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Diffstat (limited to 'src/corelib/tools/qringbuffer_p.h')
| -rw-r--r-- | src/corelib/tools/qringbuffer_p.h | 451 |
1 files changed, 451 insertions, 0 deletions
diff --git a/src/corelib/tools/qringbuffer_p.h b/src/corelib/tools/qringbuffer_p.h new file mode 100644 index 0000000000..53bbd58883 --- /dev/null +++ b/src/corelib/tools/qringbuffer_p.h @@ -0,0 +1,451 @@ +/**************************************************************************** +** +** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). +** All rights reserved. +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the QtCore module of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the Technology Preview License Agreement accompanying +** this package. +** +** 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 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 2.1 requirements +** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. +** +** In addition, as a special exception, Nokia gives you certain additional +** rights. These rights are described in the Nokia Qt LGPL Exception +** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. +** +** If you have questions regarding the use of this file, please contact +** Nokia at qt-info@nokia.com. +** +** +** +** +** +** +** +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#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 |