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< > BotCompany Repo | #1035665 // HuffmanTree

JavaX fragment (include) [tags: use-pretranspiled]

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sclass HuffmanTree is BitIO {
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  settable Node root;
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  Leaf[] characterMap = new[256];
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  settable bool debug;
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  replace print with if (debug) print.
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  /*
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  algebraic type Node {
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    constructor Branch(Node zero, Node one) {}
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    constructor Leaf(byte literal) {}
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  }
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  */
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  abstract class Node is BitIO {
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    settable Branch parent;
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    void buildSymbol(BitBuffer head, Node child) {
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      parent?.buildSymbol(head, this);
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    }
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    abstract Leaf readSymbol(BitHead head);
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  }
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  class Branch > Node {
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    gettable Node zero;
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    gettable Node one;
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    meta-for zero also as one {
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      selfType zero(Node zero) {
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        this.zero = zero;
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        zero.parent = this;
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        this;
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      }
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    }
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    public void readWrite(BitHead head) {  
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      head.exchangeBit(1);
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      head.exchange(zero, -> zero(readNode(head)));
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      head.exchange(one, -> one(readNode(head)));
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    }
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    void buildSymbol(BitBuffer head, Node child) {
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      head.add(child == one);
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      super.buildSymbol(head, child);
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    }
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    Leaf readSymbol(BitHead head) {
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      bool bit = head.readBit();
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      print("Read bit " + bit);
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      ret (bit ? one : zero).readSymbol(head);
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    }
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  }
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  class Leaf > Node {
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    gettable byte literal;
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    *() {}
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    *(int literal) { literal((byte) literal); }
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    byte get() { ret literal; }
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    selfType literal(byte b) {
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      literal = b;
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      fillCharacterMap();
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      this;
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    }
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    public void readWrite(BitHead head) {  
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      head.exchangeBit(0);
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      head.exchangeByte(literal, l1 literal);
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      print(this);
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    }
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    void fillCharacterMap {
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      characterMap[ubyteToInt(literal)] = this;
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    }
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    Leaf readSymbol(BitHead head) {
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      print("Reached symbol " + this);
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      this;
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    }
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    toString { 
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      ret "Literal " + byteToHex(literal);
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    }
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  }
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  void makeRootIfEmpty {
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    root ifNull = new Leaf(0);
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  }
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  Node readNode(BitHead head) {
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    bool type = head.peekBit();
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    Node node = type ? new Branch : new Leaf;
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    print(type ? "Branch" : "Leaf");
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    node.readWrite(head);
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    ret node;
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  }
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  public void readWrite(BitHead head) {
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    if (head.writeMode()) {
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      makeRootIfEmpty();
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      root.readWrite(head);
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    }
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    if (head.readMode())
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      root = readNode(head);
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  }
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  toString {
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    makeRootIfEmpty();
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    new LS out;
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    new StringBuilder symbol;
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    embedded void toString_collect(Node node) {
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      if (node cast Leaf) {
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        out.add(symbol + ": " + /*ubyteToHex*/quote(codePoint(ubyteToInt(node!))));
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      } else {
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        cast node to Branch;
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        symbol.append("0");
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        toString_collect(node.zero());
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        removeLast(symbol);
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        symbol.append("1");
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        toString_collect(node.one());
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        removeLast(symbol);
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      }
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    }
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    toString_collect(root);
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    ret lines(out);
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  }
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  void writeCharacter aka writeSymbol(int sym, BitHead head) {
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    sym &= 0xFF;
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    Leaf node = characterMap[sym];
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    if (node == null)
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      fail("Symbol cannot be encoded: " + sym);
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    new BitBuffer buffer;
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    node.buildSymbol(buffer, null);
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    // when there is only one symbol
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    if (buffer.isEmpty())
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      buffer.add(0);
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    for (int i = l(buffer)-1; i >= 0; i--)
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      head.writeBit(buffer.get(i));
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  }
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  int readSymbol(BitHead head) {
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    if (head.isEOF()) ret -1;
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    if (root instanceof Leaf)
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      head.advanceBit(); // don't even care
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    ret ubyteToInt(root.readSymbol(head)!);
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  }
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}

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Snippet ID: #1035665
Snippet name: HuffmanTree
Eternal ID of this version: #1035665/41
Text MD5: 7958e64a838760d732647aa3e60ed5b3
Transpilation MD5: a32895591c00765eddc0fc320d79e588
Author: stefan
Category: javax / compression
Type: JavaX fragment (include)
Public (visible to everyone): Yes
Archived (hidden from active list): No
Created/modified: 2022-07-15 20:57:14
Source code size: 3647 bytes / 158 lines
Pitched / IR pitched: No / No
Views / Downloads: 202 / 490
Version history: 40 change(s)
Referenced in: [show references]