Improve linearized pdf load/show time.

pdf/document_loader.cc

 // Copyright (c) 2010 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 "pdf/document_loader.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
+#include <algorithm>
+
 #include "base/logging.h"
 #include "base/strings/string_util.h"
-#include "net/http/http_util.h"
+#include "pdf/url_loader_wrapper.h"
 #include "ppapi/c/pp_errors.h"
-#include "ppapi/cpp/url_loader.h"
-#include "ppapi/cpp/url_request_info.h"
-#include "ppapi/cpp/url_response_info.h"
+#include "ui/gfx/range/range.h"
 
 namespace chrome_pdf {
 
 namespace {
 
-// If the headers have a byte-range response, writes the start and end
-// positions and returns true if at least the start position was parsed.
-// The end position will be set to 0 if it was not found or parsed from the
-// response.
-// Returns false if not even a start position could be parsed.
-bool GetByteRange(const std::string& headers, uint32_t* start, uint32_t* end) {
-  net::HttpUtil::HeadersIterator it(headers.begin(), headers.end(), "\n");
-  while (it.GetNext()) {
-    if (base::LowerCaseEqualsASCII(it.name(), "content-range")) {
-      std::string range = it.values().c_str();
-      if (base::StartsWith(range, "bytes",
-                           base::CompareCase::INSENSITIVE_ASCII)) {
-        range = range.substr(strlen("bytes"));
-        std::string::size_type pos = range.find('-');
-        std::string range_end;
-        if (pos != std::string::npos)
-          range_end = range.substr(pos + 1);
-        base::TrimWhitespaceASCII(range, base::TRIM_LEADING, &range);
-        base::TrimWhitespaceASCII(range_end, base::TRIM_LEADING, &range_end);
-        *start = atoi(range.c_str());
-        *end = atoi(range_end.c_str());
-        return true;
-      }
-    }
-  }
-  return false;
-}
-
-// If the headers have a multi-part response, returns the boundary name.
-// Otherwise returns an empty string.
-std::string GetMultiPartBoundary(const std::string& headers) {
-  net::HttpUtil::HeadersIterator it(headers.begin(), headers.end(), "\n");
-  while (it.GetNext()) {
-    if (base::LowerCaseEqualsASCII(it.name(), "content-type")) {
-      std::string type = base::ToLowerASCII(it.values());
-      if (base::StartsWith(type, "multipart/", base::CompareCase::SENSITIVE)) {
-        const char* boundary = strstr(type.c_str(), "boundary=");
-        if (!boundary) {
-          NOTREACHED();
-          break;
-        }
-
-        return std::string(boundary + 9);
-      }
-    }
-  }
-  return std::string();
-}
+// The distance from last received chunk, when we wait requestings data, using

[Lei Zhang, 2016/10/25 06:01:49]

typos: s/requestings/requesting/ here and I'm not sure what "type plaing" is
suppose to mean on the next line.

[snake, 2016/10/25 13:57:34]

Done.

+// current connection (like type plaing) and do not send new range request.
+// Experimentally chosen value.
+const int kChunkCloseDistance = 10;
 
 bool IsValidContentType(const std::string& type) {
   return (base::EndsWith(type, "/pdf", base::CompareCase::INSENSITIVE_ASCII) ||
           base::EndsWith(type, ".pdf", base::CompareCase::INSENSITIVE_ASCII) ||
           base::EndsWith(type, "/x-pdf",
                          base::CompareCase::INSENSITIVE_ASCII) ||
           base::EndsWith(type, "/*", base::CompareCase::INSENSITIVE_ASCII) ||
           base::EndsWith(type, "/acrobat",
                          base::CompareCase::INSENSITIVE_ASCII) ||
           base::EndsWith(type, "/unknown",
                          base::CompareCase::INSENSITIVE_ASCII));
 }
 
 }  // namespace
 
 DocumentLoader::Client::~Client() {
 }
 
+DocumentLoader::Chunk::Chunk() {}
+
+DocumentLoader::Chunk::~Chunk() {}
+
+void DocumentLoader::Chunk::Clear() {
+  chunk_index = 0;
+  data_size = 0;
+  chunk_data.reset();
+}
+
 DocumentLoader::DocumentLoader(Client* client)
-    : client_(client), partial_document_(false), request_pending_(false),
-      current_pos_(0), current_chunk_size_(0), current_chunk_read_(0),
-      document_size_(0), header_request_(true), is_multipart_(false) {
-  loader_factory_.Initialize(this);
-}
+    : client_(client), loader_factory_(this) {}
 
