source: mainline/uspace/lib/libc/generic/string.c@ da2bd08

/*
 * Copyright (c) 2005 Martin Decky
 * Copyright (c) 2008 Jiri Svoboda
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup libc
 * @{
 */
/** @file
 */

#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <ctype.h>
#include <malloc.h>
#include <errno.h>
#include <align.h>
#include <mem.h>
#include <string.h>

/** Byte mask consisting of lowest @n bits (out of 8) */
#define LO_MASK_8(n)  ((uint8_t) ((1 << (n)) - 1))

/** Byte mask consisting of lowest @n bits (out of 32) */
#define LO_MASK_32(n)  ((uint32_t) ((1 << (n)) - 1))

/** Byte mask consisting of highest @n bits (out of 8) */
#define HI_MASK_8(n)  (~LO_MASK_8(8 - (n)))

/** Number of data bits in a UTF-8 continuation byte */
#define CONT_BITS  6

/** Decode a single character from a string.
 *
 * Decode a single character from a string of size @a size. Decoding starts
 * at @a offset and this offset is moved to the beginning of the next
 * character. In case of decoding error, offset generally advances at least
 * by one. However, offset is never moved beyond size.
 *
 * @param str    String (not necessarily NULL-terminated).
 * @param offset Byte offset in string where to start decoding.
 * @param size   Size of the string (in bytes).
 *
 * @return Value of decoded character, U_SPECIAL on decoding error or
 *         NULL if attempt to decode beyond @a size.
 *
 */
wchar_t str_decode(const char *str, size_t *offset, size_t size)
{
        if (*offset + 1 > size)
                return 0;
        
        /* First byte read from string */
        uint8_t b0 = (uint8_t) str[(*offset)++];
        
        /* Determine code length */
        
        unsigned int b0_bits;  /* Data bits in first byte */
        unsigned int cbytes;   /* Number of continuation bytes */
        
        if ((b0 & 0x80) == 0) {
                /* 0xxxxxxx (Plain ASCII) */
                b0_bits = 7;
                cbytes = 0;
        } else if ((b0 & 0xe0) == 0xc0) {
                /* 110xxxxx 10xxxxxx */
                b0_bits = 5;
                cbytes = 1;
        } else if ((b0 & 0xf0) == 0xe0) {
                /* 1110xxxx 10xxxxxx 10xxxxxx */
                b0_bits = 4;
                cbytes = 2;
        } else if ((b0 & 0xf8) == 0xf0) {
                /* 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx */
                b0_bits = 3;
                cbytes = 3;
        } else {
                /* 10xxxxxx -- unexpected continuation byte */
                return U_SPECIAL;
        }
        
        if (*offset + cbytes > size)
                return U_SPECIAL;
        
        wchar_t ch = b0 & LO_MASK_8(b0_bits);
        
        /* Decode continuation bytes */
        while (cbytes > 0) {
                uint8_t b = (uint8_t) str[(*offset)++];
                
                /* Must be 10xxxxxx */
                if ((b & 0xc0) != 0x80)
                        return U_SPECIAL;
                
                /* Shift data bits to ch */
                ch = (ch << CONT_BITS) | (wchar_t) (b & LO_MASK_8(CONT_BITS));
                cbytes--;
        }
        
        return ch;
}

/** Encode a single character to string representation.
 *
 * Encode a single character to string representation (i.e. UTF-8) and store
 * it into a buffer at @a offset. Encoding starts at @a offset and this offset
 * is moved to the position where the next character can be written to.
 *
 * @param ch     Input character.
 * @param str    Output buffer.
 * @param offset Byte offset where to start writing.
 * @param size   Size of the output buffer (in bytes).
 *
 * @return EOK if the character was encoded successfully, EOVERFLOW if there
 *         was not enough space in the output buffer or EINVAL if the character
 *         code was invalid.
 */
int chr_encode(const wchar_t ch, char *str, size_t *offset, size_t size)
{
        if (*offset >= size)
                return EOVERFLOW;
        
        if (!chr_check(ch))
                return EINVAL;
        
