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