 DocumentLoader::~DocumentLoader() {
 }
 
-bool DocumentLoader::Init(const pp::URLLoader& loader,
-                          const std::string& url,
-                          const std::string& headers) {
+bool DocumentLoader::Init(std::unique_ptr<URLLoaderWrapper> loader,
+                          const std::string& url) {
   DCHECK(url_.empty());
-  url_ = url;
-  loader_ = loader;
+  DCHECK(!loader_);
 
-  std::string response_headers;
-  if (!headers.empty()) {
-    response_headers = headers;
-  } else {
-    pp::URLResponseInfo response = loader_.GetResponseInfo();
-    pp::Var headers_var = response.GetHeaders();
-
-    if (headers_var.is_string()) {
-      response_headers = headers_var.AsString();
-    }
-  }
-
-  bool accept_ranges_bytes = false;
-  bool content_encoded = false;
-  uint32_t content_length = 0;
-  std::string type;
-  std::string disposition;
+  std::string type = loader->GetContentType();
 
   // This happens for PDFs not loaded from http(s) sources.
-  if (response_headers == "Content-Type: text/plain") {
+  if (type == "text/plain") {
     if (!base::StartsWith(url, "http://",
                           base::CompareCase::INSENSITIVE_ASCII) &&
         !base::StartsWith(url, "https://",
                           base::CompareCase::INSENSITIVE_ASCII)) {
       type = "application/pdf";
     }
   }
-  if (type.empty() && !response_headers.empty()) {
-    net::HttpUtil::HeadersIterator it(response_headers.begin(),
-                                      response_headers.end(), "\n");
-    while (it.GetNext()) {
-      if (base::LowerCaseEqualsASCII(it.name(), "content-length")) {
-        content_length = atoi(it.values().c_str());
-      } else if (base::LowerCaseEqualsASCII(it.name(), "accept-ranges")) {
-        accept_ranges_bytes = base::LowerCaseEqualsASCII(it.values(), "bytes");
-      } else if (base::LowerCaseEqualsASCII(it.name(), "content-encoding")) {
-        content_encoded = true;
-      } else if (base::LowerCaseEqualsASCII(it.name(), "content-type")) {
-        type = it.values();
-        size_t semi_colon_pos = type.find(';');
-        if (semi_colon_pos != std::string::npos) {
-          type = type.substr(0, semi_colon_pos);
-        }
-        TrimWhitespaceASCII(type, base::TRIM_ALL, &type);
-      } else if (base::LowerCaseEqualsASCII(it.name(), "content-disposition")) {
-        disposition = it.values();
-      }
-    }
-  }
   if (!type.empty() && !IsValidContentType(type))
     return false;
-  if (base::StartsWith(disposition, "attachment",
+
+  if (base::StartsWith(loader->GetContentDisposition(), "attachment",
                        base::CompareCase::INSENSITIVE_ASCII))
     return false;
 
-  if (content_length > 0)
-    chunk_stream_.Preallocate(content_length);
+  url_ = url;
+  loader_ = std::move(loader);
 
-  document_size_ = content_length;
-  requests_count_ = 0;
+  if (!loader_->IsContentEncoded()) {
+    chunk_stream_.set_eof_pos(std::max(0, loader_->GetContentLength()));
+  }
+  int64_t bytes_received = 0;
+  int64_t total_bytes_to_be_received = 0;
+  if (!chunk_stream_.eof_pos() &&
+      loader_->GetDownloadProgress(&bytes_received,
+                                   &total_bytes_to_be_received)) {
+    chunk_stream_.set_eof_pos(
+        std::max(0, static_cast<int>(total_bytes_to_be_received)));
+  }
 
-  // Enable partial loading only if file size is above the threshold.
-  // It will allow avoiding latency for multiple requests.
-  if (content_length > kMinFileSize &&
-      accept_ranges_bytes &&
-      !content_encoded) {
-    LoadPartialDocument();
-  } else {
-    LoadFullDocument();
-  }
+  SetPartialLoadingEnabled(
+      partial_loading_enabled_ &&
+      !base::StartsWith(url, "file://", base::CompareCase::INSENSITIVE_ASCII) &&
+      loader_->IsAcceptRangesBytes() && !loader_->IsContentEncoded() &&
+      GetDocumentSize());
+
+  ReadMore();
   return true;
 }
 
