| 45 | // the va_list, the caller is expected to do that. |
| 46 | template <class StringType> |
| 47 | static void StringAppendVT(StringType* dst, |
| 48 | const typename StringType::value_type* format, |
| 49 | va_list ap) { |
| 50 | // First try with a small fixed size buffer. |
| 51 | // This buffer size should be kept in sync with StringUtilTest.GrowBoundary |
| 52 | // and StringUtilTest.StringPrintfBounds. |
| 53 | typename StringType::value_type stack_buf[1024]; |
| 54 | |
| 55 | va_list ap_copy; |
| 56 | va_copy(ap_copy, ap); |
| 57 | |
| 58 | #if !defined(OS_WIN) |
| 59 | ScopedClearErrno clear_errno; |
| 60 | #endif |
| 61 | int result = vsnprintfT(stack_buf, arraysize(stack_buf), format, ap_copy); |
| 62 | va_end(ap_copy); |
| 63 | |
| 64 | if (result >= 0 && result < static_cast<int>(arraysize(stack_buf))) { |
| 65 | // It fit. |
| 66 | dst->append(stack_buf, result); |
| 67 | return; |
| 68 | } |
| 69 | |
| 70 | // Repeatedly increase buffer size until it fits. |
| 71 | int mem_length = arraysize(stack_buf); |
| 72 | while (true) { |
| 73 | if (result < 0) { |
| 74 | #if defined(OS_WIN) |
| 75 | // On Windows, vsnprintfT always returns the number of characters in a |
| 76 | // fully-formatted string, so if we reach this point, something else is |
| 77 | // wrong and no amount of buffer-doubling is going to fix it. |
| 78 | return; |
| 79 | #else |
| 80 | if (errno != 0 && errno != EOVERFLOW) |
| 81 | return; |
| 82 | // Try doubling the buffer size. |
| 83 | mem_length *= 2; |
| 84 | #endif |
| 85 | } else { |
| 86 | // We need exactly "result + 1" characters. |
| 87 | mem_length = result + 1; |
| 88 | } |
| 89 | |
| 90 | if (mem_length > 32 * 1024 * 1024) { |
| 91 | // That should be plenty, don't try anything larger. This protects |
| 92 | // against huge allocations when using vsnprintfT implementations that |
| 93 | // return -1 for reasons other than overflow without setting errno. |
| 94 | DLOG(WARNING) << "Unable to printf the requested string due to size."; |
| 95 | return; |
| 96 | } |
| 97 | |
| 98 | std::vector<typename StringType::value_type> mem_buf(mem_length); |
| 99 | |
| 100 | // NOTE: You can only use a va_list once. Since we're in a while loop, we |
| 101 | // need to make a new copy each time so we don't use up the original. |
| 102 | va_copy(ap_copy, ap); |
| 103 | result = vsnprintfT(&mem_buf[0], mem_length, format, ap_copy); |
| 104 | va_end(ap_copy); |
no test coverage detected