src/net/base/filter.cc - cobalt - Git at Google

 // Copyright (c) 2011 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/base/filter.h"

 #include "base/file_path.h"
 #include "base/string_util.h"
 #include "net/base/gzip_filter.h"
 #include "net/base/io_buffer.h"
 #include "net/base/mime_util.h"

 #if !defined(__LB_SHELL__) && !defined(COBALT)
 #include "net/base/sdch_filter.h"
 #else
 // LB_SHELL doesn't use SDCH. But sdch_filter includes
 // gurl.h which we do use.
 #include "googleurl/src/gurl.h"
 #endif

 namespace {

 // Filter types (using canonical lower case only):
 const char kDeflate[]      = "deflate";
 const char kGZip[]         = "gzip";
 const char kXGZip[]        = "x-gzip";
 const char kSdch[]         = "sdch";
 // compress and x-compress are currently not supported.  If we decide to support
 // them, we'll need the same mime type compatibility hack we have for gzip.  For
 // more information, see Firefox's nsHttpChannel::ProcessNormal.

 // Mime types:
 const char kApplicationXGzip[]     = "application/x-gzip";
 const char kApplicationGzip[]      = "application/gzip";
 const char kApplicationXGunzip[]   = "application/x-gunzip";
 #if !defined(__LB_SHELL__)
 const char kTextHtml[]             = "text/html";
 #endif
 // Buffer size allocated when de-compressing data.
 const int kFilterBufSize = 32 * 1024;

 }  // namespace

 namespace net {

 FilterContext::~FilterContext() {
 }

 Filter::~Filter() {}

 // static
 Filter* Filter::Factory(const std::vector<FilterType>& filter_types,
                         const FilterContext& filter_context) {
   if (filter_types.empty())
     return NULL;

   Filter* filter_list = NULL;  // Linked list of filters.
   for (size_t i = 0; i < filter_types.size(); i++) {
     filter_list = PrependNewFilter(filter_types[i], filter_context,
                                    kFilterBufSize, filter_list);
     if (!filter_list)
       return NULL;
   }
   return filter_list;
 }

 // static
 Filter* Filter::GZipFactory() {
   return InitGZipFilter(FILTER_TYPE_GZIP, kFilterBufSize);
 }

 // static
 Filter* Filter::FactoryForTests(const std::vector<FilterType>& filter_types,
                                 const FilterContext& filter_context,
                                 int buffer_size) {
   if (filter_types.empty())
     return NULL;

   Filter* filter_list = NULL;  // Linked list of filters.
   for (size_t i = 0; i < filter_types.size(); i++) {
     filter_list = PrependNewFilter(filter_types[i], filter_context,
                                    buffer_size, filter_list);
     if (!filter_list)
       return NULL;
   }
   return filter_list;
 }

 Filter::FilterStatus Filter::ReadData(char* dest_buffer, int* dest_len) {
   const int dest_buffer_capacity = *dest_len;
   if (last_status_ == FILTER_ERROR)
     return last_status_;
   if (!next_filter_.get())
     return last_status_ = ReadFilteredData(dest_buffer, dest_len);
   if (last_status_ == FILTER_NEED_MORE_DATA && !stream_data_len())
     return next_filter_->ReadData(dest_buffer, dest_len);

   do {
     if (next_filter_->last_status() == FILTER_NEED_MORE_DATA) {
       PushDataIntoNextFilter();
       if (FILTER_ERROR == last_status_)
         return FILTER_ERROR;
     }
     *dest_len = dest_buffer_capacity;  // Reset the input/output parameter.
     next_filter_->ReadData(dest_buffer, dest_len);
     if (FILTER_NEED_MORE_DATA == last_status_)
         return next_filter_->last_status();

     // In the case where this filter has data internally, and is indicating such
     // with a last_status_ of FILTER_OK, but at the same time the next filter in
     // the chain indicated it FILTER_NEED_MORE_DATA, we have to be cautious
     // about confusing the caller.  The API confusion can appear if we return
     // FILTER_OK (suggesting we have more data in aggregate), but yet we don't
     // populate our output buffer.  When that is the case, we need to
     // alternately call our filter element, and the next_filter element until we
     // get out of this state (by pumping data into the next filter until it
     // outputs data, or it runs out of data and reports that it NEED_MORE_DATA.)
   } while (FILTER_OK == last_status_ &&
            FILTER_NEED_MORE_DATA == next_filter_->last_status() &&
            0 == *dest_len);

   if (next_filter_->last_status() == FILTER_ERROR)
     return FILTER_ERROR;
   return FILTER_OK;
 }

 bool Filter::FlushStreamBuffer(int stream_data_len) {
   DCHECK_LE(stream_data_len, stream_buffer_size_);
   if (stream_data_len <= 0 || stream_data_len > stream_buffer_size_)
     return false;

