projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 7bd0b8c0 | 1 | /* |
| fdfc35cb | 2 | char id_backspace[] = "@(#)backspace.c 1.5"; |
| 7bd0b8c0 DW |
3 | * |
| 4 | * Backspace records | |
| 5 | */ | |
| 6 | ||
| 7 | #include "fio.h" | |
| 8 | ||
| fdfc35cb DW |
9 | static char bksp[] = "backspace"; |
| 10 | char last_char(); | |
| 7bd0b8c0 | 11 | |
| fdfc35cb DW |
12 | f_back(a) |
| 13 | alist *a; | |
| 7bd0b8c0 DW |
14 | { unit *b; |
| 15 | int n,i; | |
| 16 | long x,y; | |
| 2621bc46 | 17 | |
| 7bd0b8c0 DW |
18 | lfname = NULL; |
| 19 | elist = NO; | |
| 20 | external = YES; | |
| 21 | errflag = a->aerr; | |
| 22 | lunit = a->aunit; | |
| fdfc35cb DW |
23 | if (not_legal(lunit)) |
| 24 | err(errflag, F_ERUNIT, bksp) | |
| 7bd0b8c0 | 25 | b= &units[lunit]; |
| fdfc35cb DW |
26 | if(!b->ufd && (n = fk_open(READ, SEQ, FMT, (ftnint)lunit)) ) |
| 27 | err(errflag, n, bksp) | |
| 7bd0b8c0 DW |
28 | lfname = b->ufnm; |
| 29 | if(b->uend) | |
| 30 | { b->uend = NO; | |
| 1604dff5 | 31 | clearerr(b->ufd); |
| 7bd0b8c0 DW |
32 | return(OK); |
| 33 | } | |
| fdfc35cb DW |
34 | if((x = ftell(b->ufd)) == 0) |
| 35 | return(OK); | |
| 36 | if(!b->useek) | |
| 37 | err(errflag, F_ERNOBKSP, bksp) | |
| 38 | if(b->uwrt && (n = t_runc(b, errflag))) | |
| 39 | return(n); | |
| 7bd0b8c0 DW |
40 | if(b->url) /* direct access, purely academic */ |
| 41 | { y = x%(long)b->url; | |
| 42 | x -= y?y:b->url; | |
| 43 | fseek(b->ufd,x,0); | |
| 44 | return(OK); | |
| 45 | } | |
| 46 | if(!b->ufmt) /* unformatted sequential */ | |
| 47 | { fseek(b->ufd,-(long)sizeof(int),1); | |
| 48 | fread((char *)&n,sizeof(int),1,b->ufd); | |
| 49 | fseek(b->ufd,-(long)n-2*sizeof(int),1); | |
| 50 | return(OK); | |
| 51 | } | |
| fdfc35cb | 52 | if(x == 1) /* formatted sequential */ |
| 7bd0b8c0 DW |
53 | { rewind(b->ufd); |
| 54 | return(OK); | |
| 55 | } | |
| fdfc35cb DW |
56 | if (b->uwrt && ! nowreading(b)) |
| 57 | err(errflag, errno, bksp) | |
| 58 | while (last_char(b->ufd) != '\n') /* slow but simple */ | |
| 59 | ; | |
| 7bd0b8c0 DW |
60 | return(OK); |
| 61 | } |