/filter/filter.h:

pre_filter_data_len, post_filter_buf, post_filter_data_len, etc.

[gabadie, 2016/03/16 18:09:16]

Done.

+  while (std::cin) {
+    std::cin.read(encode_buffer->data(), encode_buffer_size);
+    int encode_read_size = std::cin.gcount();
+    filter->FlushStreamBuffer(encode_read_size);
+
+    while (true) {
+      int kDecodeBufferSize = 4096;
+      char decode_buffer[kDecodeBufferSize];
+      int decode_size = kDecodeBufferSize;
+      Filter::FilterStatus filter_status =
+          filter->ReadData(decode_buffer, &decode_size);
+      std::cout.write(decode_buffer, decode_size);
+      if (filter_status == Filter::FILTER_ERROR) {
+        std::cerr << "Couldn't decode stdin properly." << std::endl;

[pasko, 2016/03/16 12:05:53]

nit: s/ properly//

[gabadie, 2016/03/16 18:09:17]

Done.

+        return 1;
+      } else if (filter_status != Filter::FILTER_OK) {
+        break;
+      }
+    }
+  }
+
+  return 0;
+}