Leahnaya/kbinxml-rs
1
0
Fork 0
mirror of https://github.com/mbilker/kbinxml-rs.git synced 2026-09-10 03:25:14 -05:00
Code Issues Actions Packages Projects Releases Wiki Activity

sixbit: pack strings without BigUint

Browse Source
This commit is contained in:
Matt Bilker
2018-09-03 21:33:19 -04:00
parent e35e986fa3
commit aee6c5182b
1 changed files with 11 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

21
src/sixbit.rs
View File

@@ -47,20 +47,21 @@ impl Sixbit {
.map(|ch| {
*BYTE_MAP.get(&ch).expect("Character must be a valid sixbit character")
});
let len = input.len() as usize;
let padding = 8 - len * 6 % 8;
let padding = if padding == 8 { 0 } else { padding };
let real_len = (len * 6 + padding) / 8;
debug!("sixbit_len: {}, real_len: {}, padding: {}", len, real_len, padding);
let len = input.len();
let real_len = (f64::from(len as u32 * 6) / 8f64).ceil() as usize;
debug!("sixbit_len: {}, real_len: {}", len, real_len);
let mut bits = BigUint::new(vec![0; real_len]);
let mut i = 0;
let mut bytes = vec![0; real_len];
for ch in sixbit_chars {
bits <<= 6;
bits |= BigUint::from_u8(ch).unwrap();
for _ in 0..6 {
// Some crazy math that works on a single bit at a time, but
// it still performs better than a `BigUint` calculation
bytes[i / 8] |= (ch >> (5 - (i % 6)) & 1) << (7 - (i % 8));
i += 1;
}
}
bits <<= padding;
let bytes = bits.to_bytes_be();
writer.write_u8(len as u8).context(KbinErrorKind::SixbitLengthWrite)?;
writer.write(&bytes).context(KbinErrorKind::SixbitWrite)?;