/*
- * Copyright 2013 Facebook, Inc.
+ * Copyright 2015 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
#define FOLLY_CURSOR_H
#include <assert.h>
+#include <cstdarg>
#include <stdexcept>
#include <string.h>
#include <type_traits>
#include <memory>
-#include "folly/Bits.h"
-#include "folly/io/IOBuf.h"
-#include "folly/Likely.h"
+#include <folly/Bits.h>
+#include <folly/io/IOBuf.h>
+#include <folly/io/IOBufQueue.h>
+#include <folly/Likely.h>
+#include <folly/Memory.h>
+#include <folly/Portability.h>
+#include <folly/Range.h>
/**
* Cursor class for fast iteration over IOBuf chains.
* access to the buffer (you need to call unshare() yourself if necessary).
**/
namespace folly { namespace io {
+
namespace detail {
-template <class Derived, typename BufType>
+template <class Derived, class BufType>
class CursorBase {
+ // 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) { }
+
+ /**
+ * Copy constructor.
+ *
+ * This also allows constructing a CursorBase from other derived types.
+ * For instance, this allows constructing a Cursor from an RWPrivateCursor.
+ */
+ template <class OtherDerived, class OtherBuf>
+ explicit CursorBase(const CursorBase<OtherDerived, OtherBuf>& cursor)
+ : crtBuf_(cursor.crtBuf_),
+ offset_(cursor.offset_),
+ buffer_(cursor.buffer_) { }
+
+ /**
+ * Reset cursor to point to a new buffer.
+ */
+ void reset(BufType* buf) {
+ crtBuf_ = buf;
+ buffer_ = buf;
+ offset_ = 0;
+ }
+
const uint8_t* data() const {
return crtBuf_->data() + offset_;
}
- // Space available in the current IOBuf. May be 0; use peek() instead which
- // will always point to a non-empty chunk of data or at the end of the
- // chain.
+ /**
+ * Return the remaining space available in the current IOBuf.
+ *
+ * May return 0 if the cursor is at the end of an IOBuf. Use peek() instead
+ * if you want to avoid this. peek() will advance to the next non-empty
+ * IOBuf (up to the end of the chain) if the cursor is currently pointing at
+ * the end of a buffer.
+ */
size_t length() const {
return crtBuf_->length() - offset_;
}
+ /**
+ * Return the space available until the end of the entire IOBuf chain.
+ */
+ size_t totalLength() const {
+ if (crtBuf_ == buffer_) {
+ return crtBuf_->computeChainDataLength() - offset_;
+ }
+ CursorBase end(buffer_->prev());
+ end.offset_ = end.buffer_->length();
+ return end - *this;
+ }
+
+ /*
+ * Return true if the cursor is at the end of the entire IOBuf chain.
+ */
+ bool isAtEnd() const {
+ // Check for the simple cases first.
+ if (offset_ != crtBuf_->length()) {
+ return false;
+ }
+ if (crtBuf_ == buffer_->prev()) {
+ return true;
+ }
+ // We are at the end of a buffer, but it isn't the last buffer.
+ // We might still be at the end if the remaining buffers in the chain are
+ // empty.
+ const IOBuf* buf = crtBuf_->next();;
+ while (buf != buffer_) {
+ if (buf->length() > 0) {
+ return false;
+ }
+ buf = buf->next();
+ }
+ return true;
+ }
+
Derived& operator+=(size_t offset) {
Derived* p = static_cast<Derived*>(this);
p->skip(offset);
return *p;
}
+ Derived operator+(size_t offset) const {
+ Derived other(*this);
+ other.skip(offset);
+ return other;
+ }
+
+ /**
+ * Compare cursors for equality/inequality.
+ *
+ * Two cursors are equal if they are pointing to the same location in the
+ * same IOBuf chain.
