// Copyright 2010 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "base/strings/stringprintf.h"
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#include <stdarg.h>
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#include <vector>
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#include "base/logging.h"
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#include "base/scoped_clear_last_error.h"
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#include "base/stl_util.h"
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#include "base/strings/string_util.h"
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namespace base {
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namespace {
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inline int vsnprintfT(char* buffer,
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size_t buf_size,
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const char* format,
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va_list argptr) {
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return base::vsnprintf(buffer, buf_size, format, argptr);
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}
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template <class StringType>
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static void StringAppendVT(StringType* dst,
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const typename StringType::value_type* format,
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va_list ap) {
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typename StringType::value_type stack_buf[1024];
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va_list ap_copy;
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va_copy(ap_copy, ap);
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ScopedClearLastError clear_errno;
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int result = vsnprintfT(stack_buf, size(stack_buf), format, ap_copy);
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va_end(ap_copy);
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if (result >= 0 && result < static_cast<int>(size(stack_buf))) {
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dst->append(stack_buf, result);
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return;
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}
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// Repeatedly increase buffer size until it fits.
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size_t mem_length = size(stack_buf);
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while (true) {
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if (result < 0) {
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#if !defined(OS_WIN)
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// On Windows, vsnprintfT always returns the number of characters in a
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// fully-formatted string, so if we reach this point, something else is
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// wrong and no amount of buffer-doubling is going to fix it.
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if (errno != 0 && errno != EOVERFLOW)
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#endif
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{
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DLOG(WARNING) << "Unable to printf the requested string due to error.";
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return;
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}
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#if !defined(OS_WIN)
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// Try doubling the buffer size.
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mem_length *= 2;
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#endif
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} else {
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// We need exactly "result + 1" characters.
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mem_length = result + 1;
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}
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if (mem_length > 32 * 1024 * 1024) {
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// That should be plenty, don't try anything larger. This protects
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// against huge allocations when using vsnprintfT implementations that
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// return -1 for reasons other than overflow without setting errno.
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DLOG(WARNING) << "Unable to printf the requested string due to size.";
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return;
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}
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std::vector<typename StringType::value_type> mem_buf(mem_length);
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// NOTE: You can only use a va_list once. Since we're in a while loop, we
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// need to make a new copy each time so we don't use up the original.
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va_copy(ap_copy, ap);
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result = vsnprintfT(&mem_buf[0], mem_length, format, ap_copy);
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va_end(ap_copy);
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if ((result >= 0) && static_cast<unsigned int>(result) < mem_length) {
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// It fit.
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dst->append(&mem_buf[0], result);
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return;
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}
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}
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}
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} // namespace
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std::string StringPrintf(const char* format, ...) {
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va_list ap;
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va_start(ap, format);
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std::string result;
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StringAppendV(&result, format, ap);
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va_end(ap);
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return result;
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}
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void StringAppendV(std::string* dst, const char* format, va_list ap) {
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StringAppendVT(dst, format, ap);
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}
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} // namespace base
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