From 7dac91d973b4fc97e2ca2d0d894b46ec3e686ff3 Mon Sep 17 00:00:00 2001
From: Martin Habovstiak <martin.habovstiak@gmail.com>
Date: Tue, 31 Oct 2023 14:12:39 +0100
Subject: [PATCH 1/3] Deprecate `capacity` and `is_empty`

These functions always return the same value so are not useful and
actually calling them is a red flag.
---
 src/ecdsa/serialized_signature.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/ecdsa/serialized_signature.rs b/src/ecdsa/serialized_signature.rs
index 1b2a65a..bf71ecc 100644
--- a/src/ecdsa/serialized_signature.rs
+++ b/src/ecdsa/serialized_signature.rs
@@ -84,6 +84,7 @@ impl SerializedSignature {
     }
 
     /// Get the capacity of the underlying data buffer.
+    #[deprecated = "This always returns 72"]
     #[inline]
     pub fn capacity(&self) -> usize { self.data.len() }
 
@@ -106,6 +107,7 @@ impl SerializedSignature {
     pub fn from_signature(sig: &Signature) -> SerializedSignature { sig.serialize_der() }
 
     /// Check if the space is zero.
+    #[deprecated = "This always returns false"]
     #[inline]
     pub fn is_empty(&self) -> bool { self.len() == 0 }
 }

From dc3eab7aaa7082be4d598edc5a1e511f5f976a38 Mon Sep 17 00:00:00 2001
From: Martin Habovstiak <martin.habovstiak@gmail.com>
Date: Tue, 31 Oct 2023 14:17:18 +0100
Subject: [PATCH 2/3] Implement `Borrow<[u8]>`, `PartialEq<[u8]>`, `Hash`

These traits were missing and could be useful if e.g. one wants to store
serialized signatures in a set/map and access them using `[u8]`.
---
 src/ecdsa/serialized_signature.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/ecdsa/serialized_signature.rs b/src/ecdsa/serialized_signature.rs
index bf71ecc..1aba65f 100644
--- a/src/ecdsa/serialized_signature.rs
+++ b/src/ecdsa/serialized_signature.rs
@@ -7,6 +7,7 @@
 //! unable to run on platforms without allocator. We implement a special type to encapsulate
 //! serialized signatures and since it's a bit more complicated it has its own module.
 
+use core::borrow::Borrow;
 use core::{fmt, ops};
 
 pub use into_iter::IntoIter;
@@ -41,11 +42,30 @@ impl PartialEq for SerializedSignature {
     fn eq(&self, other: &SerializedSignature) -> bool { **self == **other }
 }
 
+impl PartialEq<[u8]> for SerializedSignature {
+    #[inline]
+    fn eq(&self, other: &[u8]) -> bool { **self == *other }
+}
+
+impl PartialEq<SerializedSignature> for [u8] {
+    #[inline]
+    fn eq(&self, other: &SerializedSignature) -> bool { *self == **other }
+}
+
+impl core::hash::Hash for SerializedSignature {
+    fn hash<H: core::hash::Hasher>(&self, state: &mut H) { (**self).hash(state) }
+}
+
 impl AsRef<[u8]> for SerializedSignature {
     #[inline]
     fn as_ref(&self) -> &[u8] { self }
 }
 
+impl Borrow<[u8]> for SerializedSignature {
+    #[inline]
+    fn borrow(&self) -> &[u8] { self }
+}
+
 impl ops::Deref for SerializedSignature {
     type Target = [u8];
 

From 62c839c9e03b5cacb7da34aecff6eefc29f8f293 Mon Sep 17 00:00:00 2001
From: Martin Habovstiak <martin.habovstiak@gmail.com>
Date: Tue, 31 Oct 2023 14:32:09 +0100
Subject: [PATCH 3/3] Implement conversion traits

Converting signature to serialized signature and back is natural, so the
conversion traits should be implemented.
---
 src/ecdsa/serialized_signature.rs | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/ecdsa/serialized_signature.rs b/src/ecdsa/serialized_signature.rs
index 1aba65f..bfd035f 100644
--- a/src/ecdsa/serialized_signature.rs
+++ b/src/ecdsa/serialized_signature.rs
@@ -8,6 +8,7 @@
 //! serialized signatures and since it's a bit more complicated it has its own module.
 
 use core::borrow::Borrow;
+use core::convert::TryFrom;
 use core::{fmt, ops};
 
 pub use into_iter::IntoIter;
@@ -91,6 +92,28 @@ impl<'a> IntoIterator for &'a SerializedSignature {
     fn into_iter(self) -> Self::IntoIter { self.iter() }
 }
 
+impl From<Signature> for SerializedSignature {
+    fn from(value: Signature) -> Self { Self::from_signature(&value) }
+}
+
+impl<'a> From<&'a Signature> for SerializedSignature {
+    fn from(value: &'a Signature) -> Self { Self::from_signature(value) }
+}
+
+impl TryFrom<SerializedSignature> for Signature {
+    type Error = Error;
+
+    fn try_from(value: SerializedSignature) -> Result<Self, Self::Error> { value.to_signature() }
+}
+
+impl<'a> TryFrom<&'a SerializedSignature> for Signature {
+    type Error = Error;
+
+    fn try_from(value: &'a SerializedSignature) -> Result<Self, Self::Error> {
+        value.to_signature()
+    }
+}
+
 impl SerializedSignature {
     /// Creates `SerializedSignature` from data and length.
     ///