From 1b0988833a34bd45ec945c165dc01677e23c00f2 Mon Sep 17 00:00:00 2001
From: Martin Habovstiak <martin.habovstiak@gmail.com>
Date: Sat, 7 Jan 2023 16:39:11 +0100
Subject: [PATCH] Remove `ToHex`

The `ToHex` trait was replaced by either simple `Display`/`LowerHex`
where appropriate or `DisplayHex` from `bitcoin_internals` which is
faster.

This change replaces the usages and removes the trait.
---
 bitcoin/src/address.rs             |   3 +-
 bitcoin/src/blockdata/constants.rs |  17 ++--
 bitcoin/src/blockdata/script.rs    |  70 ++++++-------
 bitcoin/src/blockdata/witness.rs   |  19 ++--
 bitcoin/src/consensus/encode.rs    |   6 +-
 bitcoin/src/crypto/ecdsa.rs        |   5 +-
 bitcoin/src/crypto/key.rs          |   8 +-
 bitcoin/src/internal_macros.rs     |  18 ++--
 bitcoin/src/merkle_tree/block.rs   |   5 +-
 bitcoin/src/pow.rs                 |  24 ++---
 bitcoin/src/psbt/raw.rs            |   5 +-
 bitcoin/src/psbt/serialize.rs      |   3 +-
 bitcoin/src/serde_utils.rs         |  22 +++-
 bitcoin/src/sighash.rs             |   4 +-
 bitcoin/src/sign_message.rs        |   3 +-
 bitcoin/src/taproot.rs             |  23 +++--
 hashes/Cargo.toml                  |   4 +-
 hashes/embedded/src/main.rs        |   4 +-
 hashes/src/hash160.rs              |   4 +-
 hashes/src/hex.rs                  | 158 ++---------------------------
 hashes/src/ripemd160.rs            |   4 +-
 hashes/src/sha1.rs                 |   4 +-
 hashes/src/sha256.rs               |   4 +-
 hashes/src/sha256d.rs              |   4 +-
 hashes/src/sha256t.rs              |   6 +-
 hashes/src/sha512.rs               |   4 +-
 hashes/src/sha512_256.rs           |   4 +-
 internals/src/hex/display.rs       |  17 ++++
 28 files changed, 171 insertions(+), 281 deletions(-)

diff --git a/bitcoin/src/address.rs b/bitcoin/src/address.rs
index 9caa972f..b1d1460d 100644
--- a/bitcoin/src/address.rs
+++ b/bitcoin/src/address.rs
@@ -885,7 +885,6 @@ mod tests {
 
     use super::*;
     use crate::crypto::key::PublicKey;
-    use crate::hashes::hex::ToHex;
     use crate::internal_macros::{hex, hex_into, hex_script};
     use crate::network::constants::Network::{Bitcoin, Testnet};
 
@@ -1078,7 +1077,7 @@ mod tests {
         ];
         for vector in &valid_vectors {
             let addr: Address = vector.0.parse().unwrap();
-            assert_eq!(&addr.script_pubkey().as_bytes().to_hex(), vector.1);
+            assert_eq!(&addr.script_pubkey().to_hex_string(), vector.1);
             roundtrips(&addr);
         }
 
diff --git a/bitcoin/src/blockdata/constants.rs b/bitcoin/src/blockdata/constants.rs
index 3eeb9e03..4e7b8e39 100644
--- a/bitcoin/src/blockdata/constants.rs
+++ b/bitcoin/src/blockdata/constants.rs
@@ -192,7 +192,6 @@ impl ChainHash {
 #[cfg(test)]
 mod test {
     use super::*;
-    use crate::hashes::hex::ToHex;
     use crate::network::constants::Network;
     use crate::consensus::encode::serialize;
     use crate::blockdata::locktime::absolute;
@@ -216,7 +215,7 @@ mod test {
         assert_eq!(gen.output[0].value, 50 * COIN_VALUE);
         assert_eq!(gen.lock_time, absolute::LockTime::ZERO);
 
-        assert_eq!(gen.wtxid().to_hex(), "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b");
+        assert_eq!(gen.wtxid().to_string(), "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b");
     }
 
     #[test]
@@ -225,12 +224,12 @@ mod test {
 
         assert_eq!(gen.header.version, block::Version::ONE);
         assert_eq!(gen.header.prev_blockhash, Hash::all_zeros());
-        assert_eq!(gen.header.merkle_root.to_hex(), "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b");
+        assert_eq!(gen.header.merkle_root.to_string(), "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b");
 
         assert_eq!(gen.header.time, 1231006505);
         assert_eq!(gen.header.bits, CompactTarget::from_consensus(0x1d00ffff));
         assert_eq!(gen.header.nonce, 2083236893);
-        assert_eq!(gen.header.block_hash().to_hex(), "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f");
+        assert_eq!(gen.header.block_hash().to_string(), "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f");
     }
 
     #[test]
@@ -238,11 +237,11 @@ mod test {
         let gen = genesis_block(Network::Testnet);
         assert_eq!(gen.header.version, block::Version::ONE);
         assert_eq!(gen.header.prev_blockhash, Hash::all_zeros());
-        assert_eq!(gen.header.merkle_root.to_hex(), "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b");
+        assert_eq!(gen.header.merkle_root.to_string(), "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b");
         assert_eq!(gen.header.time, 1296688602);
         assert_eq!(gen.header.bits, CompactTarget::from_consensus(0x1d00ffff));
         assert_eq!(gen.header.nonce, 414098458);
-        assert_eq!(gen.header.block_hash().to_hex(), "000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943");
+        assert_eq!(gen.header.block_hash().to_string(), "000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943");
     }
 
     #[test]
@@ -250,11 +249,11 @@ mod test {
         let gen = genesis_block(Network::Signet);
         assert_eq!(gen.header.version, block::Version::ONE);
         assert_eq!(gen.header.prev_blockhash, Hash::all_zeros());
-        assert_eq!(gen.header.merkle_root.to_hex(), "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b");
+        assert_eq!(gen.header.merkle_root.to_string(), "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b");
         assert_eq!(gen.header.time, 1598918400);
         assert_eq!(gen.header.bits, CompactTarget::from_consensus(0x1e0377ae));
         assert_eq!(gen.header.nonce, 52613770);
-        assert_eq!(gen.header.block_hash().to_hex(), "00000008819873e925422c1ff0f99f7cc9bbb232af63a077a480a3633bee1ef6");
+        assert_eq!(gen.header.block_hash().to_string(), "00000008819873e925422c1ff0f99f7cc9bbb232af63a077a480a3633bee1ef6");
     }
 
     // The *_chain_hash tests are sanity/regression tests, they verify that the const byte array
@@ -304,7 +303,7 @@ mod test {
     // Test vector taken from: https://github.com/lightning/bolts/blob/master/00-introduction.md
     #[test]
     fn mainnet_chain_hash_test_vector() {
-        let got = ChainHash::using_genesis_block(Network::Bitcoin).to_hex();
+        let got = ChainHash::using_genesis_block(Network::Bitcoin).to_string();
         let want = "6fe28c0ab6f1b372c1a6a246ae63f74f931e8365e15a089c68d6190000000000";
         assert_eq!(got, want);
     }
diff --git a/bitcoin/src/blockdata/script.rs b/bitcoin/src/blockdata/script.rs
index 454d0c35..360ed744 100644
--- a/bitcoin/src/blockdata/script.rs
+++ b/bitcoin/src/blockdata/script.rs
@@ -53,6 +53,7 @@ use crate::prelude::*;
 use alloc::rc::Rc;
 use alloc::sync::Arc;
 use bitcoin_internals::debug_from_display;
+use bitcoin_internals::hex::display::DisplayHex;
 use crate::io;
 use core::cmp::Ordering;
 use core::convert::TryFrom;
@@ -61,7 +62,6 @@ use core::{fmt, default::Default};
 use core::ops::{Deref, DerefMut, Index, Range, RangeFull, RangeFrom, RangeTo, RangeInclusive, RangeToInclusive};
 #[cfg(feature = "rust_v_1_53")]
 use core::ops::Bound;
-use bitcoin_hashes::hex::ToHex;
 
