/*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* limitations under the License.
*/
-#ifndef FOLLY_CURSOR_H
-#define FOLLY_CURSOR_H
+#pragma once
#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/io/IOBufQueue.h"
-#include "folly/Likely.h"
-#include "folly/Memory.h"
+#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/portability/BitsFunctexcept.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_;
}
- /*
+ /**
* 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.
+ * May return 0 if the cursor is at the end of an IOBuf. Use peekBytes()
+ * instead if you want to avoid this. peekBytes() 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 {
return end - *this;
}
+ /**
+ * Return true if the cursor could advance the specified number of bytes
+ * from its current position.
+ * This is useful for applications that want to do checked reads instead of
+ * catching exceptions and is more efficient than using totalLength as it
+ * walks the minimal set of buffers in the chain to determine the result.
+ */
+ bool canAdvance(size_t amount) const {
+ const IOBuf* nextBuf = crtBuf_;
+ size_t available = length();
+ do {
+ if (available >= amount) {
+ return true;
+ }
+ amount -= available;
+ nextBuf = nextBuf->next();
+ available = nextBuf->length();
+ } while (nextBuf != buffer_);
+ return false;
+ }
+
+ /*
+ * 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;
+ }
+
+ /**
+ * Advances the cursor to the end of the entire IOBuf chain.
+ */
+ void advanceToEnd() {
+ offset_ = buffer_->prev()->length();
+ if (crtBuf_ != buffer_->prev()) {
+ crtBuf_ = buffer_->prev();
+ static_cast<Derived*>(this)->advanceDone();
+ }
+ }
+
Derived& operator+=(size_t offset) {
Derived* p = static_cast<Derived*>(this);
p->skip(offset);
return other;
}
+ Derived& operator-=(size_t offset) {
+ Derived* p = static_cast<Derived*>(this);
+ p->retreat(offset);
+ return *p;
+ }
+ Derived operator-(size_t offset) const {
+ Derived other(*this);
+ other.retreat(offset);
+ return other;
+ }
+
/**
* Compare cursors for equality/inequality.
*
}
template <class T>
- typename std::enable_if<std::is_arithmetic<T>::value, T>::type
- read() {
- T val;
- pull(&val, sizeof(T));
+ typename std::enable_if<std::is_arithmetic<T>::value, bool>::type tryRead(
+ T& val) {
+ if (LIKELY(length() >= sizeof(T))) {
+ val = loadUnaligned<T>(data());
+ offset_ += sizeof(T);
+ advanceBufferIfEmpty();
+ return true;
+ }
+ return pullAtMostSlow(&val, sizeof(T)) == sizeof(T);
+ }
+
+ template <class T>
+ bool tryReadBE(T& val) {
+ const bool result = tryRead(val);
+ val = Endian::big(val);
+ return result;
+ }
+
+ template <class T>
+ bool tryReadLE(T& val) {
+ const bool result = tryRead(val);
+ val = Endian::little(val);
+ return result;
+ }
+
+ template <class T>
+ T read() {
+ T val{};
+ if (!tryRead(val)) {
+ std::__throw_out_of_range("underflow");
+ }
return val;
}
*/
std::string readFixedString(size_t len) {
std::string str;
-
str.reserve(len);
- for (;;) {
- // Fast path: it all fits in one buffer.
- size_t available = length();
- if (LIKELY(available >= len)) {
- str.append(reinterpret_cast<const char*>(data()), len);
- offset_ += len;
- return str;
- }
-
- str.append(reinterpret_cast<const char*>(data()), available);
- if (UNLIKELY(!tryAdvanceBuffer())) {
- throw std::out_of_range("string underflow");
- }
- len -= available;
+ if (LIKELY(length() >= len)) {
+ str.append(reinterpret_cast<const char*>(data()), len);
+ offset_ += len;
+ advanceBufferIfEmpty();
+ } else {
+ readFixedStringSlow(&str, len);
}
+ return str;
}
/**
* vs. using pull().
*/
std::string readTerminatedString(
- char termChar = '\0',
- size_t maxLength = std::numeric_limits<size_t>::max()) {
- std::string str;
-
- for (;;) {
- const uint8_t* buf = data();
- size_t buflen = length();
+ char termChar = '\0',
+ size_t maxLength = std::numeric_limits<size_t>::max());
- size_t i = 0;
- while (i < buflen && buf[i] != termChar) {
- ++i;
+ /*
+ * Read all bytes until the specified predicate returns true.
+ *
+ * The predicate will be called on each byte in turn, until it returns false
+ * or until the end of the IOBuf chain is reached.
+ *
+ * Returns the result as a string.
+ */
+ template <typename Predicate>
+ std::string readWhile(const Predicate& predicate);
- // 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");
- }
- }
+ /*
+ * Read all bytes until the specified predicate returns true.
+ *
+ * This is a more generic version of readWhile() takes an arbitrary Output
+ * object, and calls Output::append() with each chunk of matching data.
