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use {Result, Tag, Tape, Value, q32};
#[derive(Clone, Debug)]
pub struct OffsetTable {
pub header: Header,
pub records: Vec<Record>,
}
table! {
#[doc = "The header of an offset table."]
#[derive(Copy)]
pub Header {
version (q32),
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 Value for OffsetTable {
fn read<T: Tape>(tape: &mut T) -> Result<Self> {
let header = try!(tape.take::<Header>());
match header.version {
q32(0x00010000) => {},
version => match &*Tag::from(version) {
b"true" | b"typ1" | b"OTTO" => {},
_ => raise!("found an unknown font format"),
},
}
let mut records = vec![];
for _ in 0..header.table_count {
records.push(try!(tape.take()));
}
Ok(OffsetTable { header: header, records: records })
}
}
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| {
try!(tape.jump(self.offset as u64));
let mut checksum: u64 = 0;
for i in 0..length {
checksum += process(i, try!(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]));
}
}