Split payload application code into a subdirectory.

This patch splits from the main libupdate_engine code the part that
is strictly used to download and apply a payload into a new static
library, moving the code to subdirectories. The new library is divided
in two subdirectories: common/ and payload_consumer/, and should not
depend on other update_engine files outside those two subdirectories.
The main difference between those two is that the common/ tools are more
generic and not tied to the payload consumer process, but otherwise they
are both compiled together.

There are still dependencies from the new libpayload_consumer library
into the main directory files and DBus generated files. Those will be
addressed in follow up CLs.

Bug: 25197634
Test: FEATURES=test emerge-link update_engine; `mm` on Brillo.

Change-Id: Id8d0204ea573627e6e26ca9ea17b9592ca95bc23
diff --git a/common/multi_range_http_fetcher.cc b/common/multi_range_http_fetcher.cc
new file mode 100644
index 0000000..0a97b6e
--- /dev/null
+++ b/common/multi_range_http_fetcher.cc
@@ -0,0 +1,190 @@
+//
+// Copyright (C) 2010 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "update_engine/common/multi_range_http_fetcher.h"
+
+#include <base/strings/stringprintf.h>
+
+#include <algorithm>
+#include <string>
+
+#include "update_engine/common/utils.h"
+
+namespace chromeos_update_engine {
+
+// Begins the transfer to the specified URL.
+// State change: Stopped -> Downloading
+// (corner case: Stopped -> Stopped for an empty request)
+void MultiRangeHttpFetcher::BeginTransfer(const std::string& url) {
+  CHECK(!base_fetcher_active_) << "BeginTransfer but already active.";
+  CHECK(!pending_transfer_ended_) << "BeginTransfer but pending.";
+  CHECK(!terminating_) << "BeginTransfer but terminating.";
+
+  if (ranges_.empty()) {
+    // Note that after the callback returns this object may be destroyed.
+    if (delegate_)
+      delegate_->TransferComplete(this, true);
+    return;
+  }
+  url_ = url;
+  current_index_ = 0;
+  bytes_received_this_range_ = 0;
+  LOG(INFO) << "starting first transfer";
+  base_fetcher_->set_delegate(this);
+  StartTransfer();
+}
+
+// State change: Downloading -> Pending transfer ended
+void MultiRangeHttpFetcher::TerminateTransfer() {
+  if (!base_fetcher_active_) {
+    LOG(INFO) << "Called TerminateTransfer but not active.";
+    // Note that after the callback returns this object may be destroyed.
+    if (delegate_)
+      delegate_->TransferTerminated(this);
+    return;
+  }
+  terminating_ = true;
+
+  if (!pending_transfer_ended_) {
+    base_fetcher_->TerminateTransfer();
+  }
+}
+
+// State change: Stopped or Downloading -> Downloading
+void MultiRangeHttpFetcher::StartTransfer() {
+  if (current_index_ >= ranges_.size()) {
+    return;
+  }
+
+  Range range = ranges_[current_index_];
+  LOG(INFO) << "starting transfer of range " << range.ToString();
+
+  bytes_received_this_range_ = 0;
+  base_fetcher_->SetOffset(range.offset());
+  if (range.HasLength())
+    base_fetcher_->SetLength(range.length());
+  else
+    base_fetcher_->UnsetLength();
+  if (delegate_)
+    delegate_->SeekToOffset(range.offset());
+  base_fetcher_active_ = true;
+  base_fetcher_->BeginTransfer(url_);
+}
+
+// State change: Downloading -> Downloading or Pending transfer ended
+void MultiRangeHttpFetcher::ReceivedBytes(HttpFetcher* fetcher,
+                                          const void* bytes,
+                                          size_t length) {
+  CHECK_LT(current_index_, ranges_.size());
+  CHECK_EQ(fetcher, base_fetcher_.get());
+  CHECK(!pending_transfer_ended_);
+  size_t next_size = length;
+  Range range = ranges_[current_index_];
+  if (range.HasLength()) {
+    next_size = std::min(next_size,
+                         range.length() - bytes_received_this_range_);
+  }
+  LOG_IF(WARNING, next_size <= 0) << "Asked to write length <= 0";
+  if (delegate_) {
+    delegate_->ReceivedBytes(this, bytes, next_size);
+  }
+  bytes_received_this_range_ += length;
+  if (range.HasLength() && bytes_received_this_range_ >= range.length()) {
+    // Terminates the current fetcher. Waits for its TransferTerminated
+    // callback before starting the next range so that we don't end up
+    // signalling the delegate that the whole multi-transfer is complete
+    // before all fetchers are really done and cleaned up.
+    pending_transfer_ended_ = true;
+    LOG(INFO) << "terminating transfer";
+    fetcher->TerminateTransfer();
+  }
+}
+
+// State change: Downloading or Pending transfer ended -> Stopped
+void MultiRangeHttpFetcher::TransferEnded(HttpFetcher* fetcher,
+                                          bool successful) {
+  CHECK(base_fetcher_active_) << "Transfer ended unexpectedly.";
+  CHECK_EQ(fetcher, base_fetcher_.get());
+  pending_transfer_ended_ = false;
+  http_response_code_ = fetcher->http_response_code();
+  LOG(INFO) << "TransferEnded w/ code " << http_response_code_;
+  if (terminating_) {
+    LOG(INFO) << "Terminating.";
+    Reset();
+    // Note that after the callback returns this object may be destroyed.
+    if (delegate_)
+      delegate_->TransferTerminated(this);
+    return;
+  }
+
+  // If we didn't get enough bytes, it's failure
+  Range range = ranges_[current_index_];
+  if (range.HasLength()) {
+    if (bytes_received_this_range_ < range.length()) {
+      // Failure
+      LOG(INFO) << "Didn't get enough bytes. Ending w/ failure.";
+      Reset();
+      // Note that after the callback returns this object may be destroyed.
+      if (delegate_)
+        delegate_->TransferComplete(this, false);
+      return;
+    }
+    // We got enough bytes and there were bytes specified, so this is success.
+    successful = true;
+  }
+
+  // If we have another transfer, do that.
+  if (current_index_ + 1 < ranges_.size()) {
+    current_index_++;
+    LOG(INFO) << "Starting next transfer (" << current_index_ << ").";
+    StartTransfer();
+    return;
+  }
+
+  LOG(INFO) << "Done w/ all transfers";
+  Reset();
+  // Note that after the callback returns this object may be destroyed.
+  if (delegate_)
+    delegate_->TransferComplete(this, successful);
+}
+
+void MultiRangeHttpFetcher::TransferComplete(HttpFetcher* fetcher,
+                                             bool successful) {
+  LOG(INFO) << "Received transfer complete.";
+  TransferEnded(fetcher, successful);
+}
+
+void MultiRangeHttpFetcher::TransferTerminated(HttpFetcher* fetcher) {
+  LOG(INFO) << "Received transfer terminated.";
+  TransferEnded(fetcher, false);
+}
+
+void MultiRangeHttpFetcher::Reset() {
+  base_fetcher_active_ = pending_transfer_ended_ = terminating_ = false;
+  current_index_ = 0;
+  bytes_received_this_range_ = 0;
+}
+
+std::string MultiRangeHttpFetcher::Range::ToString() const {
+  std::string range_str = base::StringPrintf("%jd+", offset());
+  if (HasLength())
+    range_str += std::to_string(length());
+  else
+    range_str += "?";
+  return range_str;
+}
+
+}  // namespace chromeos_update_engine