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   *
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   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
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  package com.sun.java.util.jar.pack;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.util.Arrays;
  import java.util.HashSet;
  import java.util.Set;
  import static com.sun.java.util.jar.pack.Constants.*;
  
  /**
   * Population-based coding.
   * See the section "Encodings of Uncorrelated Values" in the Pack200 spec.
   * @author John Rose
   */
  // This tactic alone reduces the final zipped rt.jar by about a percent.
  class PopulationCoding implements CodingMethod {
      Histogram vHist;   // histogram of all values
      int[]     fValues; // list of favored values
      int       fVlen;   // inclusive max index
      long[]    symtab;  // int map of favored value -> token [1..#fValues]
  
      CodingMethod favoredCoding;
      CodingMethod tokenCoding;
      CodingMethod unfavoredCoding;
  
      int L = -1;  //preferred L value for tokenCoding
  
      public void setFavoredValues(int[] fValues, int fVlen) {
          // Note:  {f} is allFavoredValues[1..fvlen], not [0..fvlen-1].
          // This is because zero is an exceptional favored value index.
          assert(fValues[0] == 0);  // must be empty
          assert(this.fValues == null);  // do not do this twice
          this.fValues = fValues;
          this.fVlen   = fVlen;
          if (L >= 0) {
              setL(L);  // reassert
          }
      }
      public void setFavoredValues(int[] fValues) {
          int lfVlen = fValues.length-1;
          setFavoredValues(fValues, lfVlen);
      }
      public void setHistogram(Histogram vHist) {
          this.vHist = vHist;
      }
      public void setL(int L) {
          this.L = L;
          if (L >= 0 && fValues != null && tokenCoding == null) {
              tokenCoding = fitTokenCoding(fVlen, L);
              assert(tokenCoding != null);
          }
      }
  
      public static Coding fitTokenCoding(int fVlen, int L) {
          // Find the smallest B s.t. (B,H,0) covers fVlen.
          if (fVlen < 256)
              // H/L do not matter when B==1
              return BandStructure.BYTE1;
          Coding longest = BandStructure.UNSIGNED5.setL(L);
          if (!longest.canRepresentUnsigned(fVlen))
              return null;  // failure; L is too sharp and fVlen too large
          Coding tc = longest;
          for (Coding shorter = longest; ; ) {
              shorter = shorter.setB(shorter.B()-1);
              if (shorter.umax() < fVlen)
                  break;
              tc = shorter;  // shorten it by reducing B
          }
          return tc;
      }
  
      public void setFavoredCoding(CodingMethod favoredCoding) {
         this.favoredCoding = favoredCoding;
     }
     public void setTokenCoding(CodingMethod tokenCoding) {
         this.tokenCoding = tokenCoding;
         this.L = -1;
         if (tokenCoding instanceof Coding && fValues != null) {
             Coding tc = (Coding) tokenCoding;
             if (tc == fitTokenCoding(fVlen, tc.L()))
                 this.L = tc.L();
             // Otherwise, it's a non-default coding.
         }
     }
     public void setUnfavoredCoding(CodingMethod unfavoredCoding) {
         this.unfavoredCoding = unfavoredCoding;
     }
 
     public int favoredValueMaxLength() {
         if (L == 0)
             return Integer.MAX_VALUE;
         else
             return BandStructure.UNSIGNED5.setL(L).umax();
     }
 
     public void resortFavoredValues() {
         Coding tc = (Coding) tokenCoding;
         // Make a local copy before reordering.
         fValues = BandStructure.realloc(fValues, 1+fVlen);
         // Resort favoredValues within each byte-size cadre.
         int fillp = 1;  // skip initial zero
         for (int n = 1; n <= tc.B(); n++) {
             int nmax = tc.byteMax(n);
             if (nmax > fVlen)
                 nmax = fVlen;
             if (nmax < tc.byteMin(n))
                 break;
             int low = fillp;
             int high = nmax+1;
             if (high == low)  continue;
             assert(high > low)
                 : high+"!>"+low;
             assert(tc.getLength(low) == n)
                 : n+" != len("+(low)+") == "+
                   tc.getLength(low);
             assert(tc.getLength(high-1) == n)
                 : n+" != len("+(high-1)+") == "+
                   tc.getLength(high-1);
             int midTarget = low + (high-low)/2;
             int mid = low;
             // Divide the values into cadres, and sort within each.
             int prevCount = -1;
             int prevLimit = low;
             for (int i = low; i < high; i++) {
                 int val = fValues[i];
                 int count = vHist.getFrequency(val);
                 if (prevCount != count) {
                     if (n == 1) {
                         // For the single-byte encoding, keep strict order
                         // among frequency groups.
                         Arrays.sort(fValues, prevLimit, i);
                     } else if (Math.abs(mid - midTarget) >
                                Math.abs(i   - midTarget)) {
                         // Find a single inflection point
                         // close to the middle of the byte-size cadre.
                         mid = i;
                     }
                     prevCount = count;
                     prevLimit = i;
                 }
             }
             if (n == 1) {
                 Arrays.sort(fValues, prevLimit, high);
             } else {
                 // Sort up to the midpoint, if any.
                 Arrays.sort(fValues, low, mid);
                 Arrays.sort(fValues, mid, high);
             }
             assert(tc.getLength(low) == tc.getLength(mid));
             assert(tc.getLength(low) == tc.getLength(high-1));
             fillp = nmax+1;
         }
         assert(fillp == fValues.length);
 
