FileReader: Cache fileSize on open for performance

include/athena/FileReader.hpp

@@ -40,8 +40,7 @@ public:
 
   void open();
   void close();
-  bool isOpen() const { return m_fileHandle != 0; }
-  bool save();
+  bool isOpen() const { return m_fileHandle != nullptr; }
   void seek(atInt64 pos, SeekOrigin origin = SeekOrigin::Current) override;
   atUint64 position() const override;
   atUint64 length() const override;
@@ -64,6 +63,7 @@ protected:
   std::string m_filename;
 #endif
   HandleType m_fileHandle;
+  atUint64 m_fileSize;
   std::unique_ptr<atUint8[]> m_cacheData;
   atInt32 m_blockSize;
   atInt32 m_curBlock;

src/athena/FileReader.cpp

@@ -38,6 +38,8 @@ void FileReader::open() {
     return;
   }
 
+  m_fileSize = utility::fileSize(m_filename);
+
   // reset error
   m_hasError = false;
 }
@@ -112,7 +114,7 @@ atUint64 FileReader::length() const {
     return 0;
   }
 
-  return utility::fileSize(m_filename);
+  return m_fileSize;
 }
 
 atUint64 FileReader::readUBytesToBuf(void* buf, atUint64 len) {
@@ -126,11 +128,10 @@ atUint64 FileReader::readUBytesToBuf(void* buf, atUint64 len) {
   if (m_blockSize <= 0)
     return fread(buf, 1, len, m_fileHandle);
   else {
-    atUint64 fs = utility::fileSize(m_filename);
-    if (m_offset >= fs)
+    if (m_offset >= m_fileSize)
       return 0;
-    if (m_offset + len >= fs)
-      len = fs - m_offset;
+    if (m_offset + len >= m_fileSize)
+      len = m_fileSize - m_offset;
 
     size_t block = m_offset / m_blockSize;
     atUint64 cacheOffset = m_offset % m_blockSize;