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// Copyright 2013 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.
// TODO(vtl): I currently potentially overflow in doing index calculations.
// E.g., |buffer_first_element_index_| and |buffer_current_num_elements_| fit
// into a |uint32_t|, but their sum may not. This is bad and poses a security
// risk. (We're currently saved by the limit on capacity -- the maximum size of
// the buffer, checked in |DataPipe::Init()|, is currently sufficiently small.
#include "mojo/system/local_data_pipe.h"
#include <algorithm>
#include "base/logging.h"
#include "mojo/system/constants.h"
namespace mojo {
namespace system {
LocalDataPipe::LocalDataPipe()
: DataPipe(true, true),
producer_open_(true),
consumer_open_(true),
buffer_first_element_index_(0),
buffer_current_num_elements_(0),
two_phase_max_elements_written_(0),
two_phase_max_elements_read_(0) {
}
MojoResult LocalDataPipe::Init(const MojoCreateDataPipeOptions* options) {
static const MojoCreateDataPipeOptions kDefaultOptions = {
sizeof(MojoCreateDataPipeOptions), // |struct_size|.
MOJO_CREATE_DATA_PIPE_OPTIONS_FLAG_NONE, // |flags|.
1u, // |element_size|.
static_cast<uint32_t>(kDefaultDataPipeCapacityBytes)
};
if (!options)
options = &kDefaultOptions;
if (options->struct_size < sizeof(*options))
return MOJO_RESULT_INVALID_ARGUMENT;
// Note: lazily allocate memory, since a common case will be that one of the
// handles is immediately passed off to another process.
return DataPipe::Init(
(options->flags & MOJO_CREATE_DATA_PIPE_OPTIONS_FLAG_MAY_DISCARD),
static_cast<size_t>(options->element_size),
static_cast<size_t>(options->capacity_num_elements));
}
LocalDataPipe::~LocalDataPipe() {
DCHECK(!producer_open_);
DCHECK(!consumer_open_);
}
void LocalDataPipe::ProducerCloseImplNoLock() {
DCHECK(producer_open_);
producer_open_ = false;
if (!buffer_current_num_elements_) {
buffer_.reset();
buffer_current_num_elements_ = 0;
}
AwakeConsumerWaitersForStateChangeNoLock();
}
MojoResult LocalDataPipe::ProducerBeginWriteDataImplNoLock(
void** buffer,
uint32_t* buffer_num_elements,
MojoWriteDataFlags flags) {
size_t max_elements_to_write = GetMaxElementsToWriteNoLock();
// TODO(vtl): Consider this return value.
if ((flags & MOJO_WRITE_DATA_FLAG_ALL_OR_NONE) &&
*buffer_num_elements < max_elements_to_write)
return MOJO_RESULT_OUT_OF_RANGE;
size_t next_index = (buffer_first_element_index_ +
buffer_current_num_elements_) % capacity_num_elements();
EnsureBufferNoLock();
*buffer = buffer_.get() + next_index * element_size();
*buffer_num_elements = static_cast<uint32_t>(max_elements_to_write);
two_phase_max_elements_written_ =
static_cast<uint32_t>(max_elements_to_write);
return MOJO_RESULT_OK;
}
MojoResult LocalDataPipe::ProducerEndWriteDataImplNoLock(
uint32_t num_elements_written) {
if (num_elements_written > two_phase_max_elements_written_) {
// Note: The two-phase write ends here even on failure.
two_phase_max_elements_written_ = 0; // For safety.
return MOJO_RESULT_INVALID_ARGUMENT;
}
buffer_current_num_elements_ += num_elements_written;
DCHECK_LE(buffer_current_num_elements_, capacity_num_elements());
two_phase_max_elements_written_ = 0; // For safety.
return MOJO_RESULT_OK;
}
MojoWaitFlags LocalDataPipe::ProducerSatisfiedFlagsNoLock() {
MojoWaitFlags rv = MOJO_WAIT_FLAG_NONE;
if (consumer_open_ && buffer_current_num_elements_ < capacity_num_elements())
rv |= MOJO_WAIT_FLAG_WRITABLE;
return rv;
}
MojoWaitFlags LocalDataPipe::ProducerSatisfiableFlagsNoLock() {
MojoWaitFlags rv = MOJO_WAIT_FLAG_NONE;
if (consumer_open_)
rv |= MOJO_WAIT_FLAG_WRITABLE;
return rv;
}
void LocalDataPipe::ConsumerCloseImplNoLock() {
DCHECK(consumer_open_);
consumer_open_ = false;
buffer_.reset();
buffer_current_num_elements_ = 0;
AwakeProducerWaitersForStateChangeNoLock();
}
MojoResult LocalDataPipe::ConsumerDiscardDataNoLock(uint32_t* num_elements,
bool all_or_none) {
// TODO(vtl): Think about the error code in this case.