        /* Unsigned version of ch (bit operations should only be done
           on unsigned types). */
        uint32_t cc = (uint32_t) ch;
        
        /* Determine how many continuation bytes are needed */
        
        unsigned int b0_bits;  /* Data bits in first byte */
        unsigned int cbytes;   /* Number of continuation bytes */
        
        if ((cc & ~LO_MASK_32(7)) == 0) {
                b0_bits = 7;
                cbytes = 0;
        } else if ((cc & ~LO_MASK_32(11)) == 0) {
                b0_bits = 5;
                cbytes = 1;
        } else if ((cc & ~LO_MASK_32(16)) == 0) {
                b0_bits = 4;
                cbytes = 2;
        } else if ((cc & ~LO_MASK_32(21)) == 0) {
                b0_bits = 3;
                cbytes = 3;
        } else {
                /* Codes longer than 21 bits are not supported */
                return EINVAL;
        }
        
        /* Check for available space in buffer */
        if (*offset + cbytes >= size)
                return EOVERFLOW;
        
        /* Encode continuation bytes */
        unsigned int i;
        for (i = cbytes; i > 0; i--) {
                str[*offset + i] = 0x80 | (cc & LO_MASK_32(CONT_BITS));
                cc = cc >> CONT_BITS;
        }
        
        /* Encode first byte */
        str[*offset] = (cc & LO_MASK_32(b0_bits)) | HI_MASK_8(8 - b0_bits - 1);
        
        /* Advance offset */
        *offset += cbytes + 1;
        
        return EOK;
}

/** Get size of string.
 *
 * Get the number of bytes which are used by the string @a str (excluding the
 * NULL-terminator).
 *
 * @param str String to consider.
 *
 * @return Number of bytes used by the string
 *
 */
size_t str_size(const char *str)
{
        size_t size = 0;
        
        while (*str++ != 0)
                size++;
        
        return size;
}

/** Get size of wide string.
 *
 * Get the number of bytes which are used by the wide string @a str (excluding the
 * NULL-terminator).
 *
 * @param str Wide string to consider.
 *
 * @return Number of bytes used by the wide string
 *
 */
size_t wstr_size(const wchar_t *str)
{
        return (wstr_length(str) * sizeof(wchar_t));
}

/** Get size of string with length limit.
 *
 * Get the number of bytes which are used by up to @a max_len first
 * characters in the string @a str. If @a max_len is greater than
 * the length of @a str, the entire string is measured (excluding the
 * NULL-terminator).
 *
 * @param str     String to consider.
 * @param max_len Maximum number of characters to measure.
 *
 * @return Number of bytes used by the characters.
 *
 */
size_t str_lsize(const char *str, size_t max_len)
{
        size_t len = 0;
        size_t offset = 0;
        
        while (len < max_len) {
                if (str_decode(str, &offset, STR_NO_LIMIT) == 0)
                        break;
                
                len++;
        }
        
        return offset;
}

/** Get size of wide string with length limit.
 *
 * Get the number of bytes which are used by up to @a max_len first
 * wide characters in the wide string @a str. If @a max_len is greater than
 * the length of @a str, the entire wide string is measured (excluding the
 * NULL-terminator).
 *
 * @param str     Wide string to consider.
 * @param max_len Maximum number of wide characters to measure.
 *
 * @return Number of bytes used by the wide characters.
 *
 */
size_t wstr_lsize(const wchar_t *str, size_t max_len)
{
        return (wstr_nlength(str, max_len * sizeof(wchar_t)) * sizeof(wchar_t));
}

