Kernel/include/printf.h

/**
 * @author (c) Eyal Rozenberg <eyalroz1@gmx.com>
 *             2021-2022, Haifa, Palestine/Israel
 * @author (c) Marco Paland (info@paland.com)
 *             2014-2019, PALANDesign Hannover, Germany
 *
 * @note Others have made smaller contributions to this file: see the
 * contributors page at https://github.com/eyalroz/printf/graphs/contributors
 * or ask one of the authors.
 *
 * @brief Small stand-alone implementation of the printf family of functions
 * (`(v)printf`, `(v)s(n)printf` etc., geared towards use on embedded systems with
 * a very limited resources.
 *
 * @note the implementations are thread-safe; re-entrant; use no functions from
 * the standard library; and do not dynamically allocate any memory.
 *
 * @license The MIT License (MIT)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#ifndef PRINTF_H_
#define PRINTF_H_

#include <types.h>

#ifdef __cplusplus
extern "C"
{
#endif

#ifdef __GNUC__
#define ATTR_PRINTF(one_based_format_index, first_arg) \
    __attribute__((format(__printf__, (one_based_format_index), (first_arg))))
#define ATTR_VPRINTF(one_based_format_index) ATTR_PRINTF((one_based_format_index), 0)
#else
#define ATTR_PRINTF((one_based_format_index), (first_arg))
#define ATTR_VPRINTF(one_based_format_index)
#endif

#ifndef PRINTF_ALIAS_STANDARD_FUNCTION_NAMES
#define PRINTF_ALIAS_STANDARD_FUNCTION_NAMES 0
#endif

#if PRINTF_ALIAS_STANDARD_FUNCTION_NAMES
#define printf printf
#define sprintf sprintf
#define vsprintf vsprintf
#define snprintf_ snprintf
#define vsnprintf vsnprintf
#define vprintf vprintf
#endif

// If you want to include this implementation file directly rather than
// link against, this will let you control the functions' visibility,
// e.g. make them static so as not to clash with other objects also
// using them.
#ifndef PRINTF_VISIBILITY
#define PRINTF_VISIBILITY
#endif

    /**
     * Prints/send a single character to some opaque output entity
     *
     * @note This function is not implemented by the library, only declared; you must provide an
     * implementation if you wish to use the @ref printf / @ref vprintf function (and possibly
     * for linking against the library, if your toolchain does not support discarding unused functions)
     *
     * @note The output could be as simple as a wrapper for the `write()` system call on a Unix-like
     * system, or even libc's @ref putchar , for replicating actual functionality of libc's @ref printf
     * function; but on an embedded system it may involve interaction with a special output device,
     * like a UART, etc.
     *
     * @note in libc's @ref putchar, the parameter type is an int; this was intended to support the
     * representation of either a proper character or EOF in a variable - but this is really not
     * meaningful to pass into @ref putchar and is discouraged today. See further discussion in:
     * @link https://stackoverflow.com/q/17452847/1593077
     *
     * @param c the single character to print
     */
    // PRINTF_VISIBILITY
    // void putchar(char c);

    /**
     * An implementation of the C standard's printf/vprintf
     *
     * @note you must implement a @ref putchar_ function for using this function - it invokes @ref putchar_
     * rather than directly performing any I/O (which insulates it from any dependence on the operating system
     * and external libraries).
     *
     * @param format A string specifying the format of the output, with %-marked specifiers of how to interpret
     * additional arguments.
     * @param arg Additional arguments to the function, one for each %-specifier in @p format string
     * @return The number of characters written into @p s, not counting the terminating null character
     */
    ///@{
    PRINTF_VISIBILITY
    int printf(const char *format, ...) ATTR_PRINTF(1, 2);
    PRINTF_VISIBILITY
    int vprintf(const char *format, va_list arg) ATTR_VPRINTF(1);
    ///@}

    /**
     * An implementation of the C standard's sprintf/vsprintf
     *
     * @note For security considerations (the potential for exceeding the buffer bounds), please consider using
     * the size-constrained variant, @ref snprintf / @ref vsnprintf , instead.
     *
     * @param s An array in which to store the formatted string. It must be large enough to fit the formatted
     * output!
     * @param format A string specifying the format of the output, with %-marked specifiers of how to interpret
     * additional arguments.
     * @param arg Additional arguments to the function, one for each specifier in @p format
     * @return The number of characters written into @p s, not counting the terminating null character
     */
    ///@{
    PRINTF_VISIBILITY
    int sprintf(char *s, const char *format, ...) ATTR_PRINTF(2, 3);
    PRINTF_VISIBILITY
    int vsprintf(char *s, const char *format, va_list arg) ATTR_VPRINTF(2);
    ///@}

    /**
     * An implementation of the C standard's snprintf/vsnprintf
     *
     * @param s An array in which to store the formatted string. It must be large enough to fit either the
     * entire formatted output, or at least @p n characters. Alternatively, it can be NULL, in which case
     * nothing will be printed, and only the number of characters which _could_ have been printed is
     * tallied and returned.
     * @param n The maximum number of characters to write to the array, including a terminating null character
     * @param format A string specifying the format of the output, with %-marked specifiers of how to interpret
     * additional arguments.
     * @param arg Additional arguments to the function, one for each specifier in @p format
     * @return The number of characters that COULD have been written into @p s, not counting the terminating
     *         null character. A value equal or larger than @p n indicates truncation. Only when the returned value
     *         is non-negative and less than @p n, the null-terminated string has been fully and successfully printed.
     */
    ///@{
    PRINTF_VISIBILITY
    int snprintf(char *s, size_t count, const char *format, ...) ATTR_PRINTF(3, 4);
    PRINTF_VISIBILITY
    int vsnprintf(char *s, size_t count, const char *format, va_list arg) ATTR_VPRINTF(3);
    ///@}

    /**
     * printf/vprintf with user-specified output function
     *
     * An alternative to @ref printf, in which the output function is specified dynamically
     * (rather than @ref putchar_ being used)
     *
     * @param out An output function which takes one character and a type-erased additional parameters
     * @param extra_arg The type-erased argument to pass to the output function @p out with each call
     * @param format A string specifying the format of the output, with %-marked specifiers of how to interpret
     * additional arguments.
     * @param arg Additional arguments to the function, one for each specifier in @p format
     * @return The number of characters for which the output f unction was invoked, not counting the terminating null character
     *
     */
    PRINTF_VISIBILITY
    int fctprintf(void (*out)(char c, void *extra_arg), void *extra_arg, const char *format, ...) ATTR_PRINTF(3, 4);
    PRINTF_VISIBILITY
    int vfctprintf(void (*out)(char c, void *extra_arg), void *extra_arg, const char *format, va_list arg) ATTR_VPRINTF(3);

#if PRINTF_ALIAS_STANDARD_FUNCTION_NAMES
#undef printf
#undef sprintf
#undef vsprintf
#undef snprintf_
#undef vsnprintf
#undef vprintf
#endif

#ifdef __cplusplus
}
#endif

#endif // PRINTF_H_