+ */
+ template <typename Predicate, typename Output>
+ void readWhile(const Predicate& predicate, Output& out);
- str.append(reinterpret_cast<const char*>(buf), i);
- if (i < buflen) {
- skip(i + 1);
- return str;
- }
+ /*
+ * Skip all bytes until the specified predicate returns true.
+ *
+ * The predicate will be called on each byte in turn, until it returns false
+ * or until the end of the IOBuf chain is reached.
+ */
+ template <typename Predicate>
+ void skipWhile(const Predicate& predicate);
- skip(i);
+ size_t skipAtMost(size_t len) {
+ if (LIKELY(length() >= len)) {
+ offset_ += len;
+ advanceBufferIfEmpty();
+ return len;
+ }
+ return skipAtMostSlow(len);
+ }
- if (UNLIKELY(!tryAdvanceBuffer())) {
- throw std::out_of_range("string underflow");
- }
+ void skip(size_t len) {
+ if (LIKELY(length() >= len)) {
+ offset_ += len;
+ advanceBufferIfEmpty();
+ } else {
+ skipSlow(len);
}
}
- explicit CursorBase(BufType* buf)
- : crtBuf_(buf)
- , offset_(0)
- , buffer_(buf) {}
+ size_t retreatAtMost(size_t len) {
+ if (len <= offset_) {
+ offset_ -= len;
+ return len;
+ }
+ return retreatAtMostSlow(len);
+ }
- // Make all the templated classes friends for copy constructor.
- template <class D, typename B> friend class CursorBase;
+ void retreat(size_t len) {
+ if (len <= offset_) {
+ offset_ -= len;
+ } else {
+ retreatSlow(len);
+ }
+ }
- template <class T>
- explicit CursorBase(const T& cursor) {
- crtBuf_ = cursor.crtBuf_;
- offset_ = cursor.offset_;
- buffer_ = cursor.buffer_;
+ 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);
}
- // reset cursor to point to a new buffer.
- void reset(BufType* buf) {
- crtBuf_ = buf;
- buffer_ = buf;
- offset_ = 0;
+ void pull(void* buf, size_t len) {
+ if (LIKELY(length() >= len)) {
+ memcpy(buf, data(), len);
+ offset_ += len;
+ advanceBufferIfEmpty();
+ } else {
+ pullSlow(buf, len);
+ }
}
/**
* Return the available data in the current buffer.
* If you want to gather more data from the chain into a contiguous region
- * (for hopefully zero-copy access), use gather() before peek().
+ * (for hopefully zero-copy access), use gather() before peekBytes().
*/
- std::pair<const uint8_t*, size_t> peek() {
+ ByteRange peekBytes() {
// Ensure that we're pointing to valid data
size_t available = length();
while (UNLIKELY(available == 0 && tryAdvanceBuffer())) {
available = length();
}
-
- return std::make_pair(data(), available);
+ return ByteRange{data(), available};
}
- void pull(void* buf, size_t len) {
- if (UNLIKELY(pullAtMost(buf, len) != len)) {
- throw std::out_of_range("underflow");
- }
+ /**
+ * Alternate version of peekBytes() that returns a std::pair
+ * instead of a ByteRange. (This method pre-dates ByteRange.)
+ *
+ * This function will eventually be deprecated.
+ */
+ std::pair<const uint8_t*, size_t> peek() {
+ auto bytes = peekBytes();
+ return std::make_pair(bytes.data(), bytes.size());
}
void clone(std::unique_ptr<folly::IOBuf>& buf, size_t len) {
if (UNLIKELY(cloneAtMost(buf, len) != len)) {
- throw std::out_of_range("underflow");
+ std::__throw_out_of_range("underflow");
}
}
void clone(folly::IOBuf& buf, size_t len) {
if (UNLIKELY(cloneAtMost(buf, len) != len)) {
- throw std::out_of_range("underflow");
- }
- }
-
- void skip(size_t len) {
- if (UNLIKELY(skipAtMost(len) != len)) {
- 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;
+ std::__throw_out_of_range("underflow");
}
}
size_t cloneAtMost(folly::IOBuf& buf, size_t len) {
- buf = folly::IOBuf();
-
std::unique_ptr<folly::IOBuf> tmp;
size_t copied = 0;
for (int loopCount = 0; true; ++loopCount) {
}
offset_ += len;
+ advanceBufferIfEmpty();
return copied + len;
}
-
if (loopCount == 0) {
crtBuf_->cloneOneInto(buf);
buf.trimStart(offset_);
size_t cloneAtMost(std::unique_ptr<folly::IOBuf>& buf, size_t len) {
if (!buf) {
- buf = make_unique<folly::IOBuf>();
+ buf = std::make_unique<folly::IOBuf>();
}
-
return cloneAtMost(*buf, len);
}
- 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;
- }
- }
-
/**
* Return the distance between two cursors.