         // Reset symtab.
         symtab = null;
     }
 
     public int getToken(int value) {
         if (symtab == null)
             symtab = makeSymtab();
         int pos = Arrays.binarySearch(symtab, (long)value << 32);
         if (pos < 0)  pos = -pos-1;
         if (pos < symtab.length && value == (int)(symtab[pos] >>> 32))
             return (int)symtab[pos];
         else
             return 0;
     }
 
     public int[][] encodeValues(int[] values, int start, int end) {
         // Compute token sequence.
         int[] tokens = new int[end-start];
         int nuv = 0;
         for (int i = 0; i < tokens.length; i++) {
             int val = values[start+i];
             int tok = getToken(val);
             if (tok != 0)
                 tokens[i] = tok;
             else
                 nuv += 1;
         }
         // Compute unfavored value sequence.
         int[] unfavoredValues = new int[nuv];
         nuv = 0;  // reset
         for (int i = 0; i < tokens.length; i++) {
             if (tokens[i] != 0)  continue;  // already covered
             int val = values[start+i];
             unfavoredValues[nuv++] = val;
         }
         assert(nuv == unfavoredValues.length);
         return new int[][]{ tokens, unfavoredValues };
     }
 
     private long[] makeSymtab() {
         long[] lsymtab = new long[fVlen];
         for (int token = 1; token <= fVlen; token++) {
             lsymtab[token-1] = ((long)fValues[token] << 32) | token;
         }
         // Index by value:
         Arrays.sort(lsymtab);
         return lsymtab;
     }
 
     private Coding getTailCoding(CodingMethod c) {
         while (c instanceof AdaptiveCoding)
             c = ((AdaptiveCoding)c).tailCoding;
         return (Coding) c;
     }
 
     // CodingMethod methods.
     public void writeArrayTo(OutputStream out, int[] a, int start, int end) throws IOException {
         int[][] vals = encodeValues(a, start, end);
         writeSequencesTo(out, vals[0], vals[1]);
     }
     void writeSequencesTo(OutputStream out, int[] tokens, int[] uValues) throws IOException {
         favoredCoding.writeArrayTo(out, fValues, 1, 1+fVlen);
         getTailCoding(favoredCoding).writeTo(out, computeSentinelValue());
         tokenCoding.writeArrayTo(out, tokens, 0, tokens.length);
         if (uValues.length > 0)
             unfavoredCoding.writeArrayTo(out, uValues, 0, uValues.length);
     }
 
    int computeSentinelValue() {
         Coding fc = getTailCoding(favoredCoding);
         if (fc.isDelta()) {
             // repeat the last favored value, using delta=0
             return 0;
         } else {
             // else repeat the shorter of the min or last value
             int min = fValues[1];
             int last = min;
             // (remember that fVlen is an inclusive limit in fValues)
             for (int i = 2; i <= fVlen; i++) {
                 last = fValues[i];
                 min = moreCentral(min, last);
             }
             int endVal;
             if (fc.getLength(min) <= fc.getLength(last))
                 return min;
             else
                 return last;
         }
    }
 
