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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#ifndef QPRIVATELINEARBUFFER_P_H
#define QPRIVATELINEARBUFFER_P_H
//
// W A R N I N G
// -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
// This is QIODevice's read buffer, optimised for read(), isEmpty() and getChar()
class QPrivateLinearBuffer
{
public:
QPrivateLinearBuffer() : len(0), first(0), buf(0), capacity(0) {
}
~QPrivateLinearBuffer() {
delete [] buf;
}
void clear() {
first = buf;
len = 0;
}
qsizetype size() const
{
return len;
}
bool isEmpty() const {
return len == 0;
}
void skip(qsizetype n)
{
if (n >= len) {
clear();
} else {
len -= n;
first += n;
}
}
int getChar() {
if (len == 0)
return -1;
int ch = uchar(*first);
len--;
first++;
return ch;
}
qsizetype read(char* target, qsizetype size)
{
qsizetype r = (std::min)(size, len);
memcpy(target, first, r);
len -= r;
first += r;
return r;
}
char* reserve(qsizetype size)
{
makeSpace(size + len, freeSpaceAtEnd);
char* writePtr = first + len;
len += size;
return writePtr;
}
void chop(qsizetype size)
{
if (size >= len) {
clear();
} else {
len -= size;
}
}
QByteArray readAll() {
char* f = first;
qsizetype l = len;
clear();
return QByteArray(f, l);
}
qsizetype readLine(char* target, qsizetype size)
{
qsizetype r = (std::min)(size, len);
char* eol = static_cast<char*>(memchr(first, '\n', r));
if (eol)
r = 1+(eol-first);
memcpy(target, first, r);
len -= r;
first += r;
return r;
}
bool canReadLine() const {
return memchr(first, '\n', len);
}
void ungetChar(char c) {
if (first == buf) {
// underflow, the existing valid data needs to move to the end of the (potentially bigger) buffer
makeSpace(len+1, freeSpaceAtStart);
}
first--;
len++;
*first = c;
}
void ungetBlock(const char* block, qsizetype size)
{
if ((first - buf) < size) {
// underflow, the existing valid data needs to move to the end of the (potentially bigger) buffer
makeSpace(len + size, freeSpaceAtStart);
}
first -= size;
len += size;
memcpy(first, block, size);
}
private:
enum FreeSpacePos {freeSpaceAtStart, freeSpaceAtEnd};
void makeSpace(size_t required, FreeSpacePos where) {
size_t newCapacity = (std::max)(capacity, size_t(QPRIVATELINEARBUFFER_BUFFERSIZE));
while (newCapacity < required)
newCapacity *= 2;
const qsizetype moveOffset = (where == freeSpaceAtEnd) ? 0 : qsizetype(newCapacity) - len;
if (newCapacity > capacity) {
// allocate more space
char* newBuf = new char[newCapacity];
memmove(newBuf + moveOffset, first, len);
delete [] buf;
buf = newBuf;
capacity = newCapacity;
} else {
// shift any existing data to make space
memmove(buf + moveOffset, first, len);
}
first = buf + moveOffset;
}
private:
// length of the unread data
qsizetype len;
// start of the unread data
char* first;
// the allocated buffer
char* buf;
// allocated buffer size
size_t capacity;
};
#endif // QPRIVATELINEARBUFFER_P_H
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