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/****************************************************************************
**
** Copyright (C) 2015 The Qt Company Ltd.
** Contact: http://www.qt.io/licensing/
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see http://www.qt.io/terms-conditions. For further
** information use the contact form at http://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 or version 3 as published by the Free
** Software Foundation and appearing in the file LICENSE.LGPLv21 and
** LICENSE.LGPLv3 included in the packaging of this file. Please review the
** following information to ensure the GNU Lesser General Public License
** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** As a special exception, The Qt Company gives you certain additional
** rights. These rights are described in The Qt Company LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#ifndef QRINGBUFFER_P_H
#define QRINGBUFFER_P_H
//
// W A R N I N G
// -------------
//
// This file is not part of the Qt API. It exists for the convenience
// of a number of Qt sources files. This header file may change from
// version to version without notice, or even be removed.
//
// We mean it.
//
#include <QtCore/qbytearray.h>
#include <QtCore/qlist.h>
QT_BEGIN_NAMESPACE
class QRingBuffer
{
public:
inline QRingBuffer(int growth = 4096) : basicBlockSize(growth) {
buffers << QByteArray();
clear();
}
inline int nextDataBlockSize() const {
return (tailBuffer == 0 ? tail : buffers.first().size()) - head;
}
inline const char *readPointer() const {
return buffers.isEmpty() ? 0 : (buffers.first().constData() + head);
}
// access the bytes at a specified position
// the out-variable length will contain the amount of bytes readable
// from there, e.g. the amount still the same QByteArray
inline const char *readPointerAtPosition(qint64 pos, qint64 &length) const {
if (buffers.isEmpty()) {
length = 0;
return 0;
}
if (pos >= bufferSize) {
length = 0;
return 0;
}
// special case: it is in the first buffer
int nextDataBlockSizeValue = nextDataBlockSize();
if (pos - head < nextDataBlockSizeValue) {
length = nextDataBlockSizeValue - pos;
return buffers.at(0).constData() + head + pos;
}
// special case: we only had one buffer and tried to read over it
if (buffers.length() == 1) {
length = 0;
return 0;
}
// skip the first
pos -= nextDataBlockSizeValue;
// normal case: it is somewhere in the second to the-one-before-the-tailBuffer
for (int i = 1; i < tailBuffer; i++) {
if (pos >= buffers[i].size()) {
pos -= buffers[i].size();
continue;
}
length = buffers[i].length() - pos;
return buffers[i].constData() + pos;
}
// it is in the tail buffer
length = tail - pos;
return buffers[tailBuffer].constData() + pos;
}
inline void free(int bytes) {
bufferSize -= bytes;
if (bufferSize < 0)
bufferSize = 0;
for (;;) {
int nextBlockSize = nextDataBlockSize();
if (bytes < nextBlockSize) {
head += bytes;
if (head == tail && tailBuffer == 0)
head = tail = 0;
break;
}
bytes -= nextBlockSize;
if (buffers.count() == 1) {
if (buffers.at(0).size() != basicBlockSize)
buffers[0].resize(basicBlockSize);
head = tail = 0;
tailBuffer = 0;
break;
}
buffers.removeAt(0);
--tailBuffer;
head = 0;
}
if (isEmpty())
clear(); // try to minify/squeeze us
}
inline char *reserve(int bytes) {
// if this is a fresh empty QRingBuffer
if (bufferSize == 0) {
buffers[0].resize(qMax(basicBlockSize, bytes));
bufferSize += bytes;
tail = bytes;
return buffers[tailBuffer].data();
}
bufferSize += bytes;
// if there is already enough space, simply return.
if (tail + bytes <= buffers.at(tailBuffer).size()) {
char *writePtr = buffers[tailBuffer].data() + tail;
tail += bytes;
return writePtr;
}
// if our buffer isn't half full yet, simply resize it.