-void DocumentLoader::LoadPartialDocument() {
-  // The current request is a full request (not a range request) so it starts at
-  // 0 and ends at |document_size_|.
-  current_chunk_size_ = document_size_;
-  current_pos_ = 0;
-  current_request_offset_ = 0;
-  current_request_size_ = 0;
-  current_request_extended_size_ = document_size_;
-  request_pending_ = true;
-
-  partial_document_ = true;
-  header_request_ = true;
-  ReadMore();
+bool DocumentLoader::IsDocumentComplete() const {
+  return chunk_stream_.IsComplete();
 }
 
-void DocumentLoader::LoadFullDocument() {
-  partial_document_ = false;
-  chunk_buffer_.clear();
-  ReadMore();
-}
-
-bool DocumentLoader::IsDocumentComplete() const {
-  if (document_size_ == 0)  // Document size unknown.
-    return false;
-  return IsDataAvailable(0, document_size_);
-}
-
-uint32_t DocumentLoader::GetAvailableData() const {
-  if (document_size_ == 0) {  // If document size is unknown.
-    return current_pos_;
-  }
-
-  std::vector<std::pair<size_t, size_t> > ranges;
-  chunk_stream_.GetMissedRanges(0, document_size_, &ranges);
-  uint32_t available = document_size_;
-  for (const auto& range : ranges)
-    available -= range.second;
-  return available;
+uint32_t DocumentLoader::GetDocumentSize() const {
+  return chunk_stream_.eof_pos();
 }
 
 void DocumentLoader::ClearPendingRequests() {
-  pending_requests_.erase(pending_requests_.begin(),
-                          pending_requests_.end());
+  pending_requests_.Clear();
 }
 
 bool DocumentLoader::GetBlock(uint32_t position,
                               uint32_t size,
                               void* buf) const {
-  return chunk_stream_.ReadData(position, size, buf);
+  return chunk_stream_.ReadData(gfx::Range(position, position + size), buf);
 }
 
 bool DocumentLoader::IsDataAvailable(uint32_t position, uint32_t size) const {
-  return chunk_stream_.IsRangeAvailable(position, size);
+  return chunk_stream_.IsRangeAvailable(gfx::Range(position, position + size));
 }
 
 void DocumentLoader::RequestData(uint32_t position, uint32_t size) {
-  DCHECK(partial_document_);
+  if (!size || IsDataAvailable(position, size)) {
+    return;
+  }
+
+  if (GetDocumentSize() && (position + size > GetDocumentSize())) {
+    return;
+  }
 
   // We have some artefact request from
   // PDFiumEngine::OnDocumentComplete() -> FPDFAvail_IsPageAvail after
   // document is complete.
   // We need this fix in PDFIum. Adding this as a work around.
   // Bug: http://code.google.com/p/chromium/issues/detail?id=79996
   // Test url:
   // http://www.icann.org/en/correspondence/holtzman-to-jeffrey-02mar11-en.pdf
-  if (IsDocumentComplete())
+  if (!loader_)
     return;
 
