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/*

* Reference Huffman coding

* Copyright (c) Project Nayuki

*

* https://www.nayuki.io/page/reference-huffman-coding

* https://github.com/nayuki/Reference-Huffman-coding

*/

import java.io.IOException;

import java.util.List;

import java.util.Objects;

/**

* Encodes symbols and writes to a Huffman-coded bit stream. Not thread-safe.

* @see HuffmanDecoder

*/

public final class HuffmanEncoder {

// The underlying bit output stream (not null).

private BitOutputStream output;

/**

* The code tree to use in the next {@link#write(int)} operation. Must be given a non-{@code null}

* value before calling write(). The tree can be changed after each symbol encoded, as long

* as the encoder and decoder have the same tree at the same point in the code stream.

*/

public CodeTree codeTree;

/**

* Constructs a Huffman encoder based on the specified bit output stream.

* @param out the bit output stream to write to

* @throws NullPointerException if the output stream is {@code null}

*/

public HuffmanEncoder(BitOutputStream out) {

Objects.requireNonNull(out);

output = out;

}

/**

* Encodes the specified symbol and writes to the Huffman-coded output stream.

* @param symbol the symbol to encode, which is non-negative and must be in the range of the code tree

* @throws IOException if an I/O exception occurred

* @throws NullPointerException if the current code tree is {@code null}

* @throws IllegalArgumentException if the symbol value is negative or has no binary code

*/

public void write(int symbol) throws IOException {

if (codeTree == null)

throw new NullPointerException("Code tree is null");

List<Integer> bits = codeTree.getCode(symbol);

for (int b : bits)

output.write(b);

}

}