   DCHECK(stream_buffer());
   // Bail out if there is more data in the stream buffer to be filtered.
   if (!stream_buffer() || stream_data_len_)
     return false;

   next_stream_data_ = stream_buffer()->data();
   stream_data_len_ = stream_data_len;
   return true;
 }

 // static
 Filter::FilterType Filter::ConvertEncodingToType(
     const std::string& filter_type) {
   FilterType type_id;
   if (LowerCaseEqualsASCII(filter_type, kDeflate)) {
     type_id = FILTER_TYPE_DEFLATE;
   } else if (LowerCaseEqualsASCII(filter_type, kGZip) ||
              LowerCaseEqualsASCII(filter_type, kXGZip)) {
     type_id = FILTER_TYPE_GZIP;
   } else if (LowerCaseEqualsASCII(filter_type, kSdch)) {
     type_id = FILTER_TYPE_SDCH;
   } else {
     // Note we also consider "identity" and "uncompressed" UNSUPPORTED as
     // filter should be disabled in such cases.
     type_id = FILTER_TYPE_UNSUPPORTED;
   }
   return type_id;
 }

 // static
 void Filter::FixupEncodingTypes(
     const FilterContext& filter_context,
     std::vector<FilterType>* encoding_types) {
   std::string mime_type;
   bool success = filter_context.GetMimeType(&mime_type);
   DCHECK(success || mime_type.empty());

   if ((1 == encoding_types->size()) &&
       (FILTER_TYPE_GZIP == encoding_types->front())) {
     if (LowerCaseEqualsASCII(mime_type, kApplicationXGzip) ||
         LowerCaseEqualsASCII(mime_type, kApplicationGzip) ||
         LowerCaseEqualsASCII(mime_type, kApplicationXGunzip))
       // The server has told us that it sent us gziped content with a gzip
       // content encoding.  Sadly, Apache mistakenly sets these headers for all
       // .gz files.  We match Firefox's nsHttpChannel::ProcessNormal and ignore
       // the Content-Encoding here.
       encoding_types->clear();

     GURL url;
     success = filter_context.GetURL(&url);
     DCHECK(success);
     FilePath filename = FilePath().AppendASCII(url.ExtractFileName());
     FilePath::StringType extension = filename.Extension();

     if (filter_context.IsDownload()) {
       // We don't want to decompress gzipped files when the user explicitly
       // asks to download them.
       // For the case of svgz files, we use the extension to distinguish
       // between svgz files and svg files compressed with gzip by the server.
       // When viewing a .svgz file, we need to uncompress it, but we don't
       // want to do that when downloading.
       // See Firefox's nonDecodableExtensions in nsExternalHelperAppService.cpp
       if (EndsWith(extension, FILE_PATH_LITERAL(".gz"), false) ||
           LowerCaseEqualsASCII(extension, ".tgz") ||
           LowerCaseEqualsASCII(extension, ".svgz"))
         encoding_types->clear();
     } else {
       // When the user does not explicitly ask to download a file, if we get a
       // supported mime type, then we attempt to decompress in order to view it.
       // However, if it's not a supported mime type, then we will attempt to
       // download it, and in that case, don't decompress .gz/.tgz files.
       if ((EndsWith(extension, FILE_PATH_LITERAL(".gz"), false) ||
            LowerCaseEqualsASCII(extension, ".tgz")) &&
           !IsSupportedMimeType(mime_type))
         encoding_types->clear();
     }
   }

 #if !defined(__LB_SHELL__) && !defined(COBALT)
   // If the request was for SDCH content, then we might need additional fixups.
   if (!filter_context.IsSdchResponse()) {
     // It was not an SDCH request, so we'll just record stats.
     if (1 < encoding_types->size()) {
       // Multiple filters were intended to only be used for SDCH (thus far!)
       SdchManager::SdchErrorRecovery(
           SdchManager::MULTIENCODING_FOR_NON_SDCH_REQUEST);
     }
     if ((1 == encoding_types->size()) &&
         (FILTER_TYPE_SDCH == encoding_types->front())) {
         SdchManager::SdchErrorRecovery(
             SdchManager::SDCH_CONTENT_ENCODE_FOR_NON_SDCH_REQUEST);
     }
     return;
   }

   // The request was tagged as an SDCH request, which means the server supplied
   // a dictionary, and we advertised it in the request.  Some proxies will do
   // very strange things to the request, or the response, so we have to handle
   // them gracefully.

