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Annotation of 3BSD/new/libI77uc/backspace.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Backspace records
                      3:  */
                      4: 
                      5: #include "fio.h"
                      6: 
                      7: char *bksp = "backspace";
                      8: char last_char();
                      9: 
                     10: f_back(a) alist *a;
                     11: {      unit *b;
                     12:        int n,i;
                     13:        long x,y;
                     14:        lfname = NULL;
                     15:        elist = NO;
                     16:        external = YES;
                     17:        errflag = a->aerr;
                     18:        lunit = a->aunit;
                     19:        if (not_legal(lunit)) err(errflag,101,bksp)
                     20:        b= &units[lunit];
                     21:        if(!b->ufd) err(errflag,114,bksp)
                     22:        lfname = b->ufnm;
                     23:        if(b->uend)
                     24:        {       b->uend = NO;
                     25:                return(OK);
                     26:        }
                     27:        if((x=ftell(b->ufd))==0) return(OK);
                     28:        if(!b->useek) err(errflag,106,bksp)
                     29:        if(b->uwrt) t_runc(b,errflag);
                     30:        if(b->url)              /* direct access, purely academic */
                     31:        {       y = x%(long)b->url;
                     32:                x -= y?y:b->url;
                     33:                fseek(b->ufd,x,0);
                     34:                return(OK);
                     35:        }
                     36:        if(!b->ufmt)            /* unformatted sequential */
                     37:        {       fseek(b->ufd,-(long)sizeof(int),1);
                     38:                fread((char *)&n,sizeof(int),1,b->ufd);
                     39:                fseek(b->ufd,-(long)n-2*sizeof(int),1);
                     40:                return(OK);
                     41:        }
                     42:        if(x==1)                        /* formatted sequential */
                     43:        {       rewind(b->ufd);
                     44:                return(OK);
                     45:        }
                     46:        while(last_char(b->ufd)!='\n'); /* slow but simple */
                     47:        return(OK);
                     48: }

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