1// Copyright 1999-2005 The RE2 Authors.  All Rights Reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5#include "util/util.h"
6#include "re2/stringpiece.h"
7
8namespace re2 {
9
10// ----------------------------------------------------------------------
11// CEscapeString()
12//    Copies 'src' to 'dest', escaping dangerous characters using
13//    C-style escape sequences.  'src' and 'dest' should not overlap.
14//    Returns the number of bytes written to 'dest' (not including the \0)
15//    or -1 if there was insufficient space.
16// ----------------------------------------------------------------------
17int CEscapeString(const char* src, int src_len, char* dest,
18                  int dest_len) {
19  const char* src_end = src + src_len;
20  int used = 0;
21
22  for (; src < src_end; src++) {
23    if (dest_len - used < 2)   // Need space for two letter escape
24      return -1;
25
26    unsigned char c = *src;
27    switch (c) {
28      case '\n': dest[used++] = '\\'; dest[used++] = 'n';  break;
29      case '\r': dest[used++] = '\\'; dest[used++] = 'r';  break;
30      case '\t': dest[used++] = '\\'; dest[used++] = 't';  break;
31      case '\"': dest[used++] = '\\'; dest[used++] = '\"'; break;
32      case '\'': dest[used++] = '\\'; dest[used++] = '\''; break;
33      case '\\': dest[used++] = '\\'; dest[used++] = '\\'; break;
34      default:
35        // Note that if we emit \xNN and the src character after that is a hex
36        // digit then that digit must be escaped too to prevent it being
37        // interpreted as part of the character code by C.
38        if (c < ' ' || c > '~') {
39          if (dest_len - used < 4) // need space for 4 letter escape
40            return -1;
41          sprintf(dest + used, "\\%03o", c);
42          used += 4;
43        } else {
44          dest[used++] = c; break;
45        }
46    }
47  }
48
49  if (dest_len - used < 1)   // make sure that there is room for \0
50    return -1;
51
52  dest[used] = '\0';   // doesn't count towards return value though
53  return used;
54}
55
56
57// ----------------------------------------------------------------------
58// CEscape()
59//    Copies 'src' to result, escaping dangerous characters using
60//    C-style escape sequences.  'src' and 'dest' should not overlap.
61// ----------------------------------------------------------------------
62string CEscape(const StringPiece& src) {
63  const int dest_length = src.size() * 4 + 1; // Maximum possible expansion
64  char* dest = new char[dest_length];
65  const int len = CEscapeString(src.data(), src.size(),
66                                dest, dest_length);
67  string s = string(dest, len);
68  delete[] dest;
69  return s;
70}
71
72string PrefixSuccessor(const StringPiece& prefix) {
73  // We can increment the last character in the string and be done
74  // unless that character is 255, in which case we have to erase the
75  // last character and increment the previous character, unless that
76  // is 255, etc. If the string is empty or consists entirely of
77  // 255's, we just return the empty string.
78  bool done = false;
79  string limit(prefix.data(), prefix.size());
80  int index = limit.length() - 1;
81  while (!done && index >= 0) {
82    if ((limit[index]&255) == 255) {
83      limit.erase(index);
84      index--;
85    } else {
86      limit[index]++;
87      done = true;
88    }
89  }
90  if (!done) {
91    return "";
92  } else {
93    return limit;
94  }
95}
96
97}  // namespace re2
98