From 104de2e0872d37cf4291d92aa9bee191a01f9c15 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 29 Feb 2016 08:10:16 +0200
Subject: Add '\0' string terminator to sha256 calculation

Failed that, an empty string will be indistinguishable from no string.
---
 butl/sha256             | 32 ++++++++++++++++++++------------
 tests/sha256/driver.cxx | 10 ++++++++--
 2 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/butl/sha256 b/butl/sha256
index 3fc9e63..d583701 100644
--- a/butl/sha256
+++ b/butl/sha256
@@ -23,27 +23,35 @@ namespace butl
   {
   public:
     sha256 ();
-    explicit sha256 (const std::string& s): sha256 () {append (s);}
-    explicit sha256 (const char* s): sha256 () {append (s);}
-    sha256 (const void* b, std::size_t n): sha256 () {append (b, n);}
 
-    // Append string (without the traling '\0').
+    // Append binary data.
     //
     void
-    append (const std::string& s) {append (s.c_str (), s.size ());}
+    append (const void*, std::size_t);
 
-    // Append C-string (without the traling '\0').
+    sha256 (const void* b, std::size_t n): sha256 () {append (b, n);}
+
+    // Append string.
+    //
+    // Note that the hash includes the '\0' terminator. Failed that, a call
+    // with an empty string will be indistinguishable from no call at all.
     //
     void
-    append (const char* s) {append (s, std::strlen (s));}
+    append (const std::string& s) {append (s.c_str (), s.size () + 1);}
 
-    // Append binary data.
-    //
     void
-    append (const void*, std::size_t);
+    append (const char* s) {append (s, std::strlen (s) + 1);}
 
-    // Extract result. It can be obtained as either a 32-byte binary digest or
-    // as a 64- character hex-encoded C-string.
+    explicit
+    sha256 (const std::string& s): sha256 () {append (s);}
+
+    explicit
+    sha256 (const char* s): sha256 () {append (s);}
+
+    // Extract result.
+    //
+    // It can be obtained as either a 32-byte binary digest or as a 64-
+    // character hex-encoded C-string.
     //
     using digest_type = std::uint8_t[32];
 
diff --git a/tests/sha256/driver.cxx b/tests/sha256/driver.cxx
index 12928b2..8c2e525 100644
--- a/tests/sha256/driver.cxx
+++ b/tests/sha256/driver.cxx
@@ -17,7 +17,13 @@ main ()
   assert (string (sha256 ().string ()) ==
           "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855");
 
+  assert (string (sha256 ("").string ()) !=
+          "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855");
+
   assert (string (sha256 ("123").string ()) ==
+          "a787b6772e3e4df1b2a04d5eee56f8570ab38825eed1b6a9bda288429b7f29a1");
+
+  assert (string (sha256 ("123", 3).string ()) ==
           "a665a45920422f9d417e4867efdc4fb8a04a1f3fff1fa07e998e86f7f7a27ae3");
 
   sha256 h;
@@ -26,9 +32,9 @@ main ()
   h.append ("3", 1);
 
   auto& b (h.binary ());
-  assert (b[0] == 0xa6 && b[31] == 0xe3);
+  assert (b[0] == 0x20 && b[31] == 0x9d);
 
   string s (h.string ());
   assert (s ==
-          "a665a45920422f9d417e4867efdc4fb8a04a1f3fff1fa07e998e86f7f7a27ae3");
+          "204d9db65789fbede7829ed77f72ba1f0fe21a833d95abad4849b82f33a69b9d");
 }
-- 
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