projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 8662e665 PW |
1 | #include "fio.h" |
| 2 | f_back(a) alist *a; | |
| 3 | { unit *b; | |
| 4 | int n,i; | |
| 5 | long x; | |
| 6 | char buf[32]; | |
| 7 | if(a->aunit >= MXUNIT || a->aunit < 0) | |
| 8 | err(a->aerr,101,"backspace") | |
| 9 | b= &units[a->aunit]; | |
| 10 | if(b->useek==0) err(a->aerr,106,"backspace") | |
| 11 | if(b->ufd==NULL) err(a->aerr,114,"backspace") | |
| 12 | if(b->uend==1) | |
| 13 | { b->uend=0; | |
| 14 | return(0); | |
| 15 | } | |
| 16 | if(b->uwrt) | |
| 17 | { t_runc(b); | |
| 18 | nowreading(b); | |
| 19 | } | |
| 20 | if(b->url>0) | |
| 21 | { | |
| 22 | x=ftell(b->ufd); | |
| 23 | x /= b->url; | |
| 24 | x *= b->url; | |
| 25 | fseek(b->ufd,x,0); | |
| 26 | return(0); | |
| 27 | } | |
| 28 | if(b->ufmt==0) | |
| 29 | { fseek(b->ufd,-(long)sizeof(int),1); | |
| 30 | fread((char *)&n,sizeof(int),1,b->ufd); | |
| 31 | fseek(b->ufd,-(long)n-2*sizeof(int),1); | |
| 32 | return(0); | |
| 33 | } | |
| 34 | for(;;) | |
| 35 | { | |
| 36 | x=ftell(b->ufd); | |
| 37 | if(x<sizeof(buf)) x=0; | |
| 38 | else x -= sizeof(buf); | |
| 39 | fseek(b->ufd,x,0); | |
| 40 | n=fread(buf,1,sizeof(buf),b->ufd); | |
| 41 | for(i=n-1;i>=0;i--) | |
| 42 | { | |
| 43 | if(buf[i]!='\n') continue; | |
| 44 | fseek(b->ufd,(long)(i-n),1); | |
| 45 | return(0); | |
| 46 | } | |
| 47 | if(x==0) return(0); | |
| 48 | else if(n==0) err(a->aerr,(EOF),"backspace") | |
| 49 | else err(a->aerr,errno,"backspace"); | |
| 50 | } | |
| 51 | } |