Merge rust-bitcoin/rust-bitcoin#3438: Implement Arbitrary for Block

0c824c9c68 Implement Arbitrary for Block (Shing Him Ng)

Pull request description:

  Implementing `Arbitrary` for `Block` and its child types

ACKs for top commit:
  apoelstra:
    ACK 0c824c9c68 successfully ran local tests
  tcharding:
    ACK 0c824c9c68

Tree-SHA512: 407acd4155ca7496bf7c59af19f103b22b4c74dd013c2e2c42aae690ba7264ecd42ed034355cf8895f2532f8cef77dfdbeac250301a6973afd5f3920be7e4310

bitcoin/src/blockdata/block.rs

@@ -12,6 +12,8 @@ use core::fmt;
 use hashes::{sha256d, HashEngine};
 use internals::compact_size;
 use io::{BufRead, Write};
+#[cfg(feature = "arbitrary")]
+use arbitrary::{Arbitrary, Unstructured};
 
 use super::Weight;
 use crate::consensus::{encode, Decodable, Encodable};
@@ -400,6 +402,30 @@ impl std::error::Error for ValidationError {
     }
 }
 
+#[cfg(feature = "arbitrary")]
+impl<'a> Arbitrary<'a> for Header {
+    fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> {
+        Ok(Header {
+            version: Version::arbitrary(u)?,
+            prev_blockhash: BlockHash::from_byte_array(u.arbitrary()?),
+            merkle_root: TxMerkleNode::from_byte_array(u.arbitrary()?),
+            time: u.arbitrary()?,
+            bits: CompactTarget::from_consensus(u.arbitrary()?),
+            nonce: u.arbitrary()?
+        })
+    }
+}
+
+#[cfg(feature = "arbitrary")]
+impl<'a> Arbitrary<'a> for Block {
+    fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> {
+        Ok(Block {
+            header: Header::arbitrary(u)?,
+            txdata: Vec::<Transaction>::arbitrary(u)?,
+        })
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use hex::{test_hex_unwrap as hex, FromHex};

primitives/src/block.rs

@@ -8,6 +8,8 @@
 //! these blocks and the blockchain.
 
 use hashes::sha256d;
+#[cfg(feature = "arbitrary")]
+use arbitrary::{Arbitrary, Unstructured};
 
 /// Bitcoin block version number.
 ///
@@ -90,3 +92,17 @@ impl BlockHash {
     /// Dummy hash used as the previous blockhash of the genesis block.
     pub const GENESIS_PREVIOUS_BLOCK_HASH: Self = Self::from_byte_array([0; 32]);
 }
+
+#[cfg(feature = "arbitrary")]
+impl<'a> Arbitrary<'a> for Version {
+    fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> {
+        // Equally weight known versions and arbitrary versions
+        let choice = u.int_in_range(0..=3)?;
+        match choice {
+            0 => Ok(Version::ONE),
+            1 => Ok(Version::TWO),
+            2 => Ok(Version::NO_SOFT_FORK_SIGNALLING),
+            _ => Ok(Version::from_consensus(u.arbitrary()?))
+        }
+    }
+}