Expose a static method for computing hash tree size

Test: th

Change-Id: I53cae3ffeaef262733faf9070815cd396590c7be

2 files changed, 8 insertions, 4 deletions

diff --git a/verity/hash_tree_builder.cpp b/verity/hash_tree_builder.cpp
index 52899a35..1cd2e291 100644
--- a/verity/hash_tree_builder.cpp
+++ b/verity/hash_tree_builder.cpp
@@ -96,18 +96,19 @@ bool HashTreeBuilder::ParseBytesArrayFromString(
   return true;
 }
 
-uint64_t HashTreeBuilder::CalculateSize(uint64_t input_size) const {
+uint64_t HashTreeBuilder::CalculateSize(
+    uint64_t input_size, size_t block_size, size_t hash_size) {
   uint64_t verity_blocks = 0;
   size_t level_blocks;
   size_t levels = 0;
   do {
     level_blocks =
-        verity_tree_blocks(input_size, block_size_, hash_size_, levels);
+        verity_tree_blocks(input_size, block_size, hash_size, levels);
     levels++;
     verity_blocks += level_blocks;
   } while (level_blocks > 1);
 
-  return verity_blocks * block_size_;
+  return verity_blocks * block_size;
 }
 
 bool HashTreeBuilder::Initialize(int64_t expected_data_size,
diff --git a/verity/include/verity/hash_tree_builder.h b/verity/include/verity/hash_tree_builder.h
index f4ceab8c..a601d1d9 100644
--- a/verity/include/verity/hash_tree_builder.h
+++ b/verity/include/verity/hash_tree_builder.h
@@ -35,7 +35,10 @@ class HashTreeBuilder {
  public:
   HashTreeBuilder(size_t block_size, const EVP_MD* md);
   // Returns the size of the verity tree in bytes given the input data size.
-  uint64_t CalculateSize(uint64_t input_size) const;
+  uint64_t CalculateSize(uint64_t input_size) const {
+      return CalculateSize(input_size, block_size_, hash_size_);
+  }
+  static uint64_t CalculateSize(uint64_t input_size, size_t block_size, size_t hash_size);
   // Gets ready for the hash tree computation. We expect |expected_data_size|
   // bytes source data.
   bool Initialize(int64_t expected_data_size,