utf.c

一个UTF的源代码,可以提供参考

#ifdef PLAN9
#include	<u.h>
#include	<libc.h>
#include	<bio.h>
#else
#include	<sys/types.h>
#include	<stdio.h>
#include	<stdlib.h>
#include	<string.h>
#include	<unistd.h>
#include	<errno.h>
#include	"plan9.h"
#endif
#include	"hdr.h"

/*
	the our_* routines are implementations for the corresponding library
	routines. for a while, i tried to actually name them wctomb etc
	but stopped that after i found a system which made wchar_t an
	unsigned char.
*/
int our_wctomb(char *s, unsigned long wc);
int our_mbtowc(wchar_t *p, char *s, unsigned n);
enum
{
	Char1	= Runeself,	Rune1	= Runeself,
	Char21	= 0xA1,		Rune21	= 0x0100,
	Char22	= 0xF6,		Rune22	= 0x4016,
	Char3	= 0xFC,		Rune3	= 0x10000,	/* really 0x38E2E */
	Esc	= 0xBE,		Bad	= Runeerror
};

#ifdef PLAN9
int	errno;
#endif

enum
{
	T1	= 0x00,
	Tx	= 0x80,
	T2	= 0xC0,
	T3	= 0xE0,
	T4	= 0xF0,
	T5	= 0xF8,
	T6	= 0xFC,

	Bit1	= 7,
	Bitx	= 6,
	Bit2	= 5,
	Bit3	= 4,
	Bit4	= 3,
	Bit5	= 2,
	Bit6	= 2,

	Mask1	= (1<<Bit1)-1,
	Maskx	= (1<<Bitx)-1,
	Mask2	= (1<<Bit2)-1,
	Mask3	= (1<<Bit3)-1,
	Mask4	= (1<<Bit4)-1,
	Mask5	= (1<<Bit5)-1,
	Mask6	= (1<<Bit6)-1,

	Wchar1	= (1UL<<Bit1)-1,
	Wchar2	= (1UL<<(Bit2+Bitx))-1,
	Wchar3	= (1UL<<(Bit3+2*Bitx))-1,
	Wchar4	= (1UL<<(Bit4+3*Bitx))-1,
	Wchar5	= (1UL<<(Bit5+4*Bitx))-1

#ifndef	EILSEQ
	, /* we hate ansi c's comma rules */
	EILSEQ	= 123
#endif /* PLAN9 */
};

int
our_wctomb(char *s, unsigned long wc)
{
	if(s == 0)
		return 0;		/* no shift states */
	if(wc & ~Wchar2) {
		if(wc & ~Wchar4) {
			if(wc & ~Wchar5) {
				/* 6 bytes */
				s[0] = T6 | ((wc >> 5*Bitx) & Mask6);
				s[1] = Tx | ((wc >> 4*Bitx) & Maskx);
				s[2] = Tx | ((wc >> 3*Bitx) & Maskx);
				s[3] = Tx | ((wc >> 2*Bitx) & Maskx);
				s[4] = Tx | ((wc >> 1*Bitx) & Maskx);
				s[5] = Tx |  (wc & Maskx);
				return 6;
			}
			/* 5 bytes */
			s[0] = T5 |  (wc >> 4*Bitx);
			s[1] = Tx | ((wc >> 3*Bitx) & Maskx);
			s[2] = Tx | ((wc >> 2*Bitx) & Maskx);
			s[3] = Tx | ((wc >> 1*Bitx) & Maskx);
			s[4] = Tx |  (wc & Maskx);
			return 5;
		}
		if(wc & ~Wchar3) {
			/* 4 bytes */
			s[0] = T4 |  (wc >> 3*Bitx);
			s[1] = Tx | ((wc >> 2*Bitx) & Maskx);
			s[2] = Tx | ((wc >> 1*Bitx) & Maskx);
			s[3] = Tx |  (wc & Maskx);
			return 4;
		}
		/* 3 bytes */
		s[0] = T3 |  (wc >> 2*Bitx);
		s[1] = Tx | ((wc >> 1*Bitx) & Maskx);
		s[2] = Tx |  (wc & Maskx);
		return 3;
	}
	if(wc & ~Wchar1) {
		/* 2 bytes */
		s[0] = T2 | (wc >> 1*Bitx);
		s[1] = Tx | (wc & Maskx);
		return 2;
	}
	/* 1 byte */
	s[0] = T1 | wc;
	return 1;
}

int
our_mbtowc(wchar_t *p, char *s, unsigned n)
{
	uchar *us;
	int c0, c1, c2, c3, c4, c5;
	unsigned long wc;
	wchar_t wchar;

	if(s == 0)
		return 0;		/* no shift states */

	if(n < 1)
		goto badlen;
	us = (uchar*)s;
	c0 = us[0];
	if(c0 >= T3) {
		if(n < 3)
			goto badlen;
		c1 = us[1] ^ Tx;
		c2 = us[2] ^ Tx;
		if((c1|c2) & T2)
			goto bad;
		if(c0 >= T5) {
			if(n < 5)
				goto badlen;
			c3 = us[3] ^ Tx;
			c4 = us[4] ^ Tx;
			if((c3|c4) & T2)
				goto bad;
			if(c0 >= T6) {
				/* 6 bytes */
				if(n < 6)
					goto badlen;
				c5 = us[5] ^ Tx;
				if(c5 & T2)
					goto bad;
				wc = ((((((((((c0 & Mask6) << Bitx) |
					c1) << Bitx) | c2) << Bitx) |
					c3) << Bitx) | c4) << Bitx) | c5;
				if(wc <= Wchar5)
					goto bad;
				*p = wchar = wc;
				return 6;
			}
			/* 5 bytes */
			wc = ((((((((c0 & Mask5) << Bitx) |
				c1) << Bitx) | c2) << Bitx) |
				c3) << Bitx) | c4;
			if(wc <= Wchar4)
				goto bad;
			*p = wchar = wc;
			return 5;
		}
		if(c0 >= T4) {
			/* 4 bytes */
			if(n < 4)
				goto badlen;
			c3 = us[3] ^ Tx;
			if(c3 & T2)
				goto bad;
			wc = ((((((c0 & Mask4) << Bitx) |
				c1) << Bitx) | c2) << Bitx) |
				c3;
			if(wc <= Wchar3)
				goto bad;
			*p = wchar = wc;
			return 4;
		}
		/* 3 bytes */
		wc = ((((c0 & Mask3) << Bitx) |
			c1) << Bitx) | c2;
		if(wc <= Wchar2)
			goto bad;
		*p = wchar = wc;
		return 3;
	}
	if(c0 >= T2) {
		/* 2 bytes */
		if(n < 2)
			goto badlen;
		c1 = us[1] ^ Tx;
		if(c1 & T2)
			goto bad;
		wc = ((c0 & Mask2) << Bitx) |
			c1;
		if(wc <= Wchar1)
			goto bad;
		*p = wchar = wc;
		return 2;
	}
	/* 1 byte */
	if(c0 >= Tx)
		goto bad;
	*p = wchar = c0;
	return 1;

bad:
	errno = EILSEQ;
	return -1;
badlen:
	return -2;
}