Add an optional global, static context

Author: sgeisler

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 +1145,16 @@ mod tests {
         assert_tokens(&sig.readable(), &[Token::BorrowedStr(SIG_STR)]);
     }
 
+    #[cfg(feature = "global-context")]
+    #[test]
+    fn test_global_context() {
+        use super::SECP256K1;
+
+        let (sk, pk) = SECP256K1.generate_keypair(&mut thread_rng());
+        let pk_from_sk = PublicKey::from_secret_key(&SECP256K1, &sk);
+        assert_eq!(pk, pk_from_sk);
+    }
+
     // For WASM, just run through our general tests in this file all at once.
     #[cfg(target_arch = "wasm32")]
     extern crate wasm_bindgen_test;