Avoid calling libsecp serialization fns when calculating length

[rust-lightning] / lightning / src / util / ser.rs

diff --git a/lightning/src/util/ser.rs b/lightning/src/util/ser.rs
index e971c6c145142a1f677437afccc51bc107c287b8..61cd1e60de0ae0a57691fa8b5b858c766c451523 100644 (file)
--- a/lightning/src/util/ser.rs
+++ b/lightning/src/util/ser.rs
@@ -19,7 +19,7 @@ use core::cmp;
 
 use bitcoin::secp256k1::Signature;
 use bitcoin::secp256k1::key::{PublicKey, SecretKey};
-use bitcoin::secp256k1::constants::{PUBLIC_KEY_SIZE, COMPACT_SIGNATURE_SIZE};
+use bitcoin::secp256k1::constants::{PUBLIC_KEY_SIZE, SECRET_KEY_SIZE, COMPACT_SIGNATURE_SIZE};
 use bitcoin::blockdata::script::Script;
 use bitcoin::blockdata::transaction::{OutPoint, Transaction, TxOut};
 use bitcoin::consensus;
@@ -185,6 +185,16 @@ pub trait Writeable {
                msg.0[..2].copy_from_slice(&(len as u16 - 2).to_be_bytes());
                msg.0
        }
+
+       /// Gets the length of this object after it has been serialized. This can be overridden to
+       /// optimize cases where we prepend an object with its length.
+       // Note that LLVM optimizes this away in most cases! Check that it isn't before you override!
+       #[inline]
+       fn serialized_length(&self) -> usize {
+               let mut len_calc = LengthCalculatingWriter(0);
+               self.write(&mut len_calc).expect("No in-memory data may fail to serialize");
+               len_calc.0
+       }
 }
 
 impl<'a, T: Writeable> Writeable for &'a T {
@@ -561,6 +571,10 @@ impl Writeable for PublicKey {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                self.serialize().write(w)
        }
+       #[inline]
+       fn serialized_length(&self) -> usize {
+               PUBLIC_KEY_SIZE
+       }
 }
 
 impl Readable for PublicKey {
@@ -575,15 +589,19 @@ impl Readable for PublicKey {
 
 impl Writeable for SecretKey {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
-               let mut ser = [0; 32];
+               let mut ser = [0; SECRET_KEY_SIZE];
                ser.copy_from_slice(&self[..]);
                ser.write(w)
        }
+       #[inline]
+       fn serialized_length(&self) -> usize {
+               SECRET_KEY_SIZE
+       }
 }
 
 impl Readable for SecretKey {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
-               let buf: [u8; 32] = Readable::read(r)?;
+               let buf: [u8; SECRET_KEY_SIZE] = Readable::read(r)?;
                match SecretKey::from_slice(&buf) {
                        Ok(key) => Ok(key),
                        Err(_) => return Err(DecodeError::InvalidValue),
@@ -610,6 +628,10 @@ impl Writeable for Signature {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                self.serialize_compact().write(w)
        }
+       #[inline]
+       fn serialized_length(&self) -> usize {
+               COMPACT_SIGNATURE_SIZE
+       }
 }
 
 impl Readable for Signature {
@@ -666,9 +688,7 @@ impl<T: Writeable> Writeable for Option<T> {
                match *self {
                        None => 0u8.write(w)?,
                        Some(ref data) => {
-                               let mut len_calc = LengthCalculatingWriter(0);
-                               data.write(&mut len_calc).expect("No in-memory data may fail to serialize");
-                               BigSize(len_calc.0 as u64 + 1).write(w)?;
+                               BigSize(data.serialized_length() as u64 + 1).write(w)?;
                                data.write(w)?;
                        }
                }