/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
 * string function definitions for NOLIBC
 * Copyright (C) 2017-2021 Willy Tarreau <w@1wt.eu>
 */

/* make sure to include all global symbols */
#include "nolibc.h"

#ifndef _NOLIBC_STRING_H
#define _NOLIBC_STRING_H

#include "arch.h"
#include "std.h"

static void *malloc(size_t len);

/*
 * As much as possible, please keep functions alphabetically sorted.
 */

static __attribute__((unused))
int memcmp(const void *s1, const void *s2, size_t n)
{
        size_t ofs = 0;
        int c1 = 0;

        while (ofs < n && !(c1 = ((unsigned char *)s1)[ofs] - ((unsigned char *)s2)[ofs])) {
                ofs++;
        }
        return c1;
}

#ifndef NOLIBC_ARCH_HAS_MEMMOVE
/* might be ignored by the compiler without -ffreestanding, then found as
 * missing.
 */
void *memmove(void *dst, const void *src, size_t len);
__attribute__((weak,unused,section(".text.nolibc_memmove")))
void *memmove(void *dst, const void *src, size_t len)
{
        size_t dir, pos;

        pos = len;
        dir = -1;

        if (dst < src) {
                pos = -1;
                dir = 1;
        }

        while (len) {
                pos += dir;
                ((char *)dst)[pos] = ((const char *)src)[pos];
                len--;
        }
        return dst;
}
#endif /* #ifndef NOLIBC_ARCH_HAS_MEMMOVE */

#ifndef NOLIBC_ARCH_HAS_MEMCPY
/* must be exported, as it's used by libgcc on ARM */
void *memcpy(void *dst, const void *src, size_t len);
__attribute__((weak,unused,section(".text.nolibc_memcpy")))
void *memcpy(void *dst, const void *src, size_t len)
{
        size_t pos = 0;

        while (pos < len) {
                ((char *)dst)[pos] = ((const char *)src)[pos];
                pos++;
        }
        return dst;
}
#endif /* #ifndef NOLIBC_ARCH_HAS_MEMCPY */

#ifndef NOLIBC_ARCH_HAS_MEMSET
/* might be ignored by the compiler without -ffreestanding, then found as
 * missing.
 */
void *memset(void *dst, int b, size_t len);
__attribute__((weak,unused,section(".text.nolibc_memset")))
void *memset(void *dst, int b, size_t len)
{
        char *p = dst;

        while (len--) {
                /* prevent gcc from recognizing memset() here */
                __asm__ volatile("");
                *(p++) = b;
        }
        return dst;
}
#endif /* #ifndef NOLIBC_ARCH_HAS_MEMSET */

#ifndef NOLIBC_ARCH_HAS_MEMCHR
static __attribute__((unused))
void *memchr(const void *s, int c, size_t len)
{
        char *p = (char *)s;

        while (len--) {
                if (*p == (char)c)
                        return p;
                p++;
        }
        return NULL;
}
#endif /* #ifndef NOLIBC_ARCH_HAS_MEMCHR */

static __attribute__((unused))
char *strchr(const char *s, int c)
{
        while (*s) {
                if (*s == (char)c)
                        return (char *)s;
                s++;
        }
        return NULL;
}

static __attribute__((unused))
int strcmp(const char *a, const char *b)
{
        unsigned int c;
        int diff;

        while (!(diff = (unsigned char)*a++ - (c = (unsigned char)*b++)) && c)
                ;
        return diff;
}

static __attribute__((unused))
char *strcpy(char *dst, const char *src)
{
        char *ret = dst;

        while ((*dst++ = *src++));
        return ret;
}

/* this function is only used with arguments that are not constants or when
 * it's not known because optimizations are disabled. Note that gcc 12
 * recognizes an strlen() pattern and replaces it with a jump to strlen(),
 * thus itself, hence the asm() statement below that's meant to disable this
 * confusing practice.
 */
size_t strlen(const char *str);
__attribute__((weak,unused,section(".text.nolibc_strlen")))
size_t strlen(const char *str)
{
        size_t len;

        for (len = 0; str[len]; len++)
                __asm__("");
        return len;
}

