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// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/strings/stringprintf.h"
#include <errno.h>
#include <vector>
#include "base/logging.h"
#include "base/scoped_clear_errno.h"
#include "base/strings/string_util.h"
namespace base {
namespace {
// Overloaded wrappers around vsnprintf and vswprintf. The buf_size parameter
// is the size of the buffer. These return the number of characters in the
// formatted string excluding the NUL terminator. If the buffer is not
// large enough to accommodate the formatted string without truncation, they
// return the number of characters that would be in the fully-formatted string
// (vsnprintf, and vswprintf on Windows), or -1 (vswprintf on POSIX platforms).
inline int vsnprintfT(char* buffer,
size_t buf_size,
const char* format,
va_list argptr) {
return base::vsnprintf(buffer, buf_size, format, argptr);
}
// Templatized backend for StringPrintF/StringAppendF. This does not finalize
// the va_list, the caller is expected to do that.
template <class StringType>
static void StringAppendVT(StringType* dst,
const typename StringType::value_type* format,
va_list ap) {
// First try with a small fixed size buffer.
// This buffer size should be kept in sync with StringUtilTest.GrowBoundary
// and StringUtilTest.StringPrintfBounds.
typename StringType::value_type stack_buf[1024];
va_list ap_copy;
va_copy(ap_copy, ap);
#if !defined(OS_WIN)
ScopedClearErrno clear_errno;
#endif
int result = vsnprintfT(stack_buf, arraysize(stack_buf), format, ap_copy);
va_end(ap_copy);
if (result >= 0 && result < static_cast<int>(arraysize(stack_buf))) {
// It fit.
dst->append(stack_buf, result);
return;
}
// Repeatedly increase buffer size until it fits.
int mem_length = arraysize(stack_buf);
while (true) {
if (result < 0) {
#if defined(OS_WIN)
// On Windows, vsnprintfT always returns the number of characters in a
// fully-formatted string, so if we reach this point, something else is
// wrong and no amount of buffer-doubling is going to fix it.
return;
#else
if (errno != 0 && errno != EOVERFLOW)
return;
// Try doubling the buffer size.
mem_length *= 2;
#endif
} else {
// We need exactly "result + 1" characters.
mem_length = result + 1;
}
if (mem_length > 32 * 1024 * 1024) {
// That should be plenty, don't try anything larger. This protects
// against huge allocations when using vsnprintfT implementations that
// return -1 for reasons other than overflow without setting errno.
DLOG(WARNING) << "Unable to printf the requested string due to size.";
return;
}
std::vector<typename StringType::value_type> mem_buf(mem_length);
// NOTE: You can only use a va_list once. Since we're in a while loop, we
// need to make a new copy each time so we don't use up the original.
va_copy(ap_copy, ap);
result = vsnprintfT(&mem_buf[0], mem_length, format, ap_copy);
va_end(ap_copy);
if ((result >= 0) && (result < mem_length)) {
// It fit.
dst->append(&mem_buf[0], result);
return;
}
}
}
} // namespace
std::string StringPrintf(const char* format, ...) {
va_list ap;
va_start(ap, format);
std::string result;
StringAppendV(&result, format, ap);
va_end(ap);
return result;
}
std::string StringPrintV(const char* format, va_list ap) {
std::string result;
StringAppendV(&result, format, ap);
return result;
}
const std::string& SStringPrintf(std::string* dst, const char* format, ...) {
va_list ap;
va_start(ap, format);
dst->clear();
StringAppendV(dst, format, ap);
va_end(ap);
return *dst;
}
void StringAppendF(std::string* dst, const char* format, ...) {
va_list ap;
va_start(ap, format);
StringAppendV(dst, format, ap);
va_end(ap);
}
void StringAppendV(std::string* dst, const char* format, va_list ap) {
StringAppendVT(dst, format, ap);
}
} // namespace base
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