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// Copyright 2019 The Pigweed Authors
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
// This size report uses pw::string::Format and std::snprintf to write a single
// printf-style string to a buffer. The number of bytes written is returned.
// This compares the overhead of using pw::string::Format to directly calling
// std::snprintf and determining the number of bytes written. It demonstrates
// that the code for using pw::string::Format is much simpler.
#include <cstddef>
#include <cstdio>
#include "pw_bloat/bloat_this_binary.h"
#include "pw_string/format.h"
#ifndef USE_FORMAT
#error "USE_FORMAT must be defined!"
#endif // USE_FORMAT
namespace pw::string {
char buffer_1[128];
char buffer_2[128];
char* volatile get_buffer_1 = buffer_1;
char* volatile get_buffer_2 = buffer_2;
volatile unsigned get_size;
unsigned OutputStringsToBuffer() {
char* buffer = get_buffer_1;
unsigned buffer_size = get_size;
// The code for using pw::string::Format is much simpler and safer.
return Format(
span(buffer, buffer_size), "hello %s %d", get_buffer_2, get_size)
#else // std::snprintf
if (buffer_size == 0u) {
return 0;
int result =
std::snprintf(buffer, buffer_size, "hello %s %d", get_buffer_2, get_size);
if (result < 0) {
buffer[0] = '\0';
return 0;
if (static_cast<size_t>(result) >= buffer_size) {
return buffer_size - 1;
return result;
#endif // USE_FORMAT
} // namespace pw::string
int main() {
return pw::string::OutputStringsToBuffer();