openethereum/src/nibbleslice.rs
2015-12-02 22:59:00 +01:00

254 lines
7.1 KiB
Rust

//! Nibble-orientated view onto byte-slice, allowing nibble-precision offsets.
use std::cmp::*;
use std::fmt;
use bytes::*;
/// Nibble-orientated view onto byte-slice, allowing nibble-precision offsets.
///
/// This is an immutable struct. No operations actually change it.
///
/// # Example
/// ```rust
/// extern crate ethcore_util;
/// use ethcore_util::nibbleslice::*;
/// fn main() {
/// let d1 = &[0x01u8, 0x23, 0x45];
/// let d2 = &[0x34u8, 0x50, 0x12];
/// let d3 = &[0x00u8, 0x12];
/// let n1 = NibbleSlice::new(d1); // 0,1,2,3,4,5
/// let n2 = NibbleSlice::new(d2); // 3,4,5,0,1,2
/// let n3 = NibbleSlice::new_offset(d3, 1); // 0,1,2
/// assert!(n1 > n3); // 0,1,2,... > 0,1,2
/// assert!(n1 < n2); // 0,... < 3,...
/// assert!(n2.mid(3) == n3); // 0,1,2 == 0,1,2
/// assert!(n1.starts_with(&n3));
/// assert_eq!(n1.common_prefix(&n3), 3);
/// assert_eq!(n2.mid(3).common_prefix(&n1), 3);
/// }
/// ```
#[derive(Copy, Clone, Eq, Ord)]
pub struct NibbleSlice<'a> {
data: &'a [u8],
offset: usize,
data_encode_suffix: &'a [u8],
offset_encode_suffix: usize,
}
impl<'a, 'view> NibbleSlice<'a> where 'a: 'view {
/// Create a new nibble slice with the given byte-slice.
pub fn new(data: &[u8]) -> NibbleSlice { NibbleSlice::new_offset(data, 0) }
/// Create a new nibble slice with the given byte-slice with a nibble offset.
pub fn new_offset(data: &'a [u8], offset: usize) -> NibbleSlice { NibbleSlice{data: data, offset: offset, data_encode_suffix: &b""[..], offset_encode_suffix: 0} }
///
pub fn new_composed(a: &'a NibbleSlice, b: &'a NibbleSlice) -> NibbleSlice<'a> { NibbleSlice{data: a.data, offset: a.offset, data_encode_suffix: b.data, offset_encode_suffix: b.offset} }
/*pub fn new_composed_bytes_offset(a: &NibbleSlice, b: &NibbleSlice) -> (Bytes, usize) {
let r: Vec<u8>::with_capacity((a.len() + b.len() + 1) / 2);
let mut i = (a.len() + b.len()) % 2;
while i < a.len() {
match i % 2 {
0 => ,
1 => ,
}
i += 1;
}
while i < a.len() + b.len() {
i += 1;
}
(r, a.len() + b.len())
}*/
/// Create a new nibble slice from the given HPE encoded data (e.g. output of `encoded()`).
pub fn from_encoded(data: &'a [u8]) -> (NibbleSlice, bool) {
(Self::new_offset(data, if data[0] & 16 == 16 {1} else {2}), data[0] & 32 == 32)
}
/// Is this an empty slice?
pub fn is_empty(&self) -> bool { self.len() == 0 }
/// Get the length (in nibbles, naturally) of this slice.
pub fn len(&self) -> usize { (self.data.len() + self.data_encode_suffix.len()) * 2 - self.offset - self.offset_encode_suffix }
/// Get the nibble at position `i`.
pub fn at(&self, i: usize) -> u8 {
let l = self.data.len() * 2 - self.offset;
if i < l {
if (self.offset + i) & 1 == 1 {
self.data[(self.offset + i) / 2] & 15u8
}
else {
self.data[(self.offset + i) / 2] >> 4
}
}
else {
let i = i - l;
if (self.offset_encode_suffix + i) & 1 == 1 {
self.data_encode_suffix[(self.offset_encode_suffix + i) / 2] & 15u8
}
else {
self.data_encode_suffix[(self.offset_encode_suffix + i) / 2] >> 4
}
}
}
/// Return object which represents a view on to this slice (further) offset by `i` nibbles.
pub fn mid(&'view self, i: usize) -> NibbleSlice<'a> { NibbleSlice{ data: self.data, offset: self.offset + i, data_encode_suffix: &b""[..], offset_encode_suffix: 0 } }
/// Do we start with the same nibbles as the whole of `them`?
pub fn starts_with(&self, them: &Self) -> bool { self.common_prefix(them) == them.len() }
/// How many of the same nibbles at the beginning do we match with `them`?
