From 37ed0fc5fd92f7ae658cbcdf4c608714688ef7bf Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Thu, 11 Sep 2014 15:44:03 +1000
Subject: [PATCH] hash: cleanup fletcher

---
 hash/adler.cpp    |  7 +++++--
 hash/fletcher.hpp | 22 +++++++++++++++-------
 test/checksum.cpp |  7 ++++---
 3 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/hash/adler.cpp b/hash/adler.cpp
index 4e6855c1..8e46fb0e 100644
--- a/hash/adler.cpp
+++ b/hash/adler.cpp
@@ -24,14 +24,17 @@
 
 static const unsigned MODULUS = 65521;
 
+//-----------------------------------------------------------------------------
 uint32_t
 adler32 (const void* restrict _data, size_t _size)
-    { return fletcher<32, MODULUS, 1, 0> (_data, _size); }
+{
+    return adler32 ((uint8_t*)_data, (uint8_t*)_data + _size);
+}
 
 
 //-----------------------------------------------------------------------------
 uint32_t
 adler32 (const uint8_t *first, const uint8_t *last)
 {
-    return adler32 (first, last - first);
+    return fletcher<32, MODULUS, 1, 0> (first, last - first);
 }
diff --git a/hash/fletcher.hpp b/hash/fletcher.hpp
index fe801b17..2f755f50 100644
--- a/hash/fletcher.hpp
+++ b/hash/fletcher.hpp
@@ -26,19 +26,27 @@
 #include <cstdlib>
 
 
-template <unsigned BITS, unsigned MODULUS, unsigned INITIAL_A, unsigned INITIAL_B>
-typename bits_type<BITS>::uint
-fletcher (const void *restrict _data, size_t size) {
-    const uint8_t *restrict data = static_cast<const uint8_t*> (_data);
-    typename bits_type<BITS>::uint A = INITIAL_A,
-                                   B = INITIAL_B;
+template <
+    unsigned OUTPUT,
+    unsigned MODULUS,
+    unsigned INITIAL_A,
+    unsigned INITIAL_B
+>
+typename bits_type<OUTPUT>::uint
+fletcher (const void *restrict _data,
+          size_t size)
+{
+    typedef typename bits_type<OUTPUT / 2>::uint temp_t;
+
+    auto data = static_cast<const uint8_t*> (_data);
+    temp_t A = INITIAL_A, B = INITIAL_B;
 
     for (size_t i = 0; i < size; ++i) {
         A = (A + data[i]) % MODULUS;
         B = (A +       B) % MODULUS;
     }
 
-    return (B << (BITS / 2)) | A;
+    return (B << (OUTPUT / 2u)) + A;
 }
 
 #endif
diff --git a/test/checksum.cpp b/test/checksum.cpp
index ebf5bf31..386b2bf2 100644
--- a/test/checksum.cpp
+++ b/test/checksum.cpp
@@ -14,11 +14,12 @@ static const char *ALPHABET = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVW
 static const struct {
     uint32_t adler;
     uint16_t bsd;
-    
+
     const char *data;
     size_t      size;
 } TESTS[] = {
-    { 0xDF5B150C, 0x52FB, ALPHABET, strlen (ALPHABET) }
+    { 0xDF5B150C, 0x52FB, ALPHABET, strlen (ALPHABET) },
+    { 0x11E60398, 0x3DC8, "Wikipedia", strlen ("Wikipedia") }
 };
 
 
@@ -26,7 +27,7 @@ int
 main (int, char**) {
     for (unsigned i = 0; i < elems (TESTS); ++i) {
         CHECK_EQ (TESTS[i].adler, adler32 (TESTS[i].data, TESTS[i].size));
-        CHECK_EQ (TESTS[i].bsd,   bsdsum (TESTS[i].data, TESTS[i].size));
+        CHECK_EQ (TESTS[i].bsd,   bsdsum  (TESTS[i].data, TESTS[i].size));
     }
 
     return EXIT_SUCCESS;