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Merge rust-bitcoin/rust-bitcoin#710: Refactor bitcoin_merkle_root functions
b454cf8 Return None from merkle_root functions (Tobin Harding) 7a8b017 Use correct spelling of merkle (Tobin Harding) Pull request description: ~Do two minor refactorings to the `bitcoin_merkle_root[_inline] functions.~ This PR has grown, is no longer a refactoring because the two functions have been changed to return an `Option`. First patch is cleanup. Here is the commit message for the second patch ``` The merkle_root of an empty tree is undefined, this is the only error case we have for the two `bitcoin_merkle_root*` functions. We can fully describe this error case by returning an `Option` if args are found to be empty. While we are at it, refactor out a recursive helper function to make reading the code between the two functions easier. ``` ACKs for top commit: Kixunil: ACK b454cf8 dr-orlovsky: ACK b454cf8 Tree-SHA512: 961714a8b0eb0dad493a1548317d875d64ca22d2d584c905c502369b5f6e5a9f8be1edd7345136b44964dc0bde7a4c43bfaff4287d1dbf7fd736da79818074e3
2 parents e5c6d65 + b454cf8 commit fe43e3c

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‎src/blockdata/block.rs

Lines changed: 14 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -176,7 +176,10 @@ impl Block {
176176

177177
/// check if merkle root of header matches merkle root of the transaction list
178178
pub fn check_merkle_root (&self) -> bool {
179-
self.header.merkle_root == self.merkle_root()
179+
match self.merkle_root() {
180+
Some(merkle_root) => self.header.merkle_root == merkle_root,
181+
None => false,
182+
}
180183
}
181184

182185
/// check if witness commitment in coinbase is matching the transaction list
@@ -197,8 +200,10 @@ impl Block {
197200
let commitment = WitnessCommitment::from_slice(&coinbase.output[pos].script_pubkey.as_bytes()[6..38]).unwrap();
198201
// witness reserved value is in coinbase input witness
199202
if coinbase.input[0].witness.len() == 1 && coinbase.input[0].witness[0].len() == 32 {
200-
let witness_root = self.witness_root();
201-
return commitment == Self::compute_witness_commitment(&witness_root, coinbase.input[0].witness[0].as_slice())
203+
match self.witness_root() {
204+
Some(witness_root) => return commitment == Self::compute_witness_commitment(&witness_root, coinbase.input[0].witness[0].as_slice()),
205+
None => return false,
206+
}
202207
}
203208
}
204209
}
@@ -207,9 +212,9 @@ impl Block {
207212
}
208213

209214
/// Calculate the transaction merkle root.
210-
pub fn merkle_root(&self) -> TxMerkleNode {
215+
pub fn merkle_root(&self) -> Option<TxMerkleNode> {
211216
let hashes = self.txdata.iter().map(|obj| obj.txid().as_hash());
212-
bitcoin_merkle_root(hashes).into()
217+
bitcoin_merkle_root(hashes).map(|h| h.into())
213218
}
214219

215220
/// compute witness commitment for the transaction list
@@ -221,7 +226,7 @@ impl Block {
221226
}
222227

223228
/// Merkle root of transactions hashed for witness
224-
pub fn witness_root(&self) -> WitnessMerkleNode {
229+
pub fn witness_root(&self) -> Option<WitnessMerkleNode> {
225230
let hashes = self.txdata.iter().enumerate().map(|(i, t)|
226231
if i == 0 {
227232
// Replace the first hash with zeroes.
@@ -230,7 +235,7 @@ impl Block {
230235
t.wtxid().as_hash()
231236
}
232237
);
233-
bitcoin_merkle_root(hashes).into()
238+
bitcoin_merkle_root(hashes).map(|h| h.into())
234239
}
235240

