source: mainline/uspace/lib/c/generic/string.c@ 8591b31

/*
 * Copyright (c) 2018 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
 */

/* Prevent an error from being generated */
#undef _HELENOS_SOURCE
#include <string.h>
#define _HELENOS_SOURCE

#include <stddef.h>
#include <str_error.h>

/** Copy string.
 *
 * Copy the string pointed to by @a s2 to the array pointed to by @a s1
 * including the terminating null character. The source and destination
 * must not overlap.
 *
 * @param s1 Destination array
 * @param s2 Source string
 * @return @a s1
 */
char *strcpy(char *s1, const char *s2)
{
        char *dp = s1;

        /* Copy characters */
        while (*s2 != '\0')
                *dp++ = *s2++;

        /* Copy the terminating null character */
        *dp++ = *s2++;

        return s1;
}

/** Copy not more than @a n characters.
 *
 * Copy not more than @a n characters from  @a s2 to @a s1. Characters
 * following a null character are not copied. If The string @a s2 is
 * shorter than @a n characters, null characters are appended to the
 * copy in @a s1, until @a n characters in all have been written.
 *
 * (I.e. @a s1 is padded with null characters up to size @a n).
 * The source and destination must not overlap.
 *
 * @param s1 Destination array
 * @param s2 Source string
 * @param n Number of characters to copy
 * @return @a s1
 */
char *strncpy(char *s1, const char *s2, size_t n)
{
        char *dp = s1;
        size_t i;

        for (i = 0; i < n; i++) {
                *dp++ = *s2;
                if (*s2 != '\0')
                        ++s2;
        }

        return s1;
}

/** Append string.
 *
 * Append a copy of string in @a s2 to the string pointed to by @a s1
 * (including the terminating null character). @a s1 and @a s2 must not
 * overlap.
 *
 * @param s1 Destination buffer holding a string to be appended to
 * @param s2 String to be appended
 * @return @a s1
 */
char *strcat(char *s1, const char *s2)
{
        char *dp = s1;

        /* Find end of first string */
        while (*dp != '\0')
                ++dp;

        /* Copy second string */
        while (*s2 != '\0')
                *dp++ = *s2++;

        /* Copy null character */
        *dp = '\0';

        return s1;
}

/** Append not more than @a n characters.
 *
 * Append a copy of max. @a n characters from string in @a s2 to the string
 * pointed to by @a s1. The resulting string is always null-terminated.
 *
 * @param s1 Destination buffer holding a string to be appended to
 * @param s2 String to be appended
 * @param n Maximum number of characters to copy
 * @return @a s1
 */
char *strncat(char *s1, const char *s2, size_t n)
{
        char *dp = s1;

        /* Find end of first string */
        while (*dp != '\0')
                ++dp;

        /* Copy second string */
        while (*s2 != '\0' && n > 0) {
                *dp++ = *s2++;
                --n;
        }

        /* Copy null character */
        *dp = '\0';

        return s1;
}

/** Compare two strings.
 *
 * @param s1 First string
 * @param s2 Second string
 * @return Greater than, equal to, less than zero if @a s1 > @a s2,
 *         @a s1 == @a s2, @a s1 < @a s2, resp.
 */
int strcmp(const char *s1, const char *s2)
{
        while (*s1 == *s2 && *s1 != '\0') {
                ++s1;
                ++s2;
        }

        return *s1 - *s2;
}

/** Compare two strings based on LC_COLLATE of current locale.
 *
 * @param s1 First string
 * @param s2 Second string
 * @return Greater than, equal to, less than zero if @a s1 > @a s2,
 *         @a s1 == @a s2, @a s1 < @a s2, resp.
 */
int strcoll(const char *s1, const char *s2)
{
        /* Note: we don't support locale other than "C" */
        return strcmp(s1, s2);
}

/** Compare not more than @a n characters.
 *
 * @param s1 First string
 * @param s2 Second string
 * @param n Maximum number of characters to compare
 * @return Greater than, equal to, less than zero if @a s1 > @a s2,
 *         @a s1 == @a s2, @a s1 < @a s2, resp. (within the first @a n chars.)
 */
int strncmp(const char *s1, const char *s2, size_t n)
{
        while (*s1 == *s2 && *s1 != '\0' && n > 0) {
                ++s1;
                ++s2;
                --n;
        }

        if (n > 0)
                return *s1 - *s2;

        return 0;
}

/** Transform string for collation.
 *
 * Transform string in @a s2 to the buffer @a s1, writing no more than
 * @a n characters (including the terminating null character). The transformed
 * string is such that using strcmp on two transformed strings should be
 * equivalent to using strcoll on the original strings.
 *
 * @param s1 Destination buffer
 * @param s2 Source string
 * @param n Max. number of characters to write (including terminating null)
 * @return Length of the transformed string not including the null terminator.
 *         If the value returned is @a n or more, the contents of the buffer
 *         pointed to by @a s1 are undefined.
 */
size_t strxfrm(char *s1, const char *s2, size_t n)
{
        size_t i;
        size_t len;

        len = strlen(s2);

        for (i = 0; i < n; i++) {
                *s1++ = *s2;
                if (*s2 == '\0')
                        break;
                ++s2;
        }

        return len;
}

/** Find the first occurrence of a character in a string.
 *
 * The character @a c is converted to char. The null character is
 * considered part of the string.
 *
 * @param s String
 * @param c Character
 * @return Pointer to the located character or @c NULL if the character
 *         does not occur in the string.
 */
char *strchr(const char *s, int c)
{
        do {
                if (*s == (char) c)
                        return (char *) s;
        } while (*s++ != '\0');

        return NULL;
}

/** Compute the size of max. initial segment consisting of a complementary
 * set of characters.
 *
 * Compute the size of the max. initial segment of @a s1 consisting only
 * of characters *not* from @a s2.
 *
 * @param s1 String to search
 * @param s2 String containing set of characters
 * @return Size of initial segment of @a s1 consisting only of characters
 *         not from @a s2.
 */
size_t strcspn(const char *s1, const char *s2)
{
        char *p;
        size_t n;

        n = 0;
        while (*s1 != '\0') {
                /* Look for current character in s2 */
                p = strchr(s2, *s1);

