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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 "nsStringBuffer.h"
#include "mozilla/MemoryReporting.h"
#include "nsISupportsImpl.h"
#include "nsString.h"
#ifdef DEBUG
# include "nsStringStats.h"
#else
# define STRING_STAT_INCREMENT(_s)
#endif
void nsStringBuffer::AddRef() {
// Memory synchronization is not required when incrementing a
// reference count. The first increment of a reference count on a
// thread is not important, since the first use of the object on a
// thread can happen before it. What is important is the transfer
// of the pointer to that thread, which may happen prior to the
// first increment on that thread. The necessary memory
// synchronization is done by the mechanism that transfers the
// pointer between threads.
#ifdef NS_BUILD_REFCNT_LOGGING
uint32_t count =
#endif
mRefCount.fetch_add(1, std::memory_order_relaxed)
#ifdef NS_BUILD_REFCNT_LOGGING
+ 1
#endif
;
STRING_STAT_INCREMENT(Share);
NS_LOG_ADDREF(this, count, "nsStringBuffer", sizeof(*this));
}
void nsStringBuffer::Release() {
// Since this may be the last release on this thread, we need
// release semantics so that prior writes on this thread are visible
// to the thread that destroys the object when it reads mValue with
// acquire semantics.
uint32_t count = mRefCount.fetch_sub(1, std::memory_order_release) - 1;
NS_LOG_RELEASE(this, count, "nsStringBuffer");
if (count == 0) {
// We're going to destroy the object on this thread, so we need
// acquire semantics to synchronize with the memory released by
// the last release on other threads, that is, to ensure that
// writes prior to that release are now visible on this thread.
count = mRefCount.load(std::memory_order_acquire);
STRING_STAT_INCREMENT(Free);
free(this); // we were allocated with |malloc|
}
}
/**
* Alloc returns a pointer to a new string header with set capacity.
*/
already_AddRefed<nsStringBuffer> nsStringBuffer::Alloc(size_t aSize) {
NS_ASSERTION(aSize != 0, "zero capacity allocation not allowed");
NS_ASSERTION(sizeof(nsStringBuffer) + aSize <= size_t(uint32_t(-1)) &&
sizeof(nsStringBuffer) + aSize > aSize,
"mStorageSize will truncate");
auto* hdr = (nsStringBuffer*)malloc(sizeof(nsStringBuffer) + aSize);
if (hdr) {
STRING_STAT_INCREMENT(Alloc);
hdr->mRefCount = 1;
hdr->mStorageSize = aSize;
NS_LOG_ADDREF(hdr, 1, "nsStringBuffer", sizeof(*hdr));
}
return already_AddRefed(hdr);
}
template <typename CharT>
static already_AddRefed<nsStringBuffer> DoCreate(const CharT* aData,
size_t aLength) {
RefPtr<nsStringBuffer> buffer =
nsStringBuffer::Alloc((aLength + 1) * sizeof(CharT));
if (MOZ_UNLIKELY(!buffer)) {
return nullptr;
}
auto* data = reinterpret_cast<CharT*>(buffer->Data());
memcpy(data, aData, aLength * sizeof(CharT));
data[aLength] = 0;
return buffer.forget();
}
already_AddRefed<nsStringBuffer> nsStringBuffer::Create(const char* aData,
size_t aLength) {
return DoCreate(aData, aLength);
}
already_AddRefed<nsStringBuffer> nsStringBuffer::Create(const char16_t* aData,
size_t aLength) {
return DoCreate(aData, aLength);
}
nsStringBuffer* nsStringBuffer::Realloc(nsStringBuffer* aHdr, size_t aSize) {
STRING_STAT_INCREMENT(Realloc);
NS_ASSERTION(aSize != 0, "zero capacity allocation not allowed");
NS_ASSERTION(sizeof(nsStringBuffer) + aSize <= size_t(uint32_t(-1)) &&
sizeof(nsStringBuffer) + aSize > aSize,
"mStorageSize will truncate");
// no point in trying to save ourselves if we hit this assertion
NS_ASSERTION(!aHdr->IsReadonly(), "|Realloc| attempted on readonly string");
// Treat this as a release and addref for refcounting purposes, since we
// just asserted that the refcount is 1. If we don't do that, refcount
// logging will claim we've leaked all sorts of stuff.
NS_LOG_RELEASE(aHdr, 0, "nsStringBuffer");
aHdr = (nsStringBuffer*)realloc(aHdr, sizeof(nsStringBuffer) + aSize);
if (aHdr) {
NS_LOG_ADDREF(aHdr, 1, "nsStringBuffer", sizeof(*aHdr));
aHdr->mStorageSize = aSize;
}
return aHdr;
}
nsStringBuffer* nsStringBuffer::FromString(const nsAString& aStr) {
if (!(aStr.mDataFlags & nsAString::DataFlags::REFCOUNTED)) {
return nullptr;
}
return FromData(aStr.mData);
}
nsStringBuffer* nsStringBuffer::FromString(const nsACString& aStr) {
if (!(aStr.mDataFlags & nsACString::DataFlags::REFCOUNTED)) {
return nullptr;
}
return FromData(aStr.mData);
}
void nsStringBuffer::ToString(uint32_t aLen, nsAString& aStr,
bool aMoveOwnership) {
char16_t* data = static_cast<char16_t*>(Data());
MOZ_DIAGNOSTIC_ASSERT(data[aLen] == char16_t(0),
"data should be null terminated");
nsAString::DataFlags flags =
nsAString::DataFlags::REFCOUNTED | nsAString::DataFlags::TERMINATED;
if (!aMoveOwnership) {
AddRef();
}
aStr.Finalize();
aStr.SetData(data, aLen, flags);
}
void nsStringBuffer::ToString(uint32_t aLen, nsACString& aStr,
bool aMoveOwnership) {
char* data = static_cast<char*>(Data());
MOZ_DIAGNOSTIC_ASSERT(data[aLen] == char(0),
"data should be null terminated");
nsACString::DataFlags flags =
nsACString::DataFlags::REFCOUNTED | nsACString::DataFlags::TERMINATED;
if (!aMoveOwnership) {
AddRef();
}
aStr.Finalize();
aStr.SetData(data, aLen, flags);
}
size_t nsStringBuffer::SizeOfIncludingThisIfUnshared(
mozilla::MallocSizeOf aMallocSizeOf) const {
return IsReadonly() ? 0 : aMallocSizeOf(this);
}
size_t nsStringBuffer::SizeOfIncludingThisEvenIfShared(
mozilla::MallocSizeOf aMallocSizeOf) const {
return aMallocSizeOf(this);
}
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