Last change
on this file since 9bf0f86 was f40a309, checked in by Thomas Lopatic <thomas@…>, 7 years ago |
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[f40a309] | 1 | /*
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| 2 | =============================================================================
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| 3 | posit.c -- position a file to a specific relative sector
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| 4 | Version 4 -- 1987-06-29 -- D.N. Lynx Crowe
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| 5 | =============================================================================
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| 6 | */
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| 7 |
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| 8 | #include "biosdefs.h"
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| 9 | #include "io.h"
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| 10 | #include "errno.h"
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| 11 | #include "stddefs.h"
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| 12 |
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| 13 | extern int _seek();
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| 14 |
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| 15 | /*
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| 16 | =============================================================================
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| 17 | posit(fd, pos) -- position file 'fd' at sector 'pos'.
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| 18 | =============================================================================
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| 19 | */
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| 20 |
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| 21 | int
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| 22 | posit(fd, pos)
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| 23 | int fd;
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| 24 | unsigned pos;
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| 25 | {
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| 26 | register struct fcb *fp;
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| 27 |
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| 28 | if ((fd < 0) OR (fd > MAXCHAN)) {
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| 29 |
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| 30 | errno = EBADF;
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| 31 | return(FAILURE);
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| 32 | }
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| 33 |
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| 34 | fp = chantab[fd].c_arg;
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| 35 |
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| 36 | if ((chantab[fd].c_seek EQ 0)
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| 37 | OR ((pos << FILESHFT) > fp->curlen)) {
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| 38 |
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| 39 | errno = EINVAL;
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| 40 | fp->modefl |= FC_ERR;
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| 41 | return(FAILURE);
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| 42 | }
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| 43 |
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| 44 | fp->curlsn = pos;
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| 45 | fp->offset = 0;
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| 46 |
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| 47 | if (_seek(fp) < 0) {
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| 48 |
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| 49 | errno = EIO;
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| 50 | fp->modefl |= FC_ERR;
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| 51 | return(FAILURE);
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| 52 | }
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| 53 |
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| 54 | return(SUCCESS);
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| 55 | }
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