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91 lines
2.7 KiB
C++
91 lines
2.7 KiB
C++
// Copyright 2013 The Chromium Authors
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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 <errno.h>
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#include <stddef.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/strings/span_printf.h"
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#include "base/strings/string_util.h"
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#include "build/build_config.h"
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namespace base {
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std::string StringPrintV(const char* format, va_list ap) {
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std::string result;
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UNSAFE_TODO(StringAppendV(&result, format, 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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// First try with a small fixed size buffer.
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// This buffer size should be kept in sync with StringUtilTest.GrowBoundary
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// and StringUtilTest.StringPrintfBounds.
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char stack_buf[1024];
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va_list ap_copy;
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va_copy(ap_copy, ap);
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base::ScopedClearLastError last_error;
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int result = UNSAFE_TODO(VSpanPrintf(stack_buf, format, ap_copy));
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va_end(ap_copy);
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if (result >= 0 && static_cast<size_t>(result) < std::size(stack_buf)) {
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// It fit.
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dst->append(stack_buf, static_cast<size_t>(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 = std::size(stack_buf);
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while (true) {
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if (result < 0) {
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#if BUILDFLAG(IS_WIN)
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// On Windows, vsnprintf 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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return;
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#else
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if (errno != 0 && errno != EOVERFLOW) {
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return;
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}
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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 = static_cast<size_t>(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 vsnprintf 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<char> 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 = UNSAFE_TODO(VSpanPrintf(mem_buf, format, ap_copy));
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va_end(ap_copy);
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if ((result >= 0) && (static_cast<size_t>(result) < mem_length)) {
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// It fit.
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dst->append(&mem_buf[0], static_cast<size_t>(result));
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return;
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}
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}
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}
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} // namespace base
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