/* An extremely minimalist syscalls.c for newlib
 * Based on riscv newlib libgloss/riscv/sys_*.c
 *
 * Copyright 2019 Clifford Wolf
 * Copyright 2019 ETH Zürich and University of Bologna
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/**********************************************************************//**
 * @file syscalls.c
 * @brief Newlib system calls
 *
 * @warning UART0 (if available) is used to read/write console data (STDIN, STDOUT, STDERR, ...).
 *
 * @note Original source file: https://github.com/openhwgroup/cv32e40p/blob/master/example_tb/core/custom/syscalls.c
 * @note Original license: SOLDERPAD HARDWARE LICENSE version 0.51
 * @note More information was derived from: https://interrupt.memfault.com/blog/boostrapping-libc-with-newlib#implementing-newlib
 **************************************************************************/

#include <sys/stat.h>
#include <sys/timeb.h>
#include <sys/times.h>
#include <utime.h>
#include <newlib.h>
#include <unistd.h>
#include <errno.h>
#include <neorv32.h>

#undef errno
extern int errno;

// defined in sw/common/crt0.S
extern const volatile unsigned int __crt0_main_exit;

/* It turns out that older newlib versions use different symbol names which goes
 * against newlib recommendations. Anyway this is fixed in later version.
 */
#if __NEWLIB__ <= 2 && __NEWLIB_MINOR__ <= 5
#    define _sbrk sbrk
#    define _write write
#    define _close close
#    define _lseek lseek
#    define _read read
#    define _fstat fstat
#    define _isatty isatty
#endif

void unimplemented_syscall()
{
  if (neorv32_uart0_available()) {
    neorv32_uart0_puts("<syscalls.c> Unimplemented system call called!\n");
  }
}

int nanosleep(const struct timespec *rqtp, struct timespec *rmtp)
{
    errno = ENOSYS;
    return -1;
}

int _access(const char *file, int mode)
{
    errno = ENOSYS;
    return -1;
}

int _chdir(const char *path)
{
    errno = ENOSYS;
    return -1;
}

int _chmod(const char *path, mode_t mode)
{
    errno = ENOSYS;
    return -1;
}

int _chown(const char *path, uid_t owner, gid_t group)
{
    errno = ENOSYS;
    return -1;
}

int _close(int file)
{
    return -1;
}

int _execve(const char *name, char *const argv[], char *const env[])
{
    errno = ENOMEM;
    return -1;
}

void _exit(int exit_status)
{
    // jump to crt0's shutdown code
    asm volatile ("la t0, __crt0_main_exit \n"
                  "jr t0                   \n");

    while(1); // will never be reached
}

int _faccessat(int dirfd, const char *file, int mode, int flags)
{
    errno = ENOSYS;
    return -1;
}

int _fork(void)
{
    errno = EAGAIN;
    return -1;
}

int _fstat(int file, struct stat *st)
{
    st->st_mode = S_IFCHR; // all files are "character special files"
    return 0;
}

int _fstatat(int dirfd, const char *file, struct stat *st, int flags)
{
    errno = ENOSYS;
    return -1;
}

int _ftime(struct timeb *tp)
{
    errno = ENOSYS;
    return -1;
}

char *_getcwd(char *buf, size_t size)
{
    errno = -ENOSYS;
    return NULL;
}

int _getpid()
{
    return 1;
}

int _gettimeofday(struct timeval *tp, void *tzp)
{
    errno = -ENOSYS;
    return -1;
}

int _isatty(int file)
{
    return (file == STDOUT_FILENO);
}

int _kill(int pid, int sig)
{
    errno = EINVAL;
    return -1;
}

int _link(const char *old_name, const char *new_name)
{
    errno = EMLINK;
    return -1;
}

off_t _lseek(int file, off_t ptr, int dir)
{
    return 0;
}

int _lstat(const char *file, struct stat *st)
{
    errno = ENOSYS;
    return -1;
}

int _open(const char *name, int flags, int mode)
{
    return -1;
}

int _openat(int dirfd, const char *name, int flags, int mode)
{
    errno = ENOSYS;
    return -1;
}

ssize_t _read(int file, void *ptr, size_t len)
{
    int read_cnt = 0;

    // read everything (STDIN, ...) from NEORV32.UART0 (if available)
    if (neorv32_uart0_available()) {
      char *char_ptr;
      char_ptr = (char *)ptr;
      while (len > 0) {
        *char_ptr++ = (char)neorv32_uart0_getc();
        read_cnt++;
        len--;
      }
    }

    return read_cnt;
}

int _stat(const char *file, struct stat *st)
{
    st->st_mode = S_IFCHR;
    return 0;
    // errno = ENOSYS;
    // return -1;
}

long _sysconf(int name)
{

    return -1;
}

clock_t _times(struct tms *buf)
{
    return -1;
}

int _unlink(const char *name)
{
    errno = ENOENT;
    return -1;
}

int _utime(const char *path, const struct utimbuf *times)
{
    errno = ENOSYS;
    return -1;
}

int _wait(int *status)
{
    errno = ECHILD;
    return -1;
}

ssize_t _write(int file, const void *ptr, size_t len)
{
    // write everything (STDOUT, STDERR, ...) to NEORV32.UART0 (if available)
    const void *eptr = ptr + len;
    if (neorv32_uart0_available()) {
      while (ptr != eptr) {
        neorv32_uart0_putc(*(char *)(ptr++));
      }
      return len;
    }
    else {
      return (size_t)0; // nothing sent
    }
}

extern char __heap_start[];
extern char __heap_end[];
static char *brk = &__heap_start[0];

int _brk(void *addr)
{
    brk = addr;
    return 0;
}

void *_sbrk(ptrdiff_t incr)
{
    char *old_brk = brk;

    if (&__heap_start[0] == &__heap_end[0]) {
        return NULL;
    }

    if ((brk += incr) < &__heap_end[0]) {
        brk += incr;
    } else {
        brk = &__heap_end[0];
    }
    return old_brk;
}