src/TortoiseMerge/libsvn_diff/eol.c

   1 /*
   2  * eol.c :  generic eol/keyword routines
   3  *
   4  * ====================================================================
   5  *    Licensed to the Apache Software Foundation (ASF) under one
   6  *    or more contributor license agreements.  See the NOTICE file
   7  *    distributed with this work for additional information
   8  *    regarding copyright ownership.  The ASF licenses this file
   9  *    to you under the Apache License, Version 2.0 (the
  10  *    "License"); you may not use this file except in compliance
  11  *    with the License.  You may obtain a copy of the License at
  12  *
  13  *      http://www.apache.org/licenses/LICENSE-2.0
  14  *
  15  *    Unless required by applicable law or agreed to in writing,
  16  *    software distributed under the License is distributed on an
  17  *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  18  *    KIND, either express or implied.  See the License for the
  19  *    specific language governing permissions and limitations
  20  *    under the License.
  21  * ====================================================================
  22  */
  23
  24
  25 \f
  26 #define APR_WANT_STRFUNC
  27
  28 #include <apr_file_io.h>
  29 #include "svn_io.h"
  30 #include "private/svn_eol_private.h"
  31 #include "private/svn_dep_compat.h"
  32
  33 /* Machine-word-sized masks used in svn_eol__find_eol_start.
  34  */
  35 char *
  36 svn_eol__find_eol_start(char *buf, apr_size_t len)
  37 {
  38 #if !SVN_UNALIGNED_ACCESS_IS_OK
  39
  40   /* On some systems, we need to make sure that buf is properly aligned
  41    * for chunky data access. This overhead is still justified because
  42    * only lines tend to be tens of chars long.
  43    */
  44   for (; (len > 0) && ((apr_uintptr_t)buf) & (sizeof(apr_uintptr_t)-1)
  45        ; ++buf, --len)
  46   {
  47     if (*buf == '\n' || *buf == '\r')
  48       return buf;
  49   }
  50
  51 #endif
  52
  53   /* Scan the input one machine word at a time. */
  54   for (; len > sizeof(apr_uintptr_t)
  55        ; buf += sizeof(apr_uintptr_t), len -= sizeof(apr_uintptr_t))
  56   {
  57     /* This is a variant of the well-known strlen test: */
  58     apr_uintptr_t chunk = *(const apr_uintptr_t *)buf;
  59
  60     /* A byte in SVN__R_TEST is \0, iff it was \r in *BUF.
  61      * Similarly, SVN__N_TEST is an indicator for \n. */
  62     apr_uintptr_t r_test = chunk ^ SVN__R_MASK;
  63     apr_uintptr_t n_test = chunk ^ SVN__N_MASK;
  64
  65     /* A byte in SVN__R_TEST can by < 0x80, iff it has been \0 before
  66      * (i.e. \r in *BUF). Dito for SVN__N_TEST. */
  67     r_test |= (r_test & SVN__LOWER_7BITS_SET) + SVN__LOWER_7BITS_SET;
  68     n_test |= (n_test & SVN__LOWER_7BITS_SET) + SVN__LOWER_7BITS_SET;
  69
  70     /* Check whether at least one of the words contains a byte <0x80
  71      * (if one is detected, there was a \r or \n in CHUNK). */
  72     if ((r_test & n_test & SVN__BIT_7_SET) != SVN__BIT_7_SET)
  73       break;
  74   }
  75
  76   /* The remaining odd bytes will be examined the naive way: */
  77   for (; len > 0; ++buf, --len)
  78     {
  79       if (*buf == '\n' || *buf == '\r')
  80         return buf;
  81     }
  82
  83   return NULL;
  84 }
  85
  86 const char *
  87 svn_eol__detect_eol(char *buf, apr_size_t len, char **eolp)
  88 {
  89   char *eol;
  90
  91   eol = svn_eol__find_eol_start(buf, len);
  92   if (eol)
  93     {
  94       if (eolp)
  95         *eolp = eol;
  96
  97       if (*eol == '\n')
  98         return "\n";
  99
 100       /* We found a CR. */
 101       ++eol;
 102       if (eol == buf + len || *eol != '\n')
 103         return "\r";
 104       return "\r\n";
 105     }
 106
 107   return NULL;
 108 }