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/*************************************************************************
* Copyright (c) 2011 AT&T Intellectual Property
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/legal/epl-v10.html
*
* Contributors: Details at https://graphviz.org
*************************************************************************/
#include "../tcl-compat.h"
#include <assert.h>
#include <cgraph/rdr.h>
#include <limits.h>
#include <stddef.h>
#include "tcldot.h"
/*
* myiodisc_afread - same api as read for libcgraph
*
* gets one line at a time from a Tcl_Channel and places it in a user buffer
* up to a maximum of n characters
*
* returns pointer to obtained line in user buffer, or
* returns NULL when last line read from memory buffer
*
* This is probably innefficient because it introduces
* one more stage of line buffering during reads (at least)
* but it is needed so that we can take full advantage
* of the Tcl_Channel mechanism.
*/
int myiodisc_afread(void* channel, char *ubuf, int n)
{
assert(n >= 0);
static Tcl_DString dstr;
static Tcl_Size strpos;
Tcl_Size nput;
if (!n) { /* a call with n==0 (from aglexinit) resets */
*ubuf = '\0';
strpos = 0;
return 0;
}
/*
* the user buffer might not be big enough to hold the line.
*/
if (strpos) {
nput = Tcl_DStringLength(&dstr) - strpos;
if (nput > n) {
/* chunk between first and last */
memcpy(ubuf, strpos + Tcl_DStringValue(&dstr), (size_t)n);
strpos += n;
nput = n;
ubuf[n] = '\0';
} else {
/* last chunk */
memcpy(ubuf, strpos + Tcl_DStringValue(&dstr), (size_t)nput);
strpos = 0;
}
} else {
Tcl_DStringFree(&dstr);
Tcl_DStringInit(&dstr);
if (Tcl_Gets((Tcl_Channel) channel, &dstr) < 0) {
/* probably EOF, but could be other read errors */
*ubuf = '\0';
return 0;
}
/* linend char(s) were stripped off by Tcl_Gets,
* append a canonical linenend. */
Tcl_DStringAppend(&dstr, "\n", 1);
if (Tcl_DStringLength(&dstr) > n) {
/* first chunk */
nput = n;
memcpy(ubuf, Tcl_DStringValue(&dstr), (size_t)n);
strpos = n;
} else {
/* single chunk */
nput = Tcl_DStringLength(&dstr);
memcpy(ubuf, Tcl_DStringValue(&dstr), (size_t)nput);
}
}
return (int)nput;
}
/* exact copy from cgraph/io.c - but that one is static */
int myiodisc_memiofread(void *chan, char *buf, int bufsize)
{
const char *ptr;
char *optr;
char c;
rdr_t *s;
if (bufsize == 0) return 0;
s = chan;
if (s->cur >= s->len)
return 0;
size_t l = 0;
ptr = s->data + s->cur;
optr = buf;
do {
*optr++ = c = *ptr++;
l++;
} while (c && c != '\n' && l < INT_MAX && (int)l < bufsize);
s->cur += l;
return (int)l;
}
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