Keeping this buffer persistently greatly helps performance

2 files changed, 8 insertions, 8 deletions

diff --git a/src/modes/cbc/cbc.cpp b/src/modes/cbc/cbc.cpp
index 65b78fbc5..bb7c56858 100644
--- a/src/modes/cbc/cbc.cpp
+++ b/src/modes/cbc/cbc.cpp
@@ -163,19 +163,17 @@ void CBC_Decryption::update(secure_vector<byte>& buffer, size_t offset)
    BOTAN_ASSERT(sz % BS == 0, "Input is full blocks");
    size_t blocks = sz / BS;
 
-   secure_vector<byte> temp(update_granularity());
-
    while(blocks)
       {
-      const size_t to_proc = std::min(sz, temp.size());
+      const size_t to_proc = std::min(sz, m_tempbuf.size());
 
-      cipher().decrypt_n(buf, &temp[0], to_proc / BS);
+      cipher().decrypt_n(buf, &m_tempbuf[0], to_proc / BS);
 
-      xor_buf(&temp[0], state_ptr(), BS);
-      xor_buf(&temp[BS], buf, to_proc - BS);
+      xor_buf(&m_tempbuf[0], state_ptr(), BS);
+      xor_buf(&m_tempbuf[BS], buf, to_proc - BS);
       copy_mem(state_ptr(), buf + (to_proc - BS), BS);
 
-      copy_mem(buf, &temp[0], to_proc);
+      copy_mem(buf, &m_tempbuf[0], to_proc);
 
       buf += to_proc;
       blocks -= to_proc / BS;
diff --git a/src/modes/cbc/cbc.h b/src/modes/cbc/cbc.h
index 8e3a72fd0..add6a206f 100644
--- a/src/modes/cbc/cbc.h
+++ b/src/modes/cbc/cbc.h
@@ -78,7 +78,7 @@ class BOTAN_DLL CBC_Decryption : public CBC_Mode
    {
    public:
       CBC_Decryption(BlockCipher* cipher, BlockCipherModePaddingMethod* padding) :
-         CBC_Mode(cipher, padding) {}
+         CBC_Mode(cipher, padding), m_tempbuf(update_granularity()) {}
 
       void update(secure_vector<byte>& blocks, size_t offset) override;
 
@@ -87,6 +87,8 @@ class BOTAN_DLL CBC_Decryption : public CBC_Mode
       size_t output_length(size_t input_length) const override;
 
       size_t minimum_final_size() const override;
+   private:
+      secure_vector<byte> m_tempbuf;
    };
 
 }