     public void readArrayFrom(InputStream in, int[] a, int start, int end) throws IOException {
         // Parameters are fCode, L, uCode.
         setFavoredValues(readFavoredValuesFrom(in, end-start));
         // Read the tokens.  Read them into the final array, for the moment.
         tokenCoding.readArrayFrom(in, a, start, end);
         // Decode the favored tokens.
         int headp = 0, tailp = -1;
         int uVlen = 0;
         for (int i = start; i < end; i++) {
             int tok = a[i];
             if (tok == 0) {
                 // Make a linked list, and decode in a second pass.
                 if (tailp < 0) {
                     headp = i;
                 } else {
                     a[tailp] = i;
                 }
                 tailp = i;
                 uVlen += 1;
             } else {
                 a[i] = fValues[tok];
             }
         }
         // Walk the linked list of "zero" locations, decoding unfavored vals.
         int[] uValues = new int[uVlen];
         if (uVlen > 0)
             unfavoredCoding.readArrayFrom(in, uValues, 0, uVlen);
         for (int i = 0; i < uVlen; i++) {
             int nextp = a[headp];
             a[headp] = uValues[i];
             headp = nextp;
         }
     }
 
     int[] readFavoredValuesFrom(InputStream in, int maxForDebug) throws IOException {
         int[] lfValues = new int[1000];  // realloc as needed
         // The set uniqueValuesForDebug records all favored values.
         // As each new value is added, we assert that the value
         // was not already in the set.
         Set<Integer> uniqueValuesForDebug = null;
         assert((uniqueValuesForDebug = new HashSet<>()) != null);
         int fillp = 1;
         maxForDebug += fillp;
         int min = Integer.MIN_VALUE;  // farthest from the center
         //int min2 = Integer.MIN_VALUE;  // emulate buggy 150.7 spec.
         int last = 0;
         CodingMethod fcm = favoredCoding;
         while (fcm instanceof AdaptiveCoding) {
             AdaptiveCoding ac = (AdaptiveCoding) fcm;
             int len = ac.headLength;
             while (fillp + len > lfValues.length) {
                 lfValues = BandStructure.realloc(lfValues);
             }
             int newFillp = fillp + len;
             ac.headCoding.readArrayFrom(in, lfValues, fillp, newFillp);
             while (fillp < newFillp) {
                 int val = lfValues[fillp++];
                 assert(uniqueValuesForDebug.add(val));
                 assert(fillp <= maxForDebug);
                 last = val;
                 min = moreCentral(min, val);
                 //min2 = moreCentral2(min2, val, min);
             }
             fcm = ac.tailCoding;
         }
         Coding fc = (Coding) fcm;
         if (fc.isDelta()) {
             for (long state = 0;;) {
                 // Read a new value:
                 state += fc.readFrom(in);
                 int val;
                 if (fc.isSubrange())
                     val = fc.reduceToUnsignedRange(state);
                 else
                     val = (int)state;
                 state = val;
                 if (fillp > 1 && (val == last || val == min)) //|| val == min2
                     break;
                 if (fillp == lfValues.length)
                     lfValues = BandStructure.realloc(lfValues);
                 lfValues[fillp++] = val;
                 assert(uniqueValuesForDebug.add(val));
                 assert(fillp <= maxForDebug);
                 last = val;
                 min = moreCentral(min, val);
                 //min2 = moreCentral(min2, val);
             }
         } else {
             for (;;) {
                 int val = fc.readFrom(in);
                 if (fillp > 1 && (val == last || val == min)) //|| val == min2
                     break;
                 if (fillp == lfValues.length)
                     lfValues = BandStructure.realloc(lfValues);
                 lfValues[fillp++] = val;
                 assert(uniqueValuesForDebug.add(val));
                 assert(fillp <= maxForDebug);
                 last = val;
                 min = moreCentral(min, val);
                 //min2 = moreCentral2(min2, val, min);
             }
         }
         return BandStructure.realloc(lfValues, fillp);
     }
 
     private static int moreCentral(int x, int y) {
         int kx = (x >> 31) ^ (x << 1);
         int ky = (y >> 31) ^ (y << 1);
         // bias kx/ky to get an unsigned comparison:
         kx -= Integer.MIN_VALUE;
         ky -= Integer.MIN_VALUE;
         int xy = (kx < ky? x: y);
         // assert that this ALU-ish version is the same:
         assert(xy == moreCentralSlow(x, y));
         return xy;
     }
 //  private static int moreCentral2(int x, int y, int min) {
 //      // Strict implementation of buggy 150.7 specification.
 //      // The bug is that the spec. says absolute-value ties are broken
 //      // in favor of positive numbers, but the suggested implementation
 //      // (also mentioned in the spec.) breaks ties in favor of negatives.
 //      if (x + y == 0)  return (x > y? x : y);
 //      return min;
 //  }
     private static int moreCentralSlow(int x, int y) {
         int ax = x;
         if (ax < 0)  ax = -ax;
         if (ax < 0)  return y;  //x is MIN_VALUE
         int ay = y;
         if (ay < 0)  ay = -ay;
         if (ay < 0)  return x;  //y is MIN_VALUE
         if (ax < ay)  return x;
         if (ax > ay)  return y;
         // At this point the absolute values agree, and the negative wins.
         return x < y ? x : y;
     }
 