 #[cfg(feature = "serde")] use serde;
 
@@ -485,6 +485,15 @@ impl Script {
         buf
     }
 
+    /// Formats the script as lower-case hex.
+    ///
+    /// This is a more convenient and performant way to write `format!("{:x}", script)`.
+    /// For better performance you should generally prefer displaying the script but if `String` is
+    /// required (this is common in tests) this method is can be used.
+    pub fn to_hex_string(&self) -> String {
+        self.as_bytes().to_lower_hex_string()
+    }
+
     /// Returns the first opcode of the script (if there is any).
     pub fn first_opcode(&self) -> Option<opcodes::All> {
         self.as_bytes().first().copied().map(From::from)
@@ -553,13 +562,6 @@ impl<'a> From<&'a Script> for Rc<Script> {
     }
 }
 
-impl ToHex for Script {
-    #[inline]
-    fn to_hex(&self) -> String {
-        self.0.to_hex()
-    }
-}
-
 /// Iterator over bytes of a script
 pub struct Bytes<'a>(core::iter::Copied<core::slice::Iter<'a, u8>>);
 
@@ -662,19 +664,13 @@ impl fmt::Display for Script {
 
 impl fmt::LowerHex for Script {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        for ch in self.bytes() {
-            write!(f, "{:02x}", ch)?;
-        }
-        Ok(())
+        fmt::LowerHex::fmt(&self.as_bytes().as_hex(), f)
     }
 }
 
 impl fmt::UpperHex for Script {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        for ch in self.bytes() {
-            write!(f, "{:02X}", ch)?;
-        }
-        Ok(())
+        fmt::UpperHex::fmt(&self.as_bytes().as_hex(), f)
     }
 }
 
@@ -1873,7 +1869,7 @@ impl serde::Serialize for Script {
         S: serde::Serializer,
     {
         if serializer.is_human_readable() {
-            serializer.serialize_str(&self.to_hex())
+            serializer.collect_str(&format_args!("{:x}", self))
         } else {
             serializer.serialize_bytes(self.as_bytes())
         }
@@ -2011,7 +2007,7 @@ mod test {
     use super::*;
     use super::write_scriptint;
 
-    use crate::hashes::hex::{FromHex, ToHex};
+    use crate::hashes::hex::FromHex;
     use crate::consensus::encode::{deserialize, serialize};
     use crate::blockdata::opcodes;
     use crate::crypto::key::PublicKey;
@@ -2209,7 +2205,7 @@ mod test {
                                    .push_opcode(OP_EQUALVERIFY)
                                    .push_opcode(OP_CHECKSIG)
                                    .into_script();
-        assert_eq!(script.to_hex(), "76a91416e1ae70ff0fa102905d4af297f6912bda6cce1988ac");
+        assert_eq!(script.to_hex_string(), "76a91416e1ae70ff0fa102905d4af297f6912bda6cce1988ac");
     }
 
     #[test]
@@ -2241,7 +2237,7 @@ mod test {
         let data = Vec::<u8>::from_hex("aa21a9ed20280f53f2d21663cac89e6bd2ad19edbabb048cda08e73ed19e9268d0afea2a").unwrap();
         let op_return = ScriptBuf::new_op_return(&data);
         assert!(op_return.is_op_return());
-        assert_eq!(op_return.to_hex(), "6a24aa21a9ed20280f53f2d21663cac89e6bd2ad19edbabb048cda08e73ed19e9268d0afea2a");
+        assert_eq!(op_return.to_hex_string(), "6a24aa21a9ed20280f53f2d21663cac89e6bd2ad19edbabb048cda08e73ed19e9268d0afea2a");
     }
 
     #[test]
@@ -2249,71 +2245,71 @@ mod test {
         let simple = Builder::new()
             .push_verify()
             .into_script();
-        assert_eq!(simple.to_hex(), "69");
+        assert_eq!(simple.to_hex_string(), "69");
         let simple2 = Builder::from(vec![])
             .push_verify()
             .into_script();
-        assert_eq!(simple2.to_hex(), "69");
+        assert_eq!(simple2.to_hex_string(), "69");
 
         let nonverify = Builder::new()
             .push_verify()
             .push_verify()
             .into_script();
-        assert_eq!(nonverify.to_hex(), "6969");
+        assert_eq!(nonverify.to_hex_string(), "6969");
         let nonverify2 = Builder::from(vec![0x69])
             .push_verify()
             .into_script();
-        assert_eq!(nonverify2.to_hex(), "6969");
+        assert_eq!(nonverify2.to_hex_string(), "6969");
 
         let equal = Builder::new()
             .push_opcode(OP_EQUAL)
             .push_verify()
             .into_script();
-        assert_eq!(equal.to_hex(), "88");
+        assert_eq!(equal.to_hex_string(), "88");
         let equal2 = Builder::from(vec![0x87])
             .push_verify()
             .into_script();
-        assert_eq!(equal2.to_hex(), "88");
+        assert_eq!(equal2.to_hex_string(), "88");
 
         let numequal = Builder::new()
             .push_opcode(OP_NUMEQUAL)
             .push_verify()
             .into_script();
-        assert_eq!(numequal.to_hex(), "9d");
+        assert_eq!(numequal.to_hex_string(), "9d");
         let numequal2 = Builder::from(vec![0x9c])
             .push_verify()
             .into_script();
-        assert_eq!(numequal2.to_hex(), "9d");
+        assert_eq!(numequal2.to_hex_string(), "9d");
 
         let checksig = Builder::new()
             .push_opcode(OP_CHECKSIG)
             .push_verify()
             .into_script();
-        assert_eq!(checksig.to_hex(), "ad");
+        assert_eq!(checksig.to_hex_string(), "ad");
         let checksig2 = Builder::from(vec![0xac])
             .push_verify()
             .into_script();
-        assert_eq!(checksig2.to_hex(), "ad");
+        assert_eq!(checksig2.to_hex_string(), "ad");
 
         let checkmultisig = Builder::new()
             .push_opcode(OP_CHECKMULTISIG)
             .push_verify()
             .into_script();
-        assert_eq!(checkmultisig.to_hex(), "af");
+        assert_eq!(checkmultisig.to_hex_string(), "af");
         let checkmultisig2 = Builder::from(vec![0xae])
             .push_verify()
             .into_script();
-        assert_eq!(checkmultisig2.to_hex(), "af");
+        assert_eq!(checkmultisig2.to_hex_string(), "af");
 
         let trick_slice = Builder::new()
             .push_slice(&[0xae]) // OP_CHECKMULTISIG
             .push_verify()
             .into_script();
-        assert_eq!(trick_slice.to_hex(), "01ae69");
+        assert_eq!(trick_slice.to_hex_string(), "01ae69");
         let trick_slice2 = Builder::from(vec![0x01, 0xae])
             .push_verify()
             .into_script();
-        assert_eq!(trick_slice2.to_hex(), "01ae69");
+        assert_eq!(trick_slice2.to_hex_string(), "01ae69");
    }
 