+ */
+ bool operator==(const Derived& other) const {
+ return (offset_ == other.offset_) && (crtBuf_ == other.crtBuf_);
+ }
+ bool operator!=(const Derived& other) const {
+ return !operator==(other);
+ }
template <class T>
- typename std::enable_if<std::is_integral<T>::value, T>::type
- read() {
+ typename std::enable_if<std::is_arithmetic<T>::value, T>::type read() {
T val;
- pull(&val, sizeof(T));
+ if (LIKELY(length() >= sizeof(T))) {
+ val = loadUnaligned<T>(data());
+ offset_ += sizeof(T);
+ advanceBufferIfEmpty();
+ } else {
+ pullSlow(&val, sizeof(T));
+ }
return val;
}
return Endian::little(read<T>());
}
- explicit CursorBase(BufType* buf)
- : crtBuf_(buf)
- , offset_(0)
- , buffer_(buf) {}
+ /**
+ * Read a fixed-length string.
+ *
+ * The std::string-based APIs should probably be avoided unless you
+ * ultimately want the data to live in an std::string. You're better off
+ * using the pull() APIs to copy into a raw buffer otherwise.
+ */
+ std::string readFixedString(size_t len) {
+ std::string str;
+ str.reserve(len);
+ if (LIKELY(length() >= len)) {
+ str.append(reinterpret_cast<const char*>(data()), len);
+ offset_ += len;
+ advanceBufferIfEmpty();
+ } else {
+ readFixedStringSlow(&str, len);
+ }
+ return str;
+ }
- // Make all the templated classes friends for copy constructor.
- template <class D, typename B> friend class CursorBase;
+ /**
+ * Read a string consisting of bytes until the given terminator character is
+ * seen. Raises an std::length_error if maxLength bytes have been processed
+ * before the terminator is seen.
+ *
+ * See comments in readFixedString() about when it's appropriate to use this
+ * vs. using pull().
+ */
+ std::string readTerminatedString(
+ char termChar = '\0',
+ size_t maxLength = std::numeric_limits<size_t>::max()) {
+ std::string str;
- template <class T>
- explicit CursorBase(const T& cursor) {
- crtBuf_ = cursor.crtBuf_;
- offset_ = cursor.offset_;
- buffer_ = cursor.buffer_;
+ for (;;) {
+ const uint8_t* buf = data();
+ size_t buflen = length();
+
+ size_t i = 0;
+ while (i < buflen && buf[i] != termChar) {
+ ++i;
+
+ // Do this check after incrementing 'i', as even though we start at the
+ // 0 byte, it still represents a single character
+ if (str.length() + i >= maxLength) {
+ throw std::length_error("string overflow");
+ }
+ }
+
+ str.append(reinterpret_cast<const char*>(buf), i);
+ if (i < buflen) {
+ skip(i + 1);
+ return str;
+ }
+
+ skip(i);
+ }
}
- // reset cursor to point to a new buffer.
- void reset(BufType* buf) {
- crtBuf_ = buf;
- buffer_ = buf;
- offset_ = 0;
+ size_t skipAtMost(size_t len) {
+ if (LIKELY(length() >= len)) {
+ offset_ += len;
+ advanceBufferIfEmpty();
+ return len;
+ }
+ return skipAtMostSlow(len);
+ }
+
+ void skip(size_t len) {
+ if (LIKELY(length() >= len)) {
+ offset_ += len;
+ advanceBufferIfEmpty();
+ } else {
+ skipSlow(len);
+ }
+ }
+
+ size_t pullAtMost(void* buf, size_t len) {
+ // Fast path: it all fits in one buffer.
