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  1. /*
  2.  * Copyright (c) 2001-2004 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup generic
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file
  35.  * @brief String functions.
  36.  *
  37.  * Strings and characters use the Universal Character Set (UCS). The standard
  38.  * strings, called just strings are encoded in UTF-8. Wide strings (encoded
  39.  * in UTF-32) are supported to a limited degree. A single character is
  40.  * represented as wchar_t.@n
  41.  *
  42.  * Overview of the terminology:@n
  43.  *
  44.  *  Term                  Meaning
  45.  *  --------------------  ----------------------------------------------------
  46.  *  byte                  8 bits stored in uint8_t (unsigned 8 bit integer)
  47.  *
  48.  *  character             UTF-32 encoded Unicode character, stored in wchar_t
  49.  *                        (signed 32 bit integer), code points 0 .. 1114111
  50.  *                        are valid
  51.  *
  52.  *  ASCII character       7 bit encoded ASCII character, stored in char
  53.  *                        (usually signed 8 bit integer), code points 0 .. 127
  54.  *                        are valid
  55.  *
  56.  *  string                UTF-8 encoded NULL-terminated Unicode string, char *
  57.  *
  58.  *  wide string           UTF-32 encoded NULL-terminated Unicode string,
  59.  *                        wchar_t *
  60.  *
  61.  *  [wide] string size    number of BYTES in a [wide] string (excluding
  62.  *                        the NULL-terminator), size_t
  63.  *
  64.  *  [wide] string length  number of CHARACTERS in a [wide] string (excluding
  65.  *                        the NULL-terminator), size_t
  66.  *
  67.  *  [wide] string width   number of display cells on a monospace display taken
  68.  *                        by a [wide] string, size_t
  69.  *
  70.  *
  71.  * Overview of string metrics:@n
  72.  *
  73.  *  Metric  Abbrev.  Type     Meaning
  74.  *  ------  ------   ------   -------------------------------------------------
  75.  *  size    n        size_t   number of BYTES in a string (excluding the
  76.  *                            NULL-terminator)
  77.  *
  78.  *  length  l        size_t   number of CHARACTERS in a string (excluding the
  79.  *                            null terminator)
  80.  *
  81.  *  width  w         size_t   number of display cells on a monospace display
  82.  *                            taken by a string
  83.  *
  84.  *
  85.  * Function naming prefixes:@n
  86.  *
  87.  *  chr_    operate on characters
  88.  *  ascii_  operate on ASCII characters
  89.  *  str_    operate on strings
  90.  *  wstr_   operate on wide strings
  91.  *
  92.  *  [w]str_[n|l|w]  operate on a prefix limited by size, length
  93.  *                  or width
  94.  *
  95.  *
  96.  * A specific character inside a [wide] string can be referred to by:@n
  97.  *
  98.  *  pointer (char *, wchar_t *)
  99.  *  byte offset (size_t)
  100.  *  character index (size_t)
  101.  *
  102.  */
  103.  
  104. #include <string.h>
  105. #include <print.h>
  106. #include <cpu.h>
  107. #include <arch/asm.h>
  108. #include <arch.h>
  109. #include <errno.h>
  110. #include <align.h>
  111. #include <debug.h>
  112.  
  113. /** Byte mask consisting of lowest @n bits (out of 8) */
  114. #define LO_MASK_8(n)  ((uint8_t) ((1 << (n)) - 1))
  115.  
  116. /** Byte mask consisting of lowest @n bits (out of 32) */
  117. #define LO_MASK_32(n)  ((uint32_t) ((1 << (n)) - 1))
  118.  
  119. /** Byte mask consisting of highest @n bits (out of 8) */
  120. #define HI_MASK_8(n)  (~LO_MASK_8(8 - (n)))
  121.  
  122. /** Number of data bits in a UTF-8 continuation byte */
  123. #define CONT_BITS  6
  124.  
  125. /** Decode a single character from a string.
