/* * Copyright (c) 2001-2004 Jakub Jermar * 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. */ /** * @file * @brief String functions. * * Strings and characters use the Universal Character Set (UCS). The standard * strings, called just strings are encoded in UTF-8. Wide strings (encoded * in UTF-32) are supported to a limited degree. A single character is * represented as wchar_t.@n * * Overview of the terminology:@n * * Term Meaning * -------------------- ---------------------------------------------------- * byte 8 bits stored in uint8_t (unsigned 8 bit integer) * * character UTF-32 encoded Unicode character, stored in wchar_t * (signed 32 bit integer), code points 0 .. 1114111 * are valid * * ASCII character 7 bit encoded ASCII character, stored in char * (usually signed 8 bit integer), code points 0 .. 127 * are valid * * string UTF-8 encoded NULL-terminated Unicode string, char * * * wide string UTF-32 encoded NULL-terminated Unicode string, * wchar_t * * * [wide] string size number of BYTES in a [wide] string (excluding * the NULL-terminator), size_t * * [wide] string length number of CHARACTERS in a [wide] string (excluding * the NULL-terminator), size_t * * [wide] string width number of display cells on a monospace display taken * by a [wide] string, size_t * * * Overview of string metrics:@n * * Metric Abbrev. Type Meaning * ------ ------ ------ ------------------------------------------------- * size n size_t number of BYTES in a string (excluding the * NULL-terminator) * * length l size_t number of CHARACTERS in a string (excluding the * null terminator) * * width w size_t number of display cells on a monospace display * taken by a string * * * Function naming prefixes:@n * * chr_ operate on characters * ascii_ operate on ASCII characters * str_ operate on strings * wstr_ operate on wide strings * * [w]str_[n|l|w] operate on a prefix limited by size, length * or width * * * A specific character inside a [wide] string can be referred to by:@n * * pointer (char *, wchar_t *) * byte offset (size_t) * character index (size_t) * */ #include #include /** 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(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 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 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; } /** 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; } /** 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 dest 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) { size_t src_off = 0; size_t dest_off = 0; wchar_t ch; 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'; } /** @} */