the our_* routines are implementations for the corresponding library

#include <u.h>
#include <libc.h>
#include <bio.h>
#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(unsigned long *p, char *s, unsigned n);
int runetoisoutf(char *str, Rune *rune);
int fullisorune(char *str, int n);
int isochartorune(Rune *rune, char *str);

void
utf_in(int fd, long *, struct convert *out)
{
char buf[N];
int i, j, c, n, tot;
unsigned long l;

tot = 0;
while((n = read(fd, buf+tot, N-tot)) >= 0){
tot += n;
for(i=j=0; i<=tot-UTFmax || (i<tot && (n==0 || fullrune(buf+i, tot-i))); ){
c = our_mbtowc(&l, buf+i, tot-i);
if(c == -1){
if(squawk)
warn("bad UTF sequence near byte %ld in input", ninput+i);
if(clean){
i++;
continue;
}
nerrors++;
l = Runeerror;
c = 1;
}
runes[j++] = l;
i += c;
}
OUT(out, runes, j);
tot -= i;
ninput += i;
if(tot)
memmove(buf, buf+i, tot);
if(n == 0)
break;
}
OUT(out, runes, 0);
}

void
utf_out(Rune *base, int n, long *)
{
char *p;
Rune *r;

nrunes += n;
for(r = base, p = obuf; n-- > 0; r++){
p += our_wctomb(p, *r);
}
noutput += p-obuf;
if(p > obuf)
write(1, obuf, p-obuf);
}

void
isoutf_in(int fd, long *, struct convert *out)
{
char buf[N];
int i, j, c, n, tot;

tot = 0;
while((n = read(fd, buf+tot, N-tot)) >= 0){
tot += n;
for(i=j=0; i<tot; ){
if(!fullisorune(buf+i, tot-i))
break;
c = isochartorune(&runes[j], buf+i);
if(runes[j] == Runeerror){
if(squawk)
warn("bad UTF sequence near byte %ld in input", ninput+i);
if(clean){
i++;
continue;
}
nerrors++;
}
j++;
i += c;
}
OUT(out, runes, j);
tot -= i;
ninput += i;
if(tot)
memmove(buf, buf+i, tot);
if(n == 0)
break;
}
OUT(out, runes, 0);
}

void
isoutf_out(Rune *base, int n, long *)
{
char *p;
Rune *r;

nrunes += n;
for(r = base, p = obuf; n-- > 0; r++)
p += runetoisoutf(p, r);
noutput += p-obuf;
if(p > obuf)
write(1, obuf, p-obuf);
}

enum
{
Char1 = Runeself, Rune1 = Runeself,
Char21 = 0xA1, Rune21 = 0x0100,
Char22 = 0xF6, Rune22 = 0x4016,
Char3 = 0xFC, Rune3 = 0x10000, /* really 0x38E2E */
Esc = 0xBE, Bad = Runeerror
};

static uchar U[256];
static uchar T[256];

static
void
mktable(void)
{
int i, u;

for(i=0; i<256; i++) {
u = i + (0x5E - 0xA0);
if(i < 0xA0)
u = i + (0xDF - 0x7F);
if(i < 0x7F)
u = i + (0x00 - 0x21);
if(i < 0x21)
u = i + (0xBE - 0x00);
U[i] = u;
T[u] = i;
}
}

int
isochartorune(Rune *rune, char *str)
{
int c, c1, c2;
long l;

if(U[0] == 0)
mktable();

/*
* one character sequence
* 00000-0009F => 00-9F
*/
c = *(uchar*)str;
if(c < Char1) {
*rune = c;
return 1;
}

/*
* two character sequence
* 000A0-000FF => A0; A0-FF
*/
c1 = *(uchar*)(str+1);
if(c < Char21) {
if(c1 >= Rune1 && c1 < Rune21) {
*rune = c1;
return 2;
}
goto bad;
}

/*
* two character sequence
* 00100-04015 => A1-F5; 21-7E/A0-FF
*/
c1 = U[c1];
if(c1 >= Esc)
goto bad;
if(c < Char22) {
*rune = (c-Char21)*Esc + c1 + Rune21;
return 2;
}

/*
* three character sequence
* 04016-38E2D => A6-FB; 21-7E/A0-FF
*/
c2 = U[*(uchar*)(str+2)];
if(c2 >= Esc)
goto bad;
if(c < Char3) {
l = (c-Char22)*Esc*Esc + c1*Esc + c2 + Rune22;
if(l >= Rune3)
goto bad;
*rune = l;
return 3;
}

/*
* bad decoding
*/
bad:
*rune = Bad;
return 1;
}

int
runetoisoutf(char *str, Rune *rune)
{
long c;

if(T[0] == 0)
mktable();

/*
* one character sequence
* 00000-0009F => 00-9F
*/
c = *rune;
if(c < Rune1) {
str[0] = c;
return 1;
}

/*
* two character sequence
* 000A0-000FF => A0; A0-FF
*/
if(c < Rune21) {
str[0] = Char1;
str[1] = c;
return 2;
}

/*
* two character sequence
* 00100-04015 => A1-F5; 21-7E/A0-FF
*/
if(c < Rune22) {
c -= Rune21;
str[0] = c/Esc + Char21;
str[1] = T[c%Esc];
return 2;
}

/*
* three character sequence
* 04016-38E2D => A6-FB; 21-7E/A0-FF
*/
c -= Rune22;
str[0] = c/(Esc*Esc) + Char22;
str[1] = T[c/Esc%Esc];
str[2] = T[c%Esc];
return 3;
}

int
fullisorune(char *str, int n)
{
int c;

if(n > 0) {
c = *(uchar*)str;
if(c < Char1)
return 1;
if(n > 1)
if(c < Char22 || n > 2)
return 1;
}
return 0;
}

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,
};

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

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

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

bad:
return -1;
}