pw_string/public/pw_string/format.h

// Copyright 2023 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
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// 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.
#pragma once

/// @file pw_string/format.h
///
/// The `pw::string::Format` functions are safer alternatives to `std::snprintf`
/// and `std::vsnprintf`. The `snprintf` return value is awkward to interpret,
/// and misinterpreting it can lead to serious bugs.
///
/// These functions return a `pw::StatusWithSize`. The `pw::Status` is set to
/// reflect any errors and the return value is always the number of characters
/// written before the null terminator.

#include <cstdarg>

#include "pw_preprocessor/compiler.h"
#include "pw_span/span.h"
#include "pw_status/status_with_size.h"
#include "pw_string/string.h"

namespace pw::string {

/// Writes a printf-style formatted string to the provided buffer, similarly to
/// `std::snprintf()`.
///
/// The `std::snprintf()` return value is awkward to interpret, and
/// misinterpreting it can lead to serious bugs.
///
/// @returns @rst
///
/// .. pw-status-codes::
///
///    OK: Returns the number of characters written, excluding the null
///    terminator. The buffer is always null-terminated unless it is empty.
///
///    RESOURCE_EXHAUSTED: The buffer was too small to fit the output.
///
///    INVALID_ARGUMENT: There was a formatting error.
///
/// @endrst
PW_PRINTF_FORMAT(2, 3)
StatusWithSize Format(span<char> buffer, const char* format, ...);

/// Writes a printf-style formatted string with va_list-packed arguments to the
/// provided buffer, similarly to `std::vsnprintf()`.
///
/// @returns See `pw::string::Format()`.
PW_PRINTF_FORMAT(2, 0)
StatusWithSize FormatVaList(span<char> buffer,
                            const char* format,
                            va_list args);

/// Appends a printf-style formatted string to the provided `pw::InlineString`,
/// similarly to `std::snprintf()`.
///
/// @returns See `pw::string::Format()`.
PW_PRINTF_FORMAT(2, 3)
Status Format(InlineString<>& string, const char* format, ...);

/// Appends a printf-style formatted string with va_list-packed arguments to the
/// provided `InlineString`, similarly to `std::vsnprintf()`.
///
/// @returns See `pw::string::Format()`.
PW_PRINTF_FORMAT(2, 0)
Status FormatVaList(InlineString<>& string, const char* format, va_list args);

/// Writes a printf-style format string to the provided `InlineString`,
/// overwriting any contents.
///
/// @returns See `pw::string::Format()`.
PW_PRINTF_FORMAT(2, 3)
Status FormatOverwrite(InlineString<>& string, const char* format, ...);

/// Writes a printf-style formatted string with `va_list`-packed arguments to
/// the provided `InlineString`, overwriting any contents.
///
/// @returns See `pw::string::Format()`.
PW_PRINTF_FORMAT(2, 0)
inline Status FormatOverwriteVaList(InlineString<>& string,
                                    const char* format,
                                    va_list args) {
  string.clear();
  return FormatVaList(string, format, args);
}

}  // namespace pw::string