Hasher: static contract checking, context reuse

- Store EVP_MD_CTX in a separate struct.
- Add with_context() constructor that uses an existing context.
- Switch to EVP_Digest(Init|Final)_ex for efficient context reuse.
- Make update() borrow &mut self.
- Make finalize() consume self. Add finalize_reuse() that also returns the
context which can be passed to from_context() constructor for reuse.

These changes let the type system prevent illegal calls to update() and
finalize().

1 files changed, 2 insertions, 0 deletions

diff --git a/openssl-sys/src/lib.rs b/openssl-sys/src/lib.rs
index 50186ae0..2b0c9292 100755
--- a/openssl-sys/src/lib.rs
+++ b/openssl-sys/src/lib.rs
@@ -340,8 +340,10 @@ extern "C" {
     pub fn EVP_CipherFinal(ctx: *mut EVP_CIPHER_CTX, res: *mut u8, len: &mut c_int);
 
     pub fn EVP_DigestInit(ctx: *mut EVP_MD_CTX, typ: *const EVP_MD);
+    pub fn EVP_DigestInit_ex(ctx: *mut EVP_MD_CTX, typ: *const EVP_MD, imple: *const ENGINE);
     pub fn EVP_DigestUpdate(ctx: *mut EVP_MD_CTX, data: *const u8, n: c_uint);
     pub fn EVP_DigestFinal(ctx: *mut EVP_MD_CTX, res: *mut u8, n: *mut u32);
+    pub fn EVP_DigestFinal_ex(ctx: *mut EVP_MD_CTX, res: *mut u8, n: *mut u32);
 
     pub fn EVP_MD_CTX_create() -> *mut EVP_MD_CTX;
     pub fn EVP_MD_CTX_destroy(ctx: *mut EVP_MD_CTX);