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
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
if not modules then modules = { } end modules ['util-fil'] = {
version = 1.001,
comment = "companion to luat-lib.mkiv",
author = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
copyright = "PRAGMA ADE / ConTeXt Development Team",
license = "see context related readme files"
}
local byte = string.byte
local extract = bit32.extract
-- Here are a few helpers (the starting point were old ones I used for parsing
-- flac files). In Lua 5.3 we can probably do this better. Some code will move
-- here.
utilities = utilities or { }
local files = { }
utilities.files = files
local zerobased = { }
function files.open(filename,zb)
local f = io.open(filename,"rb")
if f then
zerobased[f] = zb or false
end
return f
end
function files.close(f)
zerobased[f] = nil
f:close()
end
function files.size(f)
return f:seek("end")
end
function files.setposition(f,n)
if zerobased[f] then
f:seek("set",n)
else
f:seek("set",n - 1)
end
end
function files.getposition(f)
if zerobased[f] then
return f:seek()
else
return f:seek() + 1
end
end
function files.look(f,n,chars)
local p = f:seek()
local s = f:read(n)
f:seek("set",p)
if chars then
return s
else
return byte(s,1,#s)
end
end
function files.skip(f,n)
if n == 1 then
f:read(n)
else
f:seek("set",f:seek()+n)
end
end
function files.readbyte(f)
return byte(f:read(1))
end
function files.readbytes(f,n)
return byte(f:read(n),1,n)
end
function files.readchar(f)
return f:read(1)
end
function files.readstring(f,n)
return f:read(n or 1)
end
function files.readinteger1(f) -- one byte
local n = byte(f:read(1))
if n >= 0x80 then
-- return n - 0xFF - 1
return n - 0x100
else
return n
end
end
files.readcardinal1 = files.readbyte -- one byte
files.readcardinal = files.readcardinal1
files.readinteger = files.readinteger1
function files.readcardinal2(f)
local a, b = byte(f:read(2),1,2)
return 0x100 * a + b
end
function files.readinteger2(f)
local a, b = byte(f:read(2),1,2)
local n = 0x100 * a + b
if n >= 0x8000 then
-- return n - 0xFFFF - 1
return n - 0x10000
else
return n
end
end
function files.readcardinal3(f)
local a, b, c = byte(f:read(3),1,3)
return 0x10000 * a + 0x100 * b + c
end
function files.readinteger3(f)
local a, b, c = byte(f:read(3),1,3)
local n = 0x10000 * a + 0x100 * b + c
if n >= 0x80000 then
-- return n - 0xFFFFFF - 1
return n - 0x1000000
else
return n
end
end
function files.readcardinal4(f)
local a, b, c, d = byte(f:read(4),1,4)
return 0x1000000 * a + 0x10000 * b + 0x100 * c + d
end
function files.readinteger4(f)
local a, b, c, d = byte(f:read(4),1,4)
local n = 0x1000000 * a + 0x10000 * b + 0x100 * c + d
if n >= 0x8000000 then
-- return n - 0xFFFFFFFF - 1
return n - 0x100000000
else
return n
end
end
function files.readfixed4(f)
local a, b, c, d = byte(f:read(4),1,4)
local n = 0x100 * a + b
if n >= 0x8000 then
-- return n - 0xFFFF - 1 + (0x100 * c + d)/0xFFFF
return n - 0x10000 + (0x100 * c + d)/0xFFFF
else
return n + (0x100 * c + d)/0xFFFF
end
end
function files.read2dot14(f)
local a, b = byte(f:read(2),1,2)
local n = 0x100 * a + b
local m = extract(n,0,30)
if n > 0x7FFF then
n = extract(n,30,2)
return m/0x4000 - 4
else
n = extract(n,30,2)
return n + m/0x4000
end
end
function files.skipshort(f,n)
f:read(2*(n or 1))
end
function files.skiplong(f,n)
f:read(4*(n or 1))
end
|
