HIR Deserialise - Add a 1KB buffer to the front

2 files changed, 42 insertions, 4 deletions

diff --git a/src/hir/serialise_lowlevel.cpp b/src/hir/serialise_lowlevel.cpp
index a8f69eb2..1678b114 100644
--- a/src/hir/serialise_lowlevel.cpp
+++ b/src/hir/serialise_lowlevel.cpp
@@ -22,16 +22,51 @@ void ::HIR::serialise::Writer::write(const void* buf, size_t len)
 
 
 ::HIR::serialise::Reader::Reader(const ::std::string& filename):
-    m_backing( filename )
+    m_backing( filename ),
+    m_buffer(),
+    m_buffer_ofs(0)
 {
+    m_buffer.reserve(1024);
     m_is.push( ::boost::iostreams::zlib_decompressor() );
     m_is.push( m_backing );
 }
 
 void ::HIR::serialise::Reader::read(void* buf, size_t len)
 {
-    m_is.read(reinterpret_cast<char*>(buf), len);
-    if( !m_is ) {
-        throw "";
+    size_t rem = m_buffer.size() - m_buffer_ofs;
+    if( m_buffer_ofs < m_buffer.size() ) {
+        if( len <= rem ) {
+            memcpy(buf, m_buffer.data() + m_buffer_ofs, len);
+            m_buffer_ofs += len;
+            return ;
+        }
+        else {
+            memcpy(buf, m_buffer.data() + m_buffer_ofs, rem);
+            m_buffer_ofs += rem;
+            len -= rem;
+        }
+    }
+    // m_bufer_ofs == m_buffer.size()
+    
+    if( len >= m_buffer.capacity() )
+    {
+        // If the new read is longer than the buffer size, skip the buffer.
+        m_is.read(reinterpret_cast<char*>(buf), len);
+    }
+    else
+    {
+        m_buffer.resize( m_buffer.capacity(), 0 );
+        m_buffer_ofs = 0;
+        m_is.read(reinterpret_cast<char*>(m_buffer.data()), m_buffer.capacity());
+        size_t dat_len = m_is.gcount();
+        
+        if( dat_len == 0 )
+            throw "";
+        if( dat_len < len )
+            throw "";
+        
+        m_buffer.resize( dat_len );
+        memcpy(reinterpret_cast<uint8_t*>(buf) + rem, m_buffer.data(), len);
+        m_buffer_ofs = len;
     }
 }
diff --git a/src/hir/serialise_lowlevel.hpp b/src/hir/serialise_lowlevel.hpp
index 34464683..c1e4a4c8 100644
--- a/src/hir/serialise_lowlevel.hpp
+++ b/src/hir/serialise_lowlevel.hpp
@@ -127,6 +127,9 @@ class Reader
 {
     ::std::ifstream m_backing;
     ::boost::iostreams::filtering_istream  m_is;
+    
+    ::std::vector<uint8_t>  m_buffer;
+    unsigned int    m_buffer_ofs;
 public:
     Reader(const ::std::string& path);
     Reader(const Writer&) = delete;