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researchv8 Dan Cross

/*
 * Seek for standard library.  Coordinates with buffering.
 */

#include	<stdio.h>

long lseek();

fseek(iop, offset, ptrname)
	register FILE *iop;
	long offset;
{
	register d;
	register flag = iop->_flag;
	register long p;

	iop->_flag &= ~_IOEOF;
	if (flag & _IOWRT)
		fflush(iop);
	if (flag & _IORW)
		iop->_flag &= ~(_IOWRT|_IOREAD);
	if ((flag&_IOREAD) && !(flag&_IONBF) && ptrname!=2) do {
		p = lseek(fileno(iop), 0L, 1);
		if (p < 0)
			break;
		d = iop->_cnt;
		if (ptrname == 1) {
			offset += p - d;
			ptrname = 0;
		}
		if (offset < 0)
			break;
		if (flag & _IORW)
			break;
		p -= offset;
		if (p >= 0 && p <= iop->_ptr - iop->_base + d)
			d -= (int)p;
		else {
			d = (unsigned int)offset % BUFSIZ;
			if (d == 0)	/* leave room for ungetc */
				break;
			lseek(fileno(iop), offset - d, 0);
			if (_filbuf(iop) == EOF)
				break;
			if (--d > iop->_cnt)	/* partial buffer */
				break;
		}
		iop->_cnt -= d;
		iop->_ptr += d;
		return (0);
	} while (0);
	if (flag & (_IORW|_IOREAD)) {
		iop->_cnt = 0;
		iop->_ptr = iop->_base;
	}
	return (lseek(fileno(iop), offset, ptrname) < 0? -1: 0);
}

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