a state machine for interpreting big5 (hk format).

#include <u.h>
#include <libc.h>
#include <bio.h>
#include "hdr.h"
#include "conv.h"
#include "big5.h"

/*
a state machine for interpreting big5 (hk format).
*/
void
big5proc(int c, Rune **r, long input_loc)
{
static enum { state0, state1 } state = state0;
static int lastc;
long n, ch, f, cold = c;

switch(state)
{
case state0: /* idle state */
if(c < 0)
return;
if(c >= 0xA1){
lastc = c;
state = state1;
return;
}
if(c == 26)
c = '\n';
emit(c);
return;

case state1: /* seen a font spec */
if(c >= 64 && c <= 126)
c -= 64;
else if(c >= 161 && c <= 254)
c = c-161 + 63;
else {
nerrors++;
if(squawk)
warn("bad big5 glyph (from 0x%x,0x%lx) near byte %ld in %s",
lastc, cold, input_loc, file);
if(!clean)
emit(BADMAP);
state = state0;
return;
}
if(lastc >= 161 && lastc <= 254)
f = lastc - 161;
else {
nerrors++;
if(squawk)
warn("bad big5 font %d (from 0x%x,0x%lx) near byte %ld in %s",
lastc-161, lastc, cold, input_loc, file);
if(!clean)
emit(BADMAP);
state = state0;
return;
}
n = f*BIG5FONT + c;
if(n < BIG5MAX)
ch = tabbig5[n];
else
ch = -1;
if(ch < 0){
nerrors++;
if(squawk)
warn("unknown big5 %ld (from 0x%x,0x%lx) near byte %ld in %s",
n, lastc, cold, input_loc, file);
if(!clean)
emit(BADMAP);
} else
emit(ch);
state = state0;
}
}

void
big5_in(int fd, long *, struct convert *out)
{
Rune ob[N];
Rune *r, *re;
uchar ibuf[N];
int n, i;
long nin;

r = ob;
re = ob+N-3;
nin = 0;
while((n = read(fd, ibuf, sizeof ibuf)) > 0){
for(i = 0; i < n; i++){
big5proc(ibuf[i], &r, nin++);
if(r >= re){
OUT(out, ob, r-ob);
r = ob;
}
}
if(r > ob){
OUT(out, ob, r-ob);
r = ob;
}
}
big5proc(-1, &r, nin);
if(r > ob)
OUT(out, ob, r-ob);
OUT(out, ob, 0);
}

void
big5_out(Rune *base, int n, long *)
{
char *p;
int i;
Rune r;
static int first = 1;

if(first){
first = 0;
for(i = 0; i < NRUNE; i++)
tab[i] = -1;
for(i = 0; i < BIG5MAX; i++)
if(tabbig5[i] != -1)
tab[tabbig5[i]] = i;
}
nrunes += n;
p = obuf;
for(i = 0; i < n; i++){
r = base[i];
if(r < 128)
*p++ = r;
else {
if(r < NRUNE && tab[r] != -1){
r = tab[r];
if(r >= BIG5MAX){
*p++ = 0xA1;
*p++ = r-BIG5MAX;
continue;
} else {
*p++ = 0xA1 + (r/BIG5FONT);
r = r%BIG5FONT;
if(r <= 62) r += 64;
else r += 0xA1-63;
*p++ = r;
continue;
}
}
if(squawk)
warn("rune 0x%x not in output cs", r);
nerrors++;
if(clean)
continue;
*p++ = BYTEBADMAP;
}
}
noutput += p-obuf;
if(p > obuf)
write(1, obuf, p-obuf);
}