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       1             : /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
       2             :  *
       3             :  * This Source Code Form is subject to the terms of the Mozilla Public
       4             :  * License, v. 2.0. If a copy of the MPL was not distributed with this
       5             :  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
       6             : 
       7             : #ifndef nsReadLine_h__
       8             : #define nsReadLine_h__
       9             : 
      10             : #include "nsIInputStream.h"
      11             : #include "mozilla/Likely.h"
      12             : 
      13             : /**
      14             :  * @file
      15             :  * Functions to read complete lines from an input stream.
      16             :  *
      17             :  * To properly use the helper function in here (NS_ReadLine) the caller should
      18             :  * create a nsLineBuffer<T> with new, and pass it to NS_ReadLine every time it
      19             :  * wants a line out.
      20             :  *
      21             :  * When done, the object should be deleted.
      22             :  */
      23             : 
      24             : /**
      25             :  * @internal
      26             :  * Buffer size. This many bytes will be buffered. If a line is longer than this,
      27             :  * the partial line will be appended to the out parameter of NS_ReadLine and the
      28             :  * buffer will be emptied.
      29             :  * Note: if you change this constant, please update the regression test in
      30             :  * netwerk/test/unit/test_readline.js accordingly (bug 397850).
      31             :  */
      32             : #define kLineBufferSize 4096
      33             : 
      34             : /**
      35             :  * @internal
      36             :  * Line buffer structure, buffers data from an input stream.
      37             :  * The buffer is empty when |start| == |end|.
      38             :  * Invariant: |start| <= |end|
      39             :  */
      40             : template<typename CharT>
      41             : class nsLineBuffer {
      42             :   public:
      43           3 :     nsLineBuffer() : start(buf), end(buf) { }
      44             : 
      45             :   CharT buf[kLineBufferSize+1];
      46             :   CharT* start;
      47             :   CharT* end;
      48             : };
      49             : 
      50             : /**
      51             :  * Read a line from an input stream. Lines are separated by '\r' (0x0D) or '\n'
      52             :  * (0x0A), or "\r\n" or "\n\r".
      53             :  *
      54             :  * @param aStream
      55             :  *        The stream to read from
      56             :  * @param aBuffer
      57             :  *        The line buffer to use.  A single line buffer must not be used with
      58             :  *        different input streams.
      59             :  * @param aLine [out]
      60             :  *        The string where the line will be stored.
      61             :  * @param more [out]
      62             :  *        Whether more data is available in the buffer. If true, NS_ReadLine may
      63             :  *        be called again to read further lines. Otherwise, further calls to
      64             :  *        NS_ReadLine will return an error.
      65             :  *
      66             :  * @retval NS_OK
      67             :  *         Read successful
      68             :  * @retval error
      69             :  *         Input stream returned an error upon read. See
      70             :  *         nsIInputStream::read.
      71             :  */
      72             : template<typename CharT, class StreamType, class StringType>
      73             : nsresult
      74         217 : NS_ReadLine (StreamType* aStream, nsLineBuffer<CharT> * aBuffer,
      75             :              StringType & aLine, bool *more)
      76             : {
      77         217 :   CharT eolchar = 0; // the first eol char or 1 after \r\n or \n\r is found
      78             : 
      79         217 :   aLine.Truncate();
      80             : 
      81           1 :   while (1) { // will be returning out of this loop on eol or eof
      82         218 :     if (aBuffer->start == aBuffer->end) { // buffer is empty.  Read into it.
      83             :       uint32_t bytesRead;
      84           4 :       nsresult rv = aStream->Read(aBuffer->buf, kLineBufferSize, &bytesRead);
      85           4 :       if (NS_FAILED(rv) || MOZ_UNLIKELY(bytesRead == 0)) {
      86           1 :         *more = false;
      87           1 :         return rv;
      88             :       }
      89           3 :       aBuffer->start = aBuffer->buf;
      90           3 :       aBuffer->end = aBuffer->buf + bytesRead;
      91           3 :       *(aBuffer->end) = '\0';
      92             :     }
      93             : 
      94             :     /*
      95             :      * Walk the buffer looking for an end-of-line.
      96             :      * There are 3 cases to consider:
      97             :      *  1. the eol char is the last char in the buffer
      98             :      *  2. the eol char + one more char at the end of the buffer
      99             :      *  3. the eol char + two or more chars at the end of the buffer
     100             :      * we need at least one char after the first eol char to determine if
     101             :      * it's a \r\n or \n\r sequence (and skip over it), and we need one
     102             :      * more char after the end-of-line to set |more| correctly.
     103             :      */
     104         217 :     CharT* current = aBuffer->start;
     105         217 :     if (MOZ_LIKELY(eolchar == 0)) {
     106       13617 :       for ( ; current < aBuffer->end; ++current) {
     107        6917 :         if (*current == '\n' || *current == '\r') {
     108         217 :           eolchar = *current;
     109         217 :           *current++ = '\0';
     110         217 :           aLine.Append(aBuffer->start);
     111         217 :           break;
     112             :         }
     113             :       }
     114             :     }
     115         217 :     if (MOZ_LIKELY(eolchar != 0)) {
     116         263 :       for ( ; current < aBuffer->end; ++current) {
     117         239 :         if ((eolchar == '\r' && *current == '\n') ||
     118         194 :             (eolchar == '\n' && *current == '\r')) {
     119          23 :           eolchar = 1;
     120          23 :           continue;
     121             :         }
     122         216 :         aBuffer->start = current;
     123         216 :         *more = true;
     124         216 :         return NS_OK;
     125             :       }
     126             :     }
     127             : 
     128           1 :     if (eolchar == 0)
     129           0 :       aLine.Append(aBuffer->start);
     130           1 :     aBuffer->start = aBuffer->end; // mark the buffer empty
     131             :   }
     132             : }
     133             : 
     134             : #endif // nsReadLine_h__