     #[test]
@@ -2361,10 +2357,10 @@ mod test {
     #[test]
     fn script_hashes() {
         let script = hex_script!("410446ef0102d1ec5240f0d061a4246c1bdef63fc3dbab7733052fbbf0ecd8f41fc26bf049ebb4f9527f374280259e7cfa99c48b0e3f39c51347a19a5819651503a5ac");
-        assert_eq!(script.script_hash().to_hex(), "8292bcfbef1884f73c813dfe9c82fd7e814291ea");
-        assert_eq!(script.wscript_hash().to_hex(), "3e1525eb183ad4f9b3c5fa3175bdca2a52e947b135bbb90383bf9f6408e2c324");
+        assert_eq!(script.script_hash().to_string(), "8292bcfbef1884f73c813dfe9c82fd7e814291ea");
+        assert_eq!(script.wscript_hash().to_string(), "3e1525eb183ad4f9b3c5fa3175bdca2a52e947b135bbb90383bf9f6408e2c324");
 	assert_eq!(
-	    hex_script!("20d85a959b0290bf19bb89ed43c916be835475d013da4b362117393e25a48229b8ac").tapscript_leaf_hash().to_hex(),
+	    hex_script!("20d85a959b0290bf19bb89ed43c916be835475d013da4b362117393e25a48229b8ac").tapscript_leaf_hash().to_string(),
 	    "5b75adecf53548f3ec6ad7d78383bf84cc57b55a3127c72b9a2481752dd88b21"
 	);
     }
diff --git a/bitcoin/src/blockdata/witness.rs b/bitcoin/src/blockdata/witness.rs
index afe1f1d6..ff1168c4 100644
--- a/bitcoin/src/blockdata/witness.rs
+++ b/bitcoin/src/blockdata/witness.rs
@@ -388,7 +388,6 @@ impl serde::Serialize for Witness {
     where
         S: serde::Serializer,
     {
-        use crate::hashes::hex::ToHex;
         use serde::ser::SerializeSeq;
 
         let human_readable = serializer.is_human_readable();
@@ -396,7 +395,7 @@ impl serde::Serialize for Witness {
 
         for elem in self.iter() {
             if human_readable {
-                seq.serialize_element(&elem.to_hex())?;
+                seq.serialize_element(&crate::serde_utils::SerializeBytesAsHex(elem))?;
             } else {
                 seq.serialize_element(&elem)?;
             }
@@ -490,8 +489,8 @@ impl From<Vec<&[u8]>> for Witness {
 mod test {
     use super::*;
 
+    use bitcoin_internals::hex::display::DisplayHex;
     use crate::consensus::{deserialize, serialize};
-    use crate::hashes::hex::ToHex;
     use crate::internal_macros::hex;
     use crate::Transaction;
     use crate::secp256k1::ecdsa;
@@ -654,15 +653,15 @@ mod test {
 
         let expected_wit = ["304502210084622878c94f4c356ce49c8e33a063ec90f6ee9c0208540888cfab056cd1fca9022014e8dbfdfa46d318c6887afd92dcfa54510e057565e091d64d2ee3a66488f82c01", "026e181ffb98ebfe5a64c983073398ea4bcd1548e7b971b4c175346a25a1c12e95"];
         for (i, wit_el) in tx.input[0].witness.iter().enumerate() {
-            assert_eq!(expected_wit[i], wit_el.to_hex());
+            assert_eq!(expected_wit[i], wit_el.to_lower_hex_string());
         }
-        assert_eq!(expected_wit[1], tx.input[0].witness.last().unwrap().to_hex());
-        assert_eq!(expected_wit[0], tx.input[0].witness.second_to_last().unwrap().to_hex());
-        assert_eq!(expected_wit[0], tx.input[0].witness.nth(0).unwrap().to_hex());
-        assert_eq!(expected_wit[1], tx.input[0].witness.nth(1).unwrap().to_hex());
+        assert_eq!(expected_wit[1], tx.input[0].witness.last().unwrap().to_lower_hex_string());
+        assert_eq!(expected_wit[0], tx.input[0].witness.second_to_last().unwrap().to_lower_hex_string());
+        assert_eq!(expected_wit[0], tx.input[0].witness.nth(0).unwrap().to_lower_hex_string());
+        assert_eq!(expected_wit[1], tx.input[0].witness.nth(1).unwrap().to_lower_hex_string());
         assert_eq!(None, tx.input[0].witness.nth(2));
-        assert_eq!(expected_wit[0], tx.input[0].witness[0].to_hex());
-        assert_eq!(expected_wit[1], tx.input[0].witness[1].to_hex());
+        assert_eq!(expected_wit[0], tx.input[0].witness[0].to_lower_hex_string());
+        assert_eq!(expected_wit[1], tx.input[0].witness[1].to_lower_hex_string());
 
         let tx_bytes_back = serialize(&tx);
         assert_eq!(tx_bytes_back, tx_bytes);
diff --git a/bitcoin/src/consensus/encode.rs b/bitcoin/src/consensus/encode.rs
index 30200d3f..c19fb6c3 100644
--- a/bitcoin/src/consensus/encode.rs
+++ b/bitcoin/src/consensus/encode.rs
@@ -21,6 +21,7 @@ use crate::prelude::*;
 use core::{fmt, mem, u32, convert::From};
 
 use bitcoin_internals::write_err;
+use bitcoin_internals::hex::display::DisplayHex;
 
 use crate::hashes::{sha256d, Hash, sha256};
 use crate::hash_types::{BlockHash, FilterHash, TxMerkleNode, FilterHeader};
@@ -29,7 +30,6 @@ use crate::io::{self, Cursor, Read};
 use crate::psbt;
 use crate::bip152::{ShortId, PrefilledTransaction};
 use crate::taproot::TapLeafHash;
-use crate::hashes::hex::ToHex;
 
 use crate::blockdata::transaction::{TxOut, Transaction, TxIn};
 #[cfg(feature = "std")]
@@ -73,7 +73,7 @@ impl fmt::Display for Error {
             Error::OversizedVectorAllocation { requested: ref r, max: ref m } => write!(f,
                 "allocation of oversized vector: requested {}, maximum {}", r, m),
             Error::InvalidChecksum { expected: ref e, actual: ref a } => write!(f,
-                "invalid checksum: expected {}, actual {}", e.to_hex(), a.to_hex()),
+                "invalid checksum: expected {:x}, actual {:x}", e.as_hex(), a.as_hex()),
             Error::NonMinimalVarInt => write!(f, "non-minimal varint"),
             Error::ParseFailed(ref s) => write!(f, "parse failed: {}", s),
             Error::UnsupportedSegwitFlag(ref swflag) => write!(f,
@@ -124,7 +124,7 @@ pub fn serialize<T: Encodable + ?Sized>(data: &T) -> Vec<u8> {
 
 /// Encodes an object into a hex-encoded string.
 pub fn serialize_hex<T: Encodable + ?Sized>(data: &T) -> String {
-    serialize(data)[..].to_hex()
+    serialize(data).to_lower_hex_string()
 }
 
