91 lines
2.2 KiB
Rust
91 lines
2.2 KiB
Rust
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//! Generete trie root
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//use std::collections::HashMap;
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//use hash::*;
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//use rlp;
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///
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/// Hex-prefix Notation. First nibble has flags: oddness = 2^0 & termination = 2^1.
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///
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/// The "termination marker" and "leaf-node" specifier are completely equivalent.
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///
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/// Input values are in range `[0, 0xf]`.
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///
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/// ```markdown
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/// [0,0,1,2,3,4,5] 0x10012345 // 7 > 4
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/// [0,1,2,3,4,5] 0x00012345 // 6 > 4
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/// [1,2,3,4,5] 0x112345 // 5 > 3
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/// [0,0,1,2,3,4] 0x00001234 // 6 > 3
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/// [0,1,2,3,4] 0x101234 // 5 > 3
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/// [1,2,3,4] 0x001234 // 4 > 3
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/// [0,0,1,2,3,4,5,T] 0x30012345 // 7 > 4
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/// [0,0,1,2,3,4,T] 0x20001234 // 6 > 4
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/// [0,1,2,3,4,5,T] 0x20012345 // 6 > 4
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/// [1,2,3,4,5,T] 0x312345 // 5 > 3
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/// [1,2,3,4,T] 0x201234 // 4 > 3
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/// ```
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///
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/// ```rust
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/// extern crate ethcore_util as util;
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/// use util::triehash::*;
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///
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/// fn main() {
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/// let v = vec![0, 0, 1, 2, 3, 4, 5];
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/// let e = vec![0x10, 0x01, 0x23, 0x45];
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/// let h = hex_prefix_encode(&v, false);
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/// assert_eq!(h, e);
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///
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/// let v = vec![0, 1, 2, 3, 4, 5];
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/// let e = vec![0x00, 0x01, 0x23, 0x45];
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/// let h = hex_prefix_encode(&v, false);
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/// assert_eq!(h, e);
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///
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/// let v = vec![0, 1, 2, 3, 4, 5];
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/// let e = vec![0x20, 0x01, 0x23, 0x45];
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/// let h = hex_prefix_encode(&v, true);
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/// assert_eq!(h, e);
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///
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/// let v = vec![1, 2, 3, 4, 5];
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/// let e = vec![0x31, 0x23, 0x45];
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/// let h = hex_prefix_encode(&v, true);
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/// assert_eq!(h, e);
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///
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/// let v = vec![1, 2, 3, 4];
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/// let e = vec![0x00, 0x12, 0x34];
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/// let h = hex_prefix_encode(&v, false);
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/// assert_eq!(h, e);
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/// }
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/// ```
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///
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pub fn hex_prefix_encode(hex: &[u8], leaf: bool) -> Vec<u8> {
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let inlen = hex.len();
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let oddness_factor = inlen % 2;
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// next even number divided by two
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let reslen = (inlen + 2) >> 1;
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let mut res = vec![];
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res.reserve(reslen);
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let first_byte = {
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let mut bits = ((inlen as u8 & 1) + (2 * leaf as u8)) << 4;
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if oddness_factor == 1 {
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bits += hex[0];
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}
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bits
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};
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res.push(first_byte);
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let mut offset = oddness_factor;
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while offset < inlen {
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let byte = (hex[offset] << 4) + hex[offset + 1];
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res.push(byte);
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offset += 2;
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}
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res
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}
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#[cfg(test)]
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mod tests {
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}
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