1#include <unistd.h>
2#include "lt_types.h"
3
4// Return number of bytes in the UTF-8 sequence which begins with a given byte.
5int wchar_len(byte b) {
6	if ((b & 0xE0) == 0xC0) return 2;
7	if ((b & 0xF0) == 0xE0) return 3;
8	if ((b & 0xF8) == 0xF0) return 4;
9	return 1;
10}
11
12void store_wchar(byte** p, wchar ch) {
13	if (ch < 0x80) {
14		*(*p)++ = (char) ch;
15	} else if (ch < 0x800) {
16		*(*p)++ = (byte) (0xC0 | ((ch >> 6) & 0x1F));
17		*(*p)++ = (byte) (0x80 | (ch & 0x3F));
18	} else if (ch < 0x10000) {
19		*(*p)++ = (byte) (0xE0 | ((ch >> 12) & 0x0F));
20		*(*p)++ = (byte) (0x80 | ((ch >> 6) & 0x3F));
21		*(*p)++ = (byte) (0x80 | (ch & 0x3F));
22	} else {
23		*(*p)++ = (byte) (0xF0 | ((ch >> 18) & 0x07));
24		*(*p)++ = (byte) (0x80 | ((ch >> 12) & 0x3F));
25		*(*p)++ = (byte) (0x80 | ((ch >> 6) & 0x3F));
26		*(*p)++ = (byte) (0x80 | (ch & 0x3F));
27	}
28}
29
30wchar load_wchar(const byte** p) {
31	wchar ch;
32	switch (wchar_len(**p)) {
33	default:
34		ch = *(*p)++ & 0xFF;
35		break;
36	case 2:
37		ch = (*(*p)++ & 0x1F) << 6;
38		ch |= *(*p)++ & 0x3F;
39		break;
40	case 3:
41		ch = (*(*p)++ & 0x0F) << 12;
42		ch |= (*(*p)++ & 0x3F) << 6;
43		ch |= (*(*p)++ & 0x3F);
44		break;
45	case 4:
46		ch = (*(*p)++ & 0x07) << 18;
47		ch |= (*(*p)++ & 0x3F) << 12;
48		ch |= (*(*p)++ & 0x3F) << 6;
49		ch |= (*(*p)++ & 0x3F);
50		break;
51	}
52	return ch;
53}
54
55wchar read_wchar(int fd) {
56	byte cbuf[UNICODE_MAX_BYTES];
57	int n = read(fd, &cbuf[0], 1);
58	if (n <= 0)
59		return 0;
60	int len = wchar_len(cbuf[0]);
61	int i;
62	for (i = 1; i < len; ++i) {
63		int n = read(fd, &cbuf[i], 1);
64		if (n != 1) return 0;
65	}
66	const byte* cp = cbuf;
67	wchar ch = load_wchar(&cp);
68	// assert(cp-cbuf == len);
69	return ch;
70}
71