 /// Deserializes an object from a vector, will error if said deserialization
diff --git a/bitcoin/src/crypto/ecdsa.rs b/bitcoin/src/crypto/ecdsa.rs
index 8a8cc7d6..a0420098 100644
--- a/bitcoin/src/crypto/ecdsa.rs
+++ b/bitcoin/src/crypto/ecdsa.rs
@@ -9,6 +9,7 @@ use core::str::FromStr;
 use core::{fmt, iter};
 
 use bitcoin_internals::write_err;
+use bitcoin_internals::hex::display::DisplayHex;
 use secp256k1;
 
 use crate::prelude::*;
@@ -58,8 +59,8 @@ impl Signature {
 
 impl fmt::Display for Signature {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        hex::format_hex(&self.sig.serialize_der(), f)?;
-        hex::format_hex(&[self.hash_ty as u8], f)
+        fmt::LowerHex::fmt(&self.sig.serialize_der().as_hex(), f)?;
+        fmt::LowerHex::fmt(&[self.hash_ty as u8].as_hex(), f)
     }
 }
 
diff --git a/bitcoin/src/crypto/key.rs b/bitcoin/src/crypto/key.rs
index 6c91efa4..52075794 100644
--- a/bitcoin/src/crypto/key.rs
+++ b/bitcoin/src/crypto/key.rs
@@ -548,7 +548,7 @@ mod tests {
     use super::{PrivateKey, PublicKey, SortKey};
     use secp256k1::Secp256k1;
     use std::str::FromStr;
-    use crate::hashes::hex::{FromHex, ToHex};
+    use crate::hashes::hex::FromHex;
     use crate::network::constants::Network::Testnet;
     use crate::network::constants::Network::Bitcoin;
     use crate::address::Address;
@@ -593,15 +593,15 @@ mod tests {
     fn test_pubkey_hash() {
         let pk = PublicKey::from_str("032e58afe51f9ed8ad3cc7897f634d881fdbe49a81564629ded8156bebd2ffd1af").unwrap();
         let upk = PublicKey::from_str("042e58afe51f9ed8ad3cc7897f634d881fdbe49a81564629ded8156bebd2ffd1af191923a2964c177f5b5923ae500fca49e99492d534aa3759d6b25a8bc971b133").unwrap();
-        assert_eq!(pk.pubkey_hash().to_hex(), "9511aa27ef39bbfa4e4f3dd15f4d66ea57f475b4");
-        assert_eq!(upk.pubkey_hash().to_hex(), "ac2e7daf42d2c97418fd9f78af2de552bb9c6a7a");
+        assert_eq!(pk.pubkey_hash().to_string(), "9511aa27ef39bbfa4e4f3dd15f4d66ea57f475b4");
+        assert_eq!(upk.pubkey_hash().to_string(), "ac2e7daf42d2c97418fd9f78af2de552bb9c6a7a");
     }
 
     #[test]
     fn test_wpubkey_hash() {
         let pk = PublicKey::from_str("032e58afe51f9ed8ad3cc7897f634d881fdbe49a81564629ded8156bebd2ffd1af").unwrap();
         let upk = PublicKey::from_str("042e58afe51f9ed8ad3cc7897f634d881fdbe49a81564629ded8156bebd2ffd1af191923a2964c177f5b5923ae500fca49e99492d534aa3759d6b25a8bc971b133").unwrap();
-        assert_eq!(pk.wpubkey_hash().unwrap().to_hex(), "9511aa27ef39bbfa4e4f3dd15f4d66ea57f475b4");
+        assert_eq!(pk.wpubkey_hash().unwrap().to_string(), "9511aa27ef39bbfa4e4f3dd15f4d66ea57f475b4");
         assert_eq!(upk.wpubkey_hash(), None);
     }
 
diff --git a/bitcoin/src/internal_macros.rs b/bitcoin/src/internal_macros.rs
index 2ae036e7..0afc9198 100644
--- a/bitcoin/src/internal_macros.rs
+++ b/bitcoin/src/internal_macros.rs
@@ -109,7 +109,8 @@ mod test_macros {
 
 /// Implements several traits for byte-based newtypes.
 /// Implements:
-/// - core::fmt::LowerHex (implies hashes::hex::ToHex)
+/// - core::fmt::LowerHex
+/// - core::fmt::UpperHex
 /// - core::fmt::Display
 /// - core::str::FromStr
 /// - hashes::hex::FromHex
@@ -134,10 +135,15 @@ macro_rules! impl_bytes_newtype {
 
         impl core::fmt::LowerHex for $t {
             fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
-                for &ch in self.0.iter() {
-                    write!(f, "{:02x}", ch)?;
-                }
-                Ok(())
+                use bitcoin_internals::hex::{Case, display};
+                display::fmt_hex_exact!(f, $len, &self.0, Case::Lower)
+            }
+        }
+
+        impl core::fmt::UpperHex for $t {
+            fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+                use bitcoin_internals::hex::{Case, display};
+                display::fmt_hex_exact!(f, $len, &self.0, Case::Upper)
             }
         }
 
@@ -184,7 +190,7 @@ macro_rules! impl_bytes_newtype {
         impl $crate::serde::Serialize for $t {
             fn serialize<S: $crate::serde::Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
                 if s.is_human_readable() {
-                    s.serialize_str(&$crate::hashes::hex::ToHex::to_hex(self))
+                    s.collect_str(self)
                 } else {
                     s.serialize_bytes(&self[..])
                 }
diff --git a/bitcoin/src/merkle_tree/block.rs b/bitcoin/src/merkle_tree/block.rs
index f7d9067f..a9470838 100644
--- a/bitcoin/src/merkle_tree/block.rs
+++ b/bitcoin/src/merkle_tree/block.rs
@@ -499,6 +499,7 @@ impl Decodable for MerkleBlock {
 
 #[cfg(test)]
 mod tests {
+    use bitcoin_internals::hex::display::DisplayHex;
     #[cfg(feature = "rand-std")]
     use secp256k1::rand::prelude::*;
 
@@ -506,7 +507,7 @@ mod tests {
     use crate::consensus::encode::{deserialize, serialize};
     #[cfg(feature = "rand-std")]
     use crate::hash_types::TxMerkleNode;
-    use crate::hashes::hex::{FromHex, ToHex};
+    use crate::hashes::hex::FromHex;
     #[cfg(feature = "rand-std")]
     use crate::hashes::Hash;
     use crate::internal_macros::hex;
@@ -656,7 +657,7 @@ mod tests {
             mb.txn.extract_matches(&mut vec![], &mut vec![]).unwrap()
         );
         // Serialize again and check that it matches the original bytes
-        assert_eq!(MB_HEX, serialize(&mb).to_hex().as_str());
+        assert_eq!(MB_HEX, serialize(&mb).to_lower_hex_string().as_str());
     }
 
     /// Create a CMerkleBlock using a list of txids which will be found in the
diff --git a/bitcoin/src/pow.rs b/bitcoin/src/pow.rs
index b9b3a9a3..633b30ed 100644
--- a/bitcoin/src/pow.rs
+++ b/bitcoin/src/pow.rs
@@ -774,21 +774,16 @@ impl fmt::Debug for U256 {
 }
 
 macro_rules! impl_hex {
-    ($hex:ident, $fmt:literal) => {
+    ($hex:ident, $case:expr) => {
         impl $hex for U256 {
             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-                if f.alternate() {
-                    write!(f, "0x")?;
-                }
-                write!(f, $fmt, self.0)?;
-                write!(f, $fmt, self.1)?;
-                Ok(())
+                bitcoin_internals::hex::display::fmt_hex_exact!(f, 32, &self.to_be_bytes(), $case)
             }
         }
     };
 }
-impl_hex!(LowerHex, "{:032x}");
-impl_hex!(UpperHex, "{:032X}");
+impl_hex!(LowerHex, bitcoin_internals::hex::Case::Lower);
+impl_hex!(UpperHex, bitcoin_internals::hex::Case::Upper);
 
 #[cfg(feature = "serde")]
 #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
@@ -797,12 +792,17 @@ impl crate::serde::Serialize for U256 {
     where
         S: crate::serde::Serializer,
     {
-        use crate::hashes::hex::ToHex;
-        let bytes = self.to_be_bytes();
+        struct DisplayHex(U256);
+
+        impl fmt::Display for DisplayHex {
+            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "{:x}", self.0) }
+        }
+
         if serializer.is_human_readable() {
             // TODO: fast hex encoding.
-            serializer.serialize_str(&bytes.to_hex())
+            serializer.collect_str(&DisplayHex(*self))
         } else {
+            let bytes = self.to_be_bytes();
             serializer.serialize_bytes(&bytes)
         }
     }
diff --git a/bitcoin/src/psbt/raw.rs b/bitcoin/src/psbt/raw.rs
index 49a1ddc1..e9770b65 100644
--- a/bitcoin/src/psbt/raw.rs
+++ b/bitcoin/src/psbt/raw.rs
@@ -6,13 +6,13 @@
 //! <https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki>.
 //!
 