   // If content encoding included SDCH, then everything is "relatively" fine.
   if (!encoding_types->empty() &&
       (FILTER_TYPE_SDCH == encoding_types->front())) {
     // Some proxies (found currently in Argentina) strip the Content-Encoding
     // text from "sdch,gzip" to a mere "sdch" without modifying the compressed
     // payload.   To handle this gracefully, we simulate the "probably" deleted
     // ",gzip" by appending a tentative gzip decode, which will default to a
     // no-op pass through filter if it doesn't get gzip headers where expected.
     if (1 == encoding_types->size()) {
       encoding_types->push_back(FILTER_TYPE_GZIP_HELPING_SDCH);
       SdchManager::SdchErrorRecovery(
           SdchManager::OPTIONAL_GUNZIP_ENCODING_ADDED);
     }
     return;
   }

   // There are now several cases to handle for an SDCH request.  Foremost, if
   // the outbound request was stripped so as not to advertise support for
   // encodings, we might get back content with no encoding, or (for example)
   // just gzip.  We have to be sure that any changes we make allow for such
   // minimal coding to work.  That issue is why we use TENTATIVE filters if we
   // add any, as those filters sniff the content, and act as pass-through
   // filters if headers are not found.

   // If the outbound GET is not modified, then the server will generally try to
   // send us SDCH encoded content.  As that content returns, there are several
   // corruptions of the header "content-encoding" that proxies may perform (and
   // have been detected in the wild).  We already dealt with the a honest
   // content encoding of "sdch,gzip" being corrupted into "sdch" with on change
   // of the actual content.  Another common corruption is to either disscard
   // the accurate content encoding, or to replace it with gzip only (again, with
   // no change in actual content). The last observed corruption it to actually
   // change the content, such as by re-gzipping it, and that may happen along
   // with corruption of the stated content encoding (wow!).

   // The one unresolved failure mode comes when we advertise a dictionary, and
   // the server tries to *send* a gzipped file (not gzip encode content), and
   // then we could do a gzip decode :-(. Since SDCH is only (currently)
   // supported server side on paths that only send HTML content, this mode has
   // never surfaced in the wild (and is unlikely to).
   // We will gather a lot of stats as we perform the fixups
   if (StartsWithASCII(mime_type, kTextHtml, false)) {
     // Suspicious case: Advertised dictionary, but server didn't use sdch, and
     // we're HTML tagged.
     if (encoding_types->empty()) {
       SdchManager::SdchErrorRecovery(
           SdchManager::ADDED_CONTENT_ENCODING);
     } else if (1 == encoding_types->size()) {
       SdchManager::SdchErrorRecovery(
           SdchManager::FIXED_CONTENT_ENCODING);
     } else {
       SdchManager::SdchErrorRecovery(
           SdchManager::FIXED_CONTENT_ENCODINGS);
     }
   } else {
     // Remarkable case!?!  We advertised an SDCH dictionary, content-encoding
     // was not marked for SDCH processing: Why did the server suggest an SDCH
     // dictionary in the first place??.  Also, the content isn't
     // tagged as HTML, despite the fact that SDCH encoding is mostly likely for
     // HTML: Did some anti-virus system strip this tag (sometimes they strip
     // accept-encoding headers on the request)??  Does the content encoding not
     // start with "text/html" for some other reason??  We'll report this as a
     // fixup to a binary file, but it probably really is text/html (some how).
     if (encoding_types->empty()) {
       SdchManager::SdchErrorRecovery(
           SdchManager::BINARY_ADDED_CONTENT_ENCODING);
     } else if (1 == encoding_types->size()) {
       SdchManager::SdchErrorRecovery(
           SdchManager::BINARY_FIXED_CONTENT_ENCODING);
     } else {
       SdchManager::SdchErrorRecovery(
           SdchManager::BINARY_FIXED_CONTENT_ENCODINGS);
     }
   }

