source: buchla-68k/orig/IOLIB/READ.C@ 0170798

Last change on this file since 0170798 was 3ae31e9, checked in by Thomas Lopatic <thomas@…>, 7 years ago

Imported original source code.
  • Property mode set to 100755
File size: 4.2 KB
Line 
1/*
2 =============================================================================
3 read.c -- file read functions for the C I/O Library
4 Version 9 -- 1987-10-28 -- D.N. Lynx Crowe
5
6 int
7 read(fd, buff, len)
8 char *buff;
9
10 Reads 'len' bytes from file 'fd' into 'buff'.
11 Returns FAILURE (-1) for errors, number of bytes read
12 if successful.
13
14 int
15 _getsec(fp, buf, len)
16 register struct fcb *fp;
17 char *buf;
18 unsigned len;
19
20 Gets 'len' bytes into 'buf' from file 'fp'.
21 Returns FAILURE (-1) for errors, SUCCESS (0) if successful.
22
23 int
24 _filerd(fp, buffer, len)
25 register struct fcb *fp;
26 char *buffer;
27 unsigned len;
28
29 Reads 'len' bytes into 'buffer' from 'fp'.
30 Returns FAILURE (-1) for errors, number of bytes read
31 if successful.
32
33 =============================================================================
34*/
35
36#define DEBUGIT 0
37
38#include "biosdefs.h"
39#include "io.h"
40#include "errno.h"
41#include "fcntl.h"
42#include "stddefs.h"
43
44#if DEBUGIT
45extern short fsdebug;
46#endif
47
48extern int _badfd(), _conin(), _seek();
49
50extern char *memcpy();
51
52int _filerd();
53
54static int (*t_read[])() = {
55
56 _badfd, /* 0 - invalid type */
57 _filerd, /* 1 - disk file read */
58 _conin /* 2 - console read */
59};
60
61/*
62
63*/
64
65/*
66 =============================================================================
67 read(fd, buff, len) -- Reads 'len' bytes from file 'fd' into 'buff'.
68 Returns FAILURE (-1) for errors, number of bytes read if successful.
69 =============================================================================
70*/
71
72int
73read(fd, buff, len)
74int fd;
75char *buff;
76unsigned len;
77{
78 register struct channel *chp;
79
80 if (fd < 0 OR fd > MAXCHAN) { /* check fd range */
81
82 errno = EBADF; /* bad fd */
83 return(FAILURE);
84 }
85
86 chp = &chantab[fd]; /* point at the channel table */
87 return((*t_read[chp->c_read])(chp->c_arg, buff, len)); /* do the read */
88}
89
90/*
91
92*/
93
94/*
95 =============================================================================
96 _getsec(fp, buf, len) -- Gets 'len' bytes into 'buf' from file 'fp'.
97 Returns FAILURE (-1) for errors, SUCCESS (0) if successful.
98 =============================================================================
99*/
100
101int
102_getsec(fp, buf, len)
103register struct fcb *fp;
104char *buf;
105unsigned len;
106{
107 if ((errno = ReadRN(fp, Wrkbuf)) NE 0) /* get current sector */
108 return(FAILURE);
109
110 memcpy(buf, Wrkbuf + fp->offset, len); /* move what we need */
111
112 if ((fp->offset = (fp->offset + len) & (BPSEC - 1)) EQ 0) {
113
114 ++fp->curlsn; /* advance the sector number */
115
116 if (_seek(fp) < 0) /* seek to the next sector */
117 return(FAILURE);
118 }
119
120 return(SUCCESS); /* return: all bytes read */
121}
122
123/*
124
125*/
126
127/*
128 =============================================================================
129 _filerd(fp, buffer, len) -- Reads 'len' bytes into 'buffer' from 'fp'.
130 Returns FAILURE (-1) for errors, number of bytes read if successful.
131 =============================================================================
132*/
133
134int
135_filerd(fp, buffer, len)
136register struct fcb *fp;
137char *buffer;
138unsigned len;
139{
140 register unsigned l;
141 register unsigned j, k;
142 register long curpos, newpos;
143
144 l = 0;
145 curpos = fp->offset + (fp->curlsn << FILESHFT);
146 newpos = curpos + len;
147
148#if DEBUGIT
149 if (fsdebug)
150 printf("_filerd(): len=%u, curpos=%ld, newpos=%ld, curlen=%ld\n",
151 len, curpos, newpos, fp->curlen);
152#endif
153
154 if (newpos GT fp->curlen) {
155
156 len = fp->curlen - curpos;
157
158#if DEBUGIT
159 if (fsdebug)
160 printf("_filerd(): len adjusted to %u\n", len);
161#endif
162 }
163
164 if (fp->offset) { /* see if we start in the middle of a sector */
165
166 if ((l = BPSEC - fp->offset) > len) /* see what we need */
167 l = len;
168
169 if (_getsec(fp, buffer, l)) /* read what we can */
170 return(len); /* return if ERROR */
171 }
172
173 if (k = (len - l) / BPSEC) /* see what we still need */
174 if ((j = blkrd(fp, buffer + l, k)) NE 0)
175 return((k - j) * BPSEC + l); /* return bytes read */
176
177 l += k * BPSEC; /* adjust l by what we just read */
178
179 if (l < len) /* see if we still need a partial sector */
180 if (_getsec(fp, buffer + l, len - l)) /* read partial sector */
181 return(l); /* return if ERROR or EOF */
182
183 return(len); /* return - got the whole thing */
184}
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