Map<IncludeFileEdge, Integer> ids = new HashMap<IncludeFileEdge, Integer>();
        encoder.writeSmallInt(value.getFileStates().size());
        for (Map.Entry<File, SourceFileState> entry : value.getFileStates().entrySet()) {
            SourceFileState sourceFileState = entry.getValue();
            fileSerializer.write(encoder, entry.getKey());

    public CompilationState() {
        fileStates = ImmutableMap.of();
    }

    public Set<File> getSourceInputs() {
        return fileStates.keySet();
    }

    public ImmutableMap<File, SourceFileState> getFileStates() {
        return fileStates;
    }

    public SourceFileState getState(File file) {
        return fileStates.get(file);
    }