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/*
 * 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 <limits.h>
#include <ctype.h>
#include <malloc.h>
#include <errno.h>
#include <align.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, count_t max_len)
{
    count_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, count_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.
 *
 */
count_t str_length(const char *str)
{
    count_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.
 *
 */
count_t wstr_length(const wchar_t *wstr)
{
    count_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.
 *
 */
count_t str_nlength(const char *str, size_t size)
{
    count_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.
 *
 */
count_t wstr_nlength(const wchar_t *str, size_t size)
{
    count_t len = 0;
    count_t limit = ALIGN_DOWN(size, sizeof(wchar_t));
    count_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, count_t max_len)
{
    wchar_t c1 = 0;
    wchar_t c2 = 0;
    
    size_t off1 = 0;
    size_t off2 = 0;
    
    count_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 NULL-terminated string.
 *
 * Copy source 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 string.
 * @param dst   Destination buffer.
 * @param count Size of the destination buffer.
 *
 */
void str_ncpy(char *dst, const char *src, size_t size)
{
    /* No space for the NULL-terminator in the buffer */
    if (size == 0)
        return;
    
    wchar_t ch;
    size_t str_off = 0;
    size_t dst_off = 0;
    
    while ((ch = str_decode(src, &str_off, STR_NO_LIMIT)) != 0) {
        if (chr_encode(ch, dst, &dst_off, size) != EOK)
            break;
    }
    
    if (dst_off >= size)
        dst[size - 1] = 0;
    else
        dst[dst_off] = 0;
}

/** 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;
    count_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;
}

/** 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.
 *
 */
const char *str_chr(const char *str, wchar_t ch)
{
    wchar_t acc;
    size_t off = 0;
    
    while ((acc = str_decode(str, &off, STR_NO_LIMIT)) != 0) {
        if (acc == ch)
            return (str + off);
    }
    
    return NULL;
}

/** 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, count_t pos, count_t max_pos)
{
    count_t len = wstr_length(str);
    
    if ((pos > len) || (pos + 1 > max_pos))
        return false;
    
    count_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, count_t pos)
{
    count_t len = wstr_length(str);
    
    if (pos >= len)
        return false;
    
    count_t i;
    for (i = pos + 1; i <= len; i++)
        str[i - 1] = str[i];
    
    return true;
}

/** Count the number of characters in the string, not including terminating 0.
 *
 * @param str       String.
 * @return      Number of characters in string.
 */
size_t strlen(const char *str) 
{
    size_t counter = 0;

    while (str[counter] != 0)
        counter++;

    return counter;
}

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

int strncmp(const char *a, const char *b, size_t n)
{
    size_t c = 0;

    while (c < n && a[c] && b[c] && (!(a[c] - b[c])))
        c++;
    
    return ( c < n ? a[c] - b[c] : 0);
    
}

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]));
}

/** Return pointer to the first occurence of character c in string.
 *
 * @param str       Scanned string.
 * @param c     Searched character (taken as one byte).
 * @return      Pointer to the matched character or NULL if it is not
 *          found in given string.
 */
char *strchr(const char *str, int c)
{
    while (*str != '\0') {
        if (*str == (char) c)
            return (char *) str;
        str++;
    }

    return NULL;
}

/** Return pointer to the last occurence of character c in string.
 *
 * @param str       Scanned string.
 * @param c     Searched character (taken as one byte).
 * @return      Pointer to the matched character or NULL if it is not
 *          found in given string.
 */
char *strrchr(const char *str, int c)
{
    char *retval = NULL;

    while (*str != '\0') {
        if (*str == (char) c)
            retval = (char *) str;
        str++;
    }

    return (char *) retval;
}

/** 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 *strcpy(char *dest, const char *src)
{
    char *orig = dest;
    
    while ((*(dest++) = *(src++)))
        ;
    return orig;
}

char *strncpy(char *dest, const char *src, size_t n)
{
    char *orig = dest;
    
    while ((*(dest++) = *(src++)) && --n)
        ;
    return orig;
}

char *strcat(char *dest, const char *src)
{
    char *orig = dest;
    while (*dest++)
        ;
    --dest;
    while ((*dest++ = *src++))
        ;
    return orig;
}

char * strdup(const char *s1)
{
    size_t len = strlen(s1) + 1;
    void *ret = malloc(len);

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

    return (char *) memcpy(ret, s1, len);
}

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 && (strchr(delim, *s) != NULL)) ++s;
    start = s;

    /* Skip over token characters. */
    while (*s && (strchr(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;
}

/** @}
 */