/*
 *  linux/lib/string.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * stupid library routines.. The optimized versions should generally be found
 * as inline code in <asm-xx/string.h>
 *
 * These are buggy as well..
 *
 * * Fri Jun 25 1999, Ingo Oeser <ioe@informatik.tu-chemnitz.de>
 * -  Added strsep() which will replace strtok() soon (because strsep() is
 *    reentrant and should be faster). Use only strsep() in new code, please.
 */

#include <asm/sections.h>
#include <config.h>
#include <limits.h>
#include <linux/compiler.h>
#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/types.h>
#include <malloc.h>

/**
 * strncasecmp - Case insensitive, length-limited string comparison
 * @s1: One string
 * @s2: The other string
 * @len: the maximum number of characters to compare
 */
int strncasecmp(const char *s1, const char *s2, size_t len)
{
        /* Yes, Virginia, it had better be unsigned */
        unsigned char c1, c2;

        c1 = 0; c2 = 0;
        if (len) {
                do {
                        c1 = *s1; c2 = *s2;
                        s1++; s2++;
                        if (!c1)
                                break;
                        if (!c2)
                                break;
                        if (c1 == c2)
                                continue;
                        c1 = tolower(c1);
                        c2 = tolower(c2);
                        if (c1 != c2)
                                break;
                } while (--len);
        }
        return (int)c1 - (int)c2;
}

/**
 * strcasecmp - Case insensitive string comparison
 * @s1: One string
 * @s2: The other string
 */
int strcasecmp(const char *s1, const char *s2)
{
        return strncasecmp(s1, s2, -1U);
}

char * ___strtok;

#ifndef __HAVE_ARCH_STRCPY
/**
 * strcpy - Copy a %NUL terminated string
 * @dest: Where to copy the string to
 * @src: Where to copy the string from
 */
char * strcpy(char * dest,const char *src)
{
        char *tmp = dest;

        while ((*dest++ = *src++) != '\0')
                /* nothing */;
        return tmp;
}
#endif

#ifndef __HAVE_ARCH_STRNCPY
/**
 * strncpy - Copy a length-limited, %NUL-terminated string
 * @dest: Where to copy the string to
 * @src: Where to copy the string from
 * @count: The maximum number of bytes to copy
 *
 * Note that unlike userspace strncpy, this does not %NUL-pad the buffer.
 * However, the result is not %NUL-terminated if the source exceeds
 * @count bytes.
 */
char * strncpy(char * dest,const char *src,size_t count)
{
        char *tmp = dest;

        while (count-- && (*dest++ = *src++) != '\0')
                /* nothing */;

        return tmp;
}
#endif

#ifndef __HAVE_ARCH_STRLCPY
/**
 * strlcpy - Copy a C-string into a sized buffer
 * @dest: Where to copy the string to
 * @src: Where to copy the string from
 * @size: size of destination buffer
 *
 * Compatible with *BSD: the result is always a valid
 * NUL-terminated string that fits in the buffer (unless,
 * of course, the buffer size is zero). It does not pad
 * out the result like strncpy() does.
 *
 * Return: strlen(src)
 */
size_t strlcpy(char *dest, const char *src, size_t size)
{
        size_t ret = strlen(src);

        if (size) {
                size_t len = (ret >= size) ? size - 1 : ret;
                memcpy(dest, src, len);
                dest[len] = '\0';
        }
        return ret;
}
#endif

#ifndef __HAVE_ARCH_STRCAT
/**
 * strcat - Append one %NUL-terminated string to another
 * @dest: The string to be appended to
 * @src: The string to append to it
 */
char * strcat(char * dest, const char * src)
{
        char *tmp = dest;

