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
8 namespace 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 // ----------------------------------------------------------------------
CEscapeString(const char * src,int src_len,char * dest,int dest_len)17 int 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 // ----------------------------------------------------------------------
CEscape(const StringPiece & src)62 string 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
PrefixSuccessor(const StringPiece & prefix)72 string 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