+use bitcoin_internals::hex::display::DisplayHex;
 use crate::prelude::*;
 use core::fmt;
 use core::convert::TryFrom;
 
 use crate::io::{self, Cursor};
 use crate::consensus::encode::{self, ReadExt, WriteExt, Decodable, Encodable, VarInt, serialize, deserialize, MAX_VEC_SIZE};
-use crate::hashes::hex;
 use crate::psbt::Error;
 
 use super::serialize::{Serialize, Deserialize};
@@ -66,8 +66,7 @@ pub struct ProprietaryKey<Subtype=ProprietaryType> where Subtype: Copy + From<u8
 
 impl fmt::Display for Key {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "type: {:#x}, key: ", self.type_value)?;
-        hex::format_hex(&self.key[..], f)
+        write!(f, "type: {:#x}, key: {:x}", self.type_value, self.key.as_hex())
     }
 }
 
diff --git a/bitcoin/src/psbt/serialize.rs b/bitcoin/src/psbt/serialize.rs
index c0a8c66b..ddbe2ec8 100644
--- a/bitcoin/src/psbt/serialize.rs
+++ b/bitcoin/src/psbt/serialize.rs
@@ -44,7 +44,8 @@ pub(crate) trait Deserialize: Sized {
 impl PartiallySignedTransaction {
     /// Serialize a value as bytes in hex.
     pub fn serialize_hex(&self) -> String {
-        bitcoin_hashes::hex::ToHex::to_hex(&self.serialize()[..])
+        use bitcoin_internals::hex::display::DisplayHex;
+        self.serialize().to_lower_hex_string()
     }
 
     /// Serialize as raw binary data
diff --git a/bitcoin/src/serde_utils.rs b/bitcoin/src/serde_utils.rs
index 9974b9fb..2d93ebc9 100644
--- a/bitcoin/src/serde_utils.rs
+++ b/bitcoin/src/serde_utils.rs
@@ -5,6 +5,20 @@
 //! This module is for special serde serializations.
 //!
 
+pub(crate) struct SerializeBytesAsHex<'a>(pub(crate) &'a [u8]);
+
+impl<'a> serde::Serialize for SerializeBytesAsHex<'a> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        use bitcoin_internals::hex::display::DisplayHex;
+
+        serializer.collect_str(&format_args!("{:x}", self.0.as_hex()))
+    }
+}
+
+
 pub mod btreemap_byte_values {
     //! Module for serialization of BTreeMaps with hex byte values.
     #![allow(missing_docs)]
@@ -13,7 +27,7 @@ pub mod btreemap_byte_values {
 
     use serde;
 
-    use crate::hashes::hex::{FromHex, ToHex};
+    use crate::hashes::hex::FromHex;
     use crate::prelude::*;
 
     pub fn serialize<S, T>(v: &BTreeMap<T, Vec<u8>>, s: S) -> Result<S::Ok, S::Error>
@@ -29,7 +43,7 @@ pub mod btreemap_byte_values {
         } else {
             let mut map = s.serialize_map(Some(v.len()))?;
             for (key, value) in v.iter() {
-                map.serialize_entry(key, &value.to_hex())?;
+                map.serialize_entry(key, &super::SerializeBytesAsHex(value))?;
             }
             map.end()
         }
@@ -237,7 +251,7 @@ pub mod hex_bytes {
 
     use serde;
 
-    use crate::hashes::hex::{FromHex, ToHex};
+    use crate::hashes::hex::FromHex;
 
     pub fn serialize<T, S>(bytes: &T, s: S) -> Result<S::Ok, S::Error>
     where
@@ -248,7 +262,7 @@ pub mod hex_bytes {
         if !s.is_human_readable() {
             serde::Serialize::serialize(bytes, s)
         } else {
-            s.serialize_str(&bytes.as_ref().to_hex())
+            serde::Serialize::serialize(&super::SerializeBytesAsHex(bytes.as_ref()), s)
         }
     }
 
diff --git a/bitcoin/src/sighash.rs b/bitcoin/src/sighash.rs
index a201a7ee..657fb3f5 100644
--- a/bitcoin/src/sighash.rs
+++ b/bitcoin/src/sighash.rs
@@ -1387,10 +1387,10 @@ mod tests {
             })
         }
 
+        use bitcoin_internals::hex::display::DisplayHex;
         use secp256k1::{self, SecretKey, XOnlyPublicKey};
 
         use crate::consensus::serde as con_serde;
-        use crate::hashes::hex::ToHex;
         use crate::taproot::{TapBranchHash, TapTweakHash};
 
         #[derive(serde::Deserialize)]
@@ -1551,7 +1551,7 @@ mod tests {
 
             assert_eq!(expected.internal_pubkey, internal_key);
             assert_eq!(expected.tweak, tweak);
-            assert_eq!(expected.sig_msg, sig_msg.to_hex());
+            assert_eq!(expected.sig_msg, sig_msg.to_lower_hex_string());
             assert_eq!(expected.sig_hash, sighash);
             assert_eq!(expected_hash_ty, hash_ty);
             assert_eq!(expected_key_spend_sig, key_spend_sig);
diff --git a/bitcoin/src/sign_message.rs b/bitcoin/src/sign_message.rs
index 6ec20175..317cb8d0 100644
--- a/bitcoin/src/sign_message.rs
+++ b/bitcoin/src/sign_message.rs
@@ -213,13 +213,12 @@ pub fn signed_msg_hash(msg: &str) -> sha256d::Hash {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::hashes::hex::ToHex;
 
     #[test]
     fn test_signed_msg_hash() {
         let hash = signed_msg_hash("test");
         assert_eq!(
-            hash.to_hex(),
+            hash.to_string(),
             "a6f87fe6d58a032c320ff8d1541656f0282c2c7bfcc69d61af4c8e8ed528e49c"
         );
     }
diff --git a/bitcoin/src/taproot.rs b/bitcoin/src/taproot.rs
index 62f9c348..aff41c47 100644
--- a/bitcoin/src/taproot.rs
+++ b/bitcoin/src/taproot.rs
@@ -1088,11 +1088,12 @@ impl std::error::Error for TaprootError {
 mod test {
     use core::str::FromStr;
 
+    use bitcoin_internals::hex::display::DisplayHex;
     use secp256k1::{VerifyOnly, XOnlyPublicKey};
 
     use super::*;
     use crate::crypto::schnorr::TapTweak;
-    use crate::hashes::hex::{FromHex, ToHex};
+    use crate::hashes::hex::FromHex;
     use crate::hashes::sha256t::Tag;
     use crate::hashes::{sha256, Hash, HashEngine};
     use crate::{Address, Network};
@@ -1140,19 +1141,19 @@ mod test {
         //   CHashWriter writer = HasherTapLeaf;
         //   writer.GetSHA256().GetHex()
         assert_eq!(
-            TapLeafHash::from_engine(TapLeafTag::engine()).to_hex(),
+            TapLeafHash::from_engine(TapLeafTag::engine()).to_string(),
             "5212c288a377d1f8164962a5a13429f9ba6a7b84e59776a52c6637df2106facb"
         );
         assert_eq!(
-            TapBranchHash::from_engine(TapBranchTag::engine()).to_hex(),
+            TapBranchHash::from_engine(TapBranchTag::engine()).to_string(),
             "53c373ec4d6f3c53c1f5fb2ff506dcefe1a0ed74874f93fa93c8214cbe9ffddf"
         );
         assert_eq!(
-            TapTweakHash::from_engine(TapTweakTag::engine()).to_hex(),
+            TapTweakHash::from_engine(TapTweakTag::engine()).to_string(),
             "8aa4229474ab0100b2d6f0687f031d1fc9d8eef92a042ad97d279bff456b15e4"
         );
         assert_eq!(
-            TapSighashHash::from_engine(TapSighashTag::engine()).to_hex(),
+            TapSighashHash::from_engine(TapSighashTag::engine()).to_string(),
             "dabc11914abcd8072900042a2681e52f8dba99ce82e224f97b5fdb7cd4b9c803"
         );
 