-  pending_requests_.push_back(std::pair<size_t, size_t>(position, size));
-  DownloadPendingRequests();
-}
-
-void DocumentLoader::RemoveCompletedRanges() {
-  // Split every request that has been partially downloaded already into smaller
-  // requests.
-  std::vector<std::pair<size_t, size_t> > ranges;
-  auto it = pending_requests_.begin();
-  while (it != pending_requests_.end()) {
-    chunk_stream_.GetMissedRanges(it->first, it->second, &ranges);
-    pending_requests_.insert(it, ranges.begin(), ranges.end());
-    ranges.clear();
-    pending_requests_.erase(it++);
-  }
-}
-
-void DocumentLoader::DownloadPendingRequests() {
-  if (request_pending_)
-    return;
-
-  uint32_t pos;
-  uint32_t size;
-  if (pending_requests_.empty()) {
-    // If the document is not complete and we have no outstanding requests,
-    // download what's left for as long as no other request gets added to
-    // |pending_requests_|.
-    pos = chunk_stream_.GetFirstMissingByte();
-    if (pos >= document_size_) {
-      // We're done downloading the document.
-      return;
-    }
-    // Start with size 0, we'll set |current_request_extended_size_| to > 0.
-    // This way this request will get cancelled as soon as the renderer wants
-    // another portion of the document.
-    size = 0;
-  } else {
-    RemoveCompletedRanges();
-
-    pos = pending_requests_.front().first;
-    size = pending_requests_.front().second;
-    if (IsDataAvailable(pos, size)) {
-      ReadComplete();
-      return;
-    }
-  }
-
-  size_t last_byte_before = chunk_stream_.GetFirstMissingByteInInterval(pos);
-  if (size < kDefaultRequestSize) {
-    // Try to extend before pos, up to size |kDefaultRequestSize|.
-    if (pos + size - last_byte_before > kDefaultRequestSize) {
-      pos += size - kDefaultRequestSize;
-      size = kDefaultRequestSize;
-    } else {
-      size += pos - last_byte_before;
-      pos = last_byte_before;
-    }
-  }
-  if (pos - last_byte_before < kDefaultRequestSize) {
-    // Don't leave a gap smaller than |kDefaultRequestSize|.
-    size += pos - last_byte_before;
-    pos = last_byte_before;
-  }
-
-  current_request_offset_ = pos;
-  current_request_size_ = size;
-
-  // Extend the request until the next downloaded byte or the end of the
-  // document.
-  size_t last_missing_byte =
-      chunk_stream_.GetLastMissingByteInInterval(pos + size - 1);
-  current_request_extended_size_ = last_missing_byte - pos + 1;
-
-  request_pending_ = true;
-
-  // Start downloading first pending request.
-  loader_.Close();
-  loader_ = client_->CreateURLLoader();
-  pp::CompletionCallback callback =
-      loader_factory_.NewCallback(&DocumentLoader::DidOpen);
-  pp::URLRequestInfo request = GetRequest(pos, current_request_extended_size_);
-  requests_count_++;
-  int rv = loader_.Open(request, callback);
-  if (rv != PP_OK_COMPLETIONPENDING)
-    callback.Run(rv);
-}
-
-pp::URLRequestInfo DocumentLoader::GetRequest(uint32_t position,
-                                              uint32_t size) const {
-  pp::URLRequestInfo request(client_->GetPluginInstance());
-  request.SetURL(url_);
-  request.SetMethod("GET");
-  request.SetFollowRedirects(true);
-  request.SetCustomReferrerURL(url_);
-
-  const size_t kBufSize = 100;
-  char buf[kBufSize];
-  // According to rfc2616, byte range specifies position of the first and last
-  // bytes in the requested range inclusively. Therefore we should subtract 1
-  // from the position + size, to get index of the last byte that needs to be
-  // downloaded.
-  base::snprintf(buf, kBufSize, "Range: bytes=%d-%d", position,
-                 position + size - 1);
-  pp::Var header(buf);
-  request.SetHeaders(header);
-
-  return request;
-}
-
-void DocumentLoader::DidOpen(int32_t result) {
-  if (result != PP_OK) {
+  RangeSet requested_chunks(chunk_stream_.GetChunksRange(position, size));
+  requested_chunks.Subtract(chunk_stream_.filled_chunks());
+  if (requested_chunks.IsEmpty()) {
     NOTREACHED();
     return;
   }
-
-  int32_t http_code = loader_.GetResponseInfo().GetStatusCode();
+  pending_requests_.Union(requested_chunks);
+}
+
+void DocumentLoader::SetPartialLoadingEnabled(bool enabled) {
+  partial_loading_enabled_ = enabled;
+  if (!enabled) {
+    is_partial_loader_active_ = false;
+  }
+}
+
