complete lz77 compress algorithm

Author: 15045120

src/main/java/com/github/myibu/algorithm/compress/Compressor.java

@@ -5,7 +5,7 @@
  * @author myibu
  * Created on 2021/10/11
  */
-public interface Compressor {
+public interface Compressor extends Debugable {
  /**
  * compress bytes
  * @param in_data input

src/main/java/com/github/myibu/algorithm/compress/Debugable.java

@@ -0,0 +1,14 @@
+package com.github.myibu.algorithm.compress;
+
+/**
+ * compressor for compress and decompress
+ * @author myibu
+ * Created on 2021/10/15
+ */
+public interface Debugable {
+ /**
+ * enable Debug or not， default should be not enabled
+ * @param isDebug is debug
+ */
+ void setDebug(boolean isDebug);
+}

src/main/java/com/github/myibu/algorithm/compress/LZ77Compressor.java

@@ -69,9 +69,6 @@ public int compress(byte[] in_data, int in_len, byte[] out_data) {
  for (int i = lStart; i < lEnd; i++) {
  lWindow[i] = in_data[ip + i];
  }
- //System.out.println("txt=" + new String() + new String(in_data) + ", sBuf="
- // + new StringBuilder(new String(sBuf)).reverse().toString() + ", lWindow=" + new String(lWindow));
-
  int llStart = sEnd - 1, rrStart = 0, llEnd = 0, rrEnd = (lp = lEnd);
  int minMatched = 1, minIndex = 0;
  while (llStart >= 0) {
@@ -95,9 +92,17 @@ public int compress(byte[] in_data, int in_len, byte[] out_data) {
  ip++;
  tuples.add(Arrays.asList(0, 0, (int)lWindow[0]));
  }
+ if (isDebug) {
+ System.out.println("Txt=" + new String() + new String(in_data) + ", SearchBuffer="
+ + new StringBuilder(new String(sBuf)).reverse().toString() + ", LookaheadWindow=" + new String(lWindow)
+ + " | " + tuples.get(tuples.size()-1)/* + " | " + (char)(tuples.get(tuples.size()-1).get(2).intValue())*/);
+ }
+ }
+ int compressedLen = doEncode(tuples, out_data);
+ if (isDebug) {
+ System.out.println("after encode: compressed rate=" + (compressedLen * 1.0 / in_len));
  }
- // System.out.println(tuples);
- return doEncode(tuples, out_data);
+ return compressedLen;
  }
 
  private int doEncode(List<List<Integer>> tuples, byte[] out_data) {
@@ -111,12 +116,16 @@ private int doEncode(List<List<Integer>> tuples, byte[] out_data) {
  bits.append(bits2);
  Bits bits3 = Bits.ofByte((byte)tuple.get(2).intValue());
  bits.append(bits3);
- // System.out.println("("+ bits1 + ", "+ bits2 + ", "+ bits3 + ")");
+ if (isDebug) {
+ System.out.println(tuple + " encoded result: " + "("+ bits1 + ", "+ bits2 + ", "+ bits3 + ")");
+ }
  finalRes.append(bits);
  }
  byte[] fr = finalRes.toByteArray();
  System.arraycopy(fr, 0, out_data, 0, fr.length);
- // System.out.println("bits: " + finalRes);
+ if (isDebug) {
+ System.out.println("after encode: bits=" + finalRes);
+ }
  return fr.length;
  }
 
@@ -145,9 +154,12 @@ public int decompress(byte[] in_data, int in_len, byte[] out_data) {
  }
  List<Bits> sortedEncodeSeq = allEncodeSeq.stream().sorted(Comparator.comparingInt(Bits::length)).collect(Collectors.toList());
  Bits bits = Bits.ofByte(in_data);
+ if (isDebug) {
+ System.out.println("before decode: bits=" + bits);
+ }
  int ip = 0;
  List<List<Integer>> tuples = new ArrayList<>();
- while (ip < bits.length()) {
+ while (ip < bits.length() && ip + e1 <= bits.length()) {
  Bits b1 = bits.subBits(ip, ip + e1);
  ip = ip + e1;
  int offset = encoder.encodeToBinary(b1);
@@ -168,7 +180,9 @@ public int decompress(byte[] in_data, int in_len, byte[] out_data) {
  tuples.add(Arrays.asList(offset, length, symbol));
  ip += 8;
  }
- // System.out.println(tuples);
+ if (isDebug) {
+ System.out.println("decode tuples=" + tuples);
+ }
  return doDecode(tuples, out_data);
  }
 
