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 #ifndef va_copy
   8 #define va_copy(d,s) ((d) = (s)) //KLUGE: for MS compilers
   9 #endif
  10
  11 namespace re2 {
  12
  13 static 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
  58 string 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
  67 void 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
  75 void 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