pub fn common_prefix(&self, them: &Self) -> usize {
let s = min(self.len(), them.len());
let mut i = 0usize;
while i < s {
if self.at(i) != them.at(i) { break; }
i += 1;
}
i
}
pub fn encoded(&self, is_leaf: bool) -> Bytes {
let l = self.len();
let mut r = Bytes::with_capacity(l / 2 + 1);
let mut i = l % 2;
r.push(if i == 1 {0x10 + self.at(0)} else {0} + if is_leaf {0x20} else {0});
while i < l {
r.push(self.at(i) * 16 + self.at(i + 1));
i += 2;
}
r
}
pub fn encoded_leftmost(&self, n: usize, is_leaf: bool) -> Bytes {
let l = min(self.len(), n);
let mut r = Bytes::with_capacity(l / 2 + 1);
let mut i = l % 2;
r.push(if i == 1 {0x10 + self.at(0)} else {0} + if is_leaf {0x20} else {0});
while i < l {
r.push(self.at(i) * 16 + self.at(i + 1));
i += 2;
}
r
}
}
impl<'a> PartialEq for NibbleSlice<'a> {
fn eq(&self, them: &Self) -> bool {
self.len() == them.len() && self.starts_with(them)
}
}
impl<'a> PartialOrd for NibbleSlice<'a> {
fn partial_cmp(&self, them: &Self) -> Option<Ordering> {
let s = min(self.len(), them.len());
let mut i = 0usize;
while i < s {
match self.at(i).partial_cmp(&them.at(i)).unwrap() {
Ordering::Less => return Some(Ordering::Less),
Ordering::Greater => return Some(Ordering::Greater),
_ => i += 1,
}
}
self.len().partial_cmp(&them.len())
}
}
impl<'a> fmt::Debug for NibbleSlice<'a> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
for i in 0..self.len() {
match i {
0 => try!(write!(f, "{:01x}", self.at(i))),
_ => try!(write!(f, "'{:01x}", self.at(i))),
}
}
Ok(())
}
}
#[cfg(test)]
mod tests {
use super::NibbleSlice;
static D: &'static [u8;3] = &[0x01u8, 0x23, 0x45];
#[test]
fn basics() {
let n = NibbleSlice::new(D);
assert_eq!(n.len(), 6);
assert!(!n.is_empty());
let n = NibbleSlice::new_offset(D, 6);
assert!(n.is_empty());
let n = NibbleSlice::new_offset(D, 3);
assert_eq!(n.len(), 3);
for i in 0..3 {
assert_eq!(n.at(i), i as u8 + 3);
}
}
#[test]
fn mid() {
let n = NibbleSlice::new(D);
let m = n.mid(2);
for i in 0..4 {
assert_eq!(m.at(i), i as u8 + 2);
}
let m = n.mid(3);
for i in 0..3 {
assert_eq!(m.at(i), i as u8 + 3);
}
}
#[test]
fn encoded() {
let n = NibbleSlice::new(D);
assert_eq!(n.encoded(false), &[0x00, 0x01, 0x23, 0x45]);
assert_eq!(n.encoded(true), &[0x20, 0x01, 0x23, 0x45]);
assert_eq!(n.mid(1).encoded(false), &[0x11, 0x23, 0x45]);
assert_eq!(n.mid(1).encoded(true), &[0x31, 0x23, 0x45]);
}
#[test]
fn from_encoded() {
let n = NibbleSlice::new(D);
assert_eq!((n, false), NibbleSlice::from_encoded(&[0x00, 0x01, 0x23, 0x45]));
assert_eq!((n, true), NibbleSlice::from_encoded(&[0x20, 0x01, 0x23, 0x45]));
assert_eq!((n.mid(1), false), NibbleSlice::from_encoded(&[0x11, 0x23, 0x45]));
assert_eq!((n.mid(1), true), NibbleSlice::from_encoded(&[0x31, 0x23, 0x45]));
}
#[test]
fn shared() {
let n = NibbleSlice::new(D);
let other = &[0x01u8, 0x23, 0x01, 0x23, 0x45, 0x67];
let m = NibbleSlice::new(other);
assert_eq!(n.common_prefix(&m), 4);
assert_eq!(m.common_prefix(&n), 4);
assert_eq!(n.mid(1).common_prefix(&m.mid(1)), 3);
assert_eq!(n.mid(1).common_prefix(&m.mid(2)), 0);
assert_eq!(n.common_prefix(&m.mid(4)), 6);
assert!(!n.starts_with(&m.mid(4)));
assert!(m.mid(4).starts_with(&n));
}
#[test]
fn compare() {
let other = &[0x01u8, 0x23, 0x01, 0x23, 0x45];
let n = NibbleSlice::new(D);
let m = NibbleSlice::new(other);
assert!(n != m);
assert!(n > m);
assert!(m < n);
assert!(n == m.mid(4));
assert!(n >= m.mid(4));
assert!(n <= m.mid(4));
}
}