From a183a6c801ae2c3c5483c9d976e5b783224f9091 Mon Sep 17 00:00:00 2001
From: Jonas Platte <jplatte+git@posteo.de>
Date: Sat, 8 Aug 2020 22:37:37 +0200
Subject: [PATCH] Add from_parts constructors for DeviceKeyId and ServerKeyId

---
 ruma-identifiers/CHANGELOG.md         |  4 ++++
 ruma-identifiers/src/device_key_id.rs | 19 ++++++++++++++++++-
 ruma-identifiers/src/server_key_id.rs | 18 +++++++++++++++++-
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/ruma-identifiers/CHANGELOG.md b/ruma-identifiers/CHANGELOG.md
index 52807092..a81eda92 100644
--- a/ruma-identifiers/CHANGELOG.md
+++ b/ruma-identifiers/CHANGELOG.md
@@ -4,6 +4,10 @@ Breaking changes:
 
 * Update strum dependency to 0.19
 
+Improvements:
+
+* Add `DeviceKeyId::from_parts` and `ServerKeyId::from_parts`
+
 # 0.17.4
 
 Bug fixes:
diff --git a/ruma-identifiers/src/device_key_id.rs b/ruma-identifiers/src/device_key_id.rs
index 491dbd42..c9a81f6c 100644
--- a/ruma-identifiers/src/device_key_id.rs
+++ b/ruma-identifiers/src/device_key_id.rs
@@ -1,6 +1,6 @@
 //! Identifiers for device keys for end-to-end encryption.
 
-use std::{num::NonZeroU8, str::FromStr};
+use std::{convert::TryInto, num::NonZeroU8, str::FromStr};
 
 use ruma_identifiers_validation::{key_algorithms::DeviceKeyAlgorithm, Error};
 
@@ -14,6 +14,23 @@ pub struct DeviceKeyId {
 }
 
 impl DeviceKeyId {
+    /// Create a `DeviceKeyId` from a `DeviceKeyAlgorithm` and a `DeviceId`.
+    pub fn from_parts(algorithm: DeviceKeyAlgorithm, device_id: &DeviceId) -> Self {
+        let algorithm: &str = algorithm.as_ref();
+        let device_id: &str = device_id.as_ref();
+
+        let mut res = String::with_capacity(algorithm.len() + 1 + device_id.len());
+        res.push_str(algorithm);
+        res.push_str(":");
+        res.push_str(device_id);
+
+        let colon_idx =
+            NonZeroU8::new(algorithm.len().try_into().expect("no algorithm name len > 255"))
+                .expect("no empty algorithm name");
+
+        DeviceKeyId { full_id: res.into(), colon_idx }
+    }
+
     /// Returns key algorithm of the device key ID.
     pub fn algorithm(&self) -> DeviceKeyAlgorithm {
         DeviceKeyAlgorithm::from_str(&self.full_id[..self.colon_idx.get() as usize]).unwrap()
diff --git a/ruma-identifiers/src/server_key_id.rs b/ruma-identifiers/src/server_key_id.rs
index efb6d168..0d4ad725 100644
--- a/ruma-identifiers/src/server_key_id.rs
+++ b/ruma-identifiers/src/server_key_id.rs
@@ -1,6 +1,6 @@
 //! Identifiers for homeserver signing keys used for federation.
 
-use std::{num::NonZeroU8, str::FromStr};
+use std::{convert::TryInto, num::NonZeroU8, str::FromStr};
 
 use ruma_identifiers_validation::{key_algorithms::ServerKeyAlgorithm, Error};
 
@@ -12,6 +12,22 @@ pub struct ServerKeyId {
 }
 
 impl ServerKeyId {
+    /// Create a `ServerKeyId` from a `ServerKeyAlgorithm` and a `ServerId`.
+    pub fn from_parts(algorithm: ServerKeyAlgorithm, version: &str) -> Self {
+        let algorithm: &str = algorithm.as_ref();
+
+        let mut res = String::with_capacity(algorithm.len() + 1 + version.len());
+        res.push_str(algorithm);
+        res.push_str(":");
+        res.push_str(version);
+
+        let colon_idx =
+            NonZeroU8::new(algorithm.len().try_into().expect("no algorithm name len > 255"))
+                .expect("no empty algorithm name");
+
+        ServerKeyId { full_id: res.into(), colon_idx }
+    }
+
     /// Returns key algorithm of the server key ID.
     pub fn algorithm(&self) -> ServerKeyAlgorithm {
         ServerKeyAlgorithm::from_str(&self.full_id[..self.colon_idx.get() as usize]).unwrap()