projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| bae7117f WH |
1 | #include "f2c.h" |
| 2 | #include "fio.h" | |
| 3 | #ifdef KR_headers | |
| 4 | integer f_back(a) alist *a; | |
| 5 | #else | |
| 6 | integer f_back(alist *a) | |
| 7 | #endif | |
| 8 | { unit *b; | |
| 9 | int i, n, ndec; | |
| 10 | #ifdef MSDOS | |
| 11 | int j, k; | |
| 12 | long w, z; | |
| 13 | #endif | |
| 14 | long x, y; | |
| 15 | char buf[32]; | |
| 16 | if(a->aunit >= MXUNIT || a->aunit < 0) | |
| 17 | err(a->aerr,101,"backspace") | |
| 18 | b= &f__units[a->aunit]; | |
| 19 | if(b->useek==0) err(a->aerr,106,"backspace") | |
| 20 | if(b->ufd==NULL) { | |
| 21 | fk_open(1, 1, a->aunit); | |
| 22 | return(0); | |
| 23 | } | |
| 24 | if(b->uend==1) | |
| 25 | { b->uend=0; | |
| 26 | return(0); | |
| 27 | } | |
| 28 | if(b->uwrt) { | |
| 29 | (void) t_runc(a); | |
| 30 | if (f__nowreading(b)) | |
| 31 | err(a->aerr,errno,"backspace") | |
| 32 | } | |
| 33 | if(b->url>0) | |
| 34 | { | |
| 35 | x=ftell(b->ufd); | |
| 36 | y = x % b->url; | |
| 37 | if(y == 0) x--; | |
| 38 | x /= b->url; | |
| 39 | x *= b->url; | |
| 40 | (void) fseek(b->ufd,x,SEEK_SET); | |
| 41 | return(0); | |
| 42 | } | |
| 43 | ||
| 44 | if(b->ufmt==0) | |
| 45 | { (void) fseek(b->ufd,-(long)sizeof(int),SEEK_CUR); | |
| 46 | (void) fread((char *)&n,sizeof(int),1,b->ufd); | |
| 47 | (void) fseek(b->ufd,-(long)n-2*sizeof(int),SEEK_CUR); | |
| 48 | return(0); | |
| 49 | } | |
| 50 | #ifdef MSDOS | |
| 51 | w = -1; | |
| 52 | #endif | |
| 53 | for(ndec = 2;; ndec = 1) | |
| 54 | { | |
| 55 | y = x=ftell(b->ufd); | |
| 56 | if(x<sizeof(buf)) x=0; | |
| 57 | else x -= sizeof(buf); | |
| 58 | (void) fseek(b->ufd,x,SEEK_SET); | |
| 59 | n=fread(buf,1,(int)(y-x), b->ufd); | |
| 60 | for(i=n-ndec;i>=0;i--) | |
| 61 | { | |
| 62 | if(buf[i]!='\n') continue; | |
| 63 | #ifdef MSDOS | |
| 64 | for(j = k = 0; j <= i; j++) | |
| 65 | if (buf[j] == '\n') | |
| 66 | k++; | |
| 67 | fseek(b->ufd,x,SEEK_SET); | |
| 68 | do { | |
| 69 | if (getc(b->ufd) == '\n') { | |
| 70 | --k; | |
| 71 | if ((z = ftell(b->ufd)) >= y) { | |
| 72 | if (w == -1) | |
| 73 | goto break2; | |
| 74 | break; | |
| 75 | } | |
| 76 | w = z; | |
| 77 | } | |
| 78 | } while(k > 0); | |
| 79 | fseek(b->ufd, w, SEEK_SET); | |
| 80 | #else | |
| 81 | fseek(b->ufd,(long)(i+1-n),SEEK_CUR); | |
| 82 | #endif | |
| 83 | return(0); | |
| 84 | } | |
| 85 | #ifdef MSDOS | |
| 86 | break2: | |
| 87 | #endif | |
| 88 | if(x==0) | |
| 89 | { | |
| 90 | (void) fseek(b->ufd, 0L, SEEK_SET); | |
| 91 | return(0); | |
| 92 | } | |
| 93 | else if(n<=0) err(a->aerr,(EOF),"backspace") | |
| 94 | (void) fseek(b->ufd, x, SEEK_SET); | |
| 95 | } | |
| 96 | } |