4.3BSD - /usr/src/lib/libc/stdio/findiop.c

   1: /*
   2:  * Copyright (c) 1983, 1985 Regents of the University of California.
   3:  * All rights reserved.  The Berkeley software License Agreement
   4:  * specifies the terms and conditions for redistribution.
   5:  */
   6: 
   7: #if defined(LIBC_SCCS) && !defined(lint)
   8: static char sccsid[] = "@(#)findiop.c	5.6 (Berkeley) 3/9/86";
   9: #endif LIBC_SCCS and not lint
  10: 
  11: #include <stdio.h>
  12: #include <errno.h>
  13: 
  14: extern int errno;
  15: 
  16: #define active(iop) ((iop)->_flag & (_IOREAD|_IOWRT|_IORW))
  17: 
  18: #define NSTATIC 20  /* stdin + stdout + stderr + the usual */
  19: 
  20: FILE _iob[NSTATIC] = {
  21:     { 0, NULL, NULL, 0, _IOREAD,        0 },    /* stdin  */
  22:     { 0, NULL, NULL, 0, _IOWRT,     1 },    /* stdout */
  23:     { 0, NULL, NULL, 0, _IOWRT|_IONBF,  2 },    /* stderr */
  24: };
  25: 
  26: extern  char    *calloc();
  27: 
  28: static  char sbuf[NSTATIC];
  29: char    *_smallbuf = sbuf;
  30: static  FILE    **iobglue;
  31: static  FILE    **endglue;
  32: 
  33: /*
  34:  * Find a free FILE for fopen et al.
  35:  * We have a fixed static array of entries, and in addition
  36:  * may allocate additional entries dynamically, up to the kernel
  37:  * limit on the number of open files.
  38:  * At first just check for a free slot in the fixed static array.
  39:  * If none are available, then we allocate a structure to glue together
  40:  * the old and new FILE entries, which are then no longer contiguous.
  41:  */
  42: FILE *
  43: _findiop()
  44: {
  45:     register FILE **iov, *iop;
  46:     register FILE *fp;
  47: 
  48:     if (iobglue == 0) {
  49:         for (iop = _iob; iop < _iob + NSTATIC; iop++)
  50:             if (!active(iop))
  51:                 return (iop);
  52: 
  53:         if (_f_morefiles() == 0) {
  54:             errno = ENOMEM;
  55:             return (NULL);
  56:         }
  57:     }
  58: 
  59:     iov = iobglue;
  60:     while (*iov != NULL && active(*iov))
  61:         if (++iov >= endglue) {
  62:             errno = EMFILE;
  63:             return (NULL);
  64:         }
  65: 
  66:     if (*iov == NULL)
  67:         *iov = (FILE *)calloc(1, sizeof **iov);
  68: 
  69:     return (*iov);
  70: }
  71: 
  72: _f_morefiles()
  73: {
  74:     register FILE **iov;
  75:     register FILE *fp;
  76:     register char *cp;
  77:     int nfiles;
  78: 
  79:     nfiles = getdtablesize();
  80: 
  81:     iobglue = (FILE **)calloc(nfiles, sizeof *iobglue);
  82:     if (iobglue == NULL)
  83:         return (0);
  84: 
  85:     endglue = iobglue + nfiles;
  86: 
  87:     for (fp = _iob, iov = iobglue; fp < &_iob[NSTATIC]; /* void */)
  88:         *iov++ = fp++;
  89: 
  90:     _smallbuf = calloc(nfiles, sizeof(*_smallbuf));
  91:     return (1);
  92: }
  93: 
  94: f_prealloc()
  95: {
  96:     register FILE **iov;
  97:     register FILE *fp;
  98: 
  99:     if (iobglue == NULL && _f_morefiles() == 0)
 100:         return;
 101: 
 102:     for (iov = iobglue; iov < endglue; iov++)
 103:         if (*iov == NULL)
 104:             *iov = (FILE *)calloc(1, sizeof **iov);
 105: }
 106: 
 107: _fwalk(function)
 108:     register int (*function)();
 109: {
 110:     register FILE **iov;
 111:     register FILE *fp;
 112: 
 113:     if (iobglue == NULL) {
 114:         for (fp = _iob; fp < &_iob[NSTATIC]; fp++)
 115:             if (active(fp))
 116:                 (*function)(fp);
 117:     } else {
 118:         for (iov = iobglue; iov < endglue; iov++)
 119:             if (*iov && active(*iov))
 120:                 (*function)(*iov);
 121:     }
 122: }
 123: 
 124: _cleanup()
 125: {
 126:     extern int fclose();
 127: 
 128:     _fwalk(fclose);
 129: }

Defined functions

Defined variables

Defined macros