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