/* See the end of this file for copyright and license terms. */

#pragma once

/**
 * @brief Header for the `kprintf()` family of functions.
 */

#include <stdarg.h>

#include <gay/cdefs.h>
#include <gay/types.h>

/**
 * @brief Print to the kernel log.
 *
 * @param fmt A printf style format string
 * @returns The amount of bytes written,
 *	or a negative number from `errno.h` on failure
 */
__attribute__(( format(printf, 1, 2) ))
int kprintf(const char *__restrict fmt, ...);

/**
 * @brief Print to the kernel log.
 *
 * @param fmt A printf style format string
 * @param args The variable arguments pointer
 * @returns The amount of bytes written,
 *	or a negative number from `errno.h` on failure
 */
int kvprintf(const char *__restrict fmt, va_list args);

/**
 * @brief Printing functions that `kprintf()` and friends call for writing.
 * Depending on the current kernel log output target (which in turn depends
 * primarily on the current runlevel), this will be implemented by different
 * subsystems.  To change the printer, call `kprintf_set_printer()`.
 */
struct kprintf_printer {
	/**
	 * @brief Write to the kernel log.
	 * The data itself may be cached in a buffer rather than written to the
	 * target immediately; `krpintf()` will call `flush()` when needed.
	 *
	 * @param printer A reference to the original structure
	 * @param buf Data to write
	 * @param len Length of `buf` in bytes
	 * @returns The amount of bytes actually written,
	 *	or a negative code from `errno.h` on failure
	 */
	ssize_t (*write)(struct kprintf_printer *printer, const void *buf, size_t len);
	/**
	 * @brief Flush the kernel log buffer.
	 * On implementations that don't have a buffer, this can be a no-op.
	 * If that is the case, this call should always return 0.
	 *
	 * @param printer A reference to the original structure
	 * @returns The amount of bytes flushed out (0 if none),
	 *	or a negative code from `errno.h` on failure
	 */
	ssize_t (*flush)(struct kprintf_printer *printer);
};

/**
 * @brief Set the current printer for the `kprintf()` family of functions.
 *
 * @param new Implementation of the write and flush functions
 * @returns 0 on success, or a negative code from `errno.h` on failure
 */
int kprintf_set_printer(struct kprintf_printer *new);

/*
 * This file is part of GayBSD.
 * Copyright (c) 2021 fef <owo@fef.moe>.
 *
 * GayBSD is nonviolent software: you may only use, redistribute, and/or
 * modify it under the terms of the Cooperative Nonviolent Public License
 * (CNPL) as found in the LICENSE file in the source code root directory
 * or at <https://git.pixie.town/thufie/npl-builder>; either version 7
 * of the license, or (at your option) any later version.
 *
 * GayBSD comes with ABSOLUTELY NO WARRANTY, to the extent
 * permitted by applicable law.  See the CNPL for details.
 */