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https://git.hardenedbsd.org/hardenedbsd/HardenedBSD.git
synced 2024-12-22 00:42:06 +01:00
82 lines
1.5 KiB
C
82 lines
1.5 KiB
C
#include "config.h"
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#include <sys/types.h>
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#include "f2c.h"
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#include "fio.h"
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integer
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f_back (alist * a)
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{
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unit *b;
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off_t v, w, x, y, z;
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uiolen n;
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FILE *f;
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f__curunit = b = &f__units[a->aunit]; /* curunit for error messages */
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if (f__init & 2)
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f__fatal (131, "I/O recursion");
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if (a->aunit >= MXUNIT || a->aunit < 0)
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err (a->aerr, 101, "backspace");
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if (b->useek == 0)
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err (a->aerr, 106, "backspace");
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if (b->ufd == NULL)
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{
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fk_open (1, 1, a->aunit);
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return (0);
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}
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if (b->uend == 1)
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{
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b->uend = 0;
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return (0);
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}
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if (b->uwrt)
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{
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t_runc (a);
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if (f__nowreading (b))
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err (a->aerr, errno, "backspace");
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}
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f = b->ufd; /* may have changed in t_runc() */
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if (b->url > 0)
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{
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x = FTELL (f);
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y = x % b->url;
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if (y == 0)
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x--;
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x /= b->url;
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x *= b->url;
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FSEEK (f, x, SEEK_SET);
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return (0);
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}
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if (b->ufmt == 0)
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{
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FSEEK (f, -(off_t) sizeof (uiolen), SEEK_CUR);
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fread ((char *) &n, sizeof (uiolen), 1, f);
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FSEEK (f, -(off_t) n - 2 * sizeof (uiolen), SEEK_CUR);
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return (0);
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}
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w = x = FTELL (f);
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z = 0;
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loop:
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while (x)
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{
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x -= x < 64 ? x : 64;
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FSEEK (f, x, SEEK_SET);
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for (y = x; y < w; y++)
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{
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if (getc (f) != '\n')
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continue;
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v = FTELL (f);
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if (v == w)
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{
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if (z)
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goto break2;
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goto loop;
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}
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z = v;
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}
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err (a->aerr, (EOF), "backspace");
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}
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break2:
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FSEEK (f, z, SEEK_SET);
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return 0;
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}
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