  126.  *
  127.  * Decode a single character from a string of size @a size. Decoding starts
  128.  * at @a offset and this offset is moved to the beginning of the next
  129.  * character. In case of decoding error, offset generally advances at least
  130.  * by one. However, offset is never moved beyond size.
  131.  *
  132.  * @param str    String (not necessarily NULL-terminated).
  133.  * @param offset Byte offset in string where to start decoding.
  134.  * @param size   Size of the string (in bytes).
  135.  *
  136.  * @return Value of decoded character, U_SPECIAL on decoding error or
  137.  *         NULL if attempt to decode beyond @a size.
  138.  *
  139.  */
  140. wchar_t str_decode(const char *str, size_t *offset, size_t size)
  141. {
  142.     if (*offset + 1 > size)
  143.         return 0;
  144.    
  145.     /* First byte read from string */
  146.     uint8_t b0 = (uint8_t) str[(*offset)++];
  147.    
  148.     /* Determine code length */
  149.    
  150.     unsigned int b0_bits;  /* Data bits in first byte */
  151.     unsigned int cbytes;   /* Number of continuation bytes */
  152.    
  153.     if ((b0 & 0x80) == 0) {
  154.         /* 0xxxxxxx (Plain ASCII) */
  155.         b0_bits = 7;
  156.         cbytes = 0;
  157.     } else if ((b0 & 0xe0) == 0xc0) {
  158.         /* 110xxxxx 10xxxxxx */
  159.         b0_bits = 5;
  160.         cbytes = 1;
  161.     } else if ((b0 & 0xf0) == 0xe0) {
  162.         /* 1110xxxx 10xxxxxx 10xxxxxx */
  163.         b0_bits = 4;
  164.         cbytes = 2;
  165.     } else if ((b0 & 0xf8) == 0xf0) {
  166.         /* 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx */
  167.         b0_bits = 3;
  168.         cbytes = 3;
  169.     } else {
  170.         /* 10xxxxxx -- unexpected continuation byte */
  171.         return U_SPECIAL;
  172.     }
  173.    
  174.     if (*offset + cbytes > size)
  175.         return U_SPECIAL;
  176.    
  177.     wchar_t ch = b0 & LO_MASK_8(b0_bits);
  178.    
  179.     /* Decode continuation bytes */
  180.     while (cbytes > 0) {
  181.         uint8_t b = (uint8_t) str[(*offset)++];
  182.        
  183.         /* Must be 10xxxxxx */
  184.         if ((b & 0xc0) != 0x80)
  185.             return U_SPECIAL;
  186.        
  187.         /* Shift data bits to ch */
  188.         ch = (ch << CONT_BITS) | (wchar_t) (b & LO_MASK_8(CONT_BITS));
  189.         cbytes--;
  190.     }
  191.    
  192.     return ch;
  193. }
  194.  
  195. /** Encode a single character to string representation.
  196.  *
  197.  * Encode a single character to string representation (i.e. UTF-8) and store
  198.  * it into a buffer at @a offset. Encoding starts at @a offset and this offset
  199.  * is moved to the position where the next character can be written to.
  200.  *
  201.  * @param ch     Input character.
  202.  * @param str    Output buffer.
  203.  * @param offset Byte offset where to start writing.
  204.  * @param size   Size of the output buffer (in bytes).
  205.  *
  206.  * @return EOK if the character was encoded successfully, EOVERFLOW if there
  207.  *     was not enough space in the output buffer or EINVAL if the character
  208.  *     code was invalid.
  209.  */
  210. int chr_encode(wchar_t ch, char *str, size_t *offset, size_t size)
  211. {
  212.     if (*offset >= size)
  213.         return EOVERFLOW;
  214.    
  215.     if (!chr_check(ch))
  216.         return EINVAL;
  217.    
  218.     /* Unsigned version of ch (bit operations should only be done
  219.        on unsigned types). */
  220.     uint32_t cc = (uint32_t) ch;
  221.    
  222.     /* Determine how many continuation bytes are needed */
  223.    
  224.     unsigned int b0_bits;  /* Data bits in first byte */
  225.     unsigned int cbytes;   /* Number of continuation bytes */
  226.    
