WIP: utf(1) #141
37
include/libutf.h
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37
include/libutf.h
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#if __STDC_VERSION__ >= 199901L
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/* C99 type definitions */
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# include <stdint.h>
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typedef uint32_t rune_t;
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#else
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/* Must hold at least 32b; see the C89 draft 2.2.4.2
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* <http://jfxpt.com/library/c89-draft.html#2.2.4.2> */
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typedef unsigned long int rune_t;
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#endif
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#include <stddef.h> /* size_t */
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/* Reverses the order of the bytes in the 32-bit value c. */
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rune_t swab32(rune_t c);
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/* Returns the byte length of a valid UTF-8 rune. */
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size_t utf8_size(rune_t c);
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/* Returns the UTF-32BE codepoint of the UTF-8 rune c. */
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rune_t utf8_to_utf32be(rune_t c);
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/* Stores the UTF-8 rune c as bytes to the memory span s. s should point to a
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* big enough memory span of chars in which to store c, a (possibly invalid)
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* UTF-8 rune. Returns a pointer to the memory location after the last written
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* byte. Returns NULL if n is not 0 and n is less than the number of bytes that
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* will be written. */
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char *utf8_to_chars(rune_t c, char *s, size_t n);
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/* Returns the UTF-8 encoding of the UTF-32BE codepoint c. m is the minimum
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* amount of bytes into which to encode the codepoint c. If m is greater than
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* 0, this function may return overlong-encoded UTF-8. */
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rune_t utf32be_to_utf8(rune_t c, size_t m);
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/* Returns the UTF-32BE codepoint of the UTF-32LE codepoint c. */
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rune_t utf32be_to_utf32le(rune_t c);
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/* Returns the UTF-32LE codepoint of the UTF-32BE codepoint c. */
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rune_t utf32le_to_utf32be(rune_t c);
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145
src/libutf.c
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145
src/libutf.c
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#include <stddef.h> /* size_t */
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#include "libutf.h"
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/* np is the pointer to the pointer to the next byte in a sequence. rp is the
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* location to which the read UTF-8 rune will be stored. If np doesn't point to
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* a valid UTF-8 rune, np and rp will be untouched and NULL will be returned.
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*/
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/* utf-8 bits |32 |24 |16 |8
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* U+001000 to U+10FFFF | 1111 0ZYY | 10YY XXXX | 10WW WWVV | 10VV UUUU *
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* U+000800 to U+00FFFF | 0000 0000 | 1110 XXXX | 10WW WWVV | 10VV UUUU *
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* U+000080 to U+0007FF | 0000 0000 | 0000 0000 | 110W WWVV | 10VV UUUU *
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* U+000000 to U+00007F | 0000 0000 | 0000 0000 | 0000 0000 | 0VVV UUUU */
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rune_t *
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chars_to_utf8(char **np, rune_t *rp){
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size_t b; /* expected byte size of the rune at *np */
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rune_t r;
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// for();
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return rp;
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}
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/* big-endian | ZZZZ YYYY | XXXX WWWW | VVVV UUUU | TTTT SSSS */
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/* little-endian | TTTT SSSS | VVVV UUUU | XXXX WWWW | ZZZZ YYYY */
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rune_t
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swab32(rune_t c){ return
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((c & 0xFF000000) >> 24)
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| ((c & 0x00FF0000) >> 8)
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| ((c & 0x0000FF00) << 8)
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| ((c & 0x000000FF) << 24);
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}
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/* From <https://en.wikipedia.org/wiki/UTF-8>, UTF-8 is encoded as follows:
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* The codepoint 0bZYYYY_XXXXWWWW_VVVVUUUU is nestled within the literal bits 0
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* and 1; letters denote nybbles here, little-endian, and certain bits are
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* labeled, also little-endian. */
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/* utf-8 bits |32 |24 |16
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* U+001000 to U+10FFFF | 1111 0ZYY | 10YY XXXX | 10WW WWVV | 10VV UUUU *
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* U+000800 to U+00FFFF | 0000 0000 | 1110 XXXX | 10WW WWVV | 10VV UUUU *
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* U+000080 to U+0007FF | 0000 0000 | 0000 0000 | 110W WWVV | 10VV UUUU *
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* U+000000 to U+00007F | 0000 0000 | 0000 0000 | 0000 0000 | 0VVV UUUU */
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size_t
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utf8_size(rune_t c){ return
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((c & 0x80000000) >> 31) /* 4B? */
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+ ((c & 0x00800000) >> 23) /* 3B? */
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+ ((c & 0x00008000) >> 15) /* 2B? */
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+ 1;
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}
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char *
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utf8_to_chars(rune_t c, char *s, size_t n){