   // Leave the existing encoding type to be processed first, and add our
   // tentative decodings to be done afterwards.  Vodaphone UK reportedyl will
   // perform a second layer of gzip encoding atop the server's sdch,gzip
   // encoding, and then claim that the content encoding is a mere gzip.  As a
   // result we'll need (in that case) to do the gunzip, plus our tentative
   // gunzip and tentative SDCH decoding.
   // This approach nicely handles the empty() list as well, and should work with
   // other (as yet undiscovered) proxies the choose to re-compressed with some
   // other encoding (such as bzip2, etc.).
   encoding_types->insert(encoding_types->begin(),
                          FILTER_TYPE_GZIP_HELPING_SDCH);
   encoding_types->insert(encoding_types->begin(), FILTER_TYPE_SDCH_POSSIBLE);
 #endif
   return;
 }

 Filter::Filter()
     : stream_buffer_(NULL),
       stream_buffer_size_(0),
       next_stream_data_(NULL),
       stream_data_len_(0),
       next_filter_(NULL),
       last_status_(FILTER_NEED_MORE_DATA) {
 }

 Filter::FilterStatus Filter::CopyOut(char* dest_buffer, int* dest_len) {
   int out_len;
   int input_len = *dest_len;
   *dest_len = 0;

   if (0 == stream_data_len_)
     return Filter::FILTER_NEED_MORE_DATA;

   out_len = std::min(input_len, stream_data_len_);
   memcpy(dest_buffer, next_stream_data_, out_len);
   *dest_len += out_len;
   stream_data_len_ -= out_len;
   if (0 == stream_data_len_) {
     next_stream_data_ = NULL;
     return Filter::FILTER_NEED_MORE_DATA;
   } else {
     next_stream_data_ += out_len;
     return Filter::FILTER_OK;
   }
 }

 // static
 Filter* Filter::InitGZipFilter(FilterType type_id, int buffer_size) {
   scoped_ptr<GZipFilter> gz_filter(new GZipFilter());
   gz_filter->InitBuffer(buffer_size);
   return gz_filter->InitDecoding(type_id) ? gz_filter.release() : NULL;
 }

 #if !defined(__LB_SHELL__) && !defined(COBALT)
 // static
 Filter* Filter::InitSdchFilter(FilterType type_id,
                                const FilterContext& filter_context,
                                int buffer_size) {
   scoped_ptr<SdchFilter> sdch_filter(new SdchFilter(filter_context));
   sdch_filter->InitBuffer(buffer_size);
   return sdch_filter->InitDecoding(type_id) ? sdch_filter.release() : NULL;
 }
 #endif

 // static
 Filter* Filter::PrependNewFilter(FilterType type_id,
                                  const FilterContext& filter_context,
                                  int buffer_size,
                                  Filter* filter_list) {
   scoped_ptr<Filter> first_filter;  // Soon to be start of chain.
   switch (type_id) {
     case FILTER_TYPE_GZIP_HELPING_SDCH:
     case FILTER_TYPE_DEFLATE:
     case FILTER_TYPE_GZIP:
       first_filter.reset(InitGZipFilter(type_id, buffer_size));
       break;
 #if !defined(__LB_SHELL__) && !defined(COBALT)
     case FILTER_TYPE_SDCH:
     case FILTER_TYPE_SDCH_POSSIBLE:
       first_filter.reset(InitSdchFilter(type_id, filter_context, buffer_size));
       break;
 #endif
     default:
       break;
   }

   if (!first_filter.get())
     return NULL;

   first_filter->next_filter_.reset(filter_list);
   return first_filter.release();
 }

 void Filter::InitBuffer(int buffer_size) {
   DCHECK(!stream_buffer());
   DCHECK_GT(buffer_size, 0);
   stream_buffer_ = new IOBuffer(buffer_size);
   stream_buffer_size_ = buffer_size;
 }

 void Filter::PushDataIntoNextFilter() {
   IOBuffer* next_buffer = next_filter_->stream_buffer();
   int next_size = next_filter_->stream_buffer_size();
   last_status_ = ReadFilteredData(next_buffer->data(), &next_size);
   if (FILTER_ERROR != last_status_)
     next_filter_->FlushStreamBuffer(next_size);
 }