if (all_or_none && *num_elements > buffer_current_num_elements_)
return MOJO_RESULT_OUT_OF_RANGE;
size_t num_elements_to_discard =
std::min(static_cast<size_t>(*num_elements),
buffer_current_num_elements_);
buffer_first_element_index_ =
(buffer_first_element_index_ + num_elements_to_discard) %
capacity_num_elements();
buffer_current_num_elements_ -= num_elements_to_discard;
AwakeProducerWaitersForStateChangeNoLock();
AwakeConsumerWaitersForStateChangeNoLock();
*num_elements = static_cast<uint32_t>(num_elements_to_discard);
return MOJO_RESULT_OK;
}
MojoResult LocalDataPipe::ConsumerQueryDataNoLock(uint32_t* num_elements) {
// Note: This cast is safe, since the capacity fits into a |uint32_t|.
*num_elements = static_cast<uint32_t>(buffer_current_num_elements_);
return MOJO_RESULT_OK;
}
MojoResult LocalDataPipe::ConsumerBeginReadDataImplNoLock(
const void** buffer,
uint32_t* buffer_num_elements,
MojoReadDataFlags flags) {
size_t max_elements_to_read = GetMaxElementsToReadNoLock();
// TODO(vtl): Consider this return value.
if ((flags & MOJO_READ_DATA_FLAG_ALL_OR_NONE) &&
*buffer_num_elements < max_elements_to_read)
return MOJO_RESULT_OUT_OF_RANGE;
// Note: This works even if |buffer_| is null.
*buffer = buffer_.get() + buffer_first_element_index_ * element_size();
*buffer_num_elements = static_cast<uint32_t>(max_elements_to_read);
two_phase_max_elements_read_ = static_cast<uint32_t>(max_elements_to_read);
return MOJO_RESULT_OK;
}
MojoResult LocalDataPipe::ConsumerEndReadDataImplNoLock(
uint32_t num_elements_read) {
if (num_elements_read > two_phase_max_elements_read_) {
// Note: The two-phase read ends here even on failure.
two_phase_max_elements_read_ = 0; // For safety.
return MOJO_RESULT_INVALID_ARGUMENT;
}
buffer_first_element_index_ += num_elements_read;
DCHECK_LE(buffer_first_element_index_, capacity_num_elements());
buffer_first_element_index_ %= capacity_num_elements();
DCHECK_LE(num_elements_read, buffer_current_num_elements_);
buffer_current_num_elements_ -= num_elements_read;
two_phase_max_elements_read_ = 0; // For safety.
return MOJO_RESULT_OK;
}
MojoWaitFlags LocalDataPipe::ConsumerSatisfiedFlagsNoLock() {
MojoWaitFlags rv = MOJO_WAIT_FLAG_NONE;
if (buffer_current_num_elements_ > 0)
rv |= MOJO_WAIT_FLAG_READABLE;
return rv;
}
MojoWaitFlags LocalDataPipe::ConsumerSatisfiableFlagsNoLock() {
MojoWaitFlags rv = MOJO_WAIT_FLAG_NONE;
if (buffer_current_num_elements_ > 0 || producer_open_)
rv |= MOJO_WAIT_FLAG_READABLE;
return rv;
}
void LocalDataPipe::EnsureBufferNoLock() {
DCHECK(producer_open_);
if (buffer_.get())
return;
buffer_.reset(static_cast<char*>(
base::AlignedAlloc(static_cast<size_t>(capacity_num_elements()) *
element_size(),
kDataPipeBufferAlignmentBytes)));
}
size_t LocalDataPipe::GetMaxElementsToWriteNoLock() {
size_t next_index = buffer_first_element_index_ +
buffer_current_num_elements_;
if (next_index >= capacity_num_elements()) {
next_index %= capacity_num_elements();
DCHECK_GE(buffer_first_element_index_, next_index);
return buffer_first_element_index_ - next_index;
}
return capacity_num_elements() - next_index;
}
size_t LocalDataPipe::GetMaxElementsToReadNoLock() {
if (buffer_first_element_index_ + buffer_current_num_elements_ >
capacity_num_elements())
return capacity_num_elements() - buffer_first_element_index_;
return buffer_current_num_elements_;
}
} // namespace system
} // namespace mojo
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