/*
- * Copyright 2017 Facebook, Inc.
+ * Copyright 2013-present Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
-
#pragma once
#include <cassert>
#include <stdexcept>
#include <type_traits>
-#include <folly/Bits.h>
#include <folly/Likely.h>
#include <folly/Memory.h>
#include <folly/Portability.h>
#include <folly/Range.h>
#include <folly/io/IOBuf.h>
#include <folly/io/IOBufQueue.h>
+#include <folly/lang/Bits.h>
#include <folly/portability/BitsFunctexcept.h>
/**
*
* RWPrivateCursor - Read-write access, assumes private access to IOBuf chain
* RWUnshareCursor - Read-write access, calls unshare on write (COW)
- * Appender - Write access, assumes private access to IOBuf chian
+ * Appender - Write access, assumes private access to IOBuf chain
*
* Note that RW cursors write in the preallocated part of buffers (that is,
* between the buffer's data() and tail()), while Appenders append to the end
// Make all the templated classes friends for copy constructor.
template <class D, typename B> friend class CursorBase;
public:
- explicit CursorBase(BufType* buf) : crtBuf_(buf), buffer_(buf) { }
+ explicit CursorBase(BufType* buf) : crtBuf_(buf), buffer_(buf) {
+ if (crtBuf_) {
+ crtPos_ = crtBegin_ = crtBuf_->data();
+ crtEnd_ = crtBuf_->tail();
+ }
+ }
/**
* Copy constructor.
*/
template <class OtherDerived, class OtherBuf>
explicit CursorBase(const CursorBase<OtherDerived, OtherBuf>& cursor)
- : crtBuf_(cursor.crtBuf_),
- offset_(cursor.offset_),
- buffer_(cursor.buffer_) { }
+ : crtBuf_(cursor.crtBuf_),
+ buffer_(cursor.buffer_),
+ crtBegin_(cursor.crtBegin_),
+ crtEnd_(cursor.crtEnd_),
+ crtPos_(cursor.crtPos_),
+ absolutePos_(cursor.absolutePos_) {}
/**
* Reset cursor to point to a new buffer.
void reset(BufType* buf) {
crtBuf_ = buf;
buffer_ = buf;
- offset_ = 0;
+ absolutePos_ = 0;
+ if (crtBuf_) {
+ crtPos_ = crtBegin_ = crtBuf_->data();
+ crtEnd_ = crtBuf_->tail();
+ }
+ }
+
+ /**
+ * Get the current Cursor position relative to the head of IOBuf chain.
+ */
+ size_t getCurrentPosition() const {
+ dcheckIntegrity();
+ return (crtPos_ - crtBegin_) + absolutePos_;
}
const uint8_t* data() const {
- return crtBuf_->data() + offset_;
+ dcheckIntegrity();
+ return crtPos_;
}
/**
* pointing at the end of a buffer.
*/
size_t length() const {
- return crtBuf_->length() - offset_;
+ dcheckIntegrity();
+ return crtEnd_ - crtPos_;
}
/**
*/
size_t totalLength() const {
if (crtBuf_ == buffer_) {
- return crtBuf_->computeChainDataLength() - offset_;
+ return crtBuf_->computeChainDataLength() - (crtPos_ - crtBegin_);
}
CursorBase end(buffer_->prev());
- end.offset_ = end.buffer_->length();
+ end.crtPos_ = end.crtEnd_;
return end - *this;
}
* Return true if the cursor is at the end of the entire IOBuf chain.
*/
bool isAtEnd() const {
+ dcheckIntegrity();
// Check for the simple cases first.
- if (offset_ != crtBuf_->length()) {
+ if (crtPos_ != crtEnd_) {
return false;
}
if (crtBuf_ == buffer_->prev()) {
* Advances the cursor to the end of the entire IOBuf chain.
*/
void advanceToEnd() {
- offset_ = buffer_->prev()->length();
- if (crtBuf_ != buffer_->prev()) {
- crtBuf_ = buffer_->prev();
+ // Simple case, we're already in the last IOBuf.
+ if (crtBuf_ == buffer_->prev()) {
+ crtPos_ = crtEnd_;
+ return;
+ }
+
+ auto* nextBuf = crtBuf_->next();
+ while (nextBuf != buffer_) {
+ absolutePos_ += crtEnd_ - crtBegin_;
+
+ crtBuf_ = nextBuf;
+ nextBuf = crtBuf_->next();
+ crtBegin_ = crtBuf_->data();
+ crtPos_ = crtEnd_ = crtBuf_->tail();
+
static_cast<Derived*>(this)->advanceDone();
}
}
* same IOBuf chain.