 }  // namespace net
	// Copyright (c) 2011 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/base/filter.h"

	#include "base/file_path.h"
	#include "base/string_util.h"
	#include "net/base/gzip_filter.h"
	#include "net/base/io_buffer.h"
	#include "net/base/mime_util.h"

	#if !defined(__LB_SHELL__) && !defined(COBALT)
	#include "net/base/sdch_filter.h"
	#else
	// LB_SHELL doesn't use SDCH. But sdch_filter includes
	// gurl.h which we do use.
	#include "googleurl/src/gurl.h"
	#endif

	namespace {

	// Filter types (using canonical lower case only):
	const char kDeflate[] = "deflate";
	const char kGZip[] = "gzip";
	const char kXGZip[] = "x-gzip";
	const char kSdch[] = "sdch";
	// compress and x-compress are currently not supported. If we decide to support
	// them, we'll need the same mime type compatibility hack we have for gzip. For
	// more information, see Firefox's nsHttpChannel::ProcessNormal.

	// Mime types:
	const char kApplicationXGzip[] = "application/x-gzip";
	const char kApplicationGzip[] = "application/gzip";
	const char kApplicationXGunzip[] = "application/x-gunzip";
	#if !defined(__LB_SHELL__)
	const char kTextHtml[] = "text/html";
	#endif
	// Buffer size allocated when de-compressing data.
	const int kFilterBufSize = 32 * 1024;

	} // namespace

	namespace net {

	FilterContext::~FilterContext() {
	}

	Filter::~Filter() {}

	// static
	Filter* Filter::Factory(const std::vector<FilterType>& filter_types,
	const FilterContext& filter_context) {
	if (filter_types.empty())
	return NULL;

	Filter* filter_list = NULL; // Linked list of filters.
	for (size_t i = 0; i < filter_types.size(); i++) {
	filter_list = PrependNewFilter(filter_types[i], filter_context,
	kFilterBufSize, filter_list);
	if (!filter_list)
	return NULL;
	}
	return filter_list;
	}

	// static
	Filter* Filter::GZipFactory() {
	return InitGZipFilter(FILTER_TYPE_GZIP, kFilterBufSize);
	}

	// static
	Filter* Filter::FactoryForTests(const std::vector<FilterType>& filter_types,
	const FilterContext& filter_context,
	int buffer_size) {
	if (filter_types.empty())
	return NULL;

	Filter* filter_list = NULL; // Linked list of filters.
	for (size_t i = 0; i < filter_types.size(); i++) {
	filter_list = PrependNewFilter(filter_types[i], filter_context,
	buffer_size, filter_list);
	if (!filter_list)
	return NULL;
	}
	return filter_list;
	}

	Filter::FilterStatus Filter::ReadData(char* dest_buffer, int* dest_len) {
	const int dest_buffer_capacity = *dest_len;
	if (last_status_ == FILTER_ERROR)
	return last_status_;
	if (!next_filter_.get())
	return last_status_ = ReadFilteredData(dest_buffer, dest_len);
	if (last_status_ == FILTER_NEED_MORE_DATA && !stream_data_len())
	return next_filter_->ReadData(dest_buffer, dest_len);

	do {
	if (next_filter_->last_status() == FILTER_NEED_MORE_DATA) {
	PushDataIntoNextFilter();
	if (FILTER_ERROR == last_status_)
	return FILTER_ERROR;
	}
	*dest_len = dest_buffer_capacity; // Reset the input/output parameter.
	next_filter_->ReadData(dest_buffer, dest_len);
	if (FILTER_NEED_MORE_DATA == last_status_)
	return next_filter_->last_status();

	// In the case where this filter has data internally, and is indicating such
	// with a last_status_ of FILTER_OK, but at the same time the next filter in
	// the chain indicated it FILTER_NEED_MORE_DATA, we have to be cautious
	// about confusing the caller. The API confusion can appear if we return
	// FILTER_OK (suggesting we have more data in aggregate), but yet we don't
	// populate our output buffer. When that is the case, we need to
	// alternately call our filter element, and the next_filter element until we
	// get out of this state (by pumping data into the next filter until it
	// outputs data, or it runs out of data and reports that it NEED_MORE_DATA.)
	} while (FILTER_OK == last_status_ &&
	FILTER_NEED_MORE_DATA == next_filter_->last_status() &&
	0 == *dest_len);

	if (next_filter_->last_status() == FILTER_ERROR)
	return FILTER_ERROR;
	return FILTER_OK;
	}

	bool Filter::FlushStreamBuffer(int stream_data_len) {
	DCHECK_LE(stream_data_len, stream_buffer_size_);
	if (stream_data_len <= 0 \|\| stream_data_len > stream_buffer_size_)
	return false;