@@ -181,7 +195,9 @@ private int doDecode(List<List<Integer>> tuples, byte[] out_data) {
  seq.append(sb);
  } else {
  int start = seq.byteLength() < s ? seq.byteLength() - offset: s - offset;
- seq.append(seq.subBits(start * 8, (start + length) * 8)).append(sb);
+ int used = seq.byteLength() < s ? 0 : seq.byteLength() - s;
+ // System.out.println("start=" + start + ", used=" + used + ", length=" + length);
+ seq.append(seq.subBits((used + start) * 8, (used + start + length) * 8)).append(sb);
  }
  }
  int len = seq.byteLength();
@@ -190,4 +206,12 @@ private int doDecode(List<List<Integer>> tuples, byte[] out_data) {
  }
  return len;
  }
+
+
+ private boolean isDebug = false;
+
+ @Override
+ public void setDebug(boolean isDebug) {
+ this.isDebug = isDebug;
+ }
 }

src/main/java/com/github/myibu/algorithm/compress/LZFCompressor.java

@@ -178,4 +178,11 @@ public int decompress(byte[] in_data, int in_len, byte[] out_data) {
  }
  return op;
  }
+
+ private boolean isDebug;
+
+ @Override
+ public void setDebug(boolean isDebug) {
+ this.isDebug = isDebug;
+ }
 }

src/main/java/com/github/myibu/algorithm/data/Bits.java

@@ -245,7 +245,7 @@ public static Bits ofByte(byte val, int len) {
  bits.table[j] = (((val>>i) & 0x01) ==1) ? Bit.ONE : Bit.ZERO;
  }
  for (; j >= 0; j--) {
- bits.table[j] = val > 0 ? Bit.ZERO : Bit.ONE;
+ bits.table[j] = val >= 0 ? Bit.ZERO : Bit.ONE;
  }
  bits.used += len;
  return bits;
@@ -272,7 +272,7 @@ public static Bits ofShort(short val, int len) {
  bits.table[j] = (((val>>i) & 0x01) ==1) ? Bit.ONE : Bit.ZERO;
  }
  for (; j >= 0; j--) {
- bits.table[j] = val > 0 ? Bit.ZERO : Bit.ONE;
+ bits.table[j] = val >= 0 ? Bit.ZERO : Bit.ONE;
  }
  bits.used += len;
  return bits;
@@ -299,7 +299,7 @@ public static Bits ofInt(int val, int len) {
  bits.table[j] = (((val>>i) & 0x01) ==1) ? Bit.ONE : Bit.ZERO;
  }
  for (; j >= 0; j--) {
- bits.table[j] = val > 0 ? Bit.ZERO : Bit.ONE;
+ bits.table[j] = val >= 0 ? Bit.ZERO : Bit.ONE;
  }
  bits.used += len;
  return bits;
@@ -378,7 +378,7 @@ public static Bits ofLong(long val, int len) {
  bits.table[j] = (((val>>i) & 0x01) ==1) ? Bit.ONE : Bit.ZERO;
  }
  for (; j >= 0; j--) {
- bits.table[j] = val > 0 ? Bit.ZERO : Bit.ONE;
+ bits.table[j] = val >= 0 ? Bit.ZERO : Bit.ONE;
  }
  bits.used += len;
  return bits;

src/test/java/com/github/myibu/algorithm/AlgorithmTest.java

@@ -168,16 +168,16 @@ public void testLZFCompressor() {
 
  @Test
  public void testLZ77Compressor() {
- // todo
- byte[] in_data = "com.github.myibu.algorithm.AlgorithmTest.testLZ77Compressor".getBytes(StandardCharsets.UTF_8);
+ String txt = "在法律或合同明确规定的情况下，如当事人一方不履行或不适当履行合同义务时，另一方有权解除合同。故合同可由当事人一方行使解除权而消灭。《中华人民共和国经济合同法》规定，如由于合同所依据的国家计划被修改或取消，由于行政命令企业必须关闭、停产或转产，由于不可抗力以及由于一方违约致使合同不能履行或履行已无必要时，允许当事人一方及时通知他方变更或解除合同。";
+ byte[] in_data = txt.getBytes(StandardCharsets.UTF_8);
  byte[] out_data = new byte[in_data.length*2];
  Compressor compressor = new LZ77Compressor();
+ compressor.setDebug(true);
  int compressed = compressor.compress(in_data, in_data.length, out_data);
  byte[] compressed_data = Arrays.copyOf(out_data, compressed);
-// System.out.println(new String(compressed_data));
  byte[] decompressed_data = new byte[compressed * 2];
  int decompressed = compressor.decompress(compressed_data, compressed, decompressed_data);
- Assert.assertEquals("com.github.myibu.algorithm.AlgorithmTest.testLZ77Compressor",
+ Assert.assertEquals(txt,
  new String(Arrays.copyOf(decompressed_data, decompressed), StandardCharsets.UTF_8));
  }