51 lines
1.5 KiB
Rust
51 lines
1.5 KiB
Rust
// ZigZag endoging used for efficient transfer of signed integers
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// https://developers.google.com/protocol-buffers/docs/encoding#types
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pub fn decode_zig_zag_32(n: u32) -> i32 {
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((n >> 1) as i32) ^ (-((n & 1) as i32))
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}
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pub fn decode_zig_zag_64(n: u64) -> i64 {
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((n >> 1) as i64) ^ (-((n & 1) as i64))
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}
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pub fn encode_zig_zag_32(n: i32) -> u32 {
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((n << 1) ^ (n >> 31)) as u32
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}
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pub fn encode_zig_zag_64(n: i64) -> u64 {
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((n << 1) ^ (n >> 63)) as u64
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}
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#[cfg(test)]
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mod test {
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use super::decode_zig_zag_32;
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use super::decode_zig_zag_64;
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use super::encode_zig_zag_32;
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use super::encode_zig_zag_64;
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#[test]
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fn test_zig_zag() {
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fn test_zig_zag_pair_64(decoded: i64, encoded: u64) {
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assert_eq!(decoded, decode_zig_zag_64(encoded));
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assert_eq!(encoded, encode_zig_zag_64(decoded));
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}
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fn test_zig_zag_pair(decoded: i32, encoded: u32) {
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assert_eq!(decoded, decode_zig_zag_32(encoded));
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assert_eq!(encoded, encode_zig_zag_32(decoded));
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test_zig_zag_pair_64(decoded as i64, encoded as u64);
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}
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test_zig_zag_pair(0, 0);
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test_zig_zag_pair(-1, 1);
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test_zig_zag_pair(1, 2);
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test_zig_zag_pair(-2, 3);
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test_zig_zag_pair(2147483647, 4294967294);
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test_zig_zag_pair(-2147483648, 4294967295);
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test_zig_zag_pair_64(9223372036854775807, 18446744073709551614);
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test_zig_zag_pair_64(-9223372036854775808, 18446744073709551615);
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}
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}
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