/* Copyright (C) 2021,2022 fef <owo@fef.moe>.  All rights reserved. */

#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
 */
int kprintf(const char *__restrict fmt, ...) __printflike(1, 2);

/**
 * @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) __printflike(1, 0);

/**
 * @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; `kprintf()` 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
	 */
	isize (*write)(struct kprintf_printer *printer, const void *buf, usize 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
	 */
	isize (*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);