Add an optional global, static context

Author: sgeisler

.travis.yml

@@ -43,6 +43,7 @@ script:
   - cargo test --verbose --features="rand rand-std"
   - cargo test --verbose --features="rand serde"
   - cargo test --verbose --features="rand serde recovery endomorphism"
+  - cargo test --verbose --features global-context
   - cargo build --verbose
   - cargo test --verbose
   - cargo build --verbose --release

Cargo.toml

@@ -29,6 +29,7 @@ rand-std = ["rand/std"]
 recovery = ["secp256k1-sys/recovery"]
 endomorphism = ["secp256k1-sys/endomorphism"]
 lowmemory = ["secp256k1-sys/lowmemory"]
+global-context = ["lazy_static"]
 
 # Use this feature to not compile the bundled libsecp256k1 C symbols,
 # but use external ones. Use this only if you know what you are doing!
@@ -38,6 +39,7 @@ external-symbols = ["secp256k1-sys/external-symbols"]
 fuzztarget = ["secp256k1-sys/fuzztarget"]
 
 [dependencies]
+lazy_static = { version = "1.4.0", optional = true }
 secp256k1-sys = { version = "0.1.1", default-features = false, path = "./secp256k1-sys" }
 
 [dev-dependencies]

src/lib.rs

@@ -160,6 +160,7 @@ pub use secp256k1_sys as ffi;
 #[cfg(all(test, feature = "serde"))] extern crate serde_test;
 #[cfg(any(test, feature = "rand"))] use rand::Rng;
 #[cfg(any(test, feature = "std"))] extern crate core;
+#[cfg(feature = "global-context")] #[macro_use] extern crate lazy_static;
 
 use core::{fmt, ptr, str};
 
@@ -179,6 +180,12 @@ use core::marker::PhantomData;
 use core::ops::Deref;
 use ffi::CPtr;
 
+#[cfg(feature = "global-context")]
+lazy_static! {
+    /// A global, static context to avoid repeatedly creating contexts where one can't be passed
+    pub static ref SECP256K1: Secp256k1<All> = Secp256k1::new();
+}
+
 #[cfg(feature = "bitcoin_hashes")]
 use bitcoin_hashes::Hash;
 
@@ -1138,6 +1145,24 @@ mod tests {
         assert_tokens(&sig.readable(), &[Token::BorrowedStr(SIG_STR)]);
     }
 
+    #[cfg(feature = "global-context")]
+    #[test]
+    fn test_global_context() {
+        use super::SECP256K1;
+
+        let sk_data = hex!("e6dd32f8761625f105c39a39f19370b3521d845a12456d60ce44debd0a362641");
+        let sk = SecretKey::from_slice(&sk_data).unwrap();
+        let msg_data = hex!("a4965ca63b7d8562736ceec36dfa5a11bf426eb65be8ea3f7a49ae363032da0d");
+        let msg = Message::from_slice(&msg_data).unwrap();
+
+        // Check usagfe as explicit parameter
+        let pk = PublicKey::from_secret_key(&SECP256K1, &sk);
+
+        // Check usage as self
+        let sig = SECP256K1.sign(&msg, &sk);
+        assert!(SECP256K1.verify(&msg, &sig, &pk).is_ok());
+    }
+
     // For WASM, just run through our general tests in this file all at once.
     #[cfg(target_arch = "wasm32")]
     extern crate wasm_bindgen_test;