+ if (LIKELY(length() >= len)) {
+ memcpy(buf, data(), len);
+ offset_ += len;
+ advanceBufferIfEmpty();
+ return len;
+ }
+ return pullAtMostSlow(buf, len);
+ }
+
+ void pull(void* buf, size_t len) {
+ if (LIKELY(length() >= len)) {
+ memcpy(buf, data(), len);
+ offset_ += len;
+ advanceBufferIfEmpty();
+ } else {
+ pullSlow(buf, len);
+ }
}
/**
while (UNLIKELY(available == 0 && tryAdvanceBuffer())) {
available = length();
}
-
return std::make_pair(data(), available);
}
- void pull(void* buf, size_t length) {
- if (UNLIKELY(pullAtMost(buf, length) != length)) {
+ void clone(std::unique_ptr<folly::IOBuf>& buf, size_t len) {
+ if (UNLIKELY(cloneAtMost(buf, len) != len)) {
throw std::out_of_range("underflow");
}
}
- void clone(std::unique_ptr<folly::IOBuf>& buf, size_t length) {
- if (UNLIKELY(cloneAtMost(buf, length) != length)) {
+ void clone(folly::IOBuf& buf, size_t len) {
+ if (UNLIKELY(cloneAtMost(buf, len) != len)) {
throw std::out_of_range("underflow");
}
}
- void skip(size_t length) {
- if (UNLIKELY(skipAtMost(length) != length)) {
- throw std::out_of_range("underflow");
- }
- }
-
- size_t pullAtMost(void* buf, size_t len) {
- uint8_t* p = reinterpret_cast<uint8_t*>(buf);
- size_t copied = 0;
- for (;;) {
- // Fast path: it all fits in one buffer.
- size_t available = length();
- if (LIKELY(available >= len)) {
- memcpy(p, data(), len);
- offset_ += len;
- return copied + len;
- }
-
- memcpy(p, data(), available);
- copied += available;
- if (UNLIKELY(!tryAdvanceBuffer())) {
- return copied;
- }
- p += available;
- len -= available;
- }
- }
-
- size_t cloneAtMost(std::unique_ptr<folly::IOBuf>& buf, size_t len) {
- buf.reset(nullptr);
+ size_t cloneAtMost(folly::IOBuf& buf, size_t len) {
+ buf = folly::IOBuf();
std::unique_ptr<folly::IOBuf> tmp;
size_t copied = 0;
- for (;;) {
+ for (int loopCount = 0; true; ++loopCount) {
// Fast path: it all fits in one buffer.
size_t available = length();
if (LIKELY(available >= len)) {
- tmp = crtBuf_->cloneOne();
- tmp->trimStart(offset_);
- tmp->trimEnd(tmp->length() - len);
- offset_ += len;
- if (!buf) {
- buf = std::move(tmp);
+ if (loopCount == 0) {
+ crtBuf_->cloneOneInto(buf);
+ buf.trimStart(offset_);
+ buf.trimEnd(buf.length() - len);
} else {
- buf->prependChain(std::move(tmp));
+ tmp = crtBuf_->cloneOne();
+ tmp->trimStart(offset_);
+ tmp->trimEnd(tmp->length() - len);
+ buf.prependChain(std::move(tmp));
}
+
+ offset_ += len;
+ advanceBufferIfEmpty();
return copied + len;
}
- tmp = crtBuf_->cloneOne();
- tmp->trimStart(offset_);
- if (!buf) {
- buf = std::move(tmp);
+ if (loopCount == 0) {
+ crtBuf_->cloneOneInto(buf);
+ buf.trimStart(offset_);
} else {
- buf->prependChain(std::move(tmp));
+ tmp = crtBuf_->cloneOne();
+ tmp->trimStart(offset_);
+ buf.prependChain(std::move(tmp));
}
copied += available;
}
}
- size_t skipAtMost(size_t len) {
- size_t skipped = 0;
- for (;;) {
- // Fast path: it all fits in one buffer.