*/
bool operator==(const Derived& other) const {
- return (offset_ == other.offset_) && (crtBuf_ == other.crtBuf_);
+ const IOBuf* crtBuf = crtBuf_;
+ auto crtPos = crtPos_;
+ // We can be pointing to the end of a buffer chunk, find first non-empty.
+ while (crtPos == crtBuf->tail() && crtBuf != buffer_->prev()) {
+ crtBuf = crtBuf->next();
+ crtPos = crtBuf->data();
+ }
+
+ const IOBuf* crtBufOther = other.crtBuf_;
+ auto crtPosOther = other.crtPos_;
+ // We can be pointing to the end of a buffer chunk, find first non-empty.
+ while (crtPosOther == crtBufOther->tail() &&
+ crtBufOther != other.buffer_->prev()) {
+ crtBufOther = crtBufOther->next();
+ crtPosOther = crtBufOther->data();
+ }
+ return (crtPos == crtPosOther) && (crtBuf == crtBufOther);
}
bool operator!=(const Derived& other) const {
return !operator==(other);
template <class T>
typename std::enable_if<std::is_arithmetic<T>::value, bool>::type tryRead(
T& val) {
- if (LIKELY(length() >= sizeof(T))) {
+ if (LIKELY(crtPos_ + sizeof(T) <= crtEnd_)) {
val = loadUnaligned<T>(data());
- offset_ += sizeof(T);
- advanceBufferIfEmpty();
+ crtPos_ += sizeof(T);
return true;
}
return pullAtMostSlow(&val, sizeof(T)) == sizeof(T);
template <class T>
T read() {
- T val{};
- if (!tryRead(val)) {
- std::__throw_out_of_range("underflow");
+ if (LIKELY(crtPos_ + sizeof(T) <= crtEnd_)) {
+ T val = loadUnaligned<T>(data());
+ crtPos_ += sizeof(T);
+ return val;
+ } else {
+ return readSlow<T>();
}
- return val;
}
template <class T>
str.reserve(len);
if (LIKELY(length() >= len)) {
str.append(reinterpret_cast<const char*>(data()), len);
- offset_ += len;
- advanceBufferIfEmpty();
+ crtPos_ += len;
} else {
readFixedStringSlow(&str, len);
}
void skipWhile(const Predicate& predicate);
size_t skipAtMost(size_t len) {
- if (LIKELY(length() >= len)) {
- offset_ += len;
- advanceBufferIfEmpty();
+ dcheckIntegrity();
+ if (LIKELY(crtPos_ + len < crtEnd_)) {
+ crtPos_ += len;
return len;
}
return skipAtMostSlow(len);
}
void skip(size_t len) {
- if (LIKELY(length() >= len)) {
- offset_ += len;
- advanceBufferIfEmpty();
+ dcheckIntegrity();
+ if (LIKELY(crtPos_ + len < crtEnd_)) {
+ crtPos_ += len;
} else {
skipSlow(len);
}
}
+ /**
+ * Skip bytes in the current IOBuf without advancing to the next one.
+ * Precondition: length() >= len
+ */
+ void skipNoAdvance(size_t len) {
+ DCHECK_LE(len, length());
+ crtPos_ += len;
+ }
+
size_t retreatAtMost(size_t len) {
- if (len <= offset_) {
- offset_ -= len;
+ dcheckIntegrity();
+ if (len <= static_cast<size_t>(crtPos_ - crtBegin_)) {
+ crtPos_ -= len;
return len;
}
return retreatAtMostSlow(len);
}
void retreat(size_t len) {
- if (len <= offset_) {
- offset_ -= len;
+ dcheckIntegrity();
+ if (len <= static_cast<size_t>(crtPos_ - crtBegin_)) {
+ crtPos_ -= len;
} else {
retreatSlow(len);
}
}
size_t pullAtMost(void* buf, size_t len) {
+ dcheckIntegrity();
// Fast path: it all fits in one buffer.
- if (LIKELY(length() >= len)) {
+ if (LIKELY(crtPos_ + len <= crtEnd_)) {
memcpy(buf, data(), len);
- offset_ += len;
- advanceBufferIfEmpty();
+ crtPos_ += len;
return len;
}
return pullAtMostSlow(buf, len);
}
void pull(void* buf, size_t len) {
- if (LIKELY(length() >= len)) {
+ dcheckIntegrity();
+ if (LIKELY(crtPos_ + len <= crtEnd_)) {
memcpy(buf, data(), len);
- offset_ += len;
- advanceBufferIfEmpty();
+ crtPos_ += len;
} else {
pullSlow(buf, len);
}
}
size_t cloneAtMost(folly::IOBuf& buf, size_t len) {
+ // We might be at the end of buffer.