/** Get number of characters in a string.
 *
 * @param str NULL-terminated string.
 *
 * @return Number of characters in string.
 *
 */
size_t str_length(const char *str)
{
        size_t len = 0;
        size_t offset = 0;
        
        while (str_decode(str, &offset, STR_NO_LIMIT) != 0)
                len++;
        
        return len;
}

/** Get number of characters in a wide string.
 *
 * @param str NULL-terminated wide string.
 *
 * @return Number of characters in @a str.
 *
 */
size_t wstr_length(const wchar_t *wstr)
{
        size_t len = 0;
        
        while (*wstr++ != 0)
                len++;
        
        return len;
}

/** Get number of characters in a string with size limit.
 *
 * @param str  NULL-terminated string.
 * @param size Maximum number of bytes to consider.
 *
 * @return Number of characters in string.
 *
 */
size_t str_nlength(const char *str, size_t size)
{
        size_t len = 0;
        size_t offset = 0;
        
        while (str_decode(str, &offset, size) != 0)
                len++;
        
        return len;
}

/** Get number of characters in a string with size limit.
 *
 * @param str  NULL-terminated string.
 * @param size Maximum number of bytes to consider.
 *
 * @return Number of characters in string.
 *
 */
size_t wstr_nlength(const wchar_t *str, size_t size)
{
        size_t len = 0;
        size_t limit = ALIGN_DOWN(size, sizeof(wchar_t));
        size_t offset = 0;
        
        while ((offset < limit) && (*str++ != 0)) {
                len++;
                offset += sizeof(wchar_t);
        }
        
        return len;
}

/** Check whether character is plain ASCII.
 *
 * @return True if character is plain ASCII.
 *
 */
bool ascii_check(wchar_t ch)
{
        if ((ch >= 0) && (ch <= 127))
                return true;
        
        return false;
}

/** Check whether character is valid
 *
 * @return True if character is a valid Unicode code point.
 *
 */
bool chr_check(wchar_t ch)
{
        if ((ch >= 0) && (ch <= 1114111))
                return true;
        
        return false;
}

/** Compare two NULL terminated strings.
 *
 * Do a char-by-char comparison of two NULL-terminated strings.
 * The strings are considered equal iff they consist of the same
 * characters on the minimum of their lengths.
 *
 * @param s1 First string to compare.
 * @param s2 Second string to compare.
 *
 * @return 0 if the strings are equal, -1 if first is smaller,
 *         1 if second smaller.
 *
 */
int str_cmp(const char *s1, const char *s2)
{
        wchar_t c1 = 0;
        wchar_t c2 = 0;
        
        size_t off1 = 0;
        size_t off2 = 0;

        while (true) {
                c1 = str_decode(s1, &off1, STR_NO_LIMIT);
                c2 = str_decode(s2, &off2, STR_NO_LIMIT);

                if (c1 < c2)
                        return -1;
                
                if (c1 > c2)
                        return 1;

                if (c1 == 0 || c2 == 0)
                        break;          
        }

        return 0;
}

/** Compare two NULL terminated strings with length limit.
 *
 * Do a char-by-char comparison of two NULL-terminated strings.
 * The strings are considered equal iff they consist of the same
 * characters on the minimum of their lengths and the length limit.
 *
 * @param s1      First string to compare.
 * @param s2      Second string to compare.
 * @param max_len Maximum number of characters to consider.
 *
 * @return 0 if the strings are equal, -1 if first is smaller,
 *         1 if second smaller.
 *
 */
int str_lcmp(const char *s1, const char *s2, size_t max_len)
{
        wchar_t c1 = 0;
        wchar_t c2 = 0;
        
        size_t off1 = 0;
        size_t off2 = 0;
        
        size_t len = 0;

        while (true) {
                if (len >= max_len)
                        break;

                c1 = str_decode(s1, &off1, STR_NO_LIMIT);
                c2 = str_decode(s2, &off2, STR_NO_LIMIT);

                if (c1 < c2)
                        return -1;

                if (c1 > c2)
                        return 1;

                if (c1 == 0 || c2 == 0)
                        break;

                ++len;  
        }

        return 0;

}

/** Copy string.
 *
 * Copy source string @a src to destination buffer @a dest.
 * No more than @a size bytes are written. If the size of the output buffer
 * is at least one byte, the output string will always be well-formed, i.e.
 * null-terminated and containing only complete characters.
 *
 * @param dst   Destination buffer.
 * @param count Size of the destination buffer (must be > 0).
 * @param src   Source string.
 */
void str_cpy(char *dest, size_t size, const char *src)
{
        wchar_t ch;
        size_t src_off;
        size_t dest_off;

