1 files changed, 13 insertions, 7 deletions
diff --git a/src/lib/stream/chacha/chacha.cpp b/src/lib/stream/chacha/chacha.cpp
index a1355cbe6..327454d79 100644
--- a/src/lib/stream/chacha/chacha.cpp
+++ b/src/lib/stream/chacha/chacha.cpp
@@ -176,11 +176,14 @@ void ChaCha::cipher(const uint8_t in[], uint8_t out[], size_t length)
 
    while(length >= m_buffer.size() - m_position)
       {
-      xor_buf(out, in, &m_buffer[m_position], m_buffer.size() - m_position);
-      length -= (m_buffer.size() - m_position);
-      in += (m_buffer.size() - m_position);
-      out += (m_buffer.size() - m_position);
+      const size_t available = m_buffer.size() - m_position;
+
+      xor_buf(out, in, &m_buffer[m_position], available);
       chacha_x8(m_buffer.data(), m_state.data(), m_rounds);
+
+      length -= available;
+      in += available;
+      out += available;
       m_position = 0;
       }
 
@@ -195,10 +198,13 @@ void ChaCha::write_keystream(uint8_t out[], size_t length)
 
    while(length >= m_buffer.size() - m_position)
       {
-      copy_mem(out, &m_buffer[m_position], m_buffer.size() - m_position);
-      length -= (m_buffer.size() - m_position);
-      out += (m_buffer.size() - m_position);
+      const size_t available = m_buffer.size() - m_position;
+
+      copy_mem(out, &m_buffer[m_position], available);
       chacha_x8(m_buffer.data(), m_state.data(), m_rounds);
+
+      length -= available;
+      out += available;
       m_position = 0;
       }