+bool DocumentLoader::ShouldCancelLoading() const {
+  if (!loader_)
+    return true;
+  if (!partial_loading_enabled_ || pending_requests_.IsEmpty())
+    return false;
+  const gfx::Range current_range(chunk_.chunk_index,
+                                 chunk_.chunk_index + kChunkCloseDistance);
+  return !pending_requests_.Intersects(current_range);
+}
+
+void DocumentLoader::ContinueDownload() {
+  if (!ShouldCancelLoading())
+    return ReadMore();
+  DCHECK(partial_loading_enabled_);
+  DCHECK(!IsDocumentComplete());
+  DCHECK(GetDocumentSize());
+
+  const uint32_t range_start =
+      pending_requests_.IsEmpty() ? 0 : pending_requests_.First().start();
+  RangeSet candidates_for_request(
+      gfx::Range(range_start, chunk_stream_.total_chunks_count()));
+  candidates_for_request.Subtract(chunk_stream_.filled_chunks());
+  DCHECK(!candidates_for_request.IsEmpty());
+  gfx::Range next_request = candidates_for_request.First();
+  if (candidates_for_request.Size() == 1 &&
+      next_request.length() < kChunkCloseDistance) {
+    // We have only request at the end, try to enlarge it to improve back order
+    // reading.
+    const int additional_chunks_count =
+        kChunkCloseDistance - next_request.length();
+    int new_start = std::max(
+        0, static_cast<int>(next_request.start()) - additional_chunks_count);
+    candidates_for_request =
+        RangeSet(gfx::Range(new_start, next_request.end()));
+    candidates_for_request.Subtract(chunk_stream_.filled_chunks());
+    next_request = candidates_for_request.Last();
+  }
+
+  loader_.reset();
+  chunk_.Clear();
+  if (!is_partial_loader_active_) {
+    client_->CancelBrowserDownload();
+    is_partial_loader_active_ = true;
+  }
+
+  const uint32_t start = next_request.start() * DataStream::kChunkSize;
+  const uint32_t length =
+      std::min(chunk_stream_.eof_pos() - start,
+               next_request.length() * DataStream::kChunkSize);
+
+  loader_ = client_->CreateURLLoader();
+
+  loader_->OpenRange(
+      url_, url_, start, length,
+      loader_factory_.NewCallback(&DocumentLoader::DidOpenPartial));
+}
+
+void DocumentLoader::DidOpenPartial(int32_t result) {
+  if (result != PP_OK) {
+    return ReadComplete();
+  }
+
+  int32_t http_code = loader_->GetStatusCode();
   if (http_code >= 400 && http_code < 500) {
     // Error accessing resource. 4xx error indicate subsequent requests
     // will fail too.
     // E.g. resource has been removed from the server while loading it.
-    // https://code.google.com/p/chromium/issues/detail?id=414827
-    return;
-  }
-
-  is_multipart_ = false;
-  current_chunk_size_ = 0;
-  current_chunk_read_ = 0;
-
-  pp::Var headers_var = loader_.GetResponseInfo().GetHeaders();
-  std::string headers;
-  if (headers_var.is_string())
-    headers = headers_var.AsString();
-
-  std::string boundary = GetMultiPartBoundary(headers);
-  if (!boundary.empty()) {
-    // Leave position untouched for now, when we read the data we'll get it.
-    is_multipart_ = true;
-    multipart_boundary_ = boundary;
-  } else {
+    return ReadComplete();
+  }
+
+  // Leave position untouched for multiparted responce for now, when we read the
+  // data we'll get it.
+  if (!loader_->IsMultipart()) {
     // Need to make sure that the server returned a byte-range, since it's
     // possible for a server to just ignore our byte-range request and just
     // return the entire document even if it supports byte-range requests.
     // i.e. sniff response to
     // http://www.act.org/compass/sample/pdf/geometry.pdf
-    current_pos_ = 0;
-    uint32_t start_pos, end_pos;
-    if (GetByteRange(headers, &start_pos, &end_pos)) {
-      current_pos_ = start_pos;
-      if (end_pos && end_pos > start_pos)
-        current_chunk_size_ = end_pos - start_pos + 1;
+    int start_pos = 0;
+    int end_pos = 0;
+    if (loader_->GetByteRange(&start_pos, &end_pos)) {
+      if (start_pos % DataStream::kChunkSize != 0) {
+        return ReadComplete();
+      }
+      DCHECK(!chunk_.chunk_data);
+      chunk_.chunk_index = chunk_stream_.GetChunkIndex(start_pos);
     } else {
-      partial_document_ = false;
-    }
-  }
-
-  ReadMore();
+      SetPartialLoadingEnabled(false);
+    }
+    return ContinueDownload();
+  }
+  // Needs more data to calc chunk index.
+  return ReadMore();
 }
 