236241
/// The size of the header + the size of the varint with the tx count + the txs themselves
@@ -371,7 +376,7 @@ mod tests {
371376
let real_decode = decode.unwrap();
372377
assert_eq!(real_decode.header.version, 1);
373378
assert_eq!(serialize(&real_decode.header.prev_blockhash), prevhash);
374-
assert_eq!(real_decode.header.merkle_root, real_decode.merkle_root());
379+
assert_eq!(real_decode.header.merkle_root, real_decode.merkle_root().unwrap());
375380
assert_eq!(serialize(&real_decode.header.merkle_root), merkle);
376381
assert_eq!(real_decode.header.time, 1231965655);
377382
assert_eq!(real_decode.header.bits, 486604799);
@@ -407,7 +412,7 @@ mod tests {
407412
assert_eq!(real_decode.header.version, 0x20000000); // VERSIONBITS but no bits set
408413
assert_eq!(serialize(&real_decode.header.prev_blockhash), prevhash);
409414
assert_eq!(serialize(&real_decode.header.merkle_root), merkle);
410-
assert_eq!(real_decode.header.merkle_root, real_decode.merkle_root());
415+
assert_eq!(real_decode.header.merkle_root, real_decode.merkle_root().unwrap());
411416
assert_eq!(real_decode.header.time, 1472004949);
412417
assert_eq!(real_decode.header.bits, 0x1a06d450);
413418
assert_eq!(real_decode.header.nonce, 1879759182);

‎src/util/hash.rs

Lines changed: 61 additions & 37 deletions
Original file line numberDiff line numberDiff line change
@@ -17,6 +17,8 @@
1717
//! merkleization.
1818
//!
1919
20+
use core::iter;
21+
2022
use prelude::*;
2123

2224
use io;
@@ -25,59 +27,81 @@ use core::cmp::min;
2527
use hashes::Hash;
2628
use consensus::encode::Encodable;
2729

28-
/// Calculates the merkle root of a list of hashes inline
29-
/// into the allocated slice.
30+
/// Calculates the merkle root of a list of *hashes*, inline (in place) in `hashes`.
3031
///
3132
/// In most cases, you'll want to use [bitcoin_merkle_root] instead.
32-
pub fn bitcoin_merkle_root_inline<T>(data: &mut [T]) -> T
33+
///
34+
/// # Returns
35+
/// - `None` if `hashes` is empty. The merkle root of an empty tree of hashes is undefined.
36+
/// - `Some(hash)` if `hashes` contains one element. A single hash is by definition the merkle root.
37+
/// - `Some(merkle_root)` if length of `hashes` is greater than one.
38+
pub fn bitcoin_merkle_root_inline<T>(hashes: &mut [T]) -> Option<T>
3339
where T: Hash + Encodable,
3440
<T as Hash>::Engine: io::Write,
3541
{
36-
// Base case
37-
if data.is_empty() {
38-
return Default::default();
39-
}
40-
if data.len() < 2 {
41-
return T::from_inner(data[0].into_inner());
42-
}
43-
// Recursion
44-
for idx in 0..((data.len() + 1) / 2) {
45-
let idx1 = 2 * idx;
46-
let idx2 = min(idx1 + 1, data.len() - 1);
47-
let mut encoder = T::engine();
48-
data[idx1].consensus_encode(&mut encoder).expect("in-memory writers don't error");
49-
data[idx2].consensus_encode(&mut encoder).expect("in-memory writers don't error");
50-
data[idx] = T::from_engine(encoder);
42+
match hashes.len() {
43+
0 => None,
44+
1 => Some(hashes[0]),
45+
_ => Some(merkle_root_r(hashes)),
5146
}
52-
let half_len = data.len() / 2 + data.len() % 2;
53-
bitcoin_merkle_root_inline(&mut data[0..half_len])
5447
}
5548