                /* If found, return current character count. */
                if (p != NULL)
                        break;

                ++s1;
                ++n;
        }

        return n;
}

/** Search string for occurrence of any of a set of characters.
 *
 * @param s1 String to search
 * @param s2 String containing a set of characters
 *
 * @return Pointer to first character found or @c NULL if not found
 */
char *strpbrk(const char *s1, const char *s2)
{
        char *p;

        while (*s1 != '\0') {
                /* Look for current character in s2 */
                p = strchr(s2, *s1);

                /* If found, return pointer to current character. */
                if (p != NULL)
                        return (char *) s1;

                ++s1;
        }

        return NULL;
}

/** Find the last occurrence of a character in a string.
 *
 * The character @a c is converted to char. The null character is
 * considered part of the string.
 *
 * @param s String
 * @param c Character
 * @return Pointer to the located character or @c NULL if the character
 *         does not occur in the string.
 */
char *strrchr(const char *s, int c)
{
        size_t i = strlen(s);

        while (i > 0) {
                if (s[i] == (char) c)
                        return (char *)s + i;
                --i;
        }

        return NULL;
}

/** Compute the size of max. initial segment consisting of a set of characters.
 *
 * Compute tha size of the max. initial segment of @a s1 consisting only
 * of characters from @a s2.
 *
 * @param s1 String to search
 * @param s2 String containing set of characters
 * @return Size of initial segment of @a s1 consisting only of characters
 *         from @a s2.
 */
size_t strspn(const char *s1, const char *s2)
{
        char *p;
        size_t n;

        n = 0;
        while (*s1 != '\0') {
                /* Look for current character in s2 */
                p = strchr(s2, *s1);

                /* If not found, return current character count. */
                if (p == NULL)
                        break;

                ++s1;
                ++n;
        }

        return n;
}

/** Find occurrence of substring in a string.
 *
 * Find the first occurrence in @a s1 of the characters in @a s2, excluding
 * the terminating null character. If s2 is an empty string, returns @a s1.
 *
 * @param s1 String to search
 * @param s2 Sequence of characters to find
 *
 * @return Pointer inside @a s1 or @c NULL if not found.
 */
char *strstr(const char *s1, const char *s2)
{
        size_t len;

        /*
         * Naive search algorithm.
         *
         * Two-Way String-Matching might be a plausible alternative
         * for larger haystack+needle combinations.
         */

        len = strlen(s2);
        while (*s1 != '\0') {
                if (strncmp(s1, s2, len) == 0)
                        return (char *) s1;
                ++s1;
        }

        return NULL;
}

/** Tokenize a string (reentrant).
 *
 * The contents of @a s1 are modified (the separators get overwritten by null
 * characters). The separators can be different each iteration, their identity\
 * is, however, lost.
 *
 * @param s1 String buffer to get the first token, @c NULL to get the next
 *           token
 * @param s2 String containing current separators
 * @return Pointer to the next token
 */
char *__strtok_r(char *s1, const char *s2, char **saveptr)
{
        char *s;
        char *tbegin;
        char *tend;

        if (s1 != NULL) {
                /* Starting tokenization of a new string */
                s = s1;
        } else {
                /* Use saved position of next token */
                s = *saveptr;

                /* Check if we ran out of tokens */
                if (s == NULL)
                        return NULL;
        }

        /* Find position of first character that is not a separator */
        tbegin = s;
        while (*tbegin != '\0' && strchr(s2, *tbegin) != NULL)
                ++tbegin;

        /* If no such character is found, there are no tokens */
        if (*tbegin == '\0')
                return NULL;

        /* Find first character that is a separator */
        tend = strpbrk(tbegin, s2);
        if (tend != NULL) {
                /* Overwrite the separator, next token starts just after */
                *tend = '\0';
                *saveptr = tend + 1;
        } else {
                /* No more tokens will be returned next time */
                *saveptr = NULL;
        }

        return tbegin;
}

/** Saved position of next token for function strtok */
static char *strtok_saveptr = NULL;

/** Tokenize a string.
 *
 * This function has internal state and thus is not reentrant.
 * ISO C says the implementation should behave as if no (standard) library
 * call calls strtok. The contents of @a s1 are modified (the separators
 * get overwritten by null characters). The separators can be different
 * each iteration, their identity is, however, lost.
 *
 * Never use this function since it's not reentrant.
 *
 * @param s1 String buffer to get the first token, @c NULL to get the next
 *           token
 * @param s2 String containing current separators
 * @return Pointer to the next token
 */
char *strtok(char *s1, const char *s2)
{
        return __strtok_r(s1, s2, &strtok_saveptr);
}

/** Map error number to a string.
 *
 * The string returned by the function may be overwritten by a subsequent
 * call to strerror (ISO C). In our implementation the function is, in fact,
 * reentrant, as the string returned is static and never modified.
 *
 * @param errnum Error number
 * @return Pointer to error message
 */
char *strerror(int errnum)
{
        return (char *) str_error(errnum);
}

/** Return number of characters in string.
 *
 * @param s String
 * @return Number of characters preceding the null character.
 */
size_t strlen(const char *s)
{
        size_t n;

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

        return n;
}

/** @}
 */