autoconfigure FILE array using getdtablesize()

[unix-history] / usr / src / lib / libc / stdio / findfp.c

/* @(#)findfp.c 1.2 (Berkeley) %G% */
#include <stdio.h>

#define NSTATIC 10      /* stdin, stdout, stderr, plus slack */

extern char *calloc();

static FILE *dummy[NSTATIC];
static FILE **iov = NULL;
static FILE **iovend;

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 */
};

static char smallbuf[NSTATIC];
static char *unbufp = NULL;

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

       if (iov == NULL) {
               unbufp  = NULL;
               iov     = NULL;
               fp      = NULL;

               nfiles = getdtablesize();
               if (nfiles > NSTATIC) {
                       fp = (FILE *)calloc(nfiles - NSTATIC, sizeof *fp);
                       if (fp != NULL) {
                               iov = (FILE **)calloc(nfiles, sizeof *iov);
                               if (iov != NULL)
                                       unbufp = calloc(nfiles, sizeof *unbufp);
                       }
               }

               if (unbufp != NULL) {
                       iovend = iov + nfiles;
                       for (iovp = iov + NSTATIC; iovp < iovend; /* void */)
                               *iovp++ = fp++;
               } else {
                       if (fp != NULL) {
                               free((char *)fp);
                               if (iov != NULL)
                                       free((char *)iov);
                       }

                       iovend  = dummy + NSTATIC;
                       iov     = dummy;
               }

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

       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);
}

char *
_smallbuf(iop)
       register FILE *iop;
{
       if (unbufp == NULL)
               return (&smallbuf[iop - _iob]);
       else
               return (&unbufp[fileno(iop)]);
}