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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef nsReadLine_h__
#define nsReadLine_h__
#include "nsIInputStream.h"
#include "mozilla/Likely.h"
/**
* @file
* Functions to read complete lines from an input stream.
*
* To properly use the helper function in here (NS_ReadLine) the caller should
* create a nsLineBuffer<T> with new, and pass it to NS_ReadLine every time it
* wants a line out.
*
* When done, the object should be deleted.
*/
/**
* @internal
* Buffer size. This many bytes will be buffered. If a line is longer than this,
* the partial line will be appended to the out parameter of NS_ReadLine and the
* buffer will be emptied.
* Note: if you change this constant, please update the regression test in
* netwerk/test/unit/test_readline.js accordingly (bug 397850).
*/
#define kLineBufferSize 4096
/**
* @internal
* Line buffer structure, buffers data from an input stream.
* The buffer is empty when |start| == |end|.
* Invariant: |start| <= |end|
*/
template <typename CharT>
class nsLineBuffer {
public:
nsLineBuffer() : start(buf), end(buf) {}
CharT buf[kLineBufferSize + 1];
CharT* start;
CharT* end;
};
/**
* Read a line from an input stream. Lines are separated by '\r' (0x0D) or '\n'
* (0x0A), or "\r\n" or "\n\r".
*
* @param aStream
* The stream to read from
* @param aBuffer
* The line buffer to use. A single line buffer must not be used with
* different input streams.
* @param aLine [out]
* The string where the line will be stored.
* @param more [out]
* Whether more data is available in the buffer. If true, NS_ReadLine may
* be called again to read further lines. Otherwise, further calls to
* NS_ReadLine will return an error.
*
* @retval NS_OK
* Read successful
* @retval error
* Input stream returned an error upon read. See
* nsIInputStream::read.
*/
template <typename CharT, class StreamType, class StringType>
nsresult NS_ReadLine(StreamType* aStream, nsLineBuffer<CharT>* aBuffer,
StringType& aLine, bool* more) {
CharT eolchar = 0; // the first eol char or 1 after \r\n or \n\r is found
aLine.Truncate();
while (true) { // will be returning out of this loop on eol or eof
if (aBuffer->start == aBuffer->end) { // buffer is empty. Read into it.
uint32_t bytesRead;
nsresult rv = aStream->Read(aBuffer->buf, kLineBufferSize, &bytesRead);
if (NS_FAILED(rv) || MOZ_UNLIKELY(bytesRead == 0)) {
*more = false;
return rv;
}
aBuffer->start = aBuffer->buf;
aBuffer->end = aBuffer->buf + bytesRead;
*(aBuffer->end) = '\0';
}
/*
* Walk the buffer looking for an end-of-line.
* There are 3 cases to consider:
* 1. the eol char is the last char in the buffer
* 2. the eol char + one more char at the end of the buffer
* 3. the eol char + two or more chars at the end of the buffer
* we need at least one char after the first eol char to determine if
* it's a \r\n or \n\r sequence (and skip over it), and we need one
* more char after the end-of-line to set |more| correctly.
*/
CharT* current = aBuffer->start;
if (MOZ_LIKELY(eolchar == 0)) {
for (; current < aBuffer->end; ++current) {
if (*current == '\n' || *current == '\r') {
eolchar = *current;
*current++ = '\0';
aLine.Append(aBuffer->start);
break;
}
}
}
if (MOZ_LIKELY(eolchar != 0)) {
for (; current < aBuffer->end; ++current) {
if ((eolchar == '\r' && *current == '\n') ||
(eolchar == '\n' && *current == '\r')) {
eolchar = 1;
continue;
}
aBuffer->start = current;
*more = true;
return NS_OK;
}
}
if (eolchar == 0) aLine.Append(aBuffer->start);
aBuffer->start = aBuffer->end; // mark the buffer empty
}
}
#endif // nsReadLine_h__
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