 void DocumentLoader::ReadMore() {
-  pp::CompletionCallback callback =
-        loader_factory_.NewCallback(&DocumentLoader::DidRead);
-  int rv = loader_.ReadResponseBody(buffer_, sizeof(buffer_), callback);
-  if (rv != PP_OK_COMPLETIONPENDING)
-    callback.Run(rv);
+  loader_->ReadResponseBody(
+      buffer_, sizeof(buffer_),
+      loader_factory_.NewCallback(&DocumentLoader::DidRead));
 }
 
 void DocumentLoader::DidRead(int32_t result) {
-  if (result <= 0) {
-    // If |result| == PP_OK, the document was loaded, otherwise an error was
-    // encountered. Either way we want to stop processing the response. In the
-    // case where an error occurred, the renderer will detect that we're missing
-    // data and will display a message.
-    ReadComplete();
-    return;
-  }
-
-  char* start = buffer_;
-  size_t length = result;
-  if (is_multipart_ && result > 2) {
-    for (int i = 2; i < result; ++i) {
-      if ((buffer_[i - 1] == '\n' && buffer_[i - 2] == '\n') ||
-          (i >= 4 && buffer_[i - 1] == '\n' && buffer_[i - 2] == '\r' &&
-           buffer_[i - 3] == '\n' && buffer_[i - 4] == '\r')) {
-        uint32_t start_pos, end_pos;
-        if (GetByteRange(std::string(buffer_, i), &start_pos, &end_pos)) {
-          current_pos_ = start_pos;
-          start += i;
-          length -= i;
-          if (end_pos && end_pos > start_pos)
-            current_chunk_size_ = end_pos - start_pos + 1;
-        }
-        break;
-      }
-    }
-
-    // Reset this flag so we don't look inside the buffer in future calls of
-    // DidRead for this response.  Note that this code DOES NOT handle multi-
-    // part responses with more than one part (we don't issue them at the
-    // moment, so they shouldn't arrive).
-    is_multipart_ = false;
-  }
-
-  if (current_chunk_size_ && current_chunk_read_ + length > current_chunk_size_)
-    length = current_chunk_size_ - current_chunk_read_;
-
-  if (length) {
-    if (document_size_ > 0) {
-      chunk_stream_.WriteData(current_pos_, start, length);
-    } else {
-      // If we did not get content-length in the response, we can't
-      // preallocate buffer for the entire document. Resizing array causing
-      // memory fragmentation issues on the large files and OOM exceptions.
-      // To fix this, we collect all chunks of the file to the list and
-      // concatenate them together after request is complete.
-      std::vector<unsigned char> buf(length);
-      memcpy(buf.data(), start, length);
-      chunk_buffer_.push_back(std::move(buf));
-    }
-    current_pos_ += length;
-    current_chunk_read_ += length;
-    client_->OnNewDataAvailable();
-  }
-
-  // Only call the renderer if we allow partial loading.
-  if (!partial_document_) {
-    ReadMore();
-    return;
-  }
-
-  UpdateRendering();
-  RemoveCompletedRanges();
-
-  if (!pending_requests_.empty()) {
-    // If there are pending requests and the current content we're downloading
-    // doesn't satisfy any of these requests, cancel the current request to
-    // fullfill those more important requests.
-    bool satisfying_pending_request =
-        SatisfyingRequest(current_request_offset_, current_request_size_);
-    for (const auto& pending_request : pending_requests_) {
-      if (SatisfyingRequest(pending_request.first, pending_request.second)) {
-        satisfying_pending_request = true;
-        break;
-      }
-    }
-    // Cancel the request as it's not satisfying any request from the
-    // renderer, unless the current request is finished in which case we let
-    // it finish cleanly.
-    if (!satisfying_pending_request &&
-        current_pos_ <
-            current_request_offset_ + current_request_extended_size_) {
-      loader_.Close();
-    }
-  }
-
-  ReadMore();
-}
-
-bool DocumentLoader::SatisfyingRequest(size_t offset, size_t size) const {
-  return offset <= current_pos_ + kDefaultRequestSize &&
-      current_pos_ < offset + size;
+  if (result < 0) {
+    // An error occurred.
+    // The renderer will detect that we're missing data and will display a
+    // message.
+    return ReadComplete();
+  }
+  if (result == 0) {
+    loader_.reset();
+    if (!is_partial_loader_active_)
+      return ReadComplete();
+    return ContinueDownload();
+  }
+  if (loader_->IsMultipart()) {
+    int start_pos = 0;
+    int end_pos = 0;
+    if (!loader_->GetByteRange(&start_pos, &end_pos)) {
+      return ReadComplete();
+    }
+    DCHECK(!chunk_.chunk_data);
+    chunk_.chunk_index = chunk_stream_.GetChunkIndex(start_pos);
+  }
+  if (!SaveChunkData(buffer_, result)) {
+    return ReadMore();
+  }
+  if (IsDocumentComplete()) {
+    return ReadComplete();
+  }
+  return ContinueDownload();
+}
+
+bool DocumentLoader::SaveChunkData(char* input, uint32_t input_size) {
+  count_of_bytes_received_ += input_size;
+  bool chunk_saved = false;
+  bool loading_pending_request = pending_requests_.Contains(chunk_.chunk_index);
+  while (input_size > 0) {
+    if (chunk_.data_size == 0) {
+      chunk_.chunk_data.reset(new DataStream::ChunkData());
+    }
+    const uint32_t new_chunk_data_len =
+        std::min(DataStream::kChunkSize - chunk_.data_size, input_size);
+    memcpy(chunk_.chunk_data->data() + chunk_.data_size, input,
+           new_chunk_data_len);
+    chunk_.data_size += new_chunk_data_len;
+    if (chunk_.data_size == DataStream::kChunkSize ||
+        chunk_stream_.eof_pos() ==
+            chunk_.chunk_index * DataStream::kChunkSize + chunk_.data_size) {
+      chunk_stream_.SetChunkData(chunk_.chunk_index,
+                                 std::move(chunk_.chunk_data));
+      pending_requests_.Subtract(
+          gfx::Range(chunk_.chunk_index, chunk_.chunk_index + 1));
+      chunk_.data_size = 0;
+      ++(chunk_.chunk_index);
+      chunk_saved = true;
+    }
+
+    input += new_chunk_data_len;
+    input_size -= new_chunk_data_len;
+  }
+
+  if (IsDocumentComplete())
+    return true;
+
+  if (!chunk_saved)
+    return false;
+
+  if (loading_pending_request &&
+      !pending_requests_.Contains(chunk_.chunk_index)) {
+    client_->OnPendingRequestComplete();
+  }
+  client_->OnNewDataAvailable();
+  return true;
 }
 