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

        return tmp;
}
#endif

#ifndef __HAVE_ARCH_STRNCAT
/**
 * strncat - Append a length-limited, %NUL-terminated string to another
 * @dest: The string to be appended to
 * @src: The string to append to it
 * @count: The maximum numbers of bytes to copy
 *
 * Note that in contrast to strncpy, strncat ensures the result is
 * terminated.
 */
char * strncat(char *dest, const char *src, size_t count)
{
        char *tmp = dest;

        if (count) {
                while (*dest)
                        dest++;
                while ((*dest++ = *src++)) {
                        if (--count == 0) {
                                *dest = '\0';
                                break;
                        }
                }
        }

        return tmp;
}
#endif

#ifndef __HAVE_ARCH_STRLCAT
/**
 * strlcat - Append a length-limited, %NUL-terminated string to another
 * @dest: The string to be appended to
 * @src: The string to append to it
 * @size: The size of @dest
 *
 * Compatible with *BSD: the result is always a valid NUL-terminated string that
 * fits in the buffer (unless, of course, the buffer size is zero). It does not
 * write past @size like strncat() does.
 *
 * Return: min(strlen(dest), size) + strlen(src)
 */
size_t strlcat(char *dest, const char *src, size_t size)
{
        size_t len = strnlen(dest, size);

        return len + strlcpy(dest + len, src, size - len);
}
#endif

#ifndef __HAVE_ARCH_STRCMP
/**
 * strcmp - Compare two strings
 * @cs: One string
 * @ct: Another string
 */
int strcmp(const char *cs, const char *ct)
{
        int ret;

        while (1) {
                unsigned char a = *cs++;
                unsigned char b = *ct++;

                ret = a - b;
                if (ret || !b)
                        break;
        }

        return ret;
}
#endif

#ifndef __HAVE_ARCH_STRNCMP
/**
 * strncmp - Compare two length-limited strings
 * @cs: One string
 * @ct: Another string
 * @count: The maximum number of bytes to compare
 */
int strncmp(const char *cs, const char *ct, size_t count)
{
        int ret = 0;

        while (count--) {
                unsigned char a = *cs++;
                unsigned char b = *ct++;

                ret = a - b;
                if (ret || !b)
                        break;
        }

        return ret;
}
#endif

#ifndef __HAVE_ARCH_STRCHR
/**
 * strchr - Find the first occurrence of a character in a string
 * @s: The string to be searched
 * @c: The character to search for
 */
char * strchr(const char * s, int c)
{
        for(; *s != (char) c; ++s)
                if (*s == '\0')
                        return NULL;
        return (char *) s;
}
#endif

const char *strchrnul(const char *s, int c)
{
        for (; *s != (char)c; ++s)
                if (*s == '\0')
                        break;
        return s;
}

#ifndef __HAVE_ARCH_STRRCHR
/**
 * strrchr - Find the last occurrence of a character in a string
 * @s: The string to be searched
 * @c: The character to search for
 */
char * strrchr(const char * s, int c)
{
       const char *p = s + strlen(s);
       do {
           if (*p == (char)c)
               return (char *)p;
       } while (--p >= s);
       return NULL;
}
#endif

#ifndef __HAVE_ARCH_STRLEN
/**
 * strlen - Find the length of a string
 * @s: The string to be sized
 */
size_t strlen(const char * s)
{
        const char *sc;

        for (sc = s; *sc != '\0'; ++sc)
                /* nothing */;
        return sc - s;
}
#endif

#ifndef __HAVE_ARCH_STRNLEN
/**
 * strnlen - Find the length of a length-limited string
 * @s: The string to be sized
 * @count: The maximum number of bytes to search
 */
size_t strnlen(const char * s, size_t count)
{
        const char *sc;

        for (sc = s; count-- && *sc != '\0'; ++sc)
                /* nothing */;
        return sc - s;
}
#endif

#ifndef __HAVE_ARCH_STRCSPN
/**
 * strcspn - Calculate the length of the initial substring of @s which does
 * not contain letters in @reject
 * @s: The string to be searched
 * @reject: The string to avoid
 */
size_t strcspn(const char *s, const char *reject)
{
        const char *p;
        const char *r;
        size_t count = 0;

        for (p = s; *p != '\0'; ++p) {
                for (r = reject; *r != '\0'; ++r) {
                        if (*p == *r)
                                return count;
                }
                ++count;
        }
        return count;
}
#endif

