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Annotation of 43BSD/ingres/source/gutil/need.c, revision 1.1.1.1

1.1       root        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: }

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