libc.h

/* Copyright (C) 2017 Daniel Page <csdsp@bristol.ac.uk>
 *
 * Use of this source code is restricted per the CC BY-NC-ND license, a copy of
 * which can be found via http://creativecommons.org (and should be included as
 * LICENSE.txt within the associated archive or repository).
 */

#ifndef __LIBC_H
#define __LIBC_H

#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

// Process IDentifier (PID) type
typedef int pid_t;

/* The definitions below capture symbolic constants within these classes:
 *
 * 1. system call identifiers (i.e., the constant used by a system call
 *    to specify which action the kernel should take),
 * 2. signal identifiers (as used by the kill system call),
 * 3. status codes for exit,
 * 4. standard file descriptors (e.g., for read and write system calls),
 * 5. platform-specific constants, which may need calibration (wrt. the
 *    underlying hardware QEMU is executed on).
 *
 * They don't *precisely* match the standard C library, but are intended
 * to act as a limited model of similar concepts.
 */

#define SYS_YIELD     (0x00)
#define SYS_WRITE     (0x01)
#define SYS_READ      (0x02)
#define SYS_FORK      (0x03)
#define SYS_EXIT      (0x04)
#define SYS_EXEC      (0x05)
#define SYS_KILL      (0x06)
#define SYS_NICE      (0x07)
#define SYS_PIPE      (0x08)
#define SYS_CLOSE     (0x09)

#define SIG_TERM      (0x00)
#define SIG_QUIT      (0x01)

#define EXIT_SUCCESS  (0)
#define EXIT_FAILURE  (1)

#define  STDIN_FILENO (0)
#define STDOUT_FILENO (1)
#define STDERR_FILENO (2)

// convert ASCII string x into integer r
extern int  atoi(char* x);
// convert integer x into ASCII string r
extern void itoa(char* r, int x);

// cooperatively yield control of processor, i.e., invoke the scheduler
extern void yield();

// write n bytes from x to   the file descriptor fd; return bytes written
extern int write(int fd, const void* x, size_t n);
// read  n bytes into x from the file descriptor fd; return bytes read
extern int  read(int fd,       void* x, size_t n);

// create a pipe and save its identifiers in fd; return 0 on success, -1 on failure
extern int  pipe(int fd[2]);
// close the file with identifier fd, return 0 on success, -1 on failure
extern int close(int fd);

// perform fork, returning 0 iff. child or > 0 iff. parent process
extern int  fork();
// perform exit, i.e., terminate process with status x
extern void exit(int x);
// perform exec, i.e., start executing program at address x
extern void exec(const void* x);

// for process identified by pid, send signal of x; return 0 on success
extern int  kill(pid_t pid, int x);
// for process identified by pid, set  priority to x
extern void nice(pid_t pid, int x);

#endif