introduce incremental md5 digester

Signed-off-by: Michael Krelin <hacker@klever.net>

2 files changed, 51 insertions, 0 deletions

diff --git a/src/eyetil.cc b/src/eyetil.cc
index 7669cb6..57ae607 100644
--- a/src/eyetil.cc
+++ b/src/eyetil.cc
@@ -72,2 +72,16 @@ binary_t binary_t::md5() const {
 
+void md5_digester::init() {
+    if(!MD5_Init(&ctx)) throw std::runtime_error("failed to MD5_Init()");
+}
+void md5_digester::update(const void *d,size_t l) {
+    if(!MD5_Update(&ctx,d,l)) throw std::runtime_error("failed to MD5_Update()");
+}
+binary_t md5_digester::final() {
+    binary_t rv(MD5_DIGEST_LENGTH);
+    if(!MD5_Final((unsigned char*)&(rv.front()), &ctx))
+        throw std::runtime_error("failed to MD5_Final()");
+    return rv;
+}
+
+
 static void make_path_for_template(const std::string& p,mode_t m) {
diff --git a/src/eyetil.h b/src/eyetil.h
index d946e71..eff2c43 100644
--- a/src/eyetil.h
+++ b/src/eyetil.h
@@ -7,2 +7,3 @@
 #include <archive_entry.h>
+#include "openssl/md5.h"
 
@@ -23,2 +24,38 @@ class binary_t : public std::vector<unsigned char> {
 
+struct md5_digester {
+    MD5_CTX ctx;
+    md5_digester() { init(); }
+
+    void init();
+    void update(const void *d,size_t l);
+    binary_t final();
+
+    template<typename T>
+    void update(const T& x) { update(&x,sizeof(x)); }
+
+    template<typename T>
+    struct update_iterator : public std::iterator<std::output_iterator_tag,T,void,T*,T&> {
+        md5_digester *d;
+        update_iterator(md5_digester *d_) : d(d_) { }
+        update_iterator(const update_iterator& x) : d(x.d) { }
+
+        update_iterator& operator*() { return *this; }
+        update_iterator& operator++() { return *this; }
+        update_iterator& operator++(int) { return *this; }
+
+        update_iterator& operator=(const T& x) {
+            d->update(x); return *this;
+        }
+    };
+
+    template<typename T>
+    update_iterator<T> updater() {
+        return update_iterator<T>(this);
+    }
+
+};
+template<> inline void md5_digester::update<binary_t>(const binary_t& x) {
+    update((const unsigned char*)&(x.front()),x.size());
+}
+
 class tmpdir_t {