     static final int[] LValuesCoded
         = { -1, 4, 8, 16, 32, 64, 128, 192, 224, 240, 248, 252 };
 
     public byte[] getMetaCoding(Coding dflt) {
         int K = fVlen;
         int LCoded = 0;
         if (tokenCoding instanceof Coding) {
             Coding tc = (Coding) tokenCoding;
             if (tc.B() == 1) {
                 LCoded = 1;
             } else if (L >= 0) {
                 assert(L == tc.L());
                 for (int i = 1; i < LValuesCoded.length; i++) {
                     if (LValuesCoded[i] == L) { LCoded = i; break; }
                 }
             }
         }
         CodingMethod tokenDflt = null;
         if (LCoded != 0 && tokenCoding == fitTokenCoding(fVlen, L)) {
             // A simple L value is enough to recover the tokenCoding.
             tokenDflt = tokenCoding;
         }
         int FDef = (favoredCoding == dflt)?1:0;
         int UDef = (unfavoredCoding == dflt || unfavoredCoding == null)?1:0;
         int TDef = (tokenCoding == tokenDflt)?1:0;
         int TDefL = (TDef == 1) ? LCoded : 0;
         assert(TDef == ((TDefL>0)?1:0));
         ByteArrayOutputStream bytes = new ByteArrayOutputStream(10);
         bytes.write(_meta_pop + FDef + 2*UDef + 4*TDefL);
         try {
             if (FDef == 0)  bytes.write(favoredCoding.getMetaCoding(dflt));
             if (TDef == 0)  bytes.write(tokenCoding.getMetaCoding(dflt));
             if (UDef == 0)  bytes.write(unfavoredCoding.getMetaCoding(dflt));
         } catch (IOException ee) {
             throw new RuntimeException(ee);
         }
         return bytes.toByteArray();
     }
     public static int parseMetaCoding(byte[] bytes, int pos, Coding dflt, CodingMethod res[]) {
         int op = bytes[pos++] & 0xFF;
         if (op < _meta_pop || op >= _meta_limit)  return pos-1; // backup
         op -= _meta_pop;
         int FDef = op % 2;
         int UDef = (op / 2) % 2;
         int TDefL = (op / 4);
         int TDef = (TDefL > 0)?1:0;
         int L = LValuesCoded[TDefL];
         CodingMethod[] FCode = {dflt}, TCode = {null}, UCode = {dflt};
         if (FDef == 0)
             pos = BandStructure.parseMetaCoding(bytes, pos, dflt, FCode);
         if (TDef == 0)
             pos = BandStructure.parseMetaCoding(bytes, pos, dflt, TCode);
         if (UDef == 0)
             pos = BandStructure.parseMetaCoding(bytes, pos, dflt, UCode);
         PopulationCoding pop = new PopulationCoding();
         pop.L = L;  // might be -1
         pop.favoredCoding   = FCode[0];
         pop.tokenCoding     = TCode[0];  // might be null!
         pop.unfavoredCoding = UCode[0];
         res[0] = pop;
         return pos;
     }
 
     private String keyString(CodingMethod m) {
         if (m instanceof Coding)
             return ((Coding)m).keyString();
         if (m == null)
             return "none";
         return m.toString();
     }
     public String toString() {
         PropMap p200 = Utils.currentPropMap();
         boolean verbose
             = (p200 != null &&
                p200.getBoolean(Utils.COM_PREFIX+"verbose.pop"));
         StringBuilder res = new StringBuilder(100);
         res.append("pop(").append("fVlen=").append(fVlen);
         if (verbose && fValues != null) {
             res.append(" fV=[");
             for (int i = 1; i <= fVlen; i++) {
                 res.append(i==1?"":",").append(fValues[i]);
             }
             res.append(";").append(computeSentinelValue());
             res.append("]");
         }
         res.append(" fc=").append(keyString(favoredCoding));
         res.append(" tc=").append(keyString(tokenCoding));
         res.append(" uc=").append(keyString(unfavoredCoding));
         res.append(")");
         return res.toString();
     }
 }