third_party/re2/util/stringprintf.cc

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