@@ -1162,19 +1163,19 @@ mod test {
         //   writer.GetSHA256().GetHex()
         // Note that Core writes the 0 length prefix when an empty vector is written.
         assert_eq!(
-            TapLeafHash::hash(&[0]).to_hex(),
+            TapLeafHash::hash(&[0]).to_string(),
             "ed1382037800c9dd938dd8854f1a8863bcdeb6705069b4b56a66ec22519d5829"
         );
         assert_eq!(
-            TapBranchHash::hash(&[0]).to_hex(),
+            TapBranchHash::hash(&[0]).to_string(),
             "92534b1960c7e6245af7d5fda2588db04aa6d646abc2b588dab2b69e5645eb1d"
         );
         assert_eq!(
-            TapTweakHash::hash(&[0]).to_hex(),
+            TapTweakHash::hash(&[0]).to_string(),
             "cd8737b5e6047fc3f16f03e8b9959e3440e1bdf6dd02f7bb899c352ad490ea1e"
         );
         assert_eq!(
-            TapSighashHash::hash(&[0]).to_hex(),
+            TapSighashHash::hash(&[0]).to_string(),
             "c2fd0de003889a09c4afcf676656a0d8a1fb706313ff7d509afb00c323c010cd"
         );
     }
@@ -1190,7 +1191,7 @@ mod test {
         let script = ScriptBuf::from_hex(script_hex).unwrap();
         let control_block =
             ControlBlock::from_slice(&Vec::<u8>::from_hex(control_block_hex).unwrap()).unwrap();
-        assert_eq!(control_block_hex, control_block.serialize().to_hex());
+        assert_eq!(control_block_hex, control_block.serialize().to_lower_hex_string());
         assert!(control_block.verify_taproot_commitment(secp, out_pk.to_inner(), &script));
     }
 
@@ -1408,7 +1409,7 @@ mod test {
 
                     let leaf_hash = TapLeafHash::from_script(&script_ver.0, script_ver.1);
                     let ctrl_blk = spend_info.control_block(script_ver).unwrap();
-                    assert_eq!(leaf_hash.to_hex(), expected_leaf_hash);
+                    assert_eq!(leaf_hash.to_string(), expected_leaf_hash);
                     assert_eq!(ctrl_blk, expected_ctrl_blk);
                 }
             }
diff --git a/hashes/Cargo.toml b/hashes/Cargo.toml
index a4b6879a..8734dd0c 100644
--- a/hashes/Cargo.toml
+++ b/hashes/Cargo.toml
@@ -13,12 +13,12 @@ edition = "2018"
 
 [features]
 default = ["std"]
-std = []
+std = ["internals/alloc"]
 schemars = ["actual-schemars", "dyn-clone"]
 # If you disable std, you can still use a Write trait via the core2 feature.
 # You can also use ToHex via the alloc feature, as it requires Vec/String.
 # And you can still just disable std by disabling default features, without enabling these two.
-alloc = ["core2/alloc"]
+alloc = ["core2/alloc", "internals/alloc"]
 serde-std = ["serde/std"]
 
 [dependencies]
diff --git a/hashes/embedded/src/main.rs b/hashes/embedded/src/main.rs
index 30921a0f..22773ad2 100644
--- a/hashes/embedded/src/main.rs
+++ b/hashes/embedded/src/main.rs
@@ -9,7 +9,7 @@ extern crate bitcoin_hashes;
 #[cfg(feature = "alloc")] use alloc_cortex_m::CortexMHeap;
 #[cfg(feature = "alloc")] use core::alloc::Layout;
 #[cfg(feature = "alloc")] use cortex_m::asm;
-#[cfg(feature = "alloc")] use bitcoin_hashes::hex::ToHex;
+#[cfg(feature = "alloc")] use alloc::string::ToString;
 
 use bitcoin_hashes::{sha256, Hash, HashEngine};
 use core2::io::Write;
@@ -57,7 +57,7 @@ fn check_result(engine: sha256::HashEngine) {
     }
 
     #[cfg(feature = "alloc")]
-    if hash.to_hex() != hash_check.to_hex() {
+    if hash.to_string() != hash_check.to_string() {
         debug::exit(debug::EXIT_FAILURE);
     }
 }
diff --git a/hashes/src/hash160.rs b/hashes/src/hash160.rs
index 89950bc4..91da3a89 100644
--- a/hashes/src/hash160.rs
+++ b/hashes/src/hash160.rs
@@ -52,7 +52,7 @@ mod tests {
     #[cfg(any(feature = "std", feature = "alloc"))]
     fn test() {
         use crate::{hash160, Hash, HashEngine};
-        use crate::hex::{FromHex, ToHex};
+        use crate::hex::FromHex;
 
         #[derive(Clone)]
         #[cfg(any(feature = "std", feature = "alloc"))]
@@ -89,7 +89,7 @@ mod tests {
             let hash = hash160::Hash::hash(&test.input[..]);
             assert_eq!(hash, hash160::Hash::from_hex(test.output_str).expect("parse hex"));
             assert_eq!(&hash[..], &test.output[..]);
-            assert_eq!(&hash.to_hex(), &test.output_str);
+            assert_eq!(&hash.to_string(), &test.output_str);
 
             // Hash through engine, checking that we can input byte by byte
             let mut engine = hash160::Hash::engine();
diff --git a/hashes/src/hex.rs b/hashes/src/hex.rs
index 570895cc..dc72131f 100644
--- a/hashes/src/hex.rs
+++ b/hashes/src/hex.rs
@@ -17,8 +17,6 @@
 
 #[cfg(any(feature = "std", feature = "alloc"))]
 use crate::alloc::{string::String, vec::Vec};
-#[cfg(feature = "alloc")]
-use crate::alloc::format;
 
 #[cfg(any(test, feature = "std"))]
 use std::io;
@@ -49,14 +47,6 @@ impl fmt::Display for Error {
     }
 }
 
-/// Trait for objects that can be serialized as hex strings.
-#[cfg(any(test, feature = "std", feature = "alloc"))]
-#[cfg_attr(docsrs, doc(cfg(any(test, feature = "std", feature = "alloc"))))]
-pub trait ToHex {
-    /// Converts to a hexadecimal representation of the object.
-    fn to_hex(&self) -> String;
-}
-
 /// Trait for objects that can be deserialized from hex strings.
 pub trait FromHex: Sized {
     /// Produces an object from a byte iterator.
@@ -70,15 +60,6 @@ pub trait FromHex: Sized {
     }
 }
 