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size_t i;
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for(i = 0; (c & 0xFF000000) == 0 && i < 4; ++i)
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c <<= 8; /* remove leading zero bytes */
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i = 4 - i; /* bytes in this rune */
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if(n != 0 && i > n)
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return NULL;
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switch(4 - i){
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case 4: *s++ = ((c & 0xFF000000) >> 24); c <<= 8;
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case 3: *s++ = ((c & 0xFF000000) >> 24); c <<= 8;
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case 2: *s++ = ((c & 0xFF000000) >> 24); c <<= 8;
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case 1: *s++ = ((c & 0xFF000000) >> 24);
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}
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return s;
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}
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/* utf-8 bits |32 |27 |22 |14 |7
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* U+001000 to U+10FFFF | 1111 0ZYY | 10YY XXXX | 10WW WWVV | 10VV UUUU *
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* U+000800 to U+00FFFF | 0000 0000 | 1110 XXXX | 10WW WWVV | 10VV UUUU *
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* U+000080 to U+0007FF | 0000 0000 | 0000 0000 | 110W WWVV | 10VV UUUU *
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* U+000000 to U+00007F | 0000 0000 | 0000 0000 | 0000 0000 | 0VVV UUUU */
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/* utf-32be bits |32 |21 |18 |12 |6
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* U+000000 to U+10FFFF | 0000 0000 | 000Z YYYY | XXXX WWWW | VVVV UUUU */
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rune_t
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utf8_to_utf32be(rune_t c){ return
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((c & 0x07000000) >> 6) /* UTF-8 b27-25 -> UTF-32 b21-19 */
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| (((c & 0x003F0000) /* UTF-8 b22-17 -> UTF-32 b18-13 */
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^ ((c & (1 << 22)) >> 1)) >> 4) /* (if UTF-8 b23, zero b22) */
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| ((c & 0x00003F00) >> 2) /* UTF-8 b14- 9 -> UTF-32 b12- 7 */
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| (c & 0x0000007F); /* UTF-32 b 7- 1 */
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}
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/* utf-32be bits |32 |21 |18 |16 |12 |6
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* U+000000 to U+10FFFF | 0000 0000 | 000Z YYYY | XXXX WWWW | VVVV UUUU */
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/* utf-8 bits |32 |27 |22 |14 |7
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* U+001000 to U+10FFFF | 1111 0ZYY | 10YY XXXX | 10WW WWVV | 10VV UUUU *
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* U+000800 to U+00FFFF | 0000 0000 | 1110 XXXX | 10WW WWVV | 10VV UUUU *
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* U+000080 to U+0007FF | 0000 0000 | 0000 0000 | 110W WWVV | 10VV UUUU *
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* U+000000 to U+00007F | 0000 0000 | 0000 0000 | 0000 0000 | 0VVV UUUU */
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rune_t
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utf32be_to_utf8(rune_t c, size_t m){
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size_t n;
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rune_t r;
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if((n = utf8_size(c)) > m)
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m = n;
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/* In tested compilers this generates roughly the same assembly as the
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* naive (no fallthroughs) approach. */
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switch(m){
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case 4:
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r = 0xF0000000 /* UTF-8 b32-29 */
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| ((c & 0x1C0000) << 6) /* UTF-32 b21-19 -> UTF-8 b27-25 */
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r |= 0x00800000 /* UTF-8 b24-23 */
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| ((c & 0x03F000) << 4); /* UTF-32 b18-13 -> UTF-8 b24-17 */
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if(0) /* if(m == 3) */
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case 3:
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r = 0x00E00000 /* 0xE == 0b1110 */ /* UTF-8 b24-21 */
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| ((c & 0x00F000) << 4); /* UTF-32 b16-13 -> UTF-8 b20-17 */
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r |= 0x00008000 /* UTF-8 b16-15 */
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| ((c & 0x000FC0) << 2); /* UTF-32 b12- 7 -> UTF-8 b14- 9 */
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if(0) /* if(m == 2) */
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case 2:
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r = 0x0000C000 /* 0xC == 0b1100 */ /* UTF-8 b16-14 */
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| ((c & 0x007C00) << 2); /* UTF-32 b11- 7 -> UTF-8 b13- 9 */
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r |= 0x00000080 /* UTF-8 b 8- 7 */
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| (c & 0x00003F); /* UTF-8 b 6- 1 */
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break; /* if(m == 1) */
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case 1:
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r = c & 0x00007F; /* 0x7 == 0b0111 */ /* UTF-8 b 7- 1 */
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}
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return r;
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}
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/* <https://www.herongyang.com/Unicode/UTF-32-UTF-32-Encoding.html> */
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/* utf-32be bits | 0000 0000 | 000Z YYYY | XXXX WWWW | VVVV UUUU */
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/* utf-32le bits | VVVV UUUU | XXXX WWWW | 000Z YYYY | 0000 0000 */
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rune_t
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utf32be_to_utf32le(rune_t c){ return
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((c & 0x000000FF) << 24)
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| ((c & 0x0000FF00) << 8)
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| ((c & 0x001F0000) >> 8);
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}
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rune_t
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utf32le_to_utf32be(rune_t c){ return
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((c & 0xFF000000) >> 24)
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| ((c & 0x00FF0000) >> 8)
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| ((c & 0x00001F00) << 8);
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}
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