        /* There must be space for a null terminator in the buffer. */
        assert(size > 0);
        
        src_off = 0;
        dest_off = 0;

        while ((ch = str_decode(src, &src_off, STR_NO_LIMIT)) != 0) {
                if (chr_encode(ch, dest, &dest_off, size - 1) != EOK)
                        break;
        }

        dest[dest_off] = '\0';
}

/** Copy size-limited substring.
 *
 * Copy prefix of string @a src of max. size @a size to destination buffer
 * @a dest. No more than @a size bytes are written. The output string will
 * always be well-formed, i.e. null-terminated and containing only complete
 * characters.
 *
 * No more than @a n bytes are read from the input string, so it does not
 * have to be null-terminated.
 *
 * @param dst   Destination buffer.
 * @param count Size of the destination buffer (must be > 0).
 * @param src   Source string.
 * @param n     Maximum number of bytes to read from @a src.
 */
void str_ncpy(char *dest, size_t size, const char *src, size_t n)
{
        wchar_t ch;
        size_t src_off;
        size_t dest_off;

        /* There must be space for a null terminator in the buffer. */
        assert(size > 0);
        
        src_off = 0;
        dest_off = 0;

        while ((ch = str_decode(src, &src_off, n)) != 0) {
                if (chr_encode(ch, dest, &dest_off, size - 1) != EOK)
                        break;
        }

        dest[dest_off] = '\0';
}

/** Append one string to another.
 *
 * Append source string @a src to string in destination buffer @a dest.
 * Size of the destination buffer is @a dest. If the size of the output buffer
 * is at least one byte, the output string will always be well-formed, i.e.
 * null-terminated and containing only complete characters.
 *
 * @param dst   Destination buffer.
 * @param count Size of the destination buffer.
 * @param src   Source string.
 */
void str_append(char *dest, size_t size, const char *src)
{
        size_t dstr_size;

        dstr_size = str_size(dest);
        str_cpy(dest + dstr_size, size - dstr_size, src);
}

/** Copy NULL-terminated wide string to string
 *
 * Copy source wide string @a src to destination buffer @a dst.
 * No more than @a size bytes are written. NULL-terminator is always
 * written after the last succesfully copied character (i.e. if the
 * destination buffer is has at least 1 byte, it will be always
 * NULL-terminated).
 *
 * @param src   Source wide string.
 * @param dst   Destination buffer.
 * @param count Size of the destination buffer.
 *
 */
void wstr_nstr(char *dst, const wchar_t *src, size_t size)
{
        /* No space for the NULL-terminator in the buffer */
        if (size == 0)
                return;
        
        wchar_t ch;
        size_t src_idx = 0;
        size_t dst_off = 0;
        
        while ((ch = src[src_idx++]) != 0) {
                if (chr_encode(ch, dst, &dst_off, size) != EOK)
                        break;
        }
        
        if (dst_off >= size)
                dst[size - 1] = 0;
        else
                dst[dst_off] = 0;
}

/** Convert string to wide string.
 *
 * Convert string @a src to wide string. The output is written to the
 * buffer specified by @a dest and @a size, which must have non-zero
 * size. The output will always be null-terminated.
 *
 * @param dest  Destination buffer.
 * @param dlen  Length of destination buffer (number of wchars).
 * @param src   Source string.
 */
void str_to_wstr(wchar_t *dest, size_t dlen, const char *src)
{
        size_t offset;
        size_t di;
        wchar_t c;

        assert(dlen > 0);

        offset = 0;
        di = 0;

        do {
                if (di >= dlen - 1)
                        break;

                c = str_decode(src, &offset, STR_NO_LIMIT);
                dest[di++] = c;
        } while (c != '\0');