- size_t available = length();
- if (LIKELY(available >= len)) {
- offset_ += len;
- return skipped + len;
- }
-
- skipped += available;
- if (UNLIKELY(!tryAdvanceBuffer())) {
- return skipped;
- }
- len -= available;
+ size_t cloneAtMost(std::unique_ptr<folly::IOBuf>& buf, size_t len) {
+ if (!buf) {
+ buf = make_unique<folly::IOBuf>();
}
+ return cloneAtMost(*buf, len);
}
/**
}
protected:
- BufType* crtBuf_;
- size_t offset_;
+ ~CursorBase() { }
- ~CursorBase(){}
+ BufType* head() {
+ return buffer_;
+ }
bool tryAdvanceBuffer() {
BufType* nextBuf = crtBuf_->next();
return true;
}
+ void advanceBufferIfEmpty() {
+ if (length() == 0) {
+ tryAdvanceBuffer();
+ }
+ }
+
+ BufType* crtBuf_;
+ size_t offset_ = 0;
+
private:
+ void readFixedStringSlow(std::string* str, size_t len) {
+ for (size_t available; (available = length()) < len; ) {
+ str->append(reinterpret_cast<const char*>(data()), available);
+ if (UNLIKELY(!tryAdvanceBuffer())) {
+ throw std::out_of_range("string underflow");
+ }
+ len -= available;
+ }
+ str->append(reinterpret_cast<const char*>(data()), len);
+ offset_ += len;
+ advanceBufferIfEmpty();
+ }
+
+ size_t pullAtMostSlow(void* buf, size_t len) {
+ uint8_t* p = reinterpret_cast<uint8_t*>(buf);
+ size_t copied = 0;
+ for (size_t available; (available = length()) < len; ) {
+ memcpy(p, data(), available);
+ copied += available;
+ if (UNLIKELY(!tryAdvanceBuffer())) {
+ return copied;
+ }
+ p += available;
+ len -= available;
+ }
+ memcpy(p, data(), len);
+ offset_ += len;
+ advanceBufferIfEmpty();
+ return copied + len;
+ }
+
+ void pullSlow(void* buf, size_t len) {
+ if (UNLIKELY(pullAtMostSlow(buf, len) != len)) {
+ throw std::out_of_range("underflow");
+ }
+ }
+
+ size_t skipAtMostSlow(size_t len) {
+ size_t skipped = 0;
+ for (size_t available; (available = length()) < len; ) {
+ skipped += available;
+ if (UNLIKELY(!tryAdvanceBuffer())) {
+ return skipped;
+ }
+ len -= available;
+ }
+ offset_ += len;
+ advanceBufferIfEmpty();
+ return skipped + len;
+ }
+
+ void skipSlow(size_t len) {
+ if (UNLIKELY(skipAtMostSlow(len) != len)) {
+ throw std::out_of_range("underflow");
+ }
+ }
+
void advanceDone() {
}
BufType* buffer_;
};
+} // namespace detail
+
+class Cursor : public detail::CursorBase<Cursor, const IOBuf> {
+ public:
+ explicit Cursor(const IOBuf* buf)
+ : detail::CursorBase<Cursor, const IOBuf>(buf) {}
+
+ template <class OtherDerived, class OtherBuf>
+ explicit Cursor(const detail::CursorBase<OtherDerived, OtherBuf>& cursor)
+ : detail::CursorBase<Cursor, const IOBuf>(cursor) {}
+};
+
+namespace detail {
+
template <class Derived>
class Writable {
public:
template <class T>
- typename std::enable_if<std::is_integral<T>::value>::type
+ typename std::enable_if<std::is_arithmetic<T>::value>::type
write(T value) {
const uint8_t* u8 = reinterpret_cast<const uint8_t*>(&value);
- push(u8, sizeof(T));
+ Derived* d = static_cast<Derived*>(this);
+ d->push(u8, sizeof(T));
}
template <class T>
void writeBE(T value) {
- write(Endian::big(value));
+ Derived* d = static_cast<Derived*>(this);
+ d->write(Endian::big(value));
}
template <class T>
void writeLE(T value) {
- write(Endian::little(value));
+ Derived* d = static_cast<Derived*>(this);
+ d->write(Endian::little(value));
}
void push(const uint8_t* buf, size_t len) {
throw std::out_of_range("overflow");
}
}
-};
-} // namespace detail
+ void push(ByteRange buf) {
+ if (this->pushAtMost(buf) != buf.size()) {
+ throw std::out_of_range("overflow");
+ }
+ }
-class Cursor : public detail::CursorBase<Cursor, const IOBuf> {
- public:
- explicit Cursor(const IOBuf* buf)
- : detail::CursorBase<Cursor, const IOBuf>(buf) {}
+ size_t pushAtMost(ByteRange buf) {
+ Derived* d = static_cast<Derived*>(this);
+ return d->pushAtMost(buf.data(), buf.size());
+ }
- template <class CursorType>
- explicit Cursor(CursorType& cursor)
- : detail::CursorBase<Cursor, const IOBuf>(cursor) {}
+ /**
+ * push len bytes of data from input cursor, data could be in an IOBuf chain.
