chrome/browser/resources/chromeos/zip_archiver/cpp/compressor_io_javascript_stream.cc

// Copyright 2017 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 "chrome/browser/resources/chromeos/zip_archiver/cpp/compressor_io_javascript_stream.h"

#include <algorithm>
#include <cstring>
#include <limits>
#include <utility>

#include "chrome/browser/resources/chromeos/zip_archiver/cpp/javascript_compressor_requestor_interface.h"
#include "ppapi/cpp/logging.h"

namespace {

// We need at least 256KB for MiniZip.
const int64_t kMaximumDataChunkSize = 512 * 1024;

}  // namespace

CompressorIOJavaScriptStream::CompressorIOJavaScriptStream(
    JavaScriptCompressorRequestorInterface* requestor)
    : requestor_(requestor),
      available_data_cond_(&shared_state_lock_),
      data_written_cond_(&shared_state_lock_),
      available_data_(false),
      buffer_offset_(-1),
      buffer_data_length_(0),
      buffer_(std::make_unique<char[]>(kMaximumDataChunkSize)) {}

CompressorIOJavaScriptStream::~CompressorIOJavaScriptStream() = default;

int64_t CompressorIOJavaScriptStream::Flush() {
  base::AutoLock al(shared_state_lock_);

  if (buffer_data_length_ == 0) {
    return 0;
  }

  // Copy the data in buffer_ to array_buffer.
  pp::VarArrayBuffer array_buffer(buffer_data_length_);
  char* array_buffer_data = static_cast<char*>(array_buffer.Map());
  memcpy(array_buffer_data, buffer_.get(), buffer_data_length_);
  array_buffer.Unmap();

  requestor_->WriteChunkRequest(buffer_offset_, buffer_data_length_,
                                array_buffer);

  // TODO(amistry): Handle spurious wakeups.
  data_written_cond_.Wait();

  int64_t written_bytes = written_bytes_;
  if (written_bytes < buffer_data_length_) {
    return -1 /* Error */;
  }

  // Reset the offset and length to the default values.
  buffer_offset_ = -1;
  buffer_data_length_ = 0;

  return written_bytes;
}

int64_t CompressorIOJavaScriptStream::Write(int64_t zip_offset,
                                            int64_t zip_length,
                                            const char* zip_buffer) {
  base::AutoLock al(shared_state_lock_);

  // The offset from which the data should be written onto the archive.
  int64_t current_offset = zip_offset;
  int64_t left_length = zip_length;
  const char* buffer_pointer = zip_buffer;

  do {
    // Flush the buffer if the data in the buffer cannot be reused.
    // The following is the brief explanation about the conditions of the
    // following if statement.
    // 1: The buffer is not in the initial state (empty).
    //    The buffer should have some data to flush.
    // 2: This write operation is not to append the data to the buffer.
    // 3: The buffer overflows if we append the data to the buffer.
    //    If we can append the new data to the current data in the buffer,
    //    we should not flush the buffer.
    // 4: The index to write is outside the buffer.
    //    If we want to write data outside the range, we first need to flush
    //    the buffer, and then cache the data in the buffer.
    if (buffer_offset_ >= 0 &&                                         /* 1 */
        (current_offset != buffer_offset_ + buffer_data_length_ ||     /* 2 */
         buffer_data_length_ + left_length > kMaximumDataChunkSize) && /* 3 */
        (current_offset < buffer_offset_ ||
         buffer_offset_ + buffer_data_length_ <
             current_offset + left_length) /* 4 */) {
      int64_t bytes_to_write = buffer_data_length_;

      base::AutoUnlock aul(shared_state_lock_);
      if (Flush() != bytes_to_write)
        return -1;
    }

    // How many bytes we should copy to buffer_ in this iteration.
    int64_t copy_length = std::min(left_length, kMaximumDataChunkSize);
    // Set up the buffer_offset_ if the buffer_ has no data.
    if (buffer_offset_ == -1 /* initial state */)
      buffer_offset_ = current_offset;
    // Calculate the relative offset from left_length.
    int64_t offset_in_buffer = current_offset - buffer_offset_;
    // Copy data from zip_buffer, which is pointed by buffer_pointer, to
    // buffer_.
    memcpy(buffer_.get() + offset_in_buffer, buffer_pointer, copy_length);

    buffer_pointer += copy_length;
    buffer_data_length_ =
        std::max(buffer_data_length_, offset_in_buffer + copy_length);
    current_offset += copy_length;
    left_length -= copy_length;
  } while (left_length > 0);

  return zip_length;
}

int64_t CompressorIOJavaScriptStream::WriteChunkDone(int64_t written_bytes) {
  base::AutoLock al(shared_state_lock_);
  written_bytes_ = written_bytes;
  data_written_cond_.Signal();
  return written_bytes;
}

int64_t CompressorIOJavaScriptStream::Read(int64_t bytes_to_read,
                                           char* destination_buffer) {
  base::AutoLock al(shared_state_lock_);

  destination_buffer_ = destination_buffer;
  requestor_->ReadFileChunkRequest(bytes_to_read);

  while (!available_data_) {
    available_data_cond_.Wait();
  }

  int64_t read_bytes = read_bytes_;
  available_data_ = false;
  return read_bytes;
}

int64_t CompressorIOJavaScriptStream::ReadFileChunkDone(
    int64_t read_bytes,
    pp::VarArrayBuffer* array_buffer) {
  base::AutoLock al(shared_state_lock_);

  // JavaScript sets a negative value in read_bytes if an error occurred while
  // reading a chunk.
  if (read_bytes >= 0) {
    char* array_buffer_data = static_cast<char*>(array_buffer->Map());
    memcpy(destination_buffer_, array_buffer_data, read_bytes);
    array_buffer->Unmap();
  }

  read_bytes_ = read_bytes;
  available_data_ = true;
  available_data_cond_.Signal();
  return read_bytes;
}