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
use {Result, Tag, Tape};
table! {
#[doc = "An offset table."]
pub OffsetTable {
header (Header),
records (Vec<Record>) |this, tape| {
tape.take_given(this.header.table_count as usize)
},
}
}
table! {
#[doc = "The header of an offset table."]
#[derive(Copy)]
pub Header {
version (u32) |_, tape| {
let value = tape.take()?;
match value {
0x00010000 => {},
value => match &*Tag::from(value) {
b"OTTO" | b"true" | b"typ1" => {},
_ => raise!("found an unknown font format"),
},
}
Ok(value)
},
table_count (u16),
search_range (u16),
entry_selector (u16),
range_shift (u16),
}
}
table! {
#[doc = "A record of an offset table."]
#[derive(Copy)]
pub Record {
tag (Tag),
checksum (u32),
offset (u32),
length (u32),
}
}
impl Record {
pub fn checksum<T, F>(&self, tape: &mut T, process: F) -> Result<bool>
where
T: Tape,
F: Fn(usize, u32) -> u32,
{
let length = ((self.length as usize + 4 - 1) & !(4 - 1)) / 4;
tape.stay(|tape| {
tape.jump(self.offset as u64)?;
let mut checksum: u64 = 0;
for i in 0..length {
checksum += process(i, tape.take()?) as u64;
}
Ok(self.checksum == checksum as u32)
})
}
}
#[cfg(test)]
mod tests {
use std::io::Cursor;
use Tag;
use super::Record;
#[test]
fn record_checksum() {
macro_rules! checksum(
($length:expr, $checksum:expr, $data:expr,) => ({
let data: &[u8] = $data;
let mut reader = Cursor::new(data);
let table = Record {
tag: Tag(*b"true"),
length: $length,
offset: 0,
checksum: $checksum,
};
table.checksum(&mut reader, |_, chunk| chunk).unwrap()
})
);
assert!(!checksum!(
3 * 4,
1 + 2 + 4,
&[0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 3],
));
assert!(checksum!(
3 * 4,
1 + 2 + 3,
&[0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 3],
));
}
}