	DCHECK(stream_buffer());
	// Bail out if there is more data in the stream buffer to be filtered.
	if (!stream_buffer() \|\| stream_data_len_)
	return false;

	next_stream_data_ = stream_buffer()->data();
	stream_data_len_ = stream_data_len;
	return true;
	}

	// static
	Filter::FilterType Filter::ConvertEncodingToType(
	const std::string& filter_type) {
	FilterType type_id;
	if (LowerCaseEqualsASCII(filter_type, kDeflate)) {
	type_id = FILTER_TYPE_DEFLATE;
	} else if (LowerCaseEqualsASCII(filter_type, kGZip) \|\|
	LowerCaseEqualsASCII(filter_type, kXGZip)) {
	type_id = FILTER_TYPE_GZIP;
	} else if (LowerCaseEqualsASCII(filter_type, kSdch)) {
	type_id = FILTER_TYPE_SDCH;
	} else {
	// Note we also consider "identity" and "uncompressed" UNSUPPORTED as
	// filter should be disabled in such cases.
	type_id = FILTER_TYPE_UNSUPPORTED;
	}
	return type_id;
	}

	// static
	void Filter::FixupEncodingTypes(
	const FilterContext& filter_context,
	std::vector<FilterType>* encoding_types) {
	std::string mime_type;
	bool success = filter_context.GetMimeType(&mime_type);
	DCHECK(success \|\| mime_type.empty());

	if ((1 == encoding_types->size()) &&
	(FILTER_TYPE_GZIP == encoding_types->front())) {
	if (LowerCaseEqualsASCII(mime_type, kApplicationXGzip) \|\|
	LowerCaseEqualsASCII(mime_type, kApplicationGzip) \|\|
	LowerCaseEqualsASCII(mime_type, kApplicationXGunzip))
	// The server has told us that it sent us gziped content with a gzip
	// content encoding. Sadly, Apache mistakenly sets these headers for all
	// .gz files. We match Firefox's nsHttpChannel::ProcessNormal and ignore
	// the Content-Encoding here.
	encoding_types->clear();

	GURL url;
	success = filter_context.GetURL(&url);
	DCHECK(success);
	FilePath filename = FilePath().AppendASCII(url.ExtractFileName());
	FilePath::StringType extension = filename.Extension();

	if (filter_context.IsDownload()) {
	// We don't want to decompress gzipped files when the user explicitly
	// asks to download them.
	// For the case of svgz files, we use the extension to distinguish
	// between svgz files and svg files compressed with gzip by the server.
	// When viewing a .svgz file, we need to uncompress it, but we don't
	// want to do that when downloading.
	// See Firefox's nonDecodableExtensions in nsExternalHelperAppService.cpp
	if (EndsWith(extension, FILE_PATH_LITERAL(".gz"), false) \|\|
	LowerCaseEqualsASCII(extension, ".tgz") \|\|
	LowerCaseEqualsASCII(extension, ".svgz"))
	encoding_types->clear();
	} else {
	// When the user does not explicitly ask to download a file, if we get a
	// supported mime type, then we attempt to decompress in order to view it.
	// However, if it's not a supported mime type, then we will attempt to
	// download it, and in that case, don't decompress .gz/.tgz files.
	if ((EndsWith(extension, FILE_PATH_LITERAL(".gz"), false) \|\|
	LowerCaseEqualsASCII(extension, ".tgz")) &&
	!IsSupportedMimeType(mime_type))
	encoding_types->clear();
	}
	}

	#if !defined(__LB_SHELL__) && !defined(COBALT)
	// If the request was for SDCH content, then we might need additional fixups.
	if (!filter_context.IsSdchResponse()) {
	// It was not an SDCH request, so we'll just record stats.
	if (1 < encoding_types->size()) {
	// Multiple filters were intended to only be used for SDCH (thus far!)
	SdchManager::SdchErrorRecovery(
	SdchManager::MULTIENCODING_FOR_NON_SDCH_REQUEST);
	}
	if ((1 == encoding_types->size()) &&
	(FILTER_TYPE_SDCH == encoding_types->front())) {
	SdchManager::SdchErrorRecovery(
	SdchManager::SDCH_CONTENT_ENCODE_FOR_NON_SDCH_REQUEST);
	}
	return;
	}

	// The request was tagged as an SDCH request, which means the server supplied
	// a dictionary, and we advertised it in the request. Some proxies will do
	// very strange things to the request, or the response, so we have to handle
	// them gracefully.

