projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 7bd0b8c0 | 1 | /* |
| 1604dff5 | 2 | char id_backspace[] = "@(#)backspace.c 1.4"; |
| 7bd0b8c0 DW |
3 | * |
| 4 | * Backspace records | |
| 5 | */ | |
| 6 | ||
| 7 | #include "fio.h" | |
| 8 | ||
| 9 | char *bksp = "backspace"; | |
| 10 | char last_char(); | |
| 11 | ||
| 12 | f_back(a) alist *a; | |
| 13 | { unit *b; | |
| 14 | int n,i; | |
| 15 | long x,y; | |
| 2621bc46 | 16 | |
| 7bd0b8c0 DW |
17 | lfname = NULL; |
| 18 | elist = NO; | |
| 19 | external = YES; | |
| 20 | errflag = a->aerr; | |
| 21 | lunit = a->aunit; | |
| 3bbbaca0 | 22 | if (not_legal(lunit)) err(errflag,F_ERUNIT,bksp) |
| 7bd0b8c0 DW |
23 | b= &units[lunit]; |
| 24 | if(!b->ufd && (n=fk_open(READ,SEQ,FMT,(ftnint)lunit)) ) | |
| 25 | err(errflag,n,bksp) | |
| 26 | lfname = b->ufnm; | |
| 27 | if(b->uend) | |
| 28 | { b->uend = NO; | |
| 1604dff5 | 29 | clearerr(b->ufd); |
| 7bd0b8c0 DW |
30 | return(OK); |
| 31 | } | |
| 32 | if((x=ftell(b->ufd))==0) return(OK); | |
| 3bbbaca0 | 33 | if(!b->useek) err(errflag,F_ERNOBKSP,bksp) |
| 2621bc46 | 34 | if(b->uwrt && (n=t_runc(b,errflag))) return(n); |
| 7bd0b8c0 DW |
35 | if(b->url) /* direct access, purely academic */ |
| 36 | { y = x%(long)b->url; | |
| 37 | x -= y?y:b->url; | |
| 38 | fseek(b->ufd,x,0); | |
| 39 | return(OK); | |
| 40 | } | |
| 41 | if(!b->ufmt) /* unformatted sequential */ | |
| 42 | { fseek(b->ufd,-(long)sizeof(int),1); | |
| 43 | fread((char *)&n,sizeof(int),1,b->ufd); | |
| 44 | fseek(b->ufd,-(long)n-2*sizeof(int),1); | |
| 45 | return(OK); | |
| 46 | } | |
| 47 | if(x==1) /* formatted sequential */ | |
| 48 | { rewind(b->ufd); | |
| 49 | return(OK); | |
| 50 | } | |
| 51 | while(last_char(b->ufd)!='\n'); /* slow but simple */ | |
| 52 | return(OK); | |
| 53 | } |