 void DocumentLoader::ReadComplete() {
-  if (!partial_document_) {
-    if (document_size_ == 0) {
-      // For the document with no 'content-length" specified we've collected all
-      // the chunks already. Let's allocate final document buffer and copy them
-      // over.
-      chunk_stream_.Preallocate(current_pos_);
-      uint32_t pos = 0;
-      for (auto& chunk : chunk_buffer_) {
-        chunk_stream_.WriteData(pos, chunk.data(), chunk.size());
-        pos += chunk.size();
-      }
-      chunk_buffer_.clear();
-    }
-    document_size_ = current_pos_;
-    client_->OnDocumentComplete();
-    return;
-  }
-
-  request_pending_ = false;
-
+  if (!GetDocumentSize()) {
+    uint32_t eof =
+        chunk_.chunk_index * DataStream::kChunkSize + chunk_.data_size;
+    if (!chunk_stream_.filled_chunks().IsEmpty()) {
+      eof = std::max(
+          chunk_stream_.filled_chunks().Last().end() * DataStream::kChunkSize,
+          eof);
+    }
+    chunk_stream_.set_eof_pos(eof);
+    if (eof == chunk_.chunk_index * DataStream::kChunkSize + chunk_.data_size) {
+      chunk_stream_.SetChunkData(chunk_.chunk_index,
+                                 std::move(chunk_.chunk_data));
+    }
+  }
+  loader_.reset();
   if (IsDocumentComplete()) {
     client_->OnDocumentComplete();
-    return;
-  }
-
-  UpdateRendering();
-  DownloadPendingRequests();
-}
-
-void DocumentLoader::UpdateRendering() {
-  if (header_request_)
-    client_->OnPartialDocumentLoaded();
-  else
-    client_->OnPendingRequestComplete();
-  header_request_ = false;
+  } else {
+    client_->OnDocumentCanceled();
+  }
+}
+
+float DocumentLoader::GetProgress() const {
+  if (!GetDocumentSize())
+    return -1;
+  if (IsDocumentComplete())
+    return 1;
+  return static_cast<float>(chunk_stream_.filled_chunks_count()) /
+         chunk_stream_.total_chunks_count();
 }
 
 }  // namespace chrome_pdf