From 88adf3f7f2e9c6f1ea3c722ead41a5579b3292bf Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Sat, 5 Oct 2019 08:30:00 +0200
Subject: Add sha{1,256}::empty()

---
 libbutl/sha1.cxx   | 10 ++++++++--
 libbutl/sha1.mxx   |  6 ++++++
 libbutl/sha256.cxx | 10 ++++++++--
 libbutl/sha256.mxx |  6 ++++++
 4 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/libbutl/sha1.cxx b/libbutl/sha1.cxx
index 1ca8a2a..3c1cbdc 100644
--- a/libbutl/sha1.cxx
+++ b/libbutl/sha1.cxx
@@ -73,7 +73,7 @@ namespace butl
 {
   sha1::
   sha1 ()
-      : done_ (false)
+      : done_ (false), empty_ (true)
   {
     SHA1_Init (reinterpret_cast<SHA1_CTX*> (buf_));
   }
@@ -81,7 +81,13 @@ namespace butl
   void sha1::
   append (const void* b, size_t n)
   {
-    SHA1_Update (reinterpret_cast<SHA1_CTX*> (buf_), b, n);
+    if (n != 0)
+    {
+      SHA1_Update (reinterpret_cast<SHA1_CTX*> (buf_), b, n);
+
+      if (empty_)
+        empty_ = false;
+    }
   }
 
   void sha1::
diff --git a/libbutl/sha1.mxx b/libbutl/sha1.mxx
index 26d4b59..f69ae5a 100644
--- a/libbutl/sha1.mxx
+++ b/libbutl/sha1.mxx
@@ -74,6 +74,11 @@ LIBBUTL_MODEXPORT namespace butl
     explicit
     sha1 (ifdstream& i): sha1 () {append (i);}
 
+    // Check if any data has been hashed.
+    //
+    bool
+    empty () const {return empty_;}
+
     // Extract result.
     //
     // It can be obtained as either a 20-byte binary digest or as a 40-
@@ -119,5 +124,6 @@ LIBBUTL_MODEXPORT namespace butl
 
     mutable digest_type bin_;
     mutable bool done_;
+    bool empty_;
   };
 }
diff --git a/libbutl/sha256.cxx b/libbutl/sha256.cxx
index 6dbe2a0..31730a2 100644
--- a/libbutl/sha256.cxx
+++ b/libbutl/sha256.cxx
@@ -67,7 +67,7 @@ namespace butl
 {
   sha256::
   sha256 ()
-      : done_ (false)
+      : done_ (false), empty_ (true)
   {
     SHA256_Init (reinterpret_cast<SHA256_CTX*> (buf_));
   }
@@ -75,7 +75,13 @@ namespace butl
   void sha256::
   append (const void* b, size_t n)
   {
-    SHA256_Update (reinterpret_cast<SHA256_CTX*> (buf_), b, n);
+    if (n != 0)
+    {
+      SHA256_Update (reinterpret_cast<SHA256_CTX*> (buf_), b, n);
+
+      if (empty_)
+        empty_ = false;
+    }
   }
 
   void sha256::
diff --git a/libbutl/sha256.mxx b/libbutl/sha256.mxx
index fca8b91..2bb58b3 100644
--- a/libbutl/sha256.mxx
+++ b/libbutl/sha256.mxx
@@ -108,6 +108,11 @@ LIBBUTL_MODEXPORT namespace butl
     explicit
     sha256 (ifdstream& i): sha256 () {append (i);}
 
+    // Check if any data has been hashed.
+    //
+    bool
+    empty () const {return empty_;}
+
     // Extract result.
     //
     // It can be obtained as either a 32-byte binary digest or as a 64-
@@ -143,6 +148,7 @@ LIBBUTL_MODEXPORT namespace butl
 
     mutable digest_type bin_;
     mutable bool done_;
+    bool empty_;
   };
 
   // Convert a SHA256 string representation (64 hex digits) to the fingerprint
-- 
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