if (tail < buffers.at(tailBuffer).size() / 2) {
buffers[tailBuffer].resize(tail + bytes);
char *writePtr = buffers[tailBuffer].data() + tail;
tail += bytes;
return writePtr;
}
// shrink this buffer to its current size
buffers[tailBuffer].resize(tail);
// create a new QByteArray with the right size
buffers << QByteArray();
++tailBuffer;
buffers[tailBuffer].resize(qMax(basicBlockSize, bytes));
tail = bytes;
return buffers[tailBuffer].data();
}
inline void truncate(int pos) {
if (pos < size())
chop(size() - pos);
}
inline void chop(int bytes) {
bufferSize -= bytes;
if (bufferSize < 0)
bufferSize = 0;
for (;;) {
// special case: head and tail are in the same buffer
if (tailBuffer == 0) {
tail -= bytes;
if (tail <= head)
tail = head = 0;
return;
}
if (bytes <= tail) {
tail -= bytes;
return;
}
bytes -= tail;
buffers.removeAt(tailBuffer);
--tailBuffer;
tail = buffers.at(tailBuffer).size();
}
if (isEmpty())
clear(); // try to minify/squeeze us
}
inline bool isEmpty() const {
return tailBuffer == 0 && tail == 0;
}
inline int getChar() {
if (isEmpty())
return -1;
char c = *readPointer();
free(1);
return int(uchar(c));
}
inline void putChar(char c) {
char *ptr = reserve(1);
*ptr = c;
}
inline void ungetChar(char c) {
--head;
if (head < 0) {
buffers.prepend(QByteArray());
buffers[0].resize(basicBlockSize);
head = basicBlockSize - 1;
++tailBuffer;
}
buffers[0][head] = c;
++bufferSize;
}
inline int size() const {
return bufferSize;
}
inline void clear() {
buffers.erase(buffers.begin() + 1, buffers.end());
buffers[0].resize(0);
buffers[0].squeeze();
head = tail = 0;
tailBuffer = 0;
bufferSize = 0;
}
inline int indexOf(char c) const {
int index = 0;
for (int i = 0; i < buffers.size(); ++i) {
int start = 0;
int end = buffers.at(i).size();
if (i == 0)
start = head;
if (i == tailBuffer)
end = tail;
const char *ptr = buffers.at(i).data() + start;
for (int j = start; j < end; ++j) {
if (*ptr++ == c)
return index;
++index;
}
}
return -1;
}
inline int indexOf(char c, int maxLength) const {
int index = 0;
int remain = qMin(size(), maxLength);
for (int i = 0; remain && i < buffers.size(); ++i) {
int start = 0;
int end = buffers.at(i).size();
if (i == 0)
start = head;
if (i == tailBuffer)
end = tail;
if (remain < end - start) {
end = start + remain;
remain = 0;
} else {
remain -= end - start;
}
const char *ptr = buffers.at(i).data() + start;
for (int j = start; j < end; ++j) {
if (*ptr++ == c)
return index;
++index;
}
}
return -1;
}
inline int read(char *data, int maxLength) {
int bytesToRead = qMin(size(), maxLength);
int readSoFar = 0;
while (readSoFar < bytesToRead) {
const char *ptr = readPointer();
int bytesToReadFromThisBlock = qMin(bytesToRead - readSoFar, nextDataBlockSize());
if (data)
memcpy(data + readSoFar, ptr, bytesToReadFromThisBlock);
readSoFar += bytesToReadFromThisBlock;
free(bytesToReadFromThisBlock);
}
return readSoFar;
}
inline QByteArray read(int maxLength) {
QByteArray tmp;
tmp.resize(qMin(maxLength, size()));
read(tmp.data(), tmp.size());
return tmp;
}
inline QByteArray readAll() {
return read(size());
}
// read an unspecified amount (will read the first buffer)
inline QByteArray read() {
if (bufferSize == 0)
return QByteArray();
// multiple buffers, just take the first one
if (head == 0 && tailBuffer != 0) {
QByteArray qba = buffers.takeFirst();
--tailBuffer;
bufferSize -= qba.length();
return qba;
}
// one buffer with good value for head. Just take it.
if (head == 0 && tailBuffer == 0) {
QByteArray qba = buffers.takeFirst();
qba.resize(tail);
buffers << QByteArray();
bufferSize = 0;
tail = 0;
return qba;
}
// Bad case: We have to memcpy.
// We can avoid by initializing the QRingBuffer with basicBlockSize of 0
// and only using this read() function.
QByteArray qba(readPointer(), nextDataBlockSize());
buffers.removeFirst();
head = 0;
if (tailBuffer == 0) {
buffers << QByteArray();
tail = 0;
} else {
--tailBuffer;
}
bufferSize -= qba.length();
return qba;
}
// append a new buffer to the end
inline void append(const QByteArray &qba) {
buffers[tailBuffer].resize(tail);
buffers << qba;
++tailBuffer;
tail = qba.length();
bufferSize += qba.length();
}
inline QByteArray peek(int maxLength) const {
int bytesToRead = qMin(size(), maxLength);
if(maxLength <= 0)
return QByteArray();
QByteArray ret;
ret.resize(bytesToRead);
int readSoFar = 0;
for (int i = 0; readSoFar < bytesToRead && i < buffers.size(); ++i) {
int start = 0;
int end = buffers.at(i).size();
if (i == 0)
start = head;
if (i == tailBuffer)
end = tail;
const int len = qMin(ret.size()-readSoFar, end-start);
memcpy(ret.data()+readSoFar, buffers.at(i).constData()+start, len);
readSoFar += len;
}
Q_ASSERT(readSoFar == ret.size());
return ret;
}
inline int skip(int length) {
return read(0, length);
}
inline int readLine(char *data, int maxLength) {
int index = indexOf('\n');
if (index == -1)
return read(data, maxLength);
if (maxLength <= 0)
return -1;
int readSoFar = 0;
while (readSoFar < index + 1 && readSoFar < maxLength - 1) {
int bytesToRead = qMin((index + 1) - readSoFar, nextDataBlockSize());
bytesToRead = qMin(bytesToRead, (maxLength - 1) - readSoFar);
memcpy(data + readSoFar, readPointer(), bytesToRead);
readSoFar += bytesToRead;
free(bytesToRead);
}
// Terminate it.
data[readSoFar] = '\0';
return readSoFar;
}
inline bool canReadLine() const {
return indexOf('\n') != -1;
}
private:
QList<QByteArray> buffers;
int head, tail;
int tailBuffer; // always buffers.size() - 1
int basicBlockSize;
int bufferSize;
};
QT_END_NAMESPACE
#endif // QRINGBUFFER_P_H
|