  227.     if ((cc & ~LO_MASK_32(7)) == 0) {
  228.         b0_bits = 7;
  229.         cbytes = 0;
  230.     } else if ((cc & ~LO_MASK_32(11)) == 0) {
  231.         b0_bits = 5;
  232.         cbytes = 1;
  233.     } else if ((cc & ~LO_MASK_32(16)) == 0) {
  234.         b0_bits = 4;
  235.         cbytes = 2;
  236.     } else if ((cc & ~LO_MASK_32(21)) == 0) {
  237.         b0_bits = 3;
  238.         cbytes = 3;
  239.     } else {
  240.         /* Codes longer than 21 bits are not supported */
  241.         return EINVAL;
  242.     }
  243.    
  244.     /* Check for available space in buffer */
  245.     if (*offset + cbytes >= size)
  246.         return EOVERFLOW;
  247.    
  248.     /* Encode continuation bytes */
  249.     unsigned int i;
  250.     for (i = cbytes; i > 0; i--) {
  251.         str[*offset + i] = 0x80 | (cc & LO_MASK_32(CONT_BITS));
  252.         cc = cc >> CONT_BITS;
  253.     }
  254.    
  255.     /* Encode first byte */
  256.     str[*offset] = (cc & LO_MASK_32(b0_bits)) | HI_MASK_8(8 - b0_bits - 1);
  257.    
  258.     /* Advance offset */
  259.     *offset += cbytes + 1;
  260.    
  261.     return EOK;
  262. }
  263.  
  264. /** Get size of string.
  265.  *
  266.  * Get the number of bytes which are used by the string @a str (excluding the
  267.  * NULL-terminator).
  268.  *
  269.  * @param str String to consider.
  270.  *
  271.  * @return Number of bytes used by the string
  272.  *
  273.  */
  274. size_t str_size(const char *str)
  275. {
  276.     size_t size = 0;
  277.    
  278.     while (*str++ != 0)
  279.         size++;
  280.    
  281.     return size;
  282. }
  283.  
  284. /** Get size of wide string.
  285.  *
  286.  * Get the number of bytes which are used by the wide string @a str (excluding the
  287.  * NULL-terminator).
  288.  *
  289.  * @param str Wide string to consider.
  290.  *
  291.  * @return Number of bytes used by the wide string
  292.  *
  293.  */
  294. size_t wstr_size(const wchar_t *str)
  295. {
  296.     return (wstr_length(str) * sizeof(wchar_t));
  297. }
  298.  
  299. /** Get size of string with length limit.
  300.  *
  301.  * Get the number of bytes which are used by up to @a max_len first
  302.  * characters in the string @a str. If @a max_len is greater than
  303.  * the length of @a str, the entire string is measured (excluding the
  304.  * NULL-terminator).
  305.  *
  306.  * @param str     String to consider.
  307.  * @param max_len Maximum number of characters to measure.
  308.  *
  309.  * @return Number of bytes used by the characters.
  310.  *
  311.  */
  312. size_t str_lsize(const char *str, size_t max_len)
  313. {
  314.     size_t len = 0;
  315.     size_t offset = 0;
  316.    
  317.     while (len < max_len) {
  318.         if (str_decode(str, &offset, STR_NO_LIMIT) == 0)
  319.             break;
  320.        
  321.         len++;
  322.     }
  323.    
  324.     return offset;
  325. }
  326.  
  327. /** Get size of wide string with length limit.
  328.  *
  329.  * Get the number of bytes which are used by up to @a max_len first
  330.  * wide characters in the wide string @a str. If @a max_len is greater than
  331.  * the length of @a str, the entire wide string is measured (excluding the
  332.  * NULL-terminator).
  333.  *
  334.  * @param str     Wide string to consider.
  335.  * @param max_len Maximum number of wide characters to measure.
  336.  *
  337.  * @return Number of bytes used by the wide characters.
