string.c

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/*
 * Copyright (C) 2015 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * 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 2 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <ctype.h>

/** @file
 *
 * String functions
 *
 */

/**
 * Fill memory region
 *
 * @v dest              Destination region
 * @v character         Fill character
 * @v len               Length
 * @ret dest            Destination region
 */
void * generic_memset ( void *dest, int character, size_t len ) {
        uint8_t *dest_bytes = dest;

        while ( len-- )
                *(dest_bytes++) = character;
        return dest;
}

/**
 * Copy memory region (forwards)
 *
 * @v dest              Destination region
 * @v src               Source region
 * @v len               Length
 * @ret dest            Destination region
 */
void * generic_memcpy ( void *dest, const void *src, size_t len ) {
        const uint8_t *src_bytes = src;
        uint8_t *dest_bytes = dest;

        while ( len-- )
                *(dest_bytes++) = *(src_bytes++);
        return dest;
}

/**
 * Copy memory region (backwards)
 *
 * @v dest              Destination region
 * @v src               Source region
 * @v len               Length
 * @ret dest            Destination region
 */
void * generic_memcpy_reverse ( void *dest, const void *src, size_t len ) {
        const uint8_t *src_bytes = ( src + len );
        uint8_t *dest_bytes = ( dest + len );

        while ( len-- )
                *(--dest_bytes) = *(--src_bytes);
        return dest;
}

/**
 * Copy (possibly overlapping) memory region
 *
 * @v dest              Destination region
 * @v src               Source region
 * @v len               Length
 * @ret dest            Destination region
 */
void * generic_memmove ( void *dest, const void *src, size_t len ) {

        if ( dest < src ) {
                return generic_memcpy ( dest, src, len );
        } else {
                return generic_memcpy_reverse ( dest, src, len );
        }
}

/**
 * Compare memory regions
 *
 * @v first             First region
 * @v second            Second region
 * @v len               Length
 * @ret diff            Difference
 */
int memcmp ( const void *first, const void *second, size_t len ) {
        const uint8_t *first_bytes = first;
        const uint8_t *second_bytes = second;
        int diff;

        while ( len-- ) {
                diff = ( *(first_bytes++) - *(second_bytes++) );
                if ( diff )
                        return diff;
        }
        return 0;
}

/**
 * Find character within a memory region
 *
 * @v src               Source region
 * @v character         Character to find
 * @v len               Length
 * @ret found           Found character, or NULL if not found
 */
void * memchr ( const void *src, int character, size_t len ) {
        const uint8_t *src_bytes = src;

        for ( ; len-- ; src_bytes++ ) {
                if ( *src_bytes == character )
                        return ( ( void * ) src_bytes );
        }
        return NULL;
}

/**
 * Swap memory regions
 *
 * @v first             First region
 * @v second            Second region
 * @v len               Length
 * @ret first           First region
 */
void * memswap ( void *first, void *second, size_t len ) {
        uint8_t *first_bytes = first;
        uint8_t *second_bytes = second;
        uint8_t temp;

        for ( ; len-- ; first_bytes++, second_bytes++ ) {
                temp = *first_bytes;
                *first_bytes = *second_bytes;
                *second_bytes = temp;
        }
        return first;
}

/**
 * Compare strings
 *
 * @v first             First string
 * @v second            Second string
 * @ret diff            Difference
 */
int strcmp ( const char *first, const char *second ) {

        return strncmp ( first, second, ~( ( size_t ) 0 ) );
}

/**
 * Compare strings
 *
 * @v first             First string
 * @v second            Second string
 * @v max               Maximum length to compare
 * @ret diff            Difference
 */
int strncmp ( const char *first, const char *second, size_t max ) {
        const uint8_t *first_bytes = ( ( const uint8_t * ) first );
        const uint8_t *second_bytes = ( ( const uint8_t * ) second );
        int diff;

        for ( ; max-- ; first_bytes++, second_bytes++ ) {
                diff = ( *first_bytes - *second_bytes );
                if ( diff )
                        return diff;
                if ( ! *first_bytes )
                        return 0;
        }
        return 0;
}