*/
}
if (otherBuf == other.buffer_) {
- throw std::out_of_range("wrap-around");
+ std::__throw_out_of_range("wrap-around");
}
len += offset_;
} else {
if (offset_ < other.offset_) {
- throw std::out_of_range("underflow");
+ std::__throw_out_of_range("underflow");
}
len += offset_ - other.offset_;
size_t operator-(const BufType* buf) const {
size_t len = 0;
- BufType *curBuf = buf;
+ const BufType* curBuf = buf;
while (curBuf != crtBuf_) {
len += curBuf->length();
curBuf = curBuf->next();
if (curBuf == buf || curBuf == buffer_) {
- throw std::out_of_range("wrap-around");
+ std::__throw_out_of_range("wrap-around");
}
}
}
protected:
- BufType* crtBuf_;
- size_t offset_;
-
- ~CursorBase(){}
+ ~CursorBase() { }
BufType* head() {
return buffer_;
return true;
}
+ bool tryRetreatBuffer() {
+ if (UNLIKELY(crtBuf_ == buffer_)) {
+ offset_ = 0;
+ return false;
+ }
+ crtBuf_ = crtBuf_->prev();
+ offset_ = crtBuf_->length();
+ static_cast<Derived*>(this)->advanceDone();
+ 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())) {
+ std::__throw_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)) {
+ std::__throw_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)) {
+ std::__throw_out_of_range("underflow");
+ }
+ }
+
+ size_t retreatAtMostSlow(size_t len) {
+ size_t retreated = 0;
+ for (size_t available; (available = offset_) < len;) {
+ retreated += available;
+ if (UNLIKELY(!tryRetreatBuffer())) {
+ return retreated;
+ }
+ len -= available;
+ }
+ offset_ -= len;
+ return retreated + len;
+ }
+
+ void retreatSlow(size_t len) {
+ if (UNLIKELY(retreatAtMostSlow(len) != len)) {
+ std::__throw_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:
void push(const uint8_t* buf, size_t len) {
Derived* d = static_cast<Derived*>(this);
if (d->pushAtMost(buf, len) != len) {
- throw std::out_of_range("overflow");
+ std::__throw_out_of_range("overflow");
}
}
-};
-} // namespace detail
+ void push(ByteRange buf) {
+ if (this->pushAtMost(buf) != buf.size()) {
+ std::__throw_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) {
+ std::__throw_out_of_range("overflow");
+ }
+ }
+
+ size_t pushAtMost(Cursor cursor, size_t len) {
+ size_t written = 0;
+ for(;;) {
+ auto currentBuffer = cursor.peekBytes();
+ const uint8_t* crtData = currentBuffer.data();
+ size_t available = currentBuffer.size();
+ 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) {}
/**
return this->crtBuf_->gather(this->offset_ + size);
}
+ using detail::Writable<RWCursor<access>>::pushAtMost;
size_t pushAtMost(const uint8_t* buf, size_t len) {
+ // We have to explicitly check for an input length of 0.
+ // We support buf being nullptr in this case, but we need to avoid calling
+ // memcpy() with a null source pointer, since that is undefined behavior
+ // even if the length is 0.
+ if (len == 0) {
+ return 0;
+ }
+
size_t copied = 0;
for (;;) {
// Fast path: the current buffer is big enough.
// Waste the rest of the current buffer and allocate a new one.
// Don't make it too small, either.
if (growth_ == 0) {
- throw std::out_of_range("can't grow buffer chain");
+ std::__throw_out_of_range("can't grow buffer chain");
}
n = std::max(n, growth_);
crtBuf_ = buffer_->prev();
}
+ using detail::Writable<Appender>::pushAtMost;
size_t pushAtMost(const uint8_t* buf, size_t len) {
+ // We have to explicitly check for an input length of 0.
+ // We support buf being nullptr in this case, but we need to avoid calling
+ // memcpy() with a null source pointer, since that is undefined behavior
+ // even if the length is 0.
+ if (len == 0) {
+ return 0;
+ }
+
size_t copied = 0;
for (;;) {
// Fast path: it all fits in one buffer.
}
}
+ /*
+ * 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_);
queue_->postallocate(sizeof(T));
}
-
+ using detail::Writable<QueueAppender>::pushAtMost;
size_t pushAtMost(const uint8_t* buf, size_t len) {
- size_t remaining = len;
+ // Fill the current buffer
+ const size_t copyLength = std::min(len, length());
+ if (copyLength != 0) {
+ memcpy(writableData(), buf, copyLength);
+ append(copyLength);
+ buf += copyLength;
+ }
+ // Allocate more buffers as necessary
+ size_t remaining = len - copyLength;
while (remaining != 0) {
auto p = queue_->preallocate(std::min(remaining, growth_),
growth_,
}
}
+ void insert(const folly::IOBuf& buf) {
+ insert(buf.clone());
+ }
+
private:
folly::IOBufQueue* queue_;
size_t growth_;
}} // folly::io
-#endif // FOLLY_CURSOR_H
+#include <folly/io/Cursor-inl.h>
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