| Revision 14548,
1.3 KB
checked in by ghudson, 24 years ago
(diff) |
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This commit was generated by cvs2svn to compensate for changes in r14547,
which included commits to RCS files with non-trunk default branches.
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| 1 | #include <sys/types.h> |
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| 2 | #include "f2c.h" |
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| 3 | #include "fio.h" |
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| 4 | #ifdef KR_headers |
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| 5 | integer f_back(a) alist *a; |
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| 6 | #else |
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| 7 | integer f_back(alist *a) |
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| 8 | #endif |
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| 9 | { unit *b; |
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| 10 | long v, w, x, y, z; |
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| 11 | uiolen n; |
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| 12 | FILE *f; |
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| 13 | |
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| 14 | f__curunit = b = &f__units[a->aunit]; /* curunit for error messages */ |
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| 15 | if (f__init & 2) |
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| 16 | f__fatal (131, "I/O recursion"); |
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| 17 | if(a->aunit >= MXUNIT || a->aunit < 0) |
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| 18 | err(a->aerr,101,"backspace"); |
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| 19 | if(b->useek==0) err(a->aerr,106,"backspace"); |
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| 20 | if((f = b->ufd) == NULL) { |
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| 21 | fk_open(1, 1, a->aunit); |
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| 22 | return(0); |
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| 23 | } |
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| 24 | if(b->uend==1) |
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| 25 | { b->uend=0; |
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| 26 | return(0); |
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| 27 | } |
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| 28 | if(b->uwrt) { |
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| 29 | (void) t_runc(a); |
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| 30 | f = b->ufd; /* t_runc might change b->ufd */ |
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| 31 | if (f__nowreading(b)) |
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| 32 | err(a->aerr,errno,"backspace"); |
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| 33 | } |
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| 34 | if(b->url>0) |
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| 35 | { |
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| 36 | x=ftell(f); |
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| 37 | y = x % b->url; |
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| 38 | if(y == 0) x--; |
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| 39 | x /= b->url; |
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| 40 | x *= b->url; |
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| 41 | (void) fseek(f,x,SEEK_SET); |
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| 42 | return(0); |
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| 43 | } |
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| 44 | |
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| 45 | if(b->ufmt==0) |
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| 46 | { fseek(f,-(long)sizeof(uiolen),SEEK_CUR); |
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| 47 | fread((char *)&n,sizeof(uiolen),1,f); |
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| 48 | fseek(f,-(long)n-2*sizeof(uiolen),SEEK_CUR); |
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| 49 | return(0); |
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| 50 | } |
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| 51 | w = x = ftell(f); |
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| 52 | z = 0; |
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| 53 | loop: |
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| 54 | while(x) { |
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| 55 | x -= x < 64 ? x : 64; |
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| 56 | fseek(f,x,SEEK_SET); |
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| 57 | for(y = x; y < w; y++) { |
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| 58 | if (getc(f) != '\n') |
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| 59 | continue; |
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| 60 | v = ftell(f); |
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| 61 | if (v == w) { |
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| 62 | if (z) |
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| 63 | goto break2; |
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| 64 | goto loop; |
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| 65 | } |
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| 66 | z = v; |
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| 67 | } |
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| 68 | err(a->aerr,(EOF),"backspace"); |
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| 69 | } |
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| 70 | break2: |
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| 71 | fseek(f, z, SEEK_SET); |
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| 72 | return 0; |
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| 73 | } |
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