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
|
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
function files.readbyte(f)
return byte(f:read(1))
end
function files.readchar(f)
return f:read(1)
end
function files.readbytes(f,n)
return byte(f:read(n),1,n)
end
function files.skipbytes(f,n)
f:read(n or 1) -- or a seek
end
function files.readinteger1(f) -- one byte
local n = byte(f:read(1))
if n >= 0x80 then
return n - 0xFF - 1
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
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.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
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
else
return n + (0x100 * c + d)/0xFFFF
end
end
function files.readstring(f,n)
return f:read(n or 1)
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
|
