/*
 * Copyright (c) 2012-2017 Richard Braun.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 * Trivial, portable implementations.
 */

#include <errno.h>
#include <stddef.h>
#include <string.h>

#include <kern/macros.h>
#include <machine/string.h>

#ifndef STRING_ARCH_MEMCPY
void *
memcpy(void *dest, const void *src, size_t n)
{
    const char *src_ptr;
    char *dest_ptr;
    size_t i;

    dest_ptr = dest;
    src_ptr = src;

    for (i = 0; i < n; i++) {
        *dest_ptr = *src_ptr;
        dest_ptr++;
        src_ptr++;
    }

    return dest;
}
#endif /* STRING_ARCH_MEMCPY */

#ifndef STRING_ARCH_MEMMOVE
void *
memmove(void *dest, const void *src, size_t n)
{
    const char *src_ptr;
    char *dest_ptr;
    size_t i;

    if (dest <= src) {
        dest_ptr = dest;
        src_ptr = src;

        for (i = 0; i < n; i++) {
            *dest_ptr = *src_ptr;
            dest_ptr++;
            src_ptr++;
        }
    } else {
        dest_ptr = dest + n - 1;
        src_ptr = src + n - 1;

        for (i = 0; i < n; i++) {
            *dest_ptr = *src_ptr;
            dest_ptr--;
            src_ptr--;
        }
    }

    return dest;
}
#endif /* STRING_ARCH_MEMMOVE */

#ifndef STRING_ARCH_MEMSET
void *
memset(void *s, int c, size_t n)
{
    char *buffer;
    size_t i;

    buffer = s;

    for (i = 0; i < n; i++) {
        buffer[i] = c;
    }

    return s;
}
#endif /* STRING_ARCH_MEMSET */

#ifndef STRING_ARCH_MEMCMP
int
memcmp(const void *s1, const void *s2, size_t n)
{
    const unsigned char *a1, *a2;
    size_t i;

    a1 = s1;
    a2 = s2;

    for (i = 0; i < n; i++) {
        if (a1[i] != a2[i]) {
            return (int)a1[i] - (int)a2[i];
        }
    }

    return 0;
}
#endif /* STRING_ARCH_MEMCMP */

#ifndef STRING_ARCH_STRLEN
size_t
strlen(const char *s)
{
    const char *start;

    start = s;

    while (*s != '\0') {
        s++;
    }

    return (s - start);
}
#endif /* STRING_ARCH_STRLEN */

#ifndef STRING_ARCH_STRCPY
char *
strcpy(char *dest, const char *src)
{
    char *tmp;

    tmp = dest;

    while ((*dest = *src) != '\0') {
        dest++;
        src++;
    }

    return tmp;
}
#endif /* STRING_ARCH_STRCPY */

size_t
strlcpy(char *dest, const char *src, size_t n)
{
    size_t len;

    len = strlen(src);

    if (n == 0) {
        goto out;
    }

    n = (len < n) ? len : n - 1;
    memcpy(dest, src, n);
    dest[n] = '\0';

out:
    return len;
}

#ifndef STRING_ARCH_STRCMP
int
strcmp(const char *s1, const char *s2)
{
    char c1, c2;

    while ((c1 = *s1) == (c2 = *s2)) {
        if (c1 == '\0') {
            return 0;
        }

        s1++;
        s2++;
    }

    /* See C11 7.24.4 Comparison functions */
    return (int)(unsigned char)c1 - (int)(unsigned char)c2;
}
#endif /* STRING_ARCH_STRCMP */

#ifndef STRING_ARCH_STRNCMP
int
strncmp(const char *s1, const char *s2, size_t n)
{
    char c1, c2;

    if (unlikely(n == 0)) {
        return 0;
    }

    while ((n != 0) && (c1 = *s1) == (c2 = *s2)) {
        if (c1 == '\0') {
            return 0;
        }

        n--;
        s1++;
        s2++;
    }

    /* See C11 7.24.4 Comparison functions */
    return (int)(unsigned char)c1 - (int)(unsigned char)c2;
}
#endif /* STRING_ARCH_STRNCMP */

#ifndef STRING_ARCH_STRCHR
char *
strchr(const char *s, int c)
{
    for (;;) {
        if (*s == c) {
            return (char *)s;
        } else if (*s == '\0') {
            return NULL;
        }

        s++;
    }
}
#endif /* STRING_ARCH_STRCHR */

const char *
strerror(int error)
{
    switch (error) {
    case 0:
        return "success";
    case ENOMEM:
        return "out of memory";
    case EAGAIN:
        return "resource temporarily unavailable";
    case EINVAL:
        return "invalid argument";
    case EBUSY:
        return "device or resource busy";
    case EFAULT:
        return "bad address";
    case ENODEV:
        return "no such device";
    case EEXIST:
        return "entry exists";
    case EIO:
        return "input/output error";
    case ESRCH:
        return "no such process";
    case ETIMEDOUT:
        return "timeout error";
    case ENOENT:
        return "no such file or directory";
    default:
        return "unknown error";
    }
}