  338.  *
  339.  */
  340. size_t wstr_lsize(const wchar_t *str, size_t max_len)
  341. {
  342.     return (wstr_nlength(str, max_len * sizeof(wchar_t)) * sizeof(wchar_t));
  343. }
  344.  
  345. /** Get number of characters in a string.
  346.  *
  347.  * @param str NULL-terminated string.
  348.  *
  349.  * @return Number of characters in string.
  350.  *
  351.  */
  352. size_t str_length(const char *str)
  353. {
  354.     size_t len = 0;
  355.     size_t offset = 0;
  356.    
  357.     while (str_decode(str, &offset, STR_NO_LIMIT) != 0)
  358.         len++;
  359.    
  360.     return len;
  361. }
  362.  
  363. /** Get number of characters in a wide string.
  364.  *
  365.  * @param str NULL-terminated wide string.
  366.  *
  367.  * @return Number of characters in @a str.
  368.  *
  369.  */
  370. size_t wstr_length(const wchar_t *wstr)
  371. {
  372.     size_t len = 0;
  373.    
  374.     while (*wstr++ != 0)
  375.         len++;
  376.    
  377.     return len;
  378. }
  379.  
  380. /** Get number of characters in a string with size limit.
  381.  *
  382.  * @param str  NULL-terminated string.
  383.  * @param size Maximum number of bytes to consider.
  384.  *
  385.  * @return Number of characters in string.
  386.  *
  387.  */
  388. size_t str_nlength(const char *str, size_t size)
  389. {
  390.     size_t len = 0;
  391.     size_t offset = 0;
  392.    
  393.     while (str_decode(str, &offset, size) != 0)
  394.         len++;
  395.    
  396.     return len;
  397. }
  398.  
  399. /** Get number of characters in a string with size limit.
  400.  *
  401.  * @param str  NULL-terminated string.
  402.  * @param size Maximum number of bytes to consider.
  403.  *
  404.  * @return Number of characters in string.
  405.  *
  406.  */
  407. size_t wstr_nlength(const wchar_t *str, size_t size)
  408. {
  409.     size_t len = 0;
  410.     size_t limit = ALIGN_DOWN(size, sizeof(wchar_t));
  411.     size_t offset = 0;
  412.    
  413.     while ((offset < limit) && (*str++ != 0)) {
  414.         len++;
  415.         offset += sizeof(wchar_t);
  416.     }
  417.    
  418.     return len;
  419. }
  420.  
  421. /** Check whether character is plain ASCII.
  422.  *
  423.  * @return True if character is plain ASCII.
  424.  *
  425.  */
  426. bool ascii_check(wchar_t ch)
  427. {
  428.     if ((ch >= 0) && (ch <= 127))
  429.         return true;
  430.    
  431.     return false;
  432. }
  433.  
  434. /** Check whether character is valid
  435.  *
  436.  * @return True if character is a valid Unicode code point.
  437.  *
  438.  */
  439. bool chr_check(wchar_t ch)
  440. {
  441.     if ((ch >= 0) && (ch <= 1114111))
  442.         return true;
  443.    
  444.     return false;
  445. }
  446.  
  447. /** Compare two NULL terminated strings.
  448.  *
  449.  * Do a char-by-char comparison of two NULL-terminated strings.
  450.  * The strings are considered equal iff they consist of the same
  451.  * characters on the minimum of their lengths.
  452.  *
  453.  * @param s1 First string to compare.
  454.  * @param s2 Second string to compare.
  455.  *
  456.  * @return 0 if the strings are equal, -1 if first is smaller,
  457.  *         1 if second smaller.
  458.  *
  459.  */
  460. int str_cmp(const char *s1, const char *s2)
  461. {
  462.     wchar_t c1 = 0;
  463.     wchar_t c2 = 0;
  464.    
  465.     size_t off1 = 0;
  466.     size_t off2 = 0;
  467.  
  468.     while (true) {
  469.         c1 = str_decode(s1, &off1, STR_NO_LIMIT);
  470.         c2 = str_decode(s2, &off2, STR_NO_LIMIT);
  471.  