-#[cfg(any(test, feature = "std", feature = "alloc"))]
-#[cfg_attr(docsrs, doc(cfg(any(test, feature = "std", feature = "alloc"))))]
-impl<T: fmt::LowerHex> ToHex for T {
-    /// Outputs the hash in hexadecimal form.
-    fn to_hex(&self) -> String {
-        format!("{:x}", self)
-    }
-}
-
 impl<T: Hash> FromHex for T {
     fn from_byte_iter<I>(iter: I) -> Result<Self, Error>
     where
@@ -170,65 +151,8 @@ impl<'a> DoubleEndedIterator for HexIterator<'a> {
 
 impl<'a> ExactSizeIterator for HexIterator<'a> {}
 
-/// Outputs hex into an object implementing `fmt::Write`.
-///
-/// This is usually more efficient than going through a `String` using [`ToHex`].
-pub fn format_hex(data: &[u8], f: &mut fmt::Formatter) -> fmt::Result {
-    let prec = f.precision().unwrap_or(2 * data.len());
-    let width = f.width().unwrap_or(2 * data.len());
-    for _ in (2 * data.len())..width {
-        f.write_str("0")?;
-    }
-    for ch in data.iter().take(prec / 2) {
-        write!(f, "{:02x}", *ch)?;
-    }
-    if prec < 2 * data.len() && prec % 2 == 1 {
-        write!(f, "{:x}", data[prec / 2] / 16)?;
-    }
-    Ok(())
-}
-
-/// Outputs hex in reverse order.
-///
-/// Used for `sha256d::Hash` whose standard hex encoding has the bytes reversed.
-pub fn format_hex_reverse(data: &[u8], f: &mut fmt::Formatter) -> fmt::Result {
-    let prec = f.precision().unwrap_or(2 * data.len());
-    let width = f.width().unwrap_or(2 * data.len());
-    for _ in (2 * data.len())..width {
-        f.write_str("0")?;
-    }
-    for ch in data.iter().rev().take(prec / 2) {
-        write!(f, "{:02x}", *ch)?;
-    }
-    if prec < 2 * data.len() && prec % 2 == 1 {
-        write!(f, "{:x}", data[data.len() - 1 - prec / 2] / 16)?;
-    }
-    Ok(())
-}
-
-#[cfg(any(test, feature = "std", feature = "alloc"))]
-#[cfg_attr(docsrs, doc(cfg(any(test, feature = "std", feature = "alloc"))))]
-impl ToHex for [u8] {
-    fn to_hex(&self) -> String {
-        use core::fmt::Write;
-        let mut ret = String::with_capacity(2 * self.len());
-        for ch in self {
-            write!(ret, "{:02x}", ch).expect("writing to string");
-        }
-        ret
-    }
-}
-
 /// A struct implementing [`io::Write`] that converts what's written to it into
 /// a hex String.
-///
-/// If you already have the data to be converted in a `Vec<u8>` use [`ToHex`]
-/// but if you have an encodable object, by using this you avoid the
-/// serialization to `Vec<u8>` by going directly to `String`.
-///
-/// Note that to achieve better perfomance than [`ToHex`] the struct must be
-/// created with the right `capacity` of the final hex string so that the inner
-/// `String` doesn't re-allocate.
 #[cfg(any(test, feature = "std", feature = "alloc"))]
 #[cfg_attr(docsrs, doc(cfg(any(test, feature = "std", feature = "alloc"))))]
 pub struct HexWriter(String);
@@ -319,8 +243,9 @@ impl_fromhex_array!(512);
 #[cfg(test)]
 mod tests {
     use super::*;
+    #[cfg(any(feature = "std", feature = "alloc"))]
+    use internals::hex::exts::DisplayHex;
 
-    use core::fmt;
     use std::io::Write;
 
     #[test]
@@ -331,86 +256,20 @@ mod tests {
 
         let parse: Vec<u8> = FromHex::from_hex(expected).expect("parse lowercase string");
         assert_eq!(parse, vec![0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef]);
-        let ser = parse.to_hex();
+        let ser = parse.to_lower_hex_string();
         assert_eq!(ser, expected);
 
         let parse: Vec<u8> = FromHex::from_hex(expected_up).expect("parse uppercase string");
         assert_eq!(parse, vec![0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef]);
-        let ser = parse.to_hex();
+        let ser = parse.to_lower_hex_string();
         assert_eq!(ser, expected);
 
         let parse: [u8; 8] = FromHex::from_hex(expected_up).expect("parse uppercase string");
         assert_eq!(parse, [0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef]);
-        let ser = parse.to_hex();
+        let ser = parse.to_lower_hex_string();
         assert_eq!(ser, expected);
     }
 
-    #[test]
-    fn hex_truncate() {
-        struct HexBytes(Vec<u8>);
-        impl fmt::LowerHex for HexBytes {
-            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-                format_hex(&self.0, f)
-            }
-        }
-
-        let bytes = HexBytes(vec![1u8, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
-
-        assert_eq!(
-            format!("{:x}", bytes),
-            "0102030405060708090a"
-        );
-
-        for i in 0..20 {
-            assert_eq!(
-                format!("{:.prec$x}", bytes, prec = i),
-                &"0102030405060708090a"[0..i]
-            );
-        }
-
-        assert_eq!(
-            format!("{:25x}", bytes),
-            "000000102030405060708090a"
-        );
-        assert_eq!(
-            format!("{:26x}", bytes),
-            "0000000102030405060708090a"
-        );
-    }
-
-    #[test]
-    fn hex_truncate_rev() {
-        struct HexBytes(Vec<u8>);
-        impl fmt::LowerHex for HexBytes {
-            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-                format_hex_reverse(&self.0, f)
-            }
-        }
-
-        let bytes = HexBytes(vec![1u8, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
-
-        assert_eq!(
-            format!("{:x}", bytes),
-            "0a090807060504030201"
-        );
-
-        for i in 0..20 {
-            assert_eq!(
-                format!("{:.prec$x}", bytes, prec = i),
-                &"0a090807060504030201"[0..i]
-            );
-        }
-
-        assert_eq!(
-            format!("{:25x}", bytes),
-            "000000a090807060504030201"
-        );
-        assert_eq!(
-            format!("{:26x}", bytes),
-            "0000000a090807060504030201"
-        );
-    }
-
     #[test]
     #[cfg(any(feature = "std", feature = "alloc"))]
     fn hex_error() {
@@ -447,18 +306,19 @@ mod tests {
 
 
     #[test]
+    #[cfg(any(feature = "std", feature = "alloc"))]
     fn hex_writer() {
         let vec: Vec<_>  = (0u8..32).collect();
         let mut writer = HexWriter::new(64);
         writer.write_all(&vec[..]).unwrap();
-        assert_eq!(vec.to_hex(), writer.result());
+        assert_eq!(vec.to_lower_hex_string(), writer.result());
     }
 }
 
 #[cfg(bench)]
 mod benches {
     use test::{Bencher, black_box};
-    use super::{ToHex, HexWriter};
+    use super::HexWriter;
     use std::io::Write;
     use crate::{sha256, Hash};
 
@@ -466,7 +326,7 @@ mod benches {
     fn bench_to_hex(bh: &mut Bencher) {
         let hash = sha256::Hash::hash(&[0; 1]);
         bh.iter(|| {
-            black_box(hash.to_hex());
+            black_box(hash.to_string());
         })
     }
 
diff --git a/hashes/src/ripemd160.rs b/hashes/src/ripemd160.rs
index 4b750978..712eecc2 100644
--- a/hashes/src/ripemd160.rs
+++ b/hashes/src/ripemd160.rs
@@ -408,7 +408,7 @@ mod tests {
     #[cfg(any(feature = "std", feature = "alloc"))]
     fn test() {
         use crate::{Hash, HashEngine, ripemd160};
-        use crate::hex::{FromHex, ToHex};
+        use crate::hex::FromHex;
 
         #[derive(Clone)]
         struct Test {
@@ -472,7 +472,7 @@ mod tests {
             let hash = ripemd160::Hash::hash(test.input.as_bytes());
             assert_eq!(hash, ripemd160::Hash::from_hex(test.output_str).expect("parse hex"));
             assert_eq!(&hash[..], &test.output[..]);
-            assert_eq!(&hash.to_hex(), &test.output_str);
+            assert_eq!(&hash.to_string(), &test.output_str);
 
