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