  472.         if (c1 < c2)
  473.             return -1;
  474.        
  475.         if (c1 > c2)
  476.             return 1;
  477.  
  478.         if (c1 == 0 || c2 == 0)
  479.             break;     
  480.     }
  481.  
  482.     return 0;
  483. }
  484.  
  485. /** Compare two NULL terminated strings with length limit.
  486.  *
  487.  * Do a char-by-char comparison of two NULL-terminated strings.
  488.  * The strings are considered equal iff they consist of the same
  489.  * characters on the minimum of their lengths and the length limit.
  490.  *
  491.  * @param s1      First string to compare.
  492.  * @param s2      Second string to compare.
  493.  * @param max_len Maximum number of characters to consider.
  494.  *
  495.  * @return 0 if the strings are equal, -1 if first is smaller,
  496.  *         1 if second smaller.
  497.  *
  498.  */
  499. int str_lcmp(const char *s1, const char *s2, size_t max_len)
  500. {
  501.     wchar_t c1 = 0;
  502.     wchar_t c2 = 0;
  503.    
  504.     size_t off1 = 0;
  505.     size_t off2 = 0;
  506.    
  507.     size_t len = 0;
  508.  
  509.     while (true) {
  510.         if (len >= max_len)
  511.             break;
  512.  
  513.         c1 = str_decode(s1, &off1, STR_NO_LIMIT);
  514.         c2 = str_decode(s2, &off2, STR_NO_LIMIT);
  515.  
  516.         if (c1 < c2)
  517.             return -1;
  518.  
  519.         if (c1 > c2)
  520.             return 1;
  521.  
  522.         if (c1 == 0 || c2 == 0)
  523.             break;
  524.  
  525.         ++len; 
  526.     }
  527.  
  528.     return 0;
  529.  
  530. }
  531.  
  532. /** Copy string.
  533.  *
  534.  * Copy source string @a src to destination buffer @a dest.
  535.  * No more than @a size bytes are written. If the size of the output buffer
  536.  * is at least one byte, the output string will always be well-formed, i.e.
  537.  * null-terminated and containing only complete characters.
  538.  *
  539.  * @param dst   Destination buffer.
  540.  * @param count Size of the destination buffer (must be > 0).
  541.  * @param src   Source string.
  542.  */
  543. void str_cpy(char *dest, size_t size, const char *src)
  544. {
  545.     wchar_t ch;
  546.     size_t src_off;
  547.     size_t dest_off;
  548.  
  549.     /* There must be space for a null terminator in the buffer. */
  550.     ASSERT(size > 0);
  551.    
  552.     src_off = 0;
  553.     dest_off = 0;
  554.  
  555.     while ((ch = str_decode(src, &src_off, STR_NO_LIMIT)) != 0) {
  556.         if (chr_encode(ch, dest, &dest_off, size - 1) != EOK)
  557.             break;
  558.     }
  559.  
  560.     dest[dest_off] = '\0';
  561. }
  562.  
  563. /** Copy size-limited substring.
  564.  *
  565.  * Copy prefix of string @a src of max. size @a size to destination buffer
  566.  * @a dest. No more than @a size bytes are written. The output string will
  567.  * always be well-formed, i.e. null-terminated and containing only complete
  568.  * characters.
  569.  *
  570.  * No more than @a n bytes are read from the input string, so it does not
  571.  * have to be null-terminated.
  572.  *
  573.  * @param dst   Destination buffer.
  574.  * @param count Size of the destination buffer (must be > 0).
  575.  * @param src   Source string.
  576.  * @param n Maximum number of bytes to read from @a src.
  577.  */
  578. void str_ncpy(char *dest, size_t size, const char *src, size_t n)
  579. {
  580.     wchar_t ch;
  581.     size_t src_off;
  582.     size_t dest_off;
  583.  
  584.     /* There must be space for a null terminator in the buffer. */
  585.     ASSERT(size > 0);
  586.    
  587.     src_off = 0;
  588.     dest_off = 0;
  589.  