+ advanceBufferIfEmpty();
+
std::unique_ptr<folly::IOBuf> tmp;
size_t copied = 0;
for (int loopCount = 0; true; ++loopCount) {
if (LIKELY(available >= len)) {
if (loopCount == 0) {
crtBuf_->cloneOneInto(buf);
- buf.trimStart(offset_);
+ buf.trimStart(crtPos_ - crtBegin_);
buf.trimEnd(buf.length() - len);
} else {
tmp = crtBuf_->cloneOne();
- tmp->trimStart(offset_);
+ tmp->trimStart(crtPos_ - crtBegin_);
tmp->trimEnd(tmp->length() - len);
buf.prependChain(std::move(tmp));
}
- offset_ += len;
+ crtPos_ += len;
advanceBufferIfEmpty();
return copied + len;
}
if (loopCount == 0) {
crtBuf_->cloneOneInto(buf);
- buf.trimStart(offset_);
+ buf.trimStart(crtPos_ - crtBegin_);
} else {
tmp = crtBuf_->cloneOne();
- tmp->trimStart(offset_);
+ tmp->trimStart(crtPos_ - crtBegin_);
buf.prependChain(std::move(tmp));
}
size_t len = 0;
if (otherBuf != crtBuf_) {
- len += otherBuf->length() - other.offset_;
+ len += other.crtEnd_ - other.crtPos_;
for (otherBuf = otherBuf->next();
otherBuf != crtBuf_ && otherBuf != other.buffer_;
std::__throw_out_of_range("wrap-around");
}
- len += offset_;
+ len += crtPos_ - crtBegin_;
} else {
- if (offset_ < other.offset_) {
+ if (crtPos_ < other.crtPos_) {
std::__throw_out_of_range("underflow");
}
- len += offset_ - other.offset_;
+ len += crtPos_ - other.crtPos_;
}
return len;
}
}
- len += offset_;
+ len += crtPos_ - crtBegin_;
return len;
}
protected:
+ void dcheckIntegrity() const {
+ DCHECK(crtBegin_ <= crtPos_ && crtPos_ <= crtEnd_);
+ DCHECK(crtBuf_ == nullptr || crtBegin_ == crtBuf_->data());
+ DCHECK(
+ crtBuf_ == nullptr ||
+ (uint64_t)(crtEnd_ - crtBegin_) == crtBuf_->length());
+ }
+
~CursorBase() { }
BufType* head() {
bool tryAdvanceBuffer() {
BufType* nextBuf = crtBuf_->next();
if (UNLIKELY(nextBuf == buffer_)) {
- offset_ = crtBuf_->length();
+ crtPos_ = crtEnd_;
return false;
}
- offset_ = 0;
+ absolutePos_ += crtEnd_ - crtBegin_;
crtBuf_ = nextBuf;
+ crtPos_ = crtBegin_ = crtBuf_->data();
+ crtEnd_ = crtBuf_->tail();
static_cast<Derived*>(this)->advanceDone();
return true;
}
bool tryRetreatBuffer() {
if (UNLIKELY(crtBuf_ == buffer_)) {
- offset_ = 0;
+ crtPos_ = crtBegin_;
return false;
}
crtBuf_ = crtBuf_->prev();
- offset_ = crtBuf_->length();
+ crtBegin_ = crtBuf_->data();
+ crtPos_ = crtEnd_ = crtBuf_->tail();
+ absolutePos_ -= crtEnd_ - crtBegin_;
static_cast<Derived*>(this)->advanceDone();
return true;
}
void advanceBufferIfEmpty() {
- if (length() == 0) {
+ dcheckIntegrity();
+ if (crtPos_ == crtEnd_) {
tryAdvanceBuffer();
}
}
BufType* crtBuf_;
- size_t offset_ = 0;
+ BufType* buffer_;
+ const uint8_t* crtBegin_{nullptr};
+ const uint8_t* crtEnd_{nullptr};
+ const uint8_t* crtPos_{nullptr};
+ size_t absolutePos_{0};
private:
+ template <class T>
+ FOLLY_NOINLINE T readSlow() {
+ T val;
+ pullSlow(&val, sizeof(T));
+ return val;
+ }
+
void readFixedStringSlow(std::string* str, size_t len) {
for (size_t available; (available = length()) < len; ) {
str->append(reinterpret_cast<const char*>(data()), available);
len -= available;
}
str->append(reinterpret_cast<const char*>(data()), len);
- offset_ += len;
+ crtPos_ += len;
advanceBufferIfEmpty();
}
len -= available;
}
memcpy(p, data(), len);
- offset_ += len;
+ crtPos_ += len;
advanceBufferIfEmpty();
return copied + len;
}
}
len -= available;
}
- offset_ += len;
+ crtPos_ += len;
advanceBufferIfEmpty();
return skipped + len;
}
size_t retreatAtMostSlow(size_t len) {
