Method writeToBuffer

vfs.go:2118–2138

writeToBuffer writes a dirty page to the write buffer for durability. If the page already exists in the buffer, it overwrites at the same offset. Otherwise, it appends to the end of the file. Must be called with f.mu held.

(pgno uint32, data []byte)

// Otherwise, it appends to the end of the file.
// Must be called with f.mu held.
func (f *VFSFile) writeToBuffer(pgno uint32, data []byte) error {
	var writeOffset int64
	if existingOff, ok := f.dirty[pgno]; ok {
		// Page already exists - overwrite at same offset
		writeOffset = existingOff
	} else {
		// New page - append to end of file
		writeOffset = f.bufferNextOff
		f.bufferNextOff += int64(len(data))
	}

	// Write page data (no header, just raw page data)
	if _, err := f.bufferFile.WriteAt(data, writeOffset); err != nil {
		return fmt.Errorf("write page to buffer: %w", err)
	}

	// Update dirty map with offset
	f.dirty[pgno] = writeOffset

	return nil
}

// clearWriteBuffer clears and resets the write buffer after successful sync.
func (f *VFSFile) clearWriteBuffer() error {