Address review feedback

Author: sellout

src/interpreter.rs

@@ -20,7 +20,8 @@ bitflags::bitflags! {
     #[derive(Copy, Clone, Debug, PartialEq, Eq)]
     /// Script verification flags
     pub struct VerificationFlags: u32 {
-        /// Evaluate P2SH subscripts (softfork safe, BIP16).
+        /// Evaluate P2SH subscripts (softfork safe,
+        /// [BIP16](https://github.com/bitcoin/bips/blob/master/bip-0016.mediawiki).
         const P2SH = 1 << 0;
 
         /// Passing a non-strict-DER signature or one with undefined hashtype to a checksig operation causes script failure.
@@ -29,19 +30,19 @@ bitflags::bitflags! {
         const StrictEnc = 1 << 1;
 
         /// Passing a non-strict-DER signature or one with S > order/2 to a checksig operation causes script failure
-        /// (softfork safe, BIP62 rule 5).
+        /// (softfork safe, [BIP62](https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki) rule 5).
         const LowS = 1 << 3;
 
-        /// verify dummy stack item consumed by CHECKMULTISIG is of zero-length (softfork safe, BIP62 rule 7).
+        /// verify dummy stack item consumed by CHECKMULTISIG is of zero-length (softfork safe, [BIP62](https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki) rule 7).
         const NullDummy = 1 << 4;
 
-        /// Using a non-push operator in the scriptSig causes script failure (softfork safe, BIP62 rule 2).
+        /// Using a non-push operator in the scriptSig causes script failure (softfork safe, [BIP62](https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki) rule 2).
         const SigPushOnly = 1 << 5;
 
         /// Require minimal encodings for all push operations (OP_0... OP_16, OP_1NEGATE where possible, direct
         /// pushes up to 75 bytes, OP_PUSHDATA up to 255 bytes, OP_PUSHDATA2 for anything larger). Evaluating
-        /// any other push causes the script to fail (BIP62 rule 3).
-        /// In addition, whenever a stack element is interpreted as a number, it must be of minimal length (BIP62 rule 4).
+        /// any other push causes the script to fail ([BIP62](https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki) rule 3).
+        /// In addition, whenever a stack element is interpreted as a number, it must be of minimal length ([BIP62](https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki) rule 4).
         /// (softfork safe)
         const MinimalData = 1 << 6;
 
@@ -58,13 +59,13 @@ bitflags::bitflags! {
         /// Require that only a single stack element remains after evaluation. This changes the success criterion from
         /// "At least one stack element must remain, and when interpreted as a boolean, it must be true" to
         /// "Exactly one stack element must remain, and when interpreted as a boolean, it must be true".
-        /// (softfork safe, BIP62 rule 6)
+        /// (softfork safe, [BIP62](https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki) rule 6)
         /// Note: CLEANSTACK should never be used without P2SH.
         const CleanStack = 1 << 8;
 
         /// Verify CHECKLOCKTIMEVERIFY
         ///
-        /// See BIP65 for details.
+        /// See [BIP65](https://github.com/bitcoin/bips/blob/master/bip-0065.mediawiki) for details.
         const CHECKLOCKTIMEVERIFY = 1 << 9;
     }
 }

src/zcash_script.rs

@@ -18,6 +18,9 @@ pub enum Error {
     Unknown(u32),
 }
 
+/// All signature hashes are 32 bits, since they are necessarily produced by SHA256.
+pub const SIGHASH_SIZE: usize = 32;
+
 /// A function which is called to obtain the sighash.
 ///    - script_code: the scriptCode being validated. Note that this not always
 ///      matches script_sig, i.e. for P2SH.
@@ -27,7 +30,7 @@ pub enum Error {
 /// reporting, but returning `None` indicates _some_ failure to produce the desired hash.
 ///
 /// TODO: Can we get the “32” from somewhere rather than hardcoding it?
-pub type SighashCalculator<'a> = &'a dyn Fn(&[u8], HashType) -> Option<[u8; 32]>;
+pub type SighashCalculator<'a> = &'a dyn Fn(&[u8], HashType) -> Option<[u8; SIGHASH_SIZE]>;
 
 /// The external API of zcash_script. This is defined to make it possible to compare the C++ and
 /// Rust implementations.
@@ -45,7 +48,6 @@ pub trait ZcashScript {
     ///  - script_pub_key: the scriptPubKey of the output being spent.
     ///  - script_sig: the scriptSig of the input being validated.
     ///  - flags: the script verification flags to use.
-    ///  - err: if not NULL, err will contain an error/success code for the operation.
     ///
     ///  Note that script verification failure is indicated by `Err(Error::Ok)`.
     fn verify_callback(