        dest[dlen - 1] = '\0';
}

/** Find first occurence of character in string.
 *
 * @param str String to search.
 * @param ch  Character to look for.
 *
 * @return Pointer to character in @a str or NULL if not found.
 */
char *str_chr(const char *str, wchar_t ch)
{
        wchar_t acc;
        size_t off = 0;
        size_t last = 0;
        
        while ((acc = str_decode(str, &off, STR_NO_LIMIT)) != 0) {
                if (acc == ch)
                        return (char *) (str + last);
                last = off;
        }
        
        return NULL;
}

/** Find last occurence of character in string.
 *
 * @param str String to search.
 * @param ch  Character to look for.
 *
 * @return Pointer to character in @a str or NULL if not found.
 */
char *str_rchr(const char *str, wchar_t ch)
{
        wchar_t acc;
        size_t off = 0;
        size_t last = 0;
        const char *res = NULL;
        
        while ((acc = str_decode(str, &off, STR_NO_LIMIT)) != 0) {
                if (acc == ch)
                        res = (str + last);
                last = off;
        }
        
        return (char *) res;
}

/** Insert a wide character into a wide string.
 *
 * Insert a wide character into a wide string at position
 * @a pos. The characters after the position are shifted.
 *
 * @param str     String to insert to.
 * @param ch      Character to insert to.
 * @param pos     Character index where to insert.
 @ @param max_pos Characters in the buffer.
 *
 * @return True if the insertion was sucessful, false if the position
 *         is out of bounds.
 *
 */
bool wstr_linsert(wchar_t *str, wchar_t ch, size_t pos, size_t max_pos)
{
        size_t len = wstr_length(str);
        
        if ((pos > len) || (pos + 1 > max_pos))
                return false;
        
        size_t i;
        for (i = len; i + 1 > pos; i--)
                str[i + 1] = str[i];
        
        str[pos] = ch;
        
        return true;
}

/** Remove a wide character from a wide string.
 *
 * Remove a wide character from a wide string at position
 * @a pos. The characters after the position are shifted.
 *
 * @param str String to remove from.
 * @param pos Character index to remove.
 *
 * @return True if the removal was sucessful, false if the position
 *         is out of bounds.
 *
 */
bool wstr_remove(wchar_t *str, size_t pos)
{
        size_t len = wstr_length(str);
        
        if (pos >= len)
                return false;
        
        size_t i;
        for (i = pos + 1; i <= len; i++)
                str[i - 1] = str[i];
        
        return true;
}

int stricmp(const char *a, const char *b)
{
        int c = 0;
        
        while (a[c] && b[c] && (!(tolower(a[c]) - tolower(b[c]))))
                c++;
        
        return (tolower(a[c]) - tolower(b[c]));
}

/** Convert string to a number. 
 * Core of strtol and strtoul functions.
 *
 * @param nptr          Pointer to string.
 * @param endptr        If not NULL, function stores here pointer to the first
 *                      invalid character.
 * @param base          Zero or number between 2 and 36 inclusive.
 * @param sgn           It's set to 1 if minus found.
 * @return              Result of conversion.
 */
static unsigned long
_strtoul(const char *nptr, char **endptr, int base, char *sgn)
{
        unsigned char c;
        unsigned long result = 0;
        unsigned long a, b;
        const char *str = nptr;
        const char *tmpptr;
        
        while (isspace(*str))
                str++;
        
        if (*str == '-') {
                *sgn = 1;
                ++str;
        } else if (*str == '+')
                ++str;
        
        if (base) {
                if ((base == 1) || (base > 36)) {
                        /* FIXME: set errno to EINVAL */
                        return 0;
                }
                if ((base == 16) && (*str == '0') && ((str[1] == 'x') ||
                    (str[1] == 'X'))) {
                        str += 2;
                }
        } else {
                base = 10;
                
                if (*str == '0') {
                        base = 8;
                        if ((str[1] == 'X') || (str[1] == 'x'))  {
                                base = 16;
                                str += 2;
                        }
                } 
        }
        
        tmpptr = str;