/* do not trust __builtin_constant_p() at -O0, as clang will emit a test and
 * the two branches, then will rely on an external definition of strlen().
 */
#if defined(__OPTIMIZE__)
#define nolibc_strlen(x) strlen(x)
#define strlen(str) ({                          \
        __builtin_constant_p((str)) ?           \
                __builtin_strlen((str)) :       \
                nolibc_strlen((str));           \
})
#endif

static __attribute__((unused))
size_t strnlen(const char *str, size_t maxlen)
{
        size_t len;

        for (len = 0; (len < maxlen) && str[len]; len++);
        return len;
}

static __attribute__((unused))
char *strdup(const char *str)
{
        size_t len;
        char *ret;

        len = strlen(str);
        ret = malloc(len + 1);
        if (__builtin_expect(ret != NULL, 1))
                memcpy(ret, str, len + 1);

        return ret;
}

static __attribute__((unused))
char *strndup(const char *str, size_t maxlen)
{
        size_t len;
        char *ret;

        len = strnlen(str, maxlen);
        ret = malloc(len + 1);
        if (__builtin_expect(ret != NULL, 1)) {
                memcpy(ret, str, len);
                ret[len] = '\0';
        }

        return ret;
}

static __attribute__((unused))
size_t strlcat(char *dst, const char *src, size_t size)
{
        size_t len = strnlen(dst, size);

        /*
         * We want len < size-1. But as size is unsigned and can wrap
         * around, we use len + 1 instead.
         */
        while (len + 1 < size) {
                dst[len] = *src;
                if (*src == '\0')
                        break;
                len++;
                src++;
        }

        if (len < size)
                dst[len] = '\0';

        while (*src++)
                len++;

        return len;
}

static __attribute__((unused))
size_t strlcpy(char *dst, const char *src, size_t size)
{
        size_t len;

        for (len = 0; len < size; len++) {
                dst[len] = src[len];
                if (!dst[len])
                        return len;
        }
        if (size)
                dst[size-1] = '\0';

        while (src[len])
                len++;

        return len;
}

static __attribute__((unused))
char *strncat(char *dst, const char *src, size_t size)
{
        char *orig = dst;

        while (*dst)
                dst++;

        while (size && (*dst = *src)) {
                src++;
                dst++;
                size--;
        }

        *dst = 0;
        return orig;
}

static __attribute__((unused))
int strncmp(const char *a, const char *b, size_t size)
{
        unsigned int c;
        int diff = 0;

        while (size-- &&
               !(diff = (unsigned char)*a++ - (c = (unsigned char)*b++)) && c)
                ;

        return diff;
}

static __attribute__((unused))
char *strncpy(char *dst, const char *src, size_t size)
{
        size_t len;

        for (len = 0; len < size; len++)
                if ((dst[len] = *src))
                        src++;
        return dst;
}

static __attribute__((unused))
char *strrchr(const char *s, int c)
{
        const char *ret = NULL;

        while (*s) {
                if (*s == (char)c)
                        ret = s;
                s++;
        }
        return (char *)ret;
}

static __attribute__((unused))
char *strstr(const char *haystack, const char *needle)
{
        size_t len_haystack, len_needle;

        len_needle = strlen(needle);
        if (!len_needle)
                return NULL;

        len_haystack = strlen(haystack);
        while (len_haystack >= len_needle) {
                if (!memcmp(haystack, needle, len_needle))
                        return (char *)haystack;
                haystack++;
                len_haystack--;
        }

        return NULL;
}

static __attribute__((unused))
int tolower(int c)
{
        if (c >= 'A' && c <= 'Z')
                return c - 'A' + 'a';
        return c;
}

static __attribute__((unused))
int toupper(int c)
{
        if (c >= 'a' && c <= 'z')
                return c - 'a' + 'A';
        return c;
}

#endif /* _NOLIBC_STRING_H */