[f40a309] | 1 | /*
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| 2 | =============================================================================
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| 3 | read.c -- file read functions for the C I/O Library
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| 4 | Version 9 -- 1987-10-28 -- D.N. Lynx Crowe
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| 5 |
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| 6 | int
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| 7 | read(fd, buff, len)
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| 8 | char *buff;
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| 9 |
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| 10 | Reads 'len' bytes from file 'fd' into 'buff'.
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| 11 | Returns FAILURE (-1) for errors, number of bytes read
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| 12 | if successful.
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| 13 |
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| 14 | int
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| 15 | _getsec(fp, buf, len)
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| 16 | register struct fcb *fp;
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| 17 | char *buf;
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| 18 | unsigned len;
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| 19 |
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| 20 | Gets 'len' bytes into 'buf' from file 'fp'.
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| 21 | Returns FAILURE (-1) for errors, SUCCESS (0) if successful.
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| 22 |
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| 23 | int
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| 24 | _filerd(fp, buffer, len)
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| 25 | register struct fcb *fp;
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| 26 | char *buffer;
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| 27 | unsigned len;
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| 28 |
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| 29 | Reads 'len' bytes into 'buffer' from 'fp'.
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| 30 | Returns FAILURE (-1) for errors, number of bytes read
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| 31 | if successful.
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| 32 |
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| 33 | =============================================================================
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| 34 | */
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| 35 |
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| 36 | #define DEBUGIT 0
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| 37 |
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| 38 | #include "biosdefs.h"
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| 39 | #include "io.h"
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| 40 | #include "errno.h"
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| 41 | #include "fcntl.h"
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| 42 | #include "stddefs.h"
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| 43 |
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| 44 | #if DEBUGIT
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| 45 | extern short fsdebug;
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| 46 | #endif
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| 47 |
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| 48 | extern int _badfd(), _conin(), _seek();
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| 49 |
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| 50 | extern char *memcpy();
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| 51 |
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| 52 | int _filerd();
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| 53 |
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| 54 | static int (*t_read[])() = {
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| 55 |
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| 56 | _badfd, /* 0 - invalid type */
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| 57 | _filerd, /* 1 - disk file read */
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| 58 | _conin /* 2 - console read */
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| 59 | };
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| 60 |
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| 61 | /* |
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| 62 |
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| 63 | */
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| 64 |
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| 65 | /*
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| 66 | =============================================================================
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| 67 | read(fd, buff, len) -- Reads 'len' bytes from file 'fd' into 'buff'.
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| 68 | Returns FAILURE (-1) for errors, number of bytes read if successful.
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| 69 | =============================================================================
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| 70 | */
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| 71 |
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| 72 | int
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| 73 | read(fd, buff, len)
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| 74 | int fd;
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| 75 | char *buff;
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| 76 | unsigned len;
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| 77 | {
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| 78 | register struct channel *chp;
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| 79 |
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| 80 | if (fd < 0 OR fd > MAXCHAN) { /* check fd range */
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| 81 |
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| 82 | errno = EBADF; /* bad fd */
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| 83 | return(FAILURE);
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| 84 | }
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| 85 |
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| 86 | chp = &chantab[fd]; /* point at the channel table */
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| 87 | return((*t_read[chp->c_read])(chp->c_arg, buff, len)); /* do the read */
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| 88 | }
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| 89 |
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| 90 | /* |
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| 91 |
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| 92 | */
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| 93 |
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| 94 | /*
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| 95 | =============================================================================
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| 96 | _getsec(fp, buf, len) -- Gets 'len' bytes into 'buf' from file 'fp'.
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| 97 | Returns FAILURE (-1) for errors, SUCCESS (0) if successful.
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| 98 | =============================================================================
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| 99 | */
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| 100 |
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| 101 | int
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| 102 | _getsec(fp, buf, len)
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| 103 | register struct fcb *fp;
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| 104 | char *buf;
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| 105 | unsigned len;
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| 106 | {
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| 107 | if ((errno = ReadRN(fp, Wrkbuf)) NE 0) /* get current sector */
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| 108 | return(FAILURE);
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| 109 |
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| 110 | memcpy(buf, Wrkbuf + fp->offset, len); /* move what we need */
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| 111 |
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| 112 | if ((fp->offset = (fp->offset + len) & (BPSEC - 1)) EQ 0) {
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| 113 |
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| 114 | ++fp->curlsn; /* advance the sector number */
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| 115 |
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| 116 | if (_seek(fp) < 0) /* seek to the next sector */
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| 117 | return(FAILURE);
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| 118 | }
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| 119 |
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| 120 | return(SUCCESS); /* return: all bytes read */
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| 121 | }
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| 122 |
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| 123 | /* |
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| 124 |
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| 125 | */
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| 126 |
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| 127 | /*
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| 128 | =============================================================================
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| 129 | _filerd(fp, buffer, len) -- Reads 'len' bytes into 'buffer' from 'fp'.
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| 130 | Returns FAILURE (-1) for errors, number of bytes read if successful.
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| 131 | =============================================================================
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| 132 | */
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| 133 |
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| 134 | int
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| 135 | _filerd(fp, buffer, len)
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| 136 | register struct fcb *fp;
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| 137 | char *buffer;
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| 138 | unsigned len;
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| 139 | {
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| 140 | register unsigned l;
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| 141 | register unsigned j, k;
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| 142 | register long curpos, newpos;
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| 143 |
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| 144 | l = 0;
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| 145 | curpos = fp->offset + (fp->curlsn << FILESHFT);
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| 146 | newpos = curpos + len;
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| 147 |
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| 148 | #if DEBUGIT
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| 149 | if (fsdebug)
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| 150 | printf("_filerd(): len=%u, curpos=%ld, newpos=%ld, curlen=%ld\n",
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| 151 | len, curpos, newpos, fp->curlen);
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| 152 | #endif
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| 153 |
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| 154 | if (newpos GT fp->curlen) {
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| 155 |
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| 156 | len = fp->curlen - curpos;
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| 157 |
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| 158 | #if DEBUGIT
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| 159 | if (fsdebug)
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| 160 | printf("_filerd(): len adjusted to %u\n", len);
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| 161 | #endif
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| 162 | }
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| 163 |
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| 164 | if (fp->offset) { /* see if we start in the middle of a sector */
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| 165 |
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| 166 | if ((l = BPSEC - fp->offset) > len) /* see what we need */
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| 167 | l = len;
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| 168 |
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| 169 | if (_getsec(fp, buffer, l)) /* read what we can */
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| 170 | return(len); /* return if ERROR */
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| 171 | }
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| 172 |
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| 173 | if (k = (len - l) / BPSEC) /* see what we still need */
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| 174 | if ((j = blkrd(fp, buffer + l, k)) NE 0)
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| 175 | return((k - j) * BPSEC + l); /* return bytes read */
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| 176 |
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| 177 | l += k * BPSEC; /* adjust l by what we just read */
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| 178 |
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| 179 | if (l < len) /* see if we still need a partial sector */
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| 180 | if (_getsec(fp, buffer + l, len - l)) /* read partial sector */
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| 181 | return(l); /* return if ERROR or EOF */
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| 182 |
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| 183 | return(len); /* return - got the whole thing */
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| 184 | }
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