From 96e1580ddfad675ca3a4e908888f1bc6c39275b1 Mon Sep 17 00:00:00 2001
From: debris <marek.kotewicz@gmail.com>
Date: Sun, 29 Nov 2015 12:22:35 +0100
Subject: [PATCH] triehash, hex_prefix_encode

---
 src/lib.rs      |  1 +
 src/triehash.rs | 90 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+)
 create mode 100644 src/triehash.rs

diff --git a/src/lib.rs b/src/lib.rs
index 27c927b2c..098e42928 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -33,6 +33,7 @@ pub mod overlaydb;
 pub mod math;
 pub mod chainfilter;
 pub mod crypto;
+pub mod triehash;
 
 //pub mod network;
 
diff --git a/src/triehash.rs b/src/triehash.rs
new file mode 100644
index 000000000..47665933b
--- /dev/null
+++ b/src/triehash.rs
@@ -0,0 +1,90 @@
+//! Generete trie root
+
+//use std::collections::HashMap;
+//use hash::*;
+//use rlp;
+
+///
+/// Hex-prefix Notation. First nibble has flags: oddness = 2^0 & termination = 2^1.
+///
+/// The "termination marker" and "leaf-node" specifier are completely equivalent.
+/// 
+/// Input values are in range `[0, 0xf]`.
+/// 
+/// ```markdown
+///  [0,0,1,2,3,4,5]   0x10012345 // 7 > 4
+///  [0,1,2,3,4,5]     0x00012345 // 6 > 4
+///  [1,2,3,4,5]       0x112345   // 5 > 3
+///  [0,0,1,2,3,4]     0x00001234 // 6 > 3
+///  [0,1,2,3,4]       0x101234   // 5 > 3
+///  [1,2,3,4]         0x001234   // 4 > 3
+///  [0,0,1,2,3,4,5,T] 0x30012345 // 7 > 4
+///  [0,0,1,2,3,4,T]   0x20001234 // 6 > 4
+///  [0,1,2,3,4,5,T]   0x20012345 // 6 > 4
+///  [1,2,3,4,5,T]     0x312345   // 5 > 3
+///  [1,2,3,4,T]       0x201234   // 4 > 3
+/// ``` 
+///  
+/// ```rust
+///	extern crate ethcore_util as util;
+///	use util::triehash::*;
+///  
+///	fn main() {
+///		let v = vec![0, 0, 1, 2, 3, 4, 5];
+///		let e = vec![0x10, 0x01, 0x23, 0x45];
+///		let h = hex_prefix_encode(&v, false);
+///		assert_eq!(h, e);
+///		
+///		let v = vec![0, 1, 2, 3, 4, 5];
+///		let e = vec![0x00, 0x01, 0x23, 0x45];
+///		let h = hex_prefix_encode(&v, false);
+///		assert_eq!(h, e);
+///		
+///		let v = vec![0, 1, 2, 3, 4, 5];
+///		let e = vec![0x20, 0x01, 0x23, 0x45];
+///		let h = hex_prefix_encode(&v, true);
+///		assert_eq!(h, e);
+///		
+///		let v = vec![1, 2, 3, 4, 5];
+///		let e = vec![0x31, 0x23, 0x45];
+///		let h = hex_prefix_encode(&v, true);
+///		assert_eq!(h, e);
+///		
+///		let v = vec![1, 2, 3, 4];
+///		let e = vec![0x00, 0x12, 0x34];
+///		let h = hex_prefix_encode(&v, false);
+///		assert_eq!(h, e);
+///	}
+/// ```
+///  
+pub fn hex_prefix_encode(hex: &[u8], leaf: bool) -> Vec<u8> {
+	let inlen = hex.len();
+	let oddness_factor = inlen % 2;
+	// next even number divided by two
+	let reslen = (inlen + 2) >> 1;
+	let mut res = vec![];
+	res.reserve(reslen);
+
+	let first_byte = {
+		let mut bits = ((inlen as u8 & 1) + (2 * leaf as u8)) << 4;
+		if oddness_factor == 1 {
+			bits += hex[0];
+		}
+		bits
+	};
+
+	res.push(first_byte);
+
+	let mut offset = oddness_factor;	
+	while offset < inlen {
+		let byte = (hex[offset] << 4) + hex[offset + 1];
+		res.push(byte);
+		offset += 2;
+	}
+
+	res
+}
+
+#[cfg(test)]
+mod tests {
+}