usr/src/lib/libc/stdio/findfp.c

/* @(#)findfp.c 1.1 (Berkeley) %G% */
#include "stdio.h"

#define NSTATIC 5       /* stdin, stdout, stderr, plus slack */

extern char *calloc();

static FILE **iov, **iovend;
static FILE *dummy[NSTATIC];

FILE _iob[NSTATIC] = {
        { 0, NULL, NULL, NULL, _IOREAD, 0 },            /* stdin  */
        { 0, NULL, NULL, NULL, _IOWRT, 1 },             /* stdout */
        { 0, NULL, NULL, NULL, _IOWRT+_IONBF, 2 },      /* stderr */
};

FILE *
_findiop()
{
        register FILE **iovp;
        register FILE *fp;
        register int nfiles;
        register int i;
        char *p;

        if (iov == NULL) {
                nfiles = getdtablesize();
                if (nfiles > NSTATIC)
                        p = calloc(1, nfiles * sizeof *iov +
                                    (nfiles - NSTATIC) * sizeof **iov);
                else
                        p = NULL;

                if (p == NULL) {
                        iov = dummy;
                        iovend = iov + NSTATIC;
                } else {
                        iov = (FILE **)p;
                        iovend = iov + nfiles;

                        fp = (FILE *)iovend;
                        for (iovp = iov + NSTATIC; iovp < iovend; /* void */)
                                *iovp++ = fp++;
                }

                for (i = 0; i < NSTATIC; i++)
                        iov[i] = &_iob[i];
        }

        for (iovp = iov; (*iovp)->_flag & (_IOREAD|_IOWRT|_IORW); /* void */)
                if (++iovp >= iovend)
                        return (NULL);

        return (*iovp);
}

_cleanup()
{
        register FILE *_lastbuf = _iob + NSTATIC;
        register FILE **iovp;
        register FILE *iop;

        if (iov == NULL)
                for (iop = _iob; iop < _lastbuf; iop++)
                        fclose(iop);
        else
                for (iovp = iov; iovp < iovend; iovp++)
                        fclose(*iovp);
}