size_t retreated = 0;
- for (size_t available; (available = offset_) < len;) {
+ for (size_t available; (available = crtPos_ - crtBegin_) < len;) {
retreated += available;
if (UNLIKELY(!tryRetreatBuffer())) {
return retreated;
}
len -= available;
}
- offset_ -= len;
+ crtPos_ -= len;
return retreated + len;
}
void advanceDone() {
}
-
- BufType* buffer_;
};
} // namespace detail
if (this->crtBuf_ != this->head() && this->totalLength() < n) {
throw std::overflow_error("cannot gather() past the end of the chain");
}
- this->crtBuf_->gather(this->offset_ + n);
+ size_t offset = this->crtPos_ - this->crtBegin_;
+ this->crtBuf_->gather(offset + n);
+ this->crtBegin_ = this->crtBuf_->data();
+ this->crtEnd_ = this->crtBuf_->tail();
+ this->crtPos_ = this->crtBegin_ + offset;
}
void gatherAtMost(size_t n) {
+ this->dcheckIntegrity();
size_t size = std::min(n, this->totalLength());
- return this->crtBuf_->gather(this->offset_ + size);
+ size_t offset = this->crtPos_ - this->crtBegin_;
+ this->crtBuf_->gather(offset + size);
+ this->crtBegin_ = this->crtBuf_->data();
+ this->crtEnd_ = this->crtBuf_->tail();
+ this->crtPos_ = this->crtBegin_ + offset;
}
using detail::Writable<RWCursor<access>>::pushAtMost;
maybeUnshare();
}
memcpy(writableData(), buf, len);
- this->offset_ += len;
+ this->crtPos_ += len;
return copied + len;
}
}
void insert(std::unique_ptr<folly::IOBuf> buf) {
- folly::IOBuf* nextBuf;
- if (this->offset_ == 0) {
+ this->dcheckIntegrity();
+ this->absolutePos_ += buf->computeChainDataLength();
+ if (this->crtPos_ == this->crtBegin_ && this->crtBuf_ != this->buffer_) {
// Can just prepend
- nextBuf = this->crtBuf_;
this->crtBuf_->prependChain(std::move(buf));
} else {
+ IOBuf* nextBuf;
std::unique_ptr<folly::IOBuf> remaining;
- if (this->crtBuf_->length() - this->offset_ > 0) {
+ if (this->crtPos_ != this->crtEnd_) {
// Need to split current IOBuf in two.
remaining = this->crtBuf_->cloneOne();
- remaining->trimStart(this->offset_);
+ remaining->trimStart(this->crtPos_ - this->crtBegin_);
nextBuf = remaining.get();
buf->prependChain(std::move(remaining));
} else {
nextBuf = this->crtBuf_->next();
}
this->crtBuf_->trimEnd(this->length());
+ this->absolutePos_ += this->crtPos_ - this->crtBegin_;
this->crtBuf_->appendChain(std::move(buf));
+
+ if (nextBuf == this->buffer_) {
+ // We've just appended to the end of the buffer, so advance to the end.
+ this->crtBuf_ = this->buffer_->prev();
+ this->crtBegin_ = this->crtBuf_->data();
+ this->crtPos_ = this->crtEnd_ = this->crtBuf_->tail();
+ // This has already been accounted for, so remove it.
+ this->absolutePos_ -= this->crtEnd_ - this->crtBegin_;
+ } else {
+ // Jump past the new links
+ this->crtBuf_ = nextBuf;
+ this->crtPos_ = this->crtBegin_ = this->crtBuf_->data();
+ this->crtEnd_ = this->crtBuf_->tail();
+ }
}
- // Jump past the new links
- this->offset_ = 0;
- this->crtBuf_ = nextBuf;
}
uint8_t* writableData() {
- return this->crtBuf_->writableData() + this->offset_;
+ this->dcheckIntegrity();
+ return this->crtBuf_->writableData() + (this->crtPos_ - this->crtBegin_);
}
private:
void maybeUnshare() {
if (UNLIKELY(maybeShared_)) {
+ size_t offset = this->crtPos_ - this->crtBegin_;
this->crtBuf_->unshareOne();
+ this->crtBegin_ = this->crtBuf_->data();
+ this->crtEnd_ = this->crtBuf_->tail();
+ this->crtPos_ = this->crtBegin_ + offset;
maybeShared_ = false;
}
}
projects / folly.git / blobdiff