#ifndef __HAVE_ARCH_STRDUP
char * strdup(const char *s)
{
        char *new;

        if ((s == NULL) ||
            ((new = malloc (strlen(s) + 1)) == NULL) ) {
                return NULL;
        }

        strcpy (new, s);
        return new;
}

char * strndup(const char *s, size_t n)
{
        size_t len;
        char *new;

        if (s == NULL)
                return NULL;

        len = strlen(s);

        if (n < len)
                len = n;

        new = malloc(len + 1);
        if (new == NULL)
                return NULL;

        strncpy(new, s, len);
        new[len] = '\0';

        return new;
}
#endif

#ifndef __HAVE_ARCH_STRSPN
/**
 * strspn - Calculate the length of the initial substring of @s which only
 *      contain letters in @accept
 * @s: The string to be searched
 * @accept: The string to search for
 */
size_t strspn(const char *s, const char *accept)
{
        const char *p;
        const char *a;
        size_t count = 0;

        for (p = s; *p != '\0'; ++p) {
                for (a = accept; *a != '\0'; ++a) {
                        if (*p == *a)
                                break;
                }
                if (*a == '\0')
                        return count;
                ++count;
        }

        return count;
}
#endif

#ifndef __HAVE_ARCH_STRPBRK
/**
 * strpbrk - Find the first occurrence of a set of characters
 * @cs: The string to be searched
 * @ct: The characters to search for
 */
char * strpbrk(const char * cs,const char * ct)
{
        const char *sc1,*sc2;

        for( sc1 = cs; *sc1 != '\0'; ++sc1) {
                for( sc2 = ct; *sc2 != '\0'; ++sc2) {
                        if (*sc1 == *sc2)
                                return (char *) sc1;
                }
        }
        return NULL;
}
#endif

#ifndef __HAVE_ARCH_STRTOK
/**
 * strtok - Split a string into tokens
 * @s: The string to be searched
 * @ct: The characters to search for
 *
 * WARNING: strtok is deprecated, use strsep instead.
 */
char * strtok(char * s,const char * ct)
{
        char *sbegin, *send;

        sbegin  = s ? s : ___strtok;
        if (!sbegin) {
                return NULL;
        }
        sbegin += strspn(sbegin,ct);
        if (*sbegin == '\0') {
                ___strtok = NULL;
                return( NULL );
        }
        send = strpbrk( sbegin, ct);
        if (send && *send != '\0')
                *send++ = '\0';
        ___strtok = send;
        return (sbegin);
}
#endif

#ifndef __HAVE_ARCH_STRSEP
/**
 * strsep - Split a string into tokens
 * @s: The string to be searched
 * @ct: The characters to search for
 *
 * strsep() updates @s to point after the token, ready for the next call.
 *
 * It returns empty tokens, too, behaving exactly like the libc function
 * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
 * Same semantics, slimmer shape. ;)
 */
char * strsep(char **s, const char *ct)
{
        char *sbegin = *s, *end;

        if (sbegin == NULL)
                return NULL;

        end = strpbrk(sbegin, ct);
        if (end)
                *end++ = '\0';
        *s = end;

        return sbegin;
}
#endif

#ifndef __HAVE_ARCH_STRSWAB
/**
 * strswab - swap adjacent even and odd bytes in %NUL-terminated string
 * s: address of the string
 *
 * returns the address of the swapped string or NULL on error. If
 * string length is odd, last byte is untouched.
 */
char *strswab(const char *s)
{
        char *p, *q;

        if ((NULL == s) || ('\0' == *s)) {
                return (NULL);
        }

        for (p=(char *)s, q=p+1; (*p != '\0') && (*q != '\0'); p+=2, q+=2) {
                char  tmp;

