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<title>/usr/web/sources/contrib/aiju/mathfs.c - Plan 9 from Bell Labs</title>


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<a href="/plan9/">Plan 9 from Bell Labs</a>’s /usr/web/sources/contrib/aiju/mathfs.c


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Copyright © 2009 Alcatel-Lucent. 
Distributed under the
<a href="/plan9/license.html">Lucent Public License version 1.02</a>.
 
<a href="/plan9/download.html">Download the Plan 9 distribution.</a>

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#include <u.h>
#include <libc.h>
#include <thread.h>
#include <fcall.h>
#include <9p.h>
#include <ctype.h>

void
mathattach(Req *req)
{
req->ofcall.qid = (Qid) {1, 0, 0x80};
req->fid->qid = req->ofcall.qid;
respond(req, nil);
}

char *
mathwalk(Fid *fid, char *name, Qid *qid)
{
static int qidcount = 2;
char opstack[10], *tops, tok, *p;
double nstack[20], *tns;

tops = opstack + nelem(opstack);
tns = nstack + nelem(nstack);
p = name;

for(;;) {
for(; *p && *p == ' '; p++);
if(isdigit(*p)) {
if(tns <= nstack)
goto error;
*--tns = strtod(p, &p);
continue;
}
tok = *p++;
switch(tok) {
case '+': case '-': case '*': case '%': case ')': case 0:
while(tops < opstack + nelem(opstack) &&
(tok != '*' && tok != '%' || *tops != '+' && *tops != '-')) {
if(*tops == '(') {
if(tok != ')')
break;
tok = -1;
tops++;
continue;
}
if(tns >= nstack + nelem(nstack) - 1)
goto error;
switch(*tops) {
case '+':
tns[1] += *tns;
break;
case '-':
tns[1] -= *tns;
break;
case '*':
tns[1] *= *tns;
break;
case '%':
tns[1] /= *tns;
break;
}
tops++;
tns++;
}
if(tok && tok != -1 && tok != ')') {
case '(':
if(tops <= opstack)
goto error;
*--tops = tok;
}
if(tok == 0)
goto out;
break;
default:
goto error;
}
}

out:
if(tops != opstack + nelem(opstack))
goto error;
if(tns != nstack + nelem(nstack) - 1)
goto error;
*qid = (Qid) {qidcount++, 0, 0};
fid->qid = *qid;
fid->aux = smprint("%g\n", *tns);
return nil;

error:
return "syntax error";
}

void
mathread(Req *req)
{
if(req->fid->aux == nil) {
respond(req, nil);
return;
}
readstr(req, (char *) req->fid->aux);
respond(req, nil);
}

void
mathdestroy(Fid *fid)
{
free(fid->aux);
}

Srv mathsrv = {
.attach = mathattach,
.walk1 = mathwalk,
.read = mathread,
.destroyfid = mathdestroy,
};

void
main()
{
postmountsrv(&mathsrv, "math", "/n/math", MREPL);
}

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