FindFp

FindFp

#include <sys/param.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include "local.h"
#include "glue.h"

int	__sdidinit;

#define	NDYNAMIC 10		/* add ten more whenever necessary */

#define	std(flags, file) \
	{0,0,0,flags,file,{0},0,__sF+file,__sclose,__sread,__sseek,__swrite, \
	 {(unsigned char *)(__sFext+file), 0}}
/*	 p r w flags file _bf z  cookie      close    read    seek    write 
	 ext */

				/* the usual - (stdin + stdout + stderr) */
static FILE usual[FOPEN_MAX - 3];
static struct __sfileext usualext[FOPEN_MAX - 3];
static struct glue uglue = { 0, FOPEN_MAX - 3, usual };

struct __sfileext __sFext[3];
FILE __sF[3] = {
	std(__SRD, STDIN_FILENO),		/* stdin */
	std(__SWR, STDOUT_FILENO),		/* stdout */
	std(__SWR|__SNBF, STDERR_FILENO)	/* stderr */
};
struct glue __sglue = { &uglue, 3, __sF };

static struct glue *
moreglue(int n)
{
	struct glue *g;
	FILE *p;
	struct __sfileext *pext;
	static FILE empty;
	char *data;

	data = malloc(sizeof(*g) + ALIGNBYTES + n * sizeof(FILE)
	    + n * sizeof(struct __sfileext));
	if (data == NULL)
		return (NULL);
	g = (struct glue *)data;
	p = (FILE *)ALIGN(data + sizeof(*g));
	pext = (struct __sfileext *)
	    (ALIGN(data + sizeof(*g)) + n * sizeof(FILE));
	g->next = NULL;
	g->niobs = n;
	g->iobs = p;
	while (--n >= 0) {
		*p = empty;
		_FILEEXT_SETUP(p, pext);
		p++;
		pext++;
	}
	return (g);
}

/*
 * Find a free FILE for fopen et al.
 */
FILE *
__sfp(void)
{
	FILE *fp;
	int n;
	struct glue *g;

	if (!__sdidinit)
		__sinit();
	for (g = &__sglue;; g = g->next) {
		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
			if (fp->_flags == 0)
				goto found;
		if (g->next == NULL && (g->next = moreglue(NDYNAMIC)) == NULL)
			break;
	}
	return (NULL);
found:
	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
	fp->_p = NULL;		/* no current pointer */
	fp->_w = 0;		/* nothing to read or write */
	fp->_r = 0;
	fp->_bf._base = NULL;	/* no buffer */
	fp->_bf._size = 0;
	fp->_lbfsize = 0;	/* not line buffered */
	fp->_file = -1;		/* no file */
/*	fp->_cookie = ; */	/* caller sets cookie, _read/_write etc */
	fp->_lb._base = NULL;	/* no line buffer */
	fp->_lb._size = 0;
	_FILEEXT_INIT(fp);
	return (fp);
}

#define getdtablesize()	sysconf(_SC_OPEN_MAX)

/*
 * XXX.  Force immediate allocation of internal memory.  Not used by stdio,
 * but documented historically for certain applications.  Bad applications.
 */
void
f_prealloc(void)
{
	struct glue *g;
	int n;

	n = getdtablesize() - FOPEN_MAX + 20;		/* 20 for slop. */
	for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next)
		/* void */;
	if (n > 0)
		g->next = moreglue(n);
}

/*
 * exit() and abort() call _cleanup() through the callback registered
 * with __atexit_register_cleanup(), set whenever we open or buffer a
 * file. This chicanery is done so that programs that do not use stdio
 * need not link it all in.
 *
 * The name `_cleanup' is, alas, fairly well known outside stdio.
 */
void
_cleanup(void)
{
	/* (void) _fwalk(fclose); */
	(void) _fwalk(__sflush);		/* `cheating' */
}

/*
 * __sinit() is called whenever stdio's internal variables must be set up.
 */
void
__sinit(void)
{
	int i;

	for (i = 0; i < FOPEN_MAX - 3; i++) {
		_FILEEXT_SETUP(usual+i, usualext+i);
	}
	/* make sure we clean up on exit */
	__atexit_register_cleanup(_cleanup); /* conservative */
	__sdidinit = 1;
}