                tmp = *p;
                *p  = *q;
                *q  = tmp;
        }

        return (char *) s;
}
#endif

#ifndef __HAVE_ARCH_MEMSET
/**
 * memset - Fill a region of memory with the given value
 * @s: Pointer to the start of the area.
 * @c: The byte to fill the area with
 * @count: The size of the area.
 *
 * Do not use memset() to access IO space, use memset_io() instead.
 */
__used void * memset(void * s,int c,size_t count)
{
        unsigned long *sl = (unsigned long *) s;
        char *s8;

#if !CONFIG_IS_ENABLED(TINY_MEMSET)
        unsigned long cl = 0;
        int i;

        /* do it one word at a time (32 bits or 64 bits) while possible */
        if ( ((ulong)s & (sizeof(*sl) - 1)) == 0) {
                for (i = 0; i < sizeof(*sl); i++) {
                        cl <<= 8;
                        cl |= c & 0xff;
                }
                while (count >= sizeof(*sl)) {
                        *sl++ = cl;
                        count -= sizeof(*sl);
                }
        }
#endif  /* fill 8 bits at a time */
        s8 = (char *)sl;
        while (count--)
                *s8++ = c;

        return s;
}
#endif

#ifndef __HAVE_ARCH_MEMCPY
/**
 * memcpy - Copy one area of memory to another
 * @dest: Where to copy to
 * @src: Where to copy from
 * @count: The size of the area.
 *
 * You should not use this function to access IO space, use memcpy_toio()
 * or memcpy_fromio() instead.
 */
__rcode __used void *memcpy(void *dest, const void *src, size_t count)
{
        unsigned long *dl = (unsigned long *)dest, *sl = (unsigned long *)src;
        char *d8, *s8;

        if (src == dest)
                return dest;

        /* while all data is aligned (common case), copy a word at a time */
        if ( (((ulong)dest | (ulong)src) & (sizeof(*dl) - 1)) == 0) {
                while (count >= sizeof(*dl)) {
                        *dl++ = *sl++;
                        count -= sizeof(*dl);
                }
        }
        /* copy the reset one byte at a time */
        d8 = (char *)dl;
        s8 = (char *)sl;
        while (count--)
                *d8++ = *s8++;

        return dest;
}
#endif

#ifndef __HAVE_ARCH_MEMMOVE
/**
 * memmove - Copy one area of memory to another
 * @dest: Where to copy to
 * @src: Where to copy from
 * @count: The size of the area.
 *
 * Unlike memcpy(), memmove() copes with overlapping areas.
 */
__rcode __used void *memmove(void *dest, const void *src, size_t count)
{
        char *tmp, *s;

        if (dest <= src || (src + count) <= dest) {
        /*
         * Use the fast memcpy implementation (ARCH optimized or lib/string.c) when it is possible:
         * - when dest is before src (assuming that memcpy is doing forward-copying)
         * - when destination don't overlap the source buffer (src + count <= dest)
         *
         * WARNING: the first optimisation cause an issue, when __HAVE_ARCH_MEMCPY is defined,
         *          __HAVE_ARCH_MEMMOVE is not defined and if the memcpy ARCH-specific
         *          implementation is not doing a forward-copying.
         *
         * No issue today because memcpy is doing a forward-copying in lib/string.c and for ARM32
         * architecture; no other arches use __HAVE_ARCH_MEMCPY without __HAVE_ARCH_MEMMOVE.
         */
                memcpy(dest, src, count);
        } else {
                tmp = (char *) dest + count;
                s = (char *) src + count;
                while (count--)
                        *--tmp = *--s;
                }

        return dest;
}
#endif

#ifndef __HAVE_ARCH_MEMCMP
/**
 * memcmp - Compare two areas of memory
 * @cs: One area of memory
 * @ct: Another area of memory
 * @count: The size of the area.
 */
__used int memcmp(const void * cs,const void * ct,size_t count)
{
        const unsigned char *su1, *su2;
        int res = 0;

        for( su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
                if ((res = *su1 - *su2) != 0)
                        break;
        return res;
}
#endif