+ * If input cursor contains less than len bytes, or this cursor has less than
+ * len bytes writable space, an out_of_range exception will be thrown.
+ */
+ void push(Cursor cursor, size_t len) {
+ if (this->pushAtMost(cursor, len) != len) {
+ throw std::out_of_range("overflow");
+ }
+ }
+
+ size_t pushAtMost(Cursor cursor, size_t len) {
+ size_t written = 0;
+ for(;;) {
+ auto currentBuffer = cursor.peek();
+ const uint8_t* crtData = currentBuffer.first;
+ size_t available = currentBuffer.second;
+ if (available == 0) {
+ // end of buffer chain
+ return written;
+ }
+ // all data is in current buffer
+ if (available >= len) {
+ this->push(crtData, len);
+ cursor.skip(len);
+ return written + len;
+ }
+
+ // write the whole current IOBuf
+ this->push(crtData, available);
+ cursor.skip(available);
+ written += available;
+ len -= available;
+ }
+ }
};
+} // namespace detail
+
enum class CursorAccess {
PRIVATE,
UNSHARE
: detail::CursorBase<RWCursor<access>, IOBuf>(buf),
maybeShared_(true) {}
- template <class CursorType>
- explicit RWCursor(CursorType& cursor)
+ template <class OtherDerived, class OtherBuf>
+ explicit RWCursor(const detail::CursorBase<OtherDerived, OtherBuf>& cursor)
: detail::CursorBase<RWCursor<access>, IOBuf>(cursor),
maybeShared_(true) {}
/**
* by coalescing subsequent buffers from the chain as necessary.
*/
void gather(size_t n) {
+ // Forbid attempts to gather beyond the end of this IOBuf chain.
+ // Otherwise we could try to coalesce the head of the chain and end up
+ // accidentally freeing it, invalidating the pointer owned by external
+ // code.
+ //
+ // If crtBuf_ == head() then IOBuf::gather() will perform all necessary
+ // checking. We only have to perform an explicit check here when calling
+ // gather() on a non-head element.
+ 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);
}
+ void gatherAtMost(size_t n) {
+ size_t size = std::min(n, this->totalLength());
+ return this->crtBuf_->gather(this->offset_ + size);
+ }
+ using detail::Writable<RWCursor<access>>::pushAtMost;
size_t pushAtMost(const uint8_t* buf, size_t len) {
size_t copied = 0;
for (;;) {
folly::IOBuf* nextBuf;
if (this->offset_ == 0) {
// Can just prepend
- nextBuf = buf.get();
+ nextBuf = this->crtBuf_;
this->crtBuf_->prependChain(std::move(buf));
} else {
std::unique_ptr<folly::IOBuf> remaining;
*/
class Appender : public detail::Writable<Appender> {
public:
- Appender(IOBuf* buf, uint32_t growth)
+ Appender(IOBuf* buf, uint64_t growth)
: buffer_(buf),
crtBuf_(buf->prev()),
growth_(growth) {
* Ensure at least n contiguous bytes available to write.
* Postcondition: length() >= n.
