From 83611295187f951290bec41a9c4831dcdaa5edad Mon Sep 17 00:00:00 2001
From: sanket1729 <sanket1729@gmail.com>
Date: Mon, 15 Nov 2021 16:00:12 -0800
Subject: [PATCH] Add SchnorrSig type

Export Sigs/Sigerrors
---
 src/lib.rs          |  4 +-
 src/util/schnorr.rs | 91 ++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 91 insertions(+), 4 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index aad5e612..8502c6b3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -135,8 +135,8 @@ pub use util::amount::SignedAmount;
 pub use util::merkleblock::MerkleBlock;
 pub use util::sighash::SchnorrSigHashType;
 
-pub use util::ecdsa;
-pub use util::schnorr;
+pub use util::ecdsa::{self, EcdsaSig, EcdsaSigError};
+pub use util::schnorr::{self, SchnorrSig, SchnorrSigError};
 #[deprecated(since = "0.26.1", note = "Please use `ecdsa::PrivateKey` instead")]
 pub use util::ecdsa::PrivateKey;
 #[deprecated(since = "0.26.1", note = "Please use `ecdsa::PublicKey` instead")]
diff --git a/src/util/schnorr.rs b/src/util/schnorr.rs
index 2a2bc19f..10455524 100644
--- a/src/util/schnorr.rs
+++ b/src/util/schnorr.rs
@@ -17,11 +17,14 @@
 //! Schnorr key types.
 //!
 
+use core::fmt;
+use prelude::*;
+
 pub use secp256k1::schnorrsig::{PublicKey, KeyPair};
-use secp256k1::{Secp256k1, Verification, constants};
+use secp256k1::{self, Secp256k1, Verification, constants};
 use hashes::Hash;
 use util::taproot::{TapBranchHash, TapTweakHash};
-use core::fmt;
+use SchnorrSigHashType;
 
 /// Untweaked Schnorr public key
 pub type UntweakedPublicKey = PublicKey;
@@ -104,3 +107,87 @@ impl TweakedPublicKey {
         self.0.serialize()
     }
 }
+
+/// A BIP340-341 serialized schnorr signature with the corresponding hash type.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
+pub struct SchnorrSig {
+    /// The underlying schnorr signature
+    pub sig: secp256k1::schnorrsig::Signature,
+    /// The corresponding hash type
+    pub hash_ty: SchnorrSigHashType,
+}
+
+impl SchnorrSig {
+
+    /// Deserialize from slice
+    pub fn from_slice(sl: &[u8]) -> Result<Self, SchnorrSigError> {
+        match sl.len() {
+            64 => {
+                // default type
+                let sig = secp256k1::schnorrsig::Signature::from_slice(sl)
+                    .map_err(SchnorrSigError::Secp256k1)?;
+                return Ok( SchnorrSig { sig, hash_ty : SchnorrSigHashType::Default });
+            },
+            65 => {
+                let (hash_ty, sig) = sl.split_last().expect("Slice len checked == 65");
+                let hash_ty = SchnorrSigHashType::from_u8(*hash_ty)
+                    .map_err(|_| SchnorrSigError::InvalidSighashType(*hash_ty))?;
+                let sig = secp256k1::schnorrsig::Signature::from_slice(sig)
+                    .map_err(SchnorrSigError::Secp256k1)?;
+                Ok(SchnorrSig { sig, hash_ty })
+            }
+            len => {
+                Err(SchnorrSigError::InvalidSchnorrSigSize(len))
+            }
+        }
+    }
+
+    /// Serialize SchnorrSig
+    pub fn to_vec(&self) -> Vec<u8> {
+        // TODO: add support to serialize to a writer to SerializedSig
+        let mut ser_sig = self.sig.as_ref().to_vec();
+        if self.hash_ty == SchnorrSigHashType::Default {
+            // default sighash type, don't add extra sighash byte
+        } else {
+            ser_sig.push(self.hash_ty as u8);
+        }
+        ser_sig
+    }
+
+}
+
+/// A schnorr sig related error.
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub enum SchnorrSigError {
+    /// Base58 encoding error
+    InvalidSighashType(u8),
+    /// Signature has valid size but does not parse correctly
+    Secp256k1(secp256k1::Error),
+    /// Invalid schnorr signature size
+    InvalidSchnorrSigSize(usize),
+}
+
+
+impl fmt::Display for SchnorrSigError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            SchnorrSigError::InvalidSighashType(hash_ty) =>
+                write!(f, "Invalid signature hash type {}", hash_ty),
+            SchnorrSigError::Secp256k1(ref e) =>
+                write!(f, "Schnorr Signature has correct len, but is malformed : {}", e),
+            SchnorrSigError::InvalidSchnorrSigSize(sz) =>
+                write!(f, "Invalid Schnorr signature size: {}", sz),
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
+impl ::std::error::Error for SchnorrSigError {}
+
+impl From<secp256k1::Error> for SchnorrSigError {
+
+    fn from(e: secp256k1::Error) -> SchnorrSigError {
+        SchnorrSigError::Secp256k1(e)
+    }
+}