The Tor Browser: netwerk/base/public/nsReadLine.h@b8a032363ba2

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

     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/. */

     7 #ifndef nsReadLine_h__

     8 #define nsReadLine_h__

    10 #include "nsIInputStream.h"

    11 #include "mozilla/Likely.h"

    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  */

    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

    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     nsLineBuffer() : start(buf), end(buf) { }

    45   CharT buf[kLineBufferSize+1];

    46   CharT* start;

    47   CharT* end;

    48 };

    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 NS_ReadLine (StreamType* aStream, nsLineBuffer<CharT> * aBuffer,

    75              StringType & aLine, bool *more)

    76 {

    77   CharT eolchar = 0; // the first eol char or 1 after \r\n or \n\r is found

    79   aLine.Truncate();

    81   while (1) { // will be returning out of this loop on eol or eof

    82     if (aBuffer->start == aBuffer->end) { // buffer is empty.  Read into it.

    83       uint32_t bytesRead;

    84       nsresult rv = aStream->Read(aBuffer->buf, kLineBufferSize, &bytesRead);

    85       if (NS_FAILED(rv) || MOZ_UNLIKELY(bytesRead == 0)) {

    86         *more = false;

    87         return rv;

    88       }

    89       aBuffer->start = aBuffer->buf;

    90       aBuffer->end = aBuffer->buf + bytesRead;

    91       *(aBuffer->end) = '\0';

    92     }

    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     CharT* current = aBuffer->start;

   105     if (MOZ_LIKELY(eolchar == 0)) {

   106       for ( ; current < aBuffer->end; ++current) {

   107         if (*current == '\n' || *current == '\r') {

   108           eolchar = *current;

   109           *current++ = '\0';

   110           aLine.Append(aBuffer->start);

   111           break;

   112         }

   113       }

   114     }

   115     if (MOZ_LIKELY(eolchar != 0)) {

   116       for ( ; current < aBuffer->end; ++current) {

   117         if ((eolchar == '\r' && *current == '\n') ||

   118             (eolchar == '\n' && *current == '\r')) {

   119           eolchar = 1;

   120           continue;

   121         }

   122         aBuffer->start = current;

   123         *more = true;

   124         return NS_OK;

   125       }

   126     }

   128     if (eolchar == 0)

   129       aLine.Append(aBuffer->start);

   130     aBuffer->start = aBuffer->end; // mark the buffer empty

   131   }

   132 }

   134 #endif // nsReadLine_h__

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