source: buchla-68k/libcio/lseek.c@ d21fc6f

Last change on this file since d21fc6f was b28a12e, checked in by Thomas Lopatic <thomas@…>, 7 years ago

Zero redundant declarations.
  • Property mode set to 100644
File size: 2.2 KB
RevLine 
[f40a309]1/*
2 =============================================================================
3 lseek.c -- position a file to a specified byte location
4 Version 7 -- 1987-10-28 -- D.N. Lynx Crowe
5 =============================================================================
6*/
7
8#define DEBUGIT 0
9
[b28a12e]10#include "ram.h"
[f40a309]11
[7258c6a]12int32_t lseek(int16_t fd, int32_t pos, int16_t how)
[f40a309]13{
14 register struct fcb *fp;
15
16 if ((fd < 0) OR (fd > MAXCHAN)) {
17
18#if DEBUGIT
19 if (fsdebug)
20 printf("lseek(%d): bad file index\n", fd);
21#endif
22
23 errno = EBADF; /* file number bad */
24 return(-1L);
25 }
26
27 if (chantab[fd].c_seek EQ 0) {
28
29#if DEBUGIT
30 if (fsdebug)
31 printf("lseek(%d): device not seekable\n", fd);
32#endif
33
34 errno = EINVAL; /* device can't seek */
35 return(-1L);
36 }
37
38 fp = chantab[fd].c_arg; /* get fcb pointer from channel table */
39
40 switch (how) { /* dispatch off of seek type */
41
42 case 2: /* relative to end of file */
43 pos += fp->curlen;
44 break;
45
46 case 1: /* relative to current position */
47 pos += fp->offset + (fp->curlsn << FILESHFT);
48
49 case 0: /* relative to start of file */
50 break;
51
52 default:
53 errno = EINVAL; /* invalid seek type */
54 return(-1L);
55 }
56/*
57
58*/
59 if (pos < 0) { /* trap seeks before BOF */
60
61 fp->offset = 0;
62 fp->curlsn = 0;
63 fp->modefl |= FC_ERR;
64
65#if DEBUGIT
66 if (fsdebug)
67 printf("lseek(%d): seek (%ld) is before BOF\n", fd, pos);
68#endif
69
70 errno = EINVAL;
71 return(-1L);
72
73 } else if (pos > fp->curlen) { /* trap seeks past EOF */
74
75 fp->offset = fp->curlen & (BPSEC -1);
76 fp->curlsn = fp->curlen >> FILESHFT;
77 fp->modefl |= FC_ERR;
78
79#if DEBUGIT
80 if (fsdebug)
81 printf("lseek(%d): seek (%ld) is after EOF (%ld)\n",
82 fd, pos, fp->curlen);
83#endif
84
85 errno = EINVAL;
86 return(-1L);
87 }
[7258c6a]88
[f40a309]89 fp->offset = pos & ((int32_t)BPSEC - 1); /* calculate sector offset */
90 fp->curlsn = pos >> FILESHFT; /* calculate logical sector */
91
92 if (_seek(fp) < 0) { /* position to the physical sector */
93
94 fp->modefl |= FC_ERR; /* couldn't seek */
95 errno = EIO;
96 return(-1L);
97 }
98
99 if (pos EQ fp->curlen)
100 fp->modefl |= FC_EOF;
101
102#if DEBUGIT
103 if (fsdebug)
104 printf("lseek(): pos=%d, curlsn=%ld, curdsn=%ld, offset=%u\n",
105 pos, fp->curlsn, fp->curdsn, fp->offset);
106#endif
107
108 return(pos); /* return current position */
109}
[6262b5c]110
111
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