Alter how buffering is performed in MDx_HashFunction:add_data; rather

than always placing the first block into the temp buffer, we only
copy the data into there if we have to (ie, if we have an incomplete
block). So calling add_data with a block that is a multiple of the
hash function's internal block size is entirely zero-copy.

1 files changed, 19 insertions, 11 deletions

diff --git a/src/mdx_hash.cpp b/src/mdx_hash.cpp
index 93fbff1e8..736ead70e 100644
--- a/src/mdx_hash.cpp
+++ b/src/mdx_hash.cpp
@@ -37,21 +37,29 @@ void MDx_HashFunction::clear() throw()
 void MDx_HashFunction::add_data(const byte input[], u32bit length)
    {
    count += length;
-   buffer.copy(position, input, length);
-   if(position + length >= HASH_BLOCK_SIZE)
+
+   if(position)
       {
-      hash(buffer.begin());
-      input += (HASH_BLOCK_SIZE - position);
-      length -= (HASH_BLOCK_SIZE - position);
-      while(length >= HASH_BLOCK_SIZE)
+      buffer.copy(position, input, length);
+
+      if(position + length >= HASH_BLOCK_SIZE)
          {
-         hash(input);
-         input += HASH_BLOCK_SIZE;
-         length -= HASH_BLOCK_SIZE;
+         hash(buffer.begin());
+         input += (HASH_BLOCK_SIZE - position);
+         length -= (HASH_BLOCK_SIZE - position);
+         position = 0;
          }
-      buffer.copy(input, length);
-      position = 0;
       }
+
+   while(length >= HASH_BLOCK_SIZE)
+      {
+      hash(input);
+      input += HASH_BLOCK_SIZE;
+      length -= HASH_BLOCK_SIZE;
+      }
+
+   buffer.copy(position, input, length);
+
    position += length;
    }