/**
 * Compare case-insensitive strings
 *
 * @v first             First string
 * @v second            Second string
 * @ret diff            Difference
 */
int strcasecmp ( const char *first, const char *second ) {

        return strncasecmp ( first, second, ~( ( size_t ) 0 ) );
}

/**
 * Compare case-insensitive strings
 *
 * @v first             First string
 * @v second            Second string
 * @v max               Maximum length to compare
 * @ret diff            Difference
 */
int strncasecmp ( const char *first, const char *second, size_t max ) {
        const uint8_t *first_bytes = ( ( const uint8_t * ) first );
        const uint8_t *second_bytes = ( ( const uint8_t * ) second );
        int diff;

        for ( ; max-- ; first_bytes++, second_bytes++ ) {
                diff = ( toupper ( *first_bytes ) -
                         toupper ( *second_bytes ) );
                if ( diff )
                        return diff;
                if ( ! *first_bytes )
                        return 0;
        }
        return 0;
}

/**
 * Get length of string
 *
 * @v src               String
 * @ret len             Length
 */
size_t strlen ( const char *src ) {

        return strnlen ( src, ~( ( size_t ) 0 ) );
}

/**
 * Get length of string
 *
 * @v src               String
 * @v max               Maximum length
 * @ret len             Length
 */
size_t strnlen ( const char *src, size_t max ) {
        const uint8_t *src_bytes = ( ( const uint8_t * ) src );
        size_t len = 0;

        while ( max-- && *(src_bytes++) )
                len++;
        return len;
}

/**
 * Find character within a string
 *
 * @v src               String
 * @v character         Character to find
 * @ret found           Found character, or NULL if not found
 */
char * strchr ( const char *src, int character ) {
        const uint8_t *src_bytes = ( ( const uint8_t * ) src );

        for ( ; ; src_bytes++ ) {
                if ( *src_bytes == character )
                        return ( ( char * ) src_bytes );
                if ( ! *src_bytes )
                        return NULL;
        }
}

/**
 * Find rightmost character within a string
 *
 * @v src               String
 * @v character         Character to find
 * @ret found           Found character, or NULL if not found
 */
char * strrchr ( const char *src, int character ) {
        const uint8_t *src_bytes = ( ( const uint8_t * ) src );
        const uint8_t *start = src_bytes;

        while ( *src_bytes )
                src_bytes++;
        for ( src_bytes-- ; src_bytes >= start ; src_bytes-- ) {
                if ( *src_bytes == character )
                        return ( ( char * ) src_bytes );
        }
        return NULL;
}

/**
 * Find substring
 *
 * @v haystack          String
 * @v needle            Substring
 * @ret found           Found substring, or NULL if not found
 */
char * strstr ( const char *haystack, const char *needle ) {
        size_t len = strlen ( needle );

        for ( ; *haystack ; haystack++ ) {
                if ( memcmp ( haystack, needle, len ) == 0 )
                        return ( ( char * ) haystack );
        }
        return NULL;
}

/**
 * Copy string
 *
 * @v dest              Destination string
 * @v src               Source string
 * @ret dnul            Terminating NUL of destination string
 */
char * stpcpy ( char *dest, const char *src ) {
        const uint8_t *src_bytes = ( ( const uint8_t * ) src );
        uint8_t *dest_bytes = ( ( uint8_t * ) dest );

        /* We cannot use strncpy(), since that would pad the destination */
        for ( ; ; src_bytes++, dest_bytes++ ) {
                *dest_bytes = *src_bytes;
                if ( ! *dest_bytes )
                        break;
        }
        return ( ( char * ) dest_bytes );
}

/**
 * Copy string
 *
 * @v dest              Destination string
 * @v src               Source string
 * @ret dest            Destination string
 */
char * strcpy ( char *dest, const char *src ) {

        stpcpy ( dest, src );
        return dest;
}

/**
 * Copy string
 *
 * @v dest              Destination string
 * @v src               Source string
 * @v max               Maximum length
 * @ret dest            Destination string
 */
char * strncpy ( char *dest, const char *src, size_t max ) {
        const uint8_t *src_bytes = ( ( const uint8_t * ) src );
        uint8_t *dest_bytes = ( ( uint8_t * ) dest );

        for ( ; max ; max--, src_bytes++, dest_bytes++ ) {
                *dest_bytes = *src_bytes;
                if ( ! *dest_bytes )
                        break;
        }
        while ( max-- )
                *(dest_bytes++) = '\0';
        return dest;
}

