128 lines
4.5 KiB
C++
128 lines
4.5 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "nsSegmentedBuffer.h"
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#include "nsNetCID.h"
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#include "nsServiceManagerUtils.h"
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#include "nsThreadUtils.h"
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#include "mozilla/ScopeExit.h"
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static constexpr uint32_t kSegmentedBufferFreeOMTThreshold = 128;
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nsresult nsSegmentedBuffer::Init(uint32_t aSegmentSize) {
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if (mSegmentArrayCount != 0) {
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return NS_ERROR_FAILURE; // initialized more than once
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}
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mSegmentSize = aSegmentSize;
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mSegmentArrayCount = NS_SEGMENTARRAY_INITIAL_COUNT;
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return NS_OK;
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}
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char* nsSegmentedBuffer::AppendNewSegment(
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mozilla::UniqueFreePtr<char> aSegment) {
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if (!mSegmentArray) {
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uint32_t bytes = mSegmentArrayCount * sizeof(char*);
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mSegmentArray = (char**)moz_xmalloc(bytes);
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memset(mSegmentArray, 0, bytes);
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}
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if (IsFull()) {
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mozilla::CheckedInt<uint32_t> newArraySize =
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mozilla::CheckedInt<uint32_t>(mSegmentArrayCount) * 2;
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mozilla::CheckedInt<uint32_t> bytes = newArraySize * sizeof(char*);
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if (!bytes.isValid()) {
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return nullptr;
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}
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mSegmentArray = (char**)moz_xrealloc(mSegmentArray, bytes.value());
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// copy wrapped content to new extension
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if (mFirstSegmentIndex > mLastSegmentIndex) {
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// deal with wrap around case
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memcpy(&mSegmentArray[mSegmentArrayCount], mSegmentArray,
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mLastSegmentIndex * sizeof(char*));
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memset(mSegmentArray, 0, mLastSegmentIndex * sizeof(char*));
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mLastSegmentIndex += mSegmentArrayCount;
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memset(&mSegmentArray[mLastSegmentIndex], 0,
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(newArraySize.value() - mLastSegmentIndex) * sizeof(char*));
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} else {
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memset(&mSegmentArray[mLastSegmentIndex], 0,
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(newArraySize.value() - mLastSegmentIndex) * sizeof(char*));
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}
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mSegmentArrayCount = newArraySize.value();
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}
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char* seg = aSegment ? aSegment.release() : (char*)malloc(mSegmentSize);
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if (!seg) {
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return nullptr;
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}
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mSegmentArray[mLastSegmentIndex] = seg;
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mLastSegmentIndex = ModSegArraySize(mLastSegmentIndex + 1);
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return seg;
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}
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mozilla::UniqueFreePtr<char> nsSegmentedBuffer::PopFirstSegment() {
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NS_ASSERTION(mSegmentArray[mFirstSegmentIndex] != nullptr,
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"deleting bad segment");
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mozilla::UniqueFreePtr<char> segment(mSegmentArray[mFirstSegmentIndex]);
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mSegmentArray[mFirstSegmentIndex] = nullptr;
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int32_t last = ModSegArraySize(mLastSegmentIndex - 1);
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if (mFirstSegmentIndex == last) {
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mLastSegmentIndex = last;
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} else {
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mFirstSegmentIndex = ModSegArraySize(mFirstSegmentIndex + 1);
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}
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return segment;
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}
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mozilla::UniqueFreePtr<char> nsSegmentedBuffer::PopLastSegment() {
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int32_t last = ModSegArraySize(mLastSegmentIndex - 1);
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NS_ASSERTION(mSegmentArray[last] != nullptr, "deleting bad segment");
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mozilla::UniqueFreePtr<char> segment(mSegmentArray[last]);
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mSegmentArray[last] = nullptr;
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mLastSegmentIndex = last;
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return segment;
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}
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bool nsSegmentedBuffer::ReallocLastSegment(size_t aNewSize) {
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int32_t last = ModSegArraySize(mLastSegmentIndex - 1);
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NS_ASSERTION(mSegmentArray[last] != nullptr, "realloc'ing bad segment");
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char* newSegment = (char*)realloc(mSegmentArray[last], aNewSize);
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if (newSegment) {
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mSegmentArray[last] = newSegment;
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return true;
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}
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return false;
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}
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void nsSegmentedBuffer::Clear() {
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// Clear out the buffer's members back to their initial state.
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uint32_t arrayCount =
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std::exchange(mSegmentArrayCount, NS_SEGMENTARRAY_INITIAL_COUNT);
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char** segmentArray = std::exchange(mSegmentArray, nullptr);
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mFirstSegmentIndex = mLastSegmentIndex = 0;
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auto freeSegmentArray = [arrayCount, segmentArray]() {
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for (uint32_t i = 0; i < arrayCount; ++i) {
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if (segmentArray[i]) {
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free(segmentArray[i]);
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}
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}
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free(segmentArray);
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};
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if (segmentArray) {
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// If we have a small number of entries, free them synchronously. In some
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// rare cases, `nsSegmentedBuffer` may be gigantic, in which case it should
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// be freed async in a background task to avoid janking this thread.
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if (arrayCount < kSegmentedBufferFreeOMTThreshold ||
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NS_FAILED(NS_DispatchBackgroundTask(NS_NewRunnableFunction(
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"nsSegmentedBuffer::Clear", freeSegmentArray)))) {
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freeSegmentArray();
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}
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}
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}
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////////////////////////////////////////////////////////////////////////////////
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