	// If content encoding included SDCH, then everything is "relatively" fine.
	if (!encoding_types->empty() &&
	(FILTER_TYPE_SDCH == encoding_types->front())) {
	// Some proxies (found currently in Argentina) strip the Content-Encoding
	// text from "sdch,gzip" to a mere "sdch" without modifying the compressed
	// payload. To handle this gracefully, we simulate the "probably" deleted
	// ",gzip" by appending a tentative gzip decode, which will default to a
	// no-op pass through filter if it doesn't get gzip headers where expected.
	if (1 == encoding_types->size()) {
	encoding_types->push_back(FILTER_TYPE_GZIP_HELPING_SDCH);
	SdchManager::SdchErrorRecovery(
	SdchManager::OPTIONAL_GUNZIP_ENCODING_ADDED);
	}
	return;
	}

	// There are now several cases to handle for an SDCH request. Foremost, if
	// the outbound request was stripped so as not to advertise support for
	// encodings, we might get back content with no encoding, or (for example)
	// just gzip. We have to be sure that any changes we make allow for such
	// minimal coding to work. That issue is why we use TENTATIVE filters if we
	// add any, as those filters sniff the content, and act as pass-through
	// filters if headers are not found.

	// If the outbound GET is not modified, then the server will generally try to
	// send us SDCH encoded content. As that content returns, there are several
	// corruptions of the header "content-encoding" that proxies may perform (and
	// have been detected in the wild). We already dealt with the a honest
	// content encoding of "sdch,gzip" being corrupted into "sdch" with on change
	// of the actual content. Another common corruption is to either disscard
	// the accurate content encoding, or to replace it with gzip only (again, with
	// no change in actual content). The last observed corruption it to actually
	// change the content, such as by re-gzipping it, and that may happen along
	// with corruption of the stated content encoding (wow!).

	// The one unresolved failure mode comes when we advertise a dictionary, and
	// the server tries to send a gzipped file (not gzip encode content), and
	// then we could do a gzip decode :-(. Since SDCH is only (currently)
	// supported server side on paths that only send HTML content, this mode has
	// never surfaced in the wild (and is unlikely to).
	// We will gather a lot of stats as we perform the fixups
	if (StartsWithASCII(mime_type, kTextHtml, false)) {
	// Suspicious case: Advertised dictionary, but server didn't use sdch, and
	// we're HTML tagged.
	if (encoding_types->empty()) {
	SdchManager::SdchErrorRecovery(
	SdchManager::ADDED_CONTENT_ENCODING);
	} else if (1 == encoding_types->size()) {
	SdchManager::SdchErrorRecovery(
	SdchManager::FIXED_CONTENT_ENCODING);
	} else {
	SdchManager::SdchErrorRecovery(
	SdchManager::FIXED_CONTENT_ENCODINGS);
	}
	} else {
	// Remarkable case!?! We advertised an SDCH dictionary, content-encoding
	// was not marked for SDCH processing: Why did the server suggest an SDCH
	// dictionary in the first place??. Also, the content isn't
	// tagged as HTML, despite the fact that SDCH encoding is mostly likely for
	// HTML: Did some anti-virus system strip this tag (sometimes they strip
	// accept-encoding headers on the request)?? Does the content encoding not
	// start with "text/html" for some other reason?? We'll report this as a
	// fixup to a binary file, but it probably really is text/html (some how).
	if (encoding_types->empty()) {
	SdchManager::SdchErrorRecovery(
	SdchManager::BINARY_ADDED_CONTENT_ENCODING);
	} else if (1 == encoding_types->size()) {
	SdchManager::SdchErrorRecovery(
	SdchManager::BINARY_FIXED_CONTENT_ENCODING);
	} else {
	SdchManager::SdchErrorRecovery(
	SdchManager::BINARY_FIXED_CONTENT_ENCODINGS);
	}
	}

