4.3BSD - /usr/ingres/source/gutil/need.c

   1: # include   <sccs.h>
   2: 
   3: SCCSID(@(#)need.c	8.2	12/18/85)
   4: 
   5: /*
   6: **  NEED.C -- general buffer allocation routines
   7: **
   8: **	allow buffers with LIFO de-allocation
   9: */
  10: 
  11: 
  12: 
  13: 
  14: 
  15: 
  16: /* structure that the routines use to allocate space */
  17: struct nodbuffer
  18: {
  19:     int nleft;      /* bytes left */
  20:     int err_num;    /* error code on overflow */
  21:     int (*err_func)();  /* error function on overflow */
  22:     char    *xfree;     /* next free byte */
  23:     char    buffer[1];  /*beginning of buffer area */
  24: };
  25: 
  26: /*
  27: **  NEED -- allocate space from a buffer
  28: **
  29: **	On buffer overflow, calls err_func from that field
  30: **	in the buffer with the error code err_code from that field
  31: **	in the buffer, then returns 0.
  32: **	need() guarantees an even adress on return.
  33: **
  34: **	Parameters:
  35: **		bf -- buffer
  36: **		nbytes -- number of bytes desired
  37: **
  38: **	Returns:
  39: **		pointer to allocated area
  40: **		on buffer overflow returns 0.
  41: **
  42: **	Side Effects:
  43: **		adjusts buffer structure to reflect allocation.
  44: */
  45: 
  46: char *
  47: need(bf, nbytes)
  48: struct nodbuffer    *bf;
  49: int         nbytes;
  50: {
  51:     register char           *x;
  52:     register struct nodbuffer   *buf;
  53:     register int            i;
  54: 
  55:     buf = bf;
  56:     i = nbytes;
  57:     if (i > buf->nleft)
  58:     {
  59:         (*buf->err_func)(buf->err_num, 0);
  60:         return (0);
  61:     }
  62:     i = (i + 3) & ~03;
  63:     x = buf->xfree;
  64:     buf->xfree += i;
  65:     buf->nleft -= i;
  66:     clrmem(x, i);
  67:     return(x);
  68: }
  69: 
  70: /*
  71: **  INITBUF -- initialize a buffer
  72: **
  73: **	Must be called before the first need() call on the buffer.
  74: **
  75: **	Parameters:
  76: **		bf -- buffer
  77: **		size -- size fo buffer area
  78: **		err_num -- error code for overflow
  79: **		err_func -- function to call with err_code on error
  80: **
  81: **	Returns:
  82: **		none
  83: **
  84: **	Side Effects:
  85: **		initializes buffer structure
  86: **
  87: **	Diagnostics:
  88: **		"initbuf : odd buffer adress 0%o" -- buffers must start
  89: **			at an even address.
  90: */
  91: 
  92: initbuf(bf, size, err_num, err_func)
  93: char    *bf;
  94: int size;
  95: int err_num;
  96: int (*err_func)();
  97: {
  98:     register struct nodbuffer   *buf;
  99:     register            i;
 100: 
 101:     buf = (struct nodbuffer *) bf;
 102:     i = (int) buf;
 103:     if (i & 03)
 104:         syserr("initbuf : odd buffer adress 0%o", buf);
 105:     buf->nleft = size - sizeof *buf;
 106:     buf->xfree = buf->buffer;
 107:     buf->err_num = err_num;
 108:     buf->err_func = err_func;
 109: }

Defined functions

Defined struct's