*/
- void ensure(uint32_t n) {
+ void ensure(uint64_t n) {
if (LIKELY(length() >= n)) {
return;
}
crtBuf_ = buffer_->prev();
}
+ using detail::Writable<Appender>::pushAtMost;
size_t pushAtMost(const uint8_t* buf, size_t len) {
size_t copied = 0;
for (;;) {
}
}
+ /*
+ * Append to the end of this buffer, using a printf() style
+ * format specifier.
+ *
+ * Note that folly/Format.h provides nicer and more type-safe mechanisms
+ * for formatting strings, which should generally be preferred over
+ * printf-style formatting. Appender objects can be used directly as an
+ * output argument for Formatter objects. For example:
+ *
+ * Appender app(&iobuf);
+ * format("{} {}", "hello", "world")(app);
+ *
+ * However, printf-style strings are still needed when dealing with existing
+ * third-party code in some cases.
+ *
+ * This will always add a nul-terminating character after the end
+ * of the output. However, the buffer data length will only be updated to
+ * include the data itself. The nul terminator will be the first byte in the
+ * buffer tailroom.
+ *
+ * This method may throw exceptions on error.
+ */
+ void printf(FOLLY_PRINTF_FORMAT const char* fmt, ...)
+ FOLLY_PRINTF_FORMAT_ATTR(2, 3);
+
+ void vprintf(const char* fmt, va_list ap);
+
+ /*
+ * Calling an Appender object with a StringPiece will append the string
+ * piece. This allows Appender objects to be used directly with
+ * Formatter.
+ */
+ void operator()(StringPiece sp) {
+ push(ByteRange(sp));
+ }
+
private:
bool tryGrowChain() {
assert(crtBuf_->next() == buffer_);
IOBuf* buffer_;
IOBuf* crtBuf_;
- uint32_t growth_;
+ uint64_t growth_;
+};
+
+class QueueAppender : public detail::Writable<QueueAppender> {
+ public:
+ /**
+ * Create an Appender that writes to a IOBufQueue. When we allocate
+ * space in the queue, we grow no more than growth bytes at once
+ * (unless you call ensure() with a bigger value yourself).
+ */
+ QueueAppender(IOBufQueue* queue, uint64_t growth) {
+ reset(queue, growth);
+ }
+
+ void reset(IOBufQueue* queue, uint64_t growth) {
+ queue_ = queue;
+ growth_ = growth;
+ }
+
+ uint8_t* writableData() {
+ return static_cast<uint8_t*>(queue_->writableTail());
+ }
+
+ size_t length() const { return queue_->tailroom(); }
+
+ void append(size_t n) { queue_->postallocate(n); }
+
+ // Ensure at least n contiguous; can go above growth_, throws if
+ // not enough room.
+ void ensure(uint64_t n) { queue_->preallocate(n, growth_); }
+
+ template <class T>
+ typename std::enable_if<std::is_arithmetic<T>::value>::type
+ write(T value) {
+ // We can't fail.
+ auto p = queue_->preallocate(sizeof(T), growth_);
+ storeUnaligned(p.first, value);
+ queue_->postallocate(sizeof(T));
+ }
+
+ using detail::Writable<QueueAppender>::pushAtMost;
+ size_t pushAtMost(const uint8_t* buf, size_t len) {
+ size_t remaining = len;
+ while (remaining != 0) {
+ auto p = queue_->preallocate(std::min(remaining, growth_),
+ growth_,
+ remaining);
+ memcpy(p.first, buf, p.second);
+ queue_->postallocate(p.second);
+ buf += p.second;
+ remaining -= p.second;
+ }
+
+ return len;
+ }
+
+ void insert(std::unique_ptr<folly::IOBuf> buf) {
+ if (buf) {
+ queue_->append(std::move(buf), true);
+ }
+ }
+
+ private:
+ folly::IOBufQueue* queue_;
+ size_t growth_;
};
}} // folly::io
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