Index.java

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package dev.advo.fs.fs;
 
/**
 * An {@link Index} points to a file in the {@code main_file_cache.dat} file.
 * @author Graham
 */
public final class Index {
 
    /**
     * Decodes a buffer into an index.
     * @param buffer The buffer.
     * @return The decoded {@link Index}.
     * @throws IllegalArgumentException if the buffer length is invalid.
     */
    public static Index decode(byte[] buffer) {
        if (buffer.length != FileSystemConstants.INDEX_SIZE) {
            throw new IllegalArgumentException("Incorrect buffer length.");
        }
        
        int size = ((buffer[0] & 0xFF) << 16) | ((buffer[1] & 0xFF) << 8) | (buffer[2] & 0xFF);
        int block = ((buffer[3] & 0xFF) << 16) | ((buffer[4] & 0xFF) << 8) | (buffer[5] & 0xFF);
        
        return new Index(size, block);
    }
    
    /**
     * The size of the file.
     */
    private final int size;
    
    /**
     * The first block of the file.
     */
    private final int block;
    
    /**
     * Creates the index.
     * @param size The size of the file.
     * @param block The first block of the file.
     */
    public Index(int size, int block) {
        this.size = size;
        this.block = block;
    }
    
    /**
     * Gets the size of the file.
     * @return The size of the file.
     */
    public int getSize() {
        return size;
    }
    
    /**
     * Gets the first block of the file.
     * @return The first block of the file.
     */
    public int getBlock() {
        return block;
    }
 
}