stringprintf.cc revision 5821806d5e7f356e8fa4b058a389a808ea183019 
1// Copyright 2002 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
7#ifndef va_copy
8#define va_copy(d,s) ((d) = (s)) //KLUGE: for MS compilers
9#endif
10
11namespace re2 {
12
13static void StringAppendV(string* dst, const char* format, va_list ap) {
14  // First try with a small fixed size buffer
15  char space[1024];
16
17  // It's possible for methods that use a va_list to invalidate
18  // the data in it upon use.  The fix is to make a copy
19  // of the structure before using it and use that copy instead.
20  va_list backup_ap;
21  va_copy(backup_ap, ap);
22  int result = vsnprintf(space, sizeof(space), format, backup_ap);
23  va_end(backup_ap);
24
25  if ((result >= 0) && (result < sizeof(space))) {
26    // It fit
27    dst->append(space, result);
28    return;
29  }
30
31  // Repeatedly increase buffer size until it fits
32  int length = sizeof(space);
33  while (true) {
34    if (result < 0) {
35      // Older behavior: just try doubling the buffer size
36      length *= 2;
37    } else {
38      // We need exactly "result+1" characters
39      length = result+1;
40    }
41    char* buf = new char[length];
42
43    // Restore the va_list before we use it again
44    va_copy(backup_ap, ap);
45    result = vsnprintf(buf, length, format, backup_ap);
46    va_end(backup_ap);
47
48    if ((result >= 0) && (result < length)) {
49      // It fit
50      dst->append(buf, result);
51      delete[] buf;
52      return;
53    }
54    delete[] buf;
55  }
56}
57
58string StringPrintf(const char* format, ...) {
59  va_list ap;
60  va_start(ap, format);
61  string result;
62  StringAppendV(&result, format, ap);
63  va_end(ap);
64  return result;
65}
66
67void SStringPrintf(string* dst, const char* format, ...) {
68  va_list ap;
69  va_start(ap, format);
70  dst->clear();
71  StringAppendV(dst, format, ap);
72  va_end(ap);
73}
74
75void StringAppendF(string* dst, const char* format, ...) {
76  va_list ap;
77  va_start(ap, format);
78  StringAppendV(dst, format, ap);
79  va_end(ap);
80}
81
82}  // namespace re2
83