Add SHA256 calculator

Based on the sha256c.c file from the FreeBSD project and ported to compile on
Linux, Mac OS, and Windows. The file is licensed under the simplified/2-clause
BSD license so the library is now MIT/BSD-licensed.

1 files changed, 76 insertions, 0 deletions

diff --git a/butl/sha256.cxx b/butl/sha256.cxx
new file mode 100644
index 0000000..feca9a7
--- /dev/null
+++ b/butl/sha256.cxx
@@ -0,0 +1,76 @@
+// file      : butl/sha256.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <butl/sha256>
+
+// C interface for sha256c.
+//
+#include <stdint.h>
+#include <stddef.h> // size_t
+
+using SHA256_CTX = butl::sha256::context;
+
+extern "C"
+{
+  static void SHA256_Init (SHA256_CTX*);
+  static void SHA256_Update (SHA256_CTX*, const void*, size_t);
+  static void SHA256_Final (uint8_t[32], SHA256_CTX*);
+
+#include "sha256c.c"
+}
+
+using namespace std;
+
+namespace butl
+{
+  sha256::
+  sha256 ()
+      : done_ (false)
+  {
+    SHA256_Init (&ctx_);
+  }
+
+  void sha256::
+  append (const void* b, size_t n)
+  {
+    SHA256_Update (&ctx_, b, n);
+  }
+
+  const sha256::digest_type& sha256::
+  binary () const
+  {
+    if (!done_)
+    {
+      SHA256_Final (bin_, &ctx_);
+      done_ = true;
+      str_[0] = '\0'; // Indicate we haven't computed the string yet.
+    }
+
+    return bin_;
+  }
+
+  static const char hex_map[16] = {
+    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+    'a', 'b', 'c', 'd', 'e', 'f'};
+
+  const char* sha256::
+  string () const
+  {
+    if (!done_)
+      binary ();
+
+    if (str_[0] == '\0')
+    {
+      for (size_t i (0); i != 32; ++i)
+      {
+        str_[i * 2]     = hex_map[bin_[i] >> 4];
+        str_[i * 2 + 1] = hex_map[bin_[i] & 0x0f];
+      }
+
+      str_[64] = '\0';
+    }
+
+    return str_;
+  }
+}