/**
 * Concatenate string
 *
 * @v dest              Destination string
 * @v src               Source string
 * @ret dest            Destination string
 */
char * strcat ( char *dest, const char *src ) {

        strcpy ( ( dest + strlen ( dest ) ), src );
        return dest;
}

/**
 * Duplicate string
 *
 * @v src               Source string
 * @ret dup             Duplicated string, or NULL if allocation failed
 */
char * strdup ( const char *src ) {

        return strndup ( src, ~( ( size_t ) 0 ) );
}

/**
 * Duplicate string
 *
 * @v src               Source string
 * @v max               Maximum length
 * @ret dup             Duplicated string, or NULL if allocation failed
 */
char * strndup ( const char *src, size_t max ) {
        size_t len = strnlen ( src, max );
        char *dup;

        dup = malloc ( len + 1 /* NUL */ );
        if ( dup ) {
                memcpy ( dup, src, len );
                dup[len] = '\0';
        }
        return dup;
}

/**
 * Calculate digit value
 *
 * @v character         Digit character
 * @ret digit           Digit value
 *
 * Invalid digits will be returned as a value greater than or equal to
 * the numeric base.
 */
unsigned int digit_value ( unsigned int character ) {

        if ( character >= 'a' )
                return ( character - ( 'a' - 10 ) );
        if ( character >= 'A' )
                return ( character - ( 'A' - 10 ) );
        if ( character <= '9' )
                return ( character - '0' );
        return character;
}

/**
 * Preprocess string for strtoul() or strtoull()
 *
 * @v string            String
 * @v negate            Final value should be negated
 * @v base              Numeric base
 * @ret string          Remaining string
 */
static const char * strtoul_pre ( const char *string, int *negate, int *base ) {

        /* Skip any leading whitespace */
        while ( isspace ( *string ) )
                string++;

        /* Process arithmetic sign, if present */
        *negate = 0;
        if ( *string == '-' ) {
                string++;
                *negate = 1;
        } else if ( *string == '+' ) {
                string++;
        }

        /* Process base, if present */
        if ( *base == 0 ) {
                *base = 10;
                if ( *string == '0' ) {
                        string++;
                        *base = 8;
                        if ( ( *string & ~0x20 ) == 'X' ) {
                                string++;
                                *base = 16;
                        }
                }
        }

        return string;
}

/**
 * Convert string to numeric value
 *
 * @v string            String
 * @v endp              End pointer (or NULL)
 * @v base              Numeric base (or zero to autodetect)
 * @ret value           Numeric value
 */
unsigned long strtoul ( const char *string, char **endp, int base ) {
        unsigned long value = 0;
        unsigned int digit;
        int negate;

        /* Preprocess string */
        string = strtoul_pre ( string, &negate, &base );

        /* Process digits */
        for ( ; ; string++ ) {
                digit = digit_value ( *string );
                if ( digit >= ( unsigned int ) base )
                        break;
                value = ( ( value * base ) + digit );
        }

        /* Negate value if, applicable */
        if ( negate )
                value = -value;

        /* Fill in end pointer, if applicable */
        if ( endp )
                *endp = ( ( char * ) string );

        return value;
}

/**
 * Convert string to numeric value
 *
 * @v string            String
 * @v endp              End pointer (or NULL)
 * @v base              Numeric base (or zero to autodetect)
 * @ret value           Numeric value
 */
unsigned long long strtoull ( const char *string, char **endp, int base ) {
        unsigned long long value = 0;
        unsigned int digit;
        int negate;

        /* Preprocess string */
        string = strtoul_pre ( string, &negate, &base );

        /* Process digits */
        for ( ; ; string++ ) {
                digit = digit_value ( *string );
                if ( digit >= ( unsigned int ) base )
                        break;
                value = ( ( value * base ) + digit );
        }

        /* Negate value if, applicable */
        if ( negate )
                value = -value;

        /* Fill in end pointer, if applicable */
        if ( endp )
                *endp = ( ( char * ) string );

        return value;
}