  590.     while ((ch = str_decode(src, &src_off, n)) != 0) {
  591.         if (chr_encode(ch, dest, &dest_off, size - 1) != EOK)
  592.             break;
  593.     }
  594.  
  595.     dest[dest_off] = '\0';
  596. }
  597.  
  598. /** Copy NULL-terminated wide string to string
  599.  *
  600.  * Copy source wide string @a src to destination buffer @a dst.
  601.  * No more than @a size bytes are written. NULL-terminator is always
  602.  * written after the last succesfully copied character (i.e. if the
  603.  * destination buffer is has at least 1 byte, it will be always
  604.  * NULL-terminated).
  605.  *
  606.  * @param src   Source wide string.
  607.  * @param dst   Destination buffer.
  608.  * @param count Size of the destination buffer.
  609.  *
  610.  */
  611. void wstr_nstr(char *dst, const wchar_t *src, size_t size)
  612. {
  613.     /* No space for the NULL-terminator in the buffer */
  614.     if (size == 0)
  615.         return;
  616.    
  617.     wchar_t ch;
  618.     size_t src_idx = 0;
  619.     size_t dst_off = 0;
  620.    
  621.     while ((ch = src[src_idx++]) != 0) {
  622.         if (chr_encode(ch, dst, &dst_off, size) != EOK)
  623.             break;
  624.     }
  625.    
  626.     if (dst_off >= size)
  627.         dst[size - 1] = 0;
  628.     else
  629.         dst[dst_off] = 0;
  630. }
  631.  
  632. /** Find first occurence of character in string.
  633.  *
  634.  * @param str String to search.
  635.  * @param ch  Character to look for.
  636.  *
  637.  * @return Pointer to character in @a str or NULL if not found.
  638.  *
  639.  */
  640. char *str_chr(const char *str, wchar_t ch)
  641. {
  642.     wchar_t acc;
  643.     size_t off = 0;
  644.     size_t last = 0;
  645.    
  646.     while ((acc = str_decode(str, &off, STR_NO_LIMIT)) != 0) {
  647.         if (acc == ch)
  648.             return (char *) (str + last);
  649.         last = off;
  650.     }
  651.    
  652.     return NULL;
  653. }
  654.  
  655. /** Insert a wide character into a wide string.
  656.  *
  657.  * Insert a wide character into a wide string at position
  658.  * @a pos. The characters after the position are shifted.
  659.  *
  660.  * @param str     String to insert to.
  661.  * @param ch      Character to insert to.
  662.  * @param pos     Character index where to insert.
  663.  @ @param max_pos Characters in the buffer.
  664.  *
  665.  * @return True if the insertion was sucessful, false if the position
  666.  *         is out of bounds.
  667.  *
  668.  */
  669. bool wstr_linsert(wchar_t *str, wchar_t ch, size_t pos, size_t max_pos)
  670. {
  671.     size_t len = wstr_length(str);
  672.    
  673.     if ((pos > len) || (pos + 1 > max_pos))
  674.         return false;
  675.    
  676.     size_t i;
  677.     for (i = len; i + 1 > pos; i--)
  678.         str[i + 1] = str[i];
  679.    
  680.     str[pos] = ch;
  681.    
  682.     return true;
  683. }
  684.  
  685. /** Remove a wide character from a wide string.
  686.  *
  687.  * Remove a wide character from a wide string at position
  688.  * @a pos. The characters after the position are shifted.
  689.  *
  690.  * @param str String to remove from.
  691.  * @param pos Character index to remove.
  692.  *
  693.  * @return True if the removal was sucessful, false if the position
  694.  *         is out of bounds.
  695.  *
  696.  */
  697. bool wstr_remove(wchar_t *str, size_t pos)
  698. {
  699.     size_t len = wstr_length(str);
  700.    
  701.     if (pos >= len)
  702.         return false;
  703.    
  704.     size_t i;
  705.     for (i = pos + 1; i <= len; i++)
  706.         str[i - 1] = str[i];
  707.    
  708.     return true;
  709. }
  710.  
  711. /** @}
  712.  */
  713.