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// 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.
// This file contains the implementation of the RingBuffer class.
#include "gpu/command_buffer/client/ring_buffer.h"
#include <algorithm>
#include "base/logging.h"
#include "gpu/command_buffer/client/cmd_buffer_helper.h"
namespace gpu {
RingBuffer::RingBuffer(unsigned int alignment, Offset base_offset,
unsigned int size, CommandBufferHelper* helper,
void* base)
: helper_(helper),
base_offset_(base_offset),
size_(size),
free_offset_(0),
in_use_offset_(0),
alignment_(alignment),
base_(static_cast<int8*>(base) - base_offset) {
}
RingBuffer::~RingBuffer() {
// Free blocks pending tokens.
while (!blocks_.empty()) {
FreeOldestBlock();
}
}
void RingBuffer::FreeOldestBlock() {
DCHECK(!blocks_.empty()) << "no free blocks";
Block& block = blocks_.front();
DCHECK(block.state != IN_USE)
<< "attempt to allocate more than maximum memory";
if (block.state == FREE_PENDING_TOKEN) {
helper_->WaitForToken(block.token);
}
in_use_offset_ += block.size;
if (in_use_offset_ == size_) {
in_use_offset_ = 0;
}
// If they match then the entire buffer is free.
if (in_use_offset_ == free_offset_) {
in_use_offset_ = 0;
free_offset_ = 0;
}
blocks_.pop_front();
}
void* RingBuffer::Alloc(unsigned int size) {
DCHECK_LE(size, size_) << "attempt to allocate more than maximum memory";
DCHECK(blocks_.empty() || blocks_.back().state != IN_USE)
<< "Attempt to alloc another block before freeing the previous.";
// Similarly to malloc, an allocation of 0 allocates at least 1 byte, to
// return different pointers every time.
if (size == 0) size = 1;
// Allocate rounded to alignment size so that the offsets are always
// memory-aligned.
size = RoundToAlignment(size);
// Wait until there is enough room.
while (size > GetLargestFreeSizeNoWaiting()) {
FreeOldestBlock();
}
if (size + free_offset_ > size_) {
// Add padding to fill space before wrapping around
blocks_.push_back(Block(free_offset_, size_ - free_offset_, PADDING));
free_offset_ = 0;
}
Offset offset = free_offset_;
blocks_.push_back(Block(offset, size, IN_USE));
free_offset_ += size;
if (free_offset_ == size_) {
free_offset_ = 0;
}
return GetPointer(offset + base_offset_);
}
void RingBuffer::FreePendingToken(void* pointer,
unsigned int token) {
Offset offset = GetOffset(pointer);
offset -= base_offset_;
DCHECK(!blocks_.empty()) << "no allocations to free";
for (Container::reverse_iterator it = blocks_.rbegin();
it != blocks_.rend();
++it) {
Block& block = *it;
if (block.offset == offset) {
DCHECK(block.state == IN_USE)
<< "block that corresponds to offset already freed";
block.token = token;
block.state = FREE_PENDING_TOKEN;
return;
}
}
NOTREACHED() << "attempt to free non-existant block";
}
void RingBuffer::DiscardBlock(void* pointer) {
Offset offset = GetOffset(pointer);
offset -= base_offset_;
DCHECK(!blocks_.empty()) << "no allocations to discard";
for (Container::reverse_iterator it = blocks_.rbegin();
it != blocks_.rend();
++it) {
Block& block = *it;
if (block.offset == offset) {
DCHECK(block.state != PADDING)
<< "block that corresponds to offset already discarded";
block.state = PADDING;
// Remove block if it were in the back along with any extra padding.
while (!blocks_.empty() && blocks_.back().state == PADDING) {
free_offset_= blocks_.back().offset;
blocks_.pop_back();
}
// Remove blocks if it were in the front along with extra padding.
while (!blocks_.empty() && blocks_.front().state == PADDING) {
blocks_.pop_front();
if (blocks_.empty())
break;
in_use_offset_ = blocks_.front().offset;
}
// In the special case when there are no blocks, we should be reset it.
if (blocks_.empty()) {
in_use_offset_ = 0;
free_offset_ = 0;
}
return;
}
}
NOTREACHED() << "attempt to discard non-existant block";
}
unsigned int RingBuffer::GetLargestFreeSizeNoWaiting() {
unsigned int last_token_read = helper_->last_token_read();
while (!blocks_.empty()) {
Block& block = blocks_.front();
if (block.token > last_token_read || block.state == IN_USE) break;
FreeOldestBlock();
}
if (free_offset_ == in_use_offset_) {
if (blocks_.empty()) {
// The entire buffer is free.
DCHECK_EQ(free_offset_, 0u);
return size_;
} else {
// The entire buffer is in use.
return 0;
}
} else if (free_offset_ > in_use_offset_) {
// It's free from free_offset_ to size_ and from 0 to in_use_offset_
return std::max(size_ - free_offset_, in_use_offset_);
} else {
// It's free from free_offset_ -> in_use_offset_;
return in_use_offset_ - free_offset_;
}
}
} // namespace gpu
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