56-
/// Calculates the merkle root of an iterator of hashes.
57-
pub fn bitcoin_merkle_root<T, I>(mut iter: I) -> T
49+
/// Calculates the merkle root of an iterator of *hashes*.
50+
///
51+
/// # Returns
52+
/// - `None` if `hashes` is empty. The merkle root of an empty tree of hashes is undefined.
53+
/// - `Some(hash)` if `hashes` contains one element. A single hash is by definition the merkle root.
54+
/// - `Some(merkle_root)` if length of `hashes` is greater than one.
55+
pub fn bitcoin_merkle_root<T, I>(mut hashes: I) -> Option<T>
5856
where T: Hash + Encodable,
5957
<T as Hash>::Engine: io::Write,
60-
I: ExactSizeIterator<Item = T>,
58+
I: Iterator<Item = T>,
6159
{
62-
// Base case
63-
if iter.len() == 0 {
64-
return Default::default();
65-
}
66-
if iter.len() == 1 {
67-
return T::from_inner(iter.next().unwrap().into_inner());
68-
}
69-
// Recursion
70-
let half_len = iter.len() / 2 + iter.len() % 2;
71-
let mut alloc = Vec::with_capacity(half_len);
72-
while let Some(hash1) = iter.next() {
60+
let first = hashes.next()?;
61+
let second = match hashes.next() {
62+
Some(second) => second,
63+
None => return Some(first),
64+
};
65+
66+
let mut hashes = iter::once(first).chain(iter::once(second)).chain(hashes);
67+
68+
// We need a local copy to pass to `merkle_root_r`. It's more efficient to do the first loop of
69+
// processing as we make the copy instead of copying the whole iterator.
70+
let (min, max) = hashes.size_hint();
71+
let mut alloc = Vec::with_capacity(max.unwrap_or(min) / 2 + 1);
72+
73+
while let Some(hash1) = hashes.next() {
7374
// If the size is odd, use the last element twice.
74-
let hash2 = iter.next().unwrap_or(hash1);
75+
let hash2 = hashes.next().unwrap_or(hash1);
7576
let mut encoder = T::engine();
7677
hash1.consensus_encode(&mut encoder).expect("in-memory writers don't error");
7778
hash2.consensus_encode(&mut encoder).expect("in-memory writers don't error");
7879
alloc.push(T::from_engine(encoder));
7980
}
80-
bitcoin_merkle_root_inline(&mut alloc)
81+
82+
Some(merkle_root_r(&mut alloc))
83+
}
84+
85+
// `hashes` must contain at least one hash.
86+
fn merkle_root_r<T>(hashes: &mut [T]) -> T
87+
where T: Hash + Encodable,
88+
<T as Hash>::Engine: io::Write,
89+
{
90+
if hashes.len() == 1 {
91+
return hashes[0]
92+
}
93+
94+
for idx in 0..((hashes.len() + 1) / 2) {
95+
let idx1 = 2 * idx;
96+
let idx2 = min(idx1 + 1, hashes.len() - 1);
97+
let mut encoder = T::engine();
98+
hashes[idx1].consensus_encode(&mut encoder).expect("in-memory writers don't error");
99+
hashes[idx2].consensus_encode(&mut encoder).expect("in-memory writers don't error");
100+
hashes[idx] = T::from_engine(encoder);
101+
}
102+
let half_len = hashes.len() / 2 + hashes.len() % 2;
103+
104+
merkle_root_r(&mut hashes[0..half_len])
81105
}
82106

83107
#[cfg(test)]
@@ -90,7 +114,7 @@ mod tests {
90114
use super::*;
91115

92116
#[test]
93-
fn both_merkel_root_functions_return_the_same_result() {
117+
fn both_merkle_root_functions_return_the_same_result() {
94118
// testnet block 000000000000045e0b1660b6445b5e5c5ab63c9a4f956be7e1e69be04fa4497b
95119
let segwit_block = Vec::from_hex("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").unwrap();
96120
let block: Block = deserialize(&segwit_block).expect("Failed to deserialize block");

‎src/util/merkleblock.rs

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -543,7 +543,7 @@ mod tests {
543543

544544
// Calculate the merkle root and height
545545
let hashes = txids.iter().map(|t| t.as_hash());
546-
let merkle_root_1: TxMerkleNode = bitcoin_merkle_root(hashes).into();
546+
let merkle_root_1: TxMerkleNode = bitcoin_merkle_root(hashes).expect("hashes is not empty").into();
547547
let mut height = 1;
548548
let mut ntx = num_tx;
549549
while ntx > 1 {

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