98e755106fBefore this change numbits_i64() was incorrect for every value of the form 0 - 2^x. This only manifested in a visible error if x%7 == 6 (so for -64, -8192, etc.) at which point `lebsize` would return a value one too large, causing a panic in commit().
82 lines
2 KiB
Rust
82 lines
2 KiB
Rust
/// The number of bytes required to encode `val` as a LEB128 integer
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pub(crate) fn lebsize(mut val: i64) -> u64 {
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if val < 0 {
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val = !val
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}
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// 1 extra for the sign bit
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leb_bytes(1 + 64 - val.leading_zeros() as u64)
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}
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/// The number of bytes required to encode `val` as a uLEB128 integer
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pub(crate) fn ulebsize(val: u64) -> u64 {
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if val == 0 {
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return 1;
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}
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leb_bytes(64 - val.leading_zeros() as u64)
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}
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fn leb_bytes(bits: u64) -> u64 {
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(bits + 6) / 7
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use proptest::prelude::*;
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proptest! {
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#[test]
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fn test_ulebsize(val in 0..u64::MAX) {
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let mut out = Vec::new();
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leb128::write::unsigned(&mut out, val).unwrap();
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let expected = out.len() as u64;
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assert_eq!(expected, ulebsize(val))
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}
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#[test]
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fn test_lebsize(val in i64::MIN..i64::MAX) {
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let mut out = Vec::new();
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leb128::write::signed(&mut out, val).unwrap();
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let expected = out.len() as u64;
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assert_eq!(expected, lebsize(val))
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}
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}
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#[test]
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fn ulebsize_examples() {
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let scenarios = vec![0, 1, 127, 128, 129, 169, u64::MAX];
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for val in scenarios {
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let mut out = Vec::new();
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leb128::write::unsigned(&mut out, val).unwrap();
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let expected = out.len() as u64;
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assert_eq!(ulebsize(val), expected, "value: {}", val)
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}
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}
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#[test]
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fn lebsize_examples() {
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let scenarios = vec![
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0,
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1,
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-1,
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63,
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64,
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-64,
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-65,
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127,
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128,
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-127,
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-128,
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-2097152,
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169,
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i64::MIN,
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i64::MAX,
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];
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for val in scenarios {
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let mut out = Vec::new();
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leb128::write::signed(&mut out, val).unwrap();
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let expected = out.len() as u64;
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assert_eq!(lebsize(val), expected, "value: {}", val)
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}
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}
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}
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