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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * 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

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package build.tools.charsetmapping;

import java.io.*;

import java.util.*;

/**

 * Reads a map in the form of a sequence of key/value-expression pairs from the

 * standard input, attempts to construct a hash map that fits within the given

 * table-size and chain-depth constraints, and, if successful, writes source

 * code to the standard output for a subclass of sun.util.PreHashedMap that

 * implements the map.

 *

 * @see sun.util.PreHashedMap

 *

 * @author Mark Reinhold

 */

public class Hasher {

    private PrintStream err = System.err;

    boolean verbose = false;

    List<String> keys = new ArrayList<>();      // Key strings

    List<String> values = new ArrayList<>();    // Value expressions

    String pkg = null;                          // Package prefix for generated class

    String cln = null;                          // Name of generated class

    String vtype = null;                        // Value type

    int maxBits = 11;                           // lg table size

    int maxDepth = 3;                           // Max chain depth

    boolean inner = false;                      // Generating an inner class?

    boolean empty = false;                      // Generating an empty table?

    Object[] ht;                                // Hash table itself

    int nb;                                     // Number of bits (lg table size)

    int md;                                     // Maximum chain depth

    int mask;                                   // Hash-code mask

    int shift;                                  // Hash-code shift size

    int hash(String w) {

        return (w.hashCode() >> shift) & mask;

    }

    // Build a hash table of size 2^nb, shifting the hash code by s bits

    //

    void build(int nb, int s) {

        this.nb = nb;

        this.shift = s;

        int n = 1 << nb;

        this.mask = n - 1;

        ht = new Object[n];

        int nw = keys.size();

        for (int i = 0; i < nw; i++) {

            String w = keys.get(i);

            String v = values.get(i);

            int h = hash(w);

            if (ht[h] == null)

                ht[h] = new Object[] { w, v };

            else

                ht[h] = new Object[] { w, v, ht[h] };

        }

        this.md = 0;

        for (int i = 0; i < n; i++) {

            int d = 1;

            for (Object[] a = (Object[])ht[i];

                 a != null && a.length > 2;

                 a = (Object[])a[2], d++);

            this.md = Math.max(md, d);

        }

    }

    Hasher build() {

        // Iterate through acceptable table sizes

        for (int nb = 2; nb < maxBits; nb++) {

            // Iterate through possible shift sizes

            for (int s = 0; s < (32 - nb); s++) {

                build(nb, s);

                if (verbose)

                    err.println("nb=" + nb + " s=" + s + " md=" + md);

                if (md <= maxDepth) {

                    // Success

                     if (verbose) {

                        if (cln != null)

                            err.print(cln + ": ");

                        err.println("Table size " + (1 << nb) + " (" + nb + " bits)"

                                    + ", shift " + shift

                                    + ", max chain depth " + md);

                    }

                    return this;

                }

            }

        }

        throw new RuntimeException("Cannot find a suitable size"

                                   + " within given constraints");

    }

    // Look for the given key in the hash table

    //

    String get(String k) {

        int h = hash(k);

        Object[] a = (Object[])ht[h];

        for (;;) {

            if (a[0].equals(k))

                return (String)a[1];

            if (a.length < 3)

                return null;

            a = (Object[])a[2];

        }

    }

    // Test that all input keys can be found in the table

    //

    Hasher test() {

        if (verbose)

            err.println();

        for (int i = 0, n = keys.size(); i < n; i++) {

            String w = keys.get(i);

            String v = get(w);

            if (verbose)

                err.println(hash(w) + "\t" + w);

            if (!v.equals(values.get(i)))

                throw new Error("Incorrect value: " + w + " --> "

                                + v + ", should be " + values.get(i));

        }

        return this;

    }

    String ind = "";                    // Indent prefix

    // Generate code for a single table entry

    //

    void genEntry(Object[] a, int depth, PrintStream out) {

        Object v = empty ? null : a[1];

        out.print("new Object[] { \"" + a[0] + "\", " + v);

        if (a.length < 3) {

            out.print(" }");

            return;

        }

        out.println(",");

        out.print(ind + "                     ");

        for (int i = 0; i < depth; i++)

            out.print("    ");

        genEntry((Object[])a[2], depth + 1, out);

        out.print(" }");

    }

    // Generate a PreHashedMap subclass from the computed hash table

    //

    Hasher generate(PrintStream out) throws IOException {

        if (cln == null)

            return this;

        if (inner)

            ind = "    ";

        if (!inner && pkg != null) {

            out.println();

            out.println("package " + pkg + ";");

            out.println();

        }

        if (inner) {

            out.println(ind + "private static final class " + cln);

        } else {

            out.println();

            out.println("public final class " + cln);

        }

        out.println(ind + "    extends sun.util.PreHashedMap<" + vtype +">");

        out.println(ind + "{");

        out.println();

        out.println(ind + "    private static final int ROWS = "

                    + ht.length + ";");

        out.println(ind + "    private static final int SIZE = "

                    + keys.size() + ";");

        out.println(ind + "    private static final int SHIFT = "

                    + shift + ";");

        out.println(ind + "    private static final int MASK = 0x"

                    + Integer.toHexString(mask) + ";");

        out.println();

        out.println(ind + "    " + (inner ? "private " : "public ")

                    + cln + "() {");

        out.println(ind + "        super(ROWS, SIZE, SHIFT, MASK);");

        out.println(ind + "    }");

        out.println();

        out.println(ind + "    protected void init(Object[] ht) {");

        for (int i = 0; i < ht.length; i++) {

            if (ht[i] == null)

                continue;

            Object[] a = (Object[])ht[i];

            out.print(ind + "        ht[" + i + "] = ");

            genEntry(a, 0, out);

            out.println(";");

        }

        out.println(ind + "    }");

        out.println();

        out.println(ind + "}");

        if (inner)

            out.println();

        return this;

    }

    private Hasher(List<String> keys, List<String> values,

                   String pkg, String cln, String vtype,

                   int maxBits, int maxDepth,

                   boolean inner, boolean empty,

                   boolean verbose) {

        this.keys = keys;

        this.values = values;

        this.pkg = pkg;

        this.cln = cln;

        this.vtype = vtype;

        this.maxBits = maxBits;

        this.maxDepth = maxDepth;

        this.inner = inner;

        this.empty = empty;

        this.verbose = verbose;

    }

    public static void genClass(PrintStream out,

                                List<String> keys, List<String> values,

                                String pkg, String cln, String vtype,

                                int maxBits, int maxDepth,

                                boolean inner, boolean empty, boolean verbose)

        throws IOException {

        new Hasher(keys, values, pkg, cln, vtype,

                   maxBits, maxDepth, inner, empty, verbose)

            .build()

            .test()

            .generate(out);

    }

}