	// Leave the existing encoding type to be processed first, and add our
	// tentative decodings to be done afterwards. Vodaphone UK reportedyl will
	// perform a second layer of gzip encoding atop the server's sdch,gzip
	// encoding, and then claim that the content encoding is a mere gzip. As a
	// result we'll need (in that case) to do the gunzip, plus our tentative
	// gunzip and tentative SDCH decoding.
	// This approach nicely handles the empty() list as well, and should work with
	// other (as yet undiscovered) proxies the choose to re-compressed with some
	// other encoding (such as bzip2, etc.).
	encoding_types->insert(encoding_types->begin(),
	FILTER_TYPE_GZIP_HELPING_SDCH);
	encoding_types->insert(encoding_types->begin(), FILTER_TYPE_SDCH_POSSIBLE);
	#endif
	return;
	}

	Filter::Filter()
	: stream_buffer_(NULL),
	stream_buffer_size_(0),
	next_stream_data_(NULL),
	stream_data_len_(0),
	next_filter_(NULL),
	last_status_(FILTER_NEED_MORE_DATA) {
	}

	Filter::FilterStatus Filter::CopyOut(char* dest_buffer, int* dest_len) {
	int out_len;
	int input_len = *dest_len;
	*dest_len = 0;

	if (0 == stream_data_len_)
	return Filter::FILTER_NEED_MORE_DATA;

	out_len = std::min(input_len, stream_data_len_);
	memcpy(dest_buffer, next_stream_data_, out_len);
	*dest_len += out_len;
	stream_data_len_ -= out_len;
	if (0 == stream_data_len_) {
	next_stream_data_ = NULL;
	return Filter::FILTER_NEED_MORE_DATA;
	} else {
	next_stream_data_ += out_len;
	return Filter::FILTER_OK;
	}
	}

	// static
	Filter* Filter::InitGZipFilter(FilterType type_id, int buffer_size) {
	scoped_ptr<GZipFilter> gz_filter(new GZipFilter());
	gz_filter->InitBuffer(buffer_size);
	return gz_filter->InitDecoding(type_id) ? gz_filter.release() : NULL;
	}

	#if !defined(__LB_SHELL__) && !defined(COBALT)
	// static
	Filter* Filter::InitSdchFilter(FilterType type_id,
	const FilterContext& filter_context,
	int buffer_size) {
	scoped_ptr<SdchFilter> sdch_filter(new SdchFilter(filter_context));
	sdch_filter->InitBuffer(buffer_size);
	return sdch_filter->InitDecoding(type_id) ? sdch_filter.release() : NULL;
	}
	#endif

	// static
	Filter* Filter::PrependNewFilter(FilterType type_id,
	const FilterContext& filter_context,
	int buffer_size,
	Filter* filter_list) {
	scoped_ptr<Filter> first_filter; // Soon to be start of chain.
	switch (type_id) {
	case FILTER_TYPE_GZIP_HELPING_SDCH:
	case FILTER_TYPE_DEFLATE:
	case FILTER_TYPE_GZIP:
	first_filter.reset(InitGZipFilter(type_id, buffer_size));
	break;
	#if !defined(__LB_SHELL__) && !defined(COBALT)
	case FILTER_TYPE_SDCH:
	case FILTER_TYPE_SDCH_POSSIBLE:
	first_filter.reset(InitSdchFilter(type_id, filter_context, buffer_size));
	break;
	#endif
	default:
	break;
	}

	if (!first_filter.get())
	return NULL;

	first_filter->next_filter_.reset(filter_list);
	return first_filter.release();
	}

	void Filter::InitBuffer(int buffer_size) {
	DCHECK(!stream_buffer());
	DCHECK_GT(buffer_size, 0);
	stream_buffer_ = new IOBuffer(buffer_size);
	stream_buffer_size_ = buffer_size;
	}

	void Filter::PushDataIntoNextFilter() {
	IOBuffer* next_buffer = next_filter_->stream_buffer();
	int next_size = next_filter_->stream_buffer_size();
	last_status_ = ReadFilteredData(next_buffer->data(), &next_size);
	if (FILTER_ERROR != last_status_)
	next_filter_->FlushStreamBuffer(next_size);
	}

	} // namespace net