             // Hash through engine, checking that we can input byte by byte
             let mut engine = ripemd160::Hash::engine();
diff --git a/hashes/src/sha1.rs b/hashes/src/sha1.rs
index f5cae9a2..d2aa2e5a 100644
--- a/hashes/src/sha1.rs
+++ b/hashes/src/sha1.rs
@@ -146,7 +146,7 @@ mod tests {
     #[cfg(any(feature = "std", feature = "alloc"))]
     fn test() {
         use crate::{sha1, Hash, HashEngine};
-        use crate::hex::{FromHex, ToHex};
+        use crate::hex::FromHex;
 
         #[derive(Clone)]
         struct Test {
@@ -198,7 +198,7 @@ mod tests {
             let hash = sha1::Hash::hash(test.input.as_bytes());
             assert_eq!(hash, sha1::Hash::from_hex(test.output_str).expect("parse hex"));
             assert_eq!(&hash[..], &test.output[..]);
-            assert_eq!(&hash.to_hex(), &test.output_str);
+            assert_eq!(&hash.to_string(), &test.output_str);
 
             // Hash through engine, checking that we can input byte by byte
             let mut engine = sha1::Hash::engine();
diff --git a/hashes/src/sha256.rs b/hashes/src/sha256.rs
index 31479b50..eafff7b7 100644
--- a/hashes/src/sha256.rs
+++ b/hashes/src/sha256.rs
@@ -326,7 +326,7 @@ mod tests {
     #[test]
     #[cfg(any(feature = "std", feature = "alloc"))]
     fn test() {
-        use crate::hex::{FromHex, ToHex};
+        use crate::hex::FromHex;
 
         #[derive(Clone)]
         struct Test {
@@ -374,7 +374,7 @@ mod tests {
             let hash = sha256::Hash::hash(test.input.as_bytes());
             assert_eq!(hash, sha256::Hash::from_hex(test.output_str).expect("parse hex"));
             assert_eq!(&hash[..], &test.output[..]);
-            assert_eq!(&hash.to_hex(), &test.output_str);
+            assert_eq!(&hash.to_string(), &test.output_str);
 
             // Hash through engine, checking that we can input byte by byte
             let mut engine = sha256::Hash::engine();
diff --git a/hashes/src/sha256d.rs b/hashes/src/sha256d.rs
index 1a3e75b3..103b264b 100644
--- a/hashes/src/sha256d.rs
+++ b/hashes/src/sha256d.rs
@@ -49,7 +49,7 @@ mod tests {
     #[cfg(any(feature = "std", feature = "alloc"))]
     fn test() {
         use crate::{sha256d, Hash, HashEngine};
-        use crate::hex::{FromHex, ToHex};
+        use crate::hex::FromHex;
 
         #[derive(Clone)]
         struct Test {
@@ -77,7 +77,7 @@ mod tests {
             let hash = sha256d::Hash::hash(test.input.as_bytes());
             assert_eq!(hash, sha256d::Hash::from_hex(test.output_str).expect("parse hex"));
             assert_eq!(&hash[..], &test.output[..]);
-            assert_eq!(&hash.to_hex(), &test.output_str);
+            assert_eq!(&hash.to_string(), &test.output_str);
 
             // Hash through engine, checking that we can input byte by byte
             let mut engine = sha256d::Hash::engine();
diff --git a/hashes/src/sha256t.rs b/hashes/src/sha256t.rs
index 578321db..59035542 100644
--- a/hashes/src/sha256t.rs
+++ b/hashes/src/sha256t.rs
@@ -123,8 +123,6 @@ macro_rules! sha256t_hash_newtype {
 mod tests {
     use crate::{sha256, sha256t};
     #[cfg(any(feature = "std", feature = "alloc"))]
-    use crate::hex::ToHex;
-    #[cfg(any(feature = "std", feature = "alloc"))]
     use crate::Hash;
 
     const TEST_MIDSTATE: [u8; 32] = [
@@ -154,11 +152,11 @@ mod tests {
     #[cfg(any(feature = "std", feature = "alloc"))]
     fn test_sha256t() {
         assert_eq!(
-            TestHash::hash(&[0]).to_hex(),
+            TestHash::hash(&[0]).to_string(),
             "29589d5122ec666ab5b4695070b6debc63881a4f85d88d93ddc90078038213ed"
         );
         assert_eq!(
-            NewTypeHash::hash(&[0]).to_hex(),
+            NewTypeHash::hash(&[0]).to_string(),
             "29589d5122ec666ab5b4695070b6debc63881a4f85d88d93ddc90078038213ed"
         );
     }
diff --git a/hashes/src/sha512.rs b/hashes/src/sha512.rs
index 8ae370f5..6a1b8a72 100644
--- a/hashes/src/sha512.rs
+++ b/hashes/src/sha512.rs
@@ -311,7 +311,7 @@ mod tests {
     #[cfg(any(feature = "std", feature = "alloc"))]
     fn test() {
         use crate::{sha512, Hash, HashEngine};
-        use crate::hex::{FromHex, ToHex};
+        use crate::hex::FromHex;
 
         #[derive(Clone)]
         struct Test {
@@ -371,7 +371,7 @@ mod tests {
             let hash = sha512::Hash::hash(test.input.as_bytes());
             assert_eq!(hash, sha512::Hash::from_hex(test.output_str).expect("parse hex"));
             assert_eq!(&hash[..], &test.output[..]);
-            assert_eq!(&hash.to_hex(), &test.output_str);
+            assert_eq!(&hash.to_string(), &test.output_str);
 
             // Hash through engine, checking that we can input byte by byte
             let mut engine = sha512::Hash::engine();
diff --git a/hashes/src/sha512_256.rs b/hashes/src/sha512_256.rs
index 32885ddb..939887c0 100644
--- a/hashes/src/sha512_256.rs
+++ b/hashes/src/sha512_256.rs
@@ -89,7 +89,7 @@ mod tests {
     #[cfg(any(feature = "std", feature = "alloc"))]
     fn test() {
         use crate::{sha512_256, Hash, HashEngine};
-        use crate::hex::{FromHex, ToHex};
+        use crate::hex::FromHex;
 
         #[derive(Clone)]
         struct Test {
@@ -157,7 +157,7 @@ mod tests {
             let hash = sha512_256::Hash::hash(test.input.as_bytes());
             assert_eq!(hash, sha512_256::Hash::from_hex(test.output_str).expect("parse hex"));
             assert_eq!(&hash[..], &test.output[..]);
-            assert_eq!(&hash.to_hex(), &test.output_str);
+            assert_eq!(&hash.to_string(), &test.output_str);
 
             // Hash through engine, checking that we can input byte by byte
             let mut engine = sha512_256::Hash::engine();
diff --git a/internals/src/hex/display.rs b/internals/src/hex/display.rs
index 1cdb980c..a95c4c72 100644
--- a/internals/src/hex/display.rs
+++ b/internals/src/hex/display.rs
@@ -111,6 +111,23 @@ impl<'a> DisplayHex for &'a [u8] {
     }
 }
 
+#[cfg(feature = "alloc")]
+#[cfg_attr(docsrs, doc(feature = "alloc"))]
+impl<'a> DisplayHex for &'a alloc::vec::Vec<u8> {
+    type Display = DisplayByteSlice<'a>;
+
+    #[inline]
+    fn as_hex(self) -> Self::Display { DisplayByteSlice { bytes: self } }
+
+    #[inline]
+    fn hex_reserve_suggestion(self) -> usize {
+        // Since the string wouldn't fit into address space if this overflows (actually even for
+        // smaller amounts) it's better to panic right away. It should also give the optimizer
+        // better opportunities.
+        self.len().checked_mul(2).expect("the string wouldn't fit into address space")
+    }
+}
+
 /// Displays byte slice as hex.
 ///
 /// Created by [`<&[u8] as DisplayHex>::display_hex`](DisplayHex::display_hex).