#ifndef __HAVE_ARCH_MEMSCAN
/**
 * memscan - Find a character in an area of memory.
 * @addr: The memory area
 * @c: The byte to search for
 * @size: The size of the area.
 *
 * returns the address of the first occurrence of @c, or 1 byte past
 * the area if @c is not found
 */
void * memscan(void * addr, int c, size_t size)
{
        unsigned char * p = (unsigned char *) addr;

        while (size) {
                if (*p == c)
                        return (void *) p;
                p++;
                size--;
        }
        return (void *) p;
}
#endif

char *memdup(const void *src, size_t len)
{
        char *p;

        p = malloc(len);
        if (!p)
                return NULL;

        memcpy(p, src, len);

        return p;
}

#ifndef __HAVE_ARCH_STRNSTR
/**
 * strnstr() - find the first substring occurrence in a NUL terminated string
 *
 * @s1:         string to be searched
 * @s2:         string to search for
 * @len:        maximum number of characters in s2 to consider
 *
 * Return:      pointer to the first occurrence or NULL
 */
char *strnstr(const char *s1, const char *s2, size_t len)
{
        size_t l1, l2;

        l1 = strnlen(s1, len);
        l2 = strlen(s2);

        for (; l1 >= l2; --l1, ++s1) {
                if (!memcmp(s1, s2, l2))
                        return (char *) s1;
        }

        return NULL;
}
#endif

#ifndef __HAVE_ARCH_STRSTR
/**
 * strstr() - find the first substring occurrence in a NUL terminated string
 *
 * @s1:         string to be searched
 * @s2:         string to search for
 * @len:        maximum number of characters in s2 to consider
 *
 * Return:      pointer to the first occurrence or NULL
 */
char *strstr(const char *s1, const char *s2)
{
        return strnstr(s1, s2, SIZE_MAX);
}
#endif

#ifndef __HAVE_ARCH_MEMCHR
/**
 * memchr - Find a character in an area of memory.
 * @s: The memory area
 * @c: The byte to search for
 * @n: The size of the area.
 *
 * returns the address of the first occurrence of @c, or %NULL
 * if @c is not found
 */
void *memchr(const void *s, int c, size_t n)
{
        const unsigned char *p = s;
        while (n-- != 0) {
                if ((unsigned char)c == *p++) {
                        return (void *)(p-1);
                }
        }
        return NULL;
}

#endif
#ifndef __HAVE_ARCH_MEMCHR_INV
static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
{
        while (bytes) {
                if (*start != value)
                        return (void *)start;
                start++;
                bytes--;
        }
        return NULL;
}
/**
 * memchr_inv - Find an unmatching character in an area of memory.
 * @start: The memory area
 * @c: Find a character other than c
 * @bytes: The size of the area.
 *
 * returns the address of the first character other than @c, or %NULL
 * if the whole buffer contains just @c.
 */
void *memchr_inv(const void *start, int c, size_t bytes)
{
        u8 value = c;
        u64 value64;
        unsigned int words, prefix;

        if (bytes <= 16)
                return check_bytes8(start, value, bytes);

        value64 = value;
        value64 |= value64 << 8;
        value64 |= value64 << 16;
        value64 |= value64 << 32;

        prefix = (unsigned long)start % 8;
        if (prefix) {
                u8 *r;

                prefix = 8 - prefix;
                r = check_bytes8(start, value, prefix);
                if (r)
                        return r;
                start += prefix;
                bytes -= prefix;
        }

        words = bytes / 8;

        while (words) {
                if (*(u64 *)start != value64)
                        return check_bytes8(start, value, 8);
                start += 8;
                words--;
        }

        return check_bytes8(start, value, bytes % 8);
}
#endif