1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
|
include <mach.h>
include <fset.h>
include "vt.h"
define SZ_VTRECFD 5120 # length, in chars, of full disk recs
# READSUBSWATH -- Read data from file whose logical unit is inputfd.
# Swap the bytes in each data word.
procedure readsubswath (inputfd, selfbuf, databuf, buflength, bp)
int inputfd # input file discriptor
int buflength # length of data buffer
bool selfbuf # self buffering flag
short databuf[buflength] # data buffer
pointer bp # buffer pointer structure pointer
int num, bleft, last_recsize
int read()
errchk read
begin
# If we are doing our own buffering, keep track of the number
# of records in each file, else let mtio do it.
last_recsize = 0
if (selfbuf) { # do our own buffering
# If there is enough data still in the buffer, just copy data
# to the output buffer and move the pointer, otherwise, read
# the next tape record.
if ((VT_BUFBOT(bp) - VT_BP(bp)) >= buflength) {
# Copy the data into the data buffer, move the pointer.
call amovs (Mems[VT_BP(bp)], databuf, buflength)
VT_BP(bp) = VT_BP(bp) + buflength
} else {
# Copy leftover data from the bottom of the input buffer
# into the top of the input buffer, reset the flags.
bleft = VT_BUFBOT(bp) - VT_BP(bp)
call amovs (Mems[VT_BP(bp)], Mems[VT_BUFP(bp)], bleft)
VT_BP(bp) = VT_BUFP(bp) + bleft
# Read in another tape record.
# Check the number of chars read. If this number is EOF or
# too short, error. If it is too long, truncate to correct
# length. This is done because some data tapes are written
# in a weird way and have some noise chars tacked on the end
# of each tape record.
iferr (num = read (inputfd, Mems[VT_BP(bp)],
10000*SZB_SHORT/SZB_CHAR)) {
call fseti (inputfd, F_VALIDATE,
SZ_VTRECFD*SZB_SHORT/SZB_CHAR)
call printf ("Error reading subswath.\n")
num = read (inputfd, Mems[VT_BP(bp)],
SZ_VTRECFD*SZB_SHORT/SZB_CHAR)
}
if (num == EOF)
call error (0, "EOF encountered on tape read")
else if (num < SZ_VTRECFD*SZB_SHORT/SZB_CHAR)
call error (0, "error on tape read, record too short")
else if (num >= SZ_VTRECFD*SZB_SHORT/SZB_CHAR &&
num < (SZ_VTRECFD+300)*SZB_SHORT/SZB_CHAR)
num = SZ_VTRECFD*SZB_SHORT/SZB_CHAR
else
call error (0, "error on tape read, record too long")
# Update the pointers, move data into the data buffer.
VT_BUFBOT(bp) = VT_BP(bp) + num
call amovs (Mems[VT_BP(bp)], databuf, buflength)
VT_BP(bp) = VT_BP(bp) + buflength
}
} else { # Let the mtio do the buffering.
iferr (num = read (inputfd, databuf,
buflength*SZB_SHORT/SZB_CHAR)) {
call fseti (inputfd, F_VALIDATE,
last_recsize*SZB_SHORT/SZB_CHAR)
call printf ("Error on tape read.\n")
num = read (inputfd, databuf, buflength*SZB_SHORT/SZB_CHAR)
}
last_recsize = num
if (num < buflength*SZB_SHORT/SZB_CHAR)
call error (0, "eof encountered when reading subswath")
}
if (BYTE_SWAP2 == YES)
call bswap2 (databuf, 1, databuf, 1, buflength * SZB_SHORT)
end
|
