/*
 *  FREAD.C
 *
 *    (c)Copyright 1992-1997 Obvious Implementations Corp.  Redistribution and
 *    use is allowed under the terms of the DICE-LICENSE FILE,
 *    DICE-LICENSE.TXT.
 *
 *  fread does not return EOF unless an error occurs.  fread returns
 *  0 or < elms when the end of file is reached.
 */

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <lib/misc.h>

#define buf ((char *)vbuf)

size_t
fread(vbuf, elmsize, elms, fi)
void *vbuf;
size_t elmsize;
size_t elms;
FILE *fi;
{
    int bytes;
    int origBytes;

    if (elmsize == 1)
	bytes = elms;
    else if (elms == 1)
	bytes = elmsize;
    else
	bytes = elms * elmsize;

    origBytes = bytes;

    if (fi && (fi->sd_Flags & __SIF_READ) && !fi->sd_Error) {
	int n = 0;	/*  actual read */

	if (bytes == 0 || (fi->sd_Flags & __SIF_EOF))
	    return(0);

	if (fi->sd_UC >= 0) {       /*  ungotten character */
	    *buf = fi->sd_UC;
	    vbuf = buf + 1;
	    fi->sd_UC = -1;
	    --bytes;
	    ++n;
	}
	if (fi->sd_RLeft > 0) {
	    int nn = (fi->sd_RLeft > bytes) ? bytes : fi->sd_RLeft;

	    movmem(fi->sd_RPtr, buf, nn);
	    fi->sd_RPtr += nn;
	    fi->sd_RLeft -= nn;
	    vbuf = buf + nn;
	    bytes -= nn;
	    n += nn;
	}
	if (bytes) {
	    if (bytes < fi->sd_BufSiz) {
		if (_filbuf(fi))        /*  on no more data return n    */
		    goto skip;
	    }
	    if (fi->sd_RLeft <= 0) {    /*  unbuffered read or too-large read */
		int nn;

		nn = read(fi->sd_Fd, buf, bytes);
		if (nn < 0) {
		    if (n == 0)
			n = -1;
		} else {
		    if (nn == 0 && n == 0) {
			if (fi->sd_Flags & __SIF_EOF)
			    n = -1;
			fi->sd_Flags |= __SIF_EOF;
		    }
		    fi->sd_Offset += nn;
		    n += nn;
		}
	    } else {
		if (fi->sd_RLeft < bytes)
		    bytes = fi->sd_RLeft;
		movmem(fi->sd_RPtr, buf, bytes);
		fi->sd_RPtr += bytes;
		fi->sd_RLeft -= bytes;
		n += bytes;
	    }
	}
skip:
	if (n < 0) {
	    fi->sd_Error = EOF;
	    fi->sd_Flags |= __SIF_EOF;	// make sure this flag is set too
	}
	if (fi->sd_Error)
	    return(fi->sd_Error);
	if (n == origBytes)
	    return(elms);
	if (n == 0)
	    return(0);
	return(n / elmsize);
    }
    return(0);
}