        while (*str) {
                c = *str;
                c = (c >= 'a' ? c - 'a' + 10 : (c >= 'A' ? c - 'A' + 10 :
                    (c <= '9' ? c - '0' : 0xff)));
                if (c > base) {
                        break;
                }
                
                a = (result & 0xff) * base + c;
                b = (result >> 8) * base + (a >> 8);
                
                if (b > (ULONG_MAX >> 8)) {
                        /* overflow */
                        /* FIXME: errno = ERANGE*/
                        return ULONG_MAX;
                }
        
                result = (b << 8) + (a & 0xff);
                ++str;
        }
        
        if (str == tmpptr) {
                /*
                 * No number was found => first invalid character is the first
                 * character of the string.
                 */
                /* FIXME: set errno to EINVAL */
                str = nptr;
                result = 0;
        }
        
        if (endptr)
                *endptr = (char *) str;

        if (nptr == str) { 
                /*FIXME: errno = EINVAL*/
                return 0;
        }

        return result;
}

/** Convert initial part of string to long int according to given base.
 * The number may begin with an arbitrary number of whitespaces followed by
 * optional sign (`+' or `-'). If the base is 0 or 16, the prefix `0x' may be
 * inserted and the number will be taken as hexadecimal one. If the base is 0
 * and the number begin with a zero, number will be taken as octal one (as with
 * base 8). Otherwise the base 0 is taken as decimal.
 *
 * @param nptr          Pointer to string.
 * @param endptr        If not NULL, function stores here pointer to the first
 *                      invalid character.
 * @param base          Zero or number between 2 and 36 inclusive.
 * @return              Result of conversion.
 */
long int strtol(const char *nptr, char **endptr, int base)
{
        char sgn = 0;
        unsigned long number = 0;
        
        number = _strtoul(nptr, endptr, base, &sgn);

        if (number > LONG_MAX) {
                if ((sgn) && (number == (unsigned long) (LONG_MAX) + 1)) {
                        /* FIXME: set 0 to errno */
                        return number;          
                }
                /* FIXME: set ERANGE to errno */
                return (sgn ? LONG_MIN : LONG_MAX);     
        }
        
        return (sgn ? -number : number);
}


/** Convert initial part of string to unsigned long according to given base.
 * The number may begin with an arbitrary number of whitespaces followed by
 * optional sign (`+' or `-'). If the base is 0 or 16, the prefix `0x' may be
 * inserted and the number will be taken as hexadecimal one. If the base is 0
 * and the number begin with a zero, number will be taken as octal one (as with
 * base 8). Otherwise the base 0 is taken as decimal.
 *
 * @param nptr          Pointer to string.
 * @param endptr        If not NULL, function stores here pointer to the first
 *                      invalid character
 * @param base          Zero or number between 2 and 36 inclusive.
 * @return              Result of conversion.
 */
unsigned long strtoul(const char *nptr, char **endptr, int base)
{
        char sgn = 0;
        unsigned long number = 0;
        
        number = _strtoul(nptr, endptr, base, &sgn);

        return (sgn ? -number : number);
}

char *str_dup(const char *src)
{
        size_t size = str_size(src);
        void *dest = malloc(size + 1);

        if (dest == NULL)
                return (char *) NULL;

        return (char *) memcpy(dest, src, size + 1);
}

char *strtok(char *s, const char *delim)
{
        static char *next;

        return strtok_r(s, delim, &next);
}

char *strtok_r(char *s, const char *delim, char **next)
{
        char *start, *end;

        if (s == NULL)
                s = *next;

        /* Skip over leading delimiters. */
        while (*s && (str_chr(delim, *s) != NULL)) ++s;
        start = s;

        /* Skip over token characters. */
        while (*s && (str_chr(delim, *s) == NULL)) ++s;
        end = s;
        *next = (*s ? s + 1 : s);

        if (start == end) {
                return NULL;    /* No more tokens. */
        }

        /* Overwrite delimiter with NULL terminator. */
        *end = '\0';
        return start;
}

/** @}
 */