/*
* Copyright (c) 2004, 2013, Oracle and/or its affiliates. All rights reserved.
* 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.
*
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package build.tools.hasher;
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 {
static final PrintStream out = System.out;
static final 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 = "String"; // 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?
void usage() {
err.println("usage: java Hasher [options] [[pkgName.]ClassName]");
err.println("options:");
err.println(" -e generate empty table (ignores value exprs)");
err.println(" -i generate a static inner class");
err.println(" -md depth max chain depth (default 3)");
err.println(" -mb bits max index bits (lg of table size, default 10)");
err.println(" -t type value type (default String)");
err.println(" -v verbose");
err.println("Key/value-expression pairs are read from standard input");
err.println("If class name is given then source is written to standard output");
System.exit(1);
}
Hasher(String[] args) {
List<String> as = Arrays.asList(args);
for (Iterator<String> i = as.iterator(); i.hasNext();) {
String a = i.next();
if (a.equals("-e")) {
empty = true;
} else if (a.equals("-i")) {
inner = true;
} else if (a.equals("-v")) {
verbose = true;
} else if (a.equals("-md")) {
if (!i.hasNext())
usage();
maxDepth = Integer.parseInt(i.next());
} else if (a.equals("-mb")) {
if (!i.hasNext())
usage();
maxBits = Integer.parseInt(i.next());
} else if (a.equals("-t")) {
if (!i.hasNext())
usage();
vtype = i.next();
} else if (a.startsWith("-")) {
usage();
} else {
int j = a.lastIndexOf('.');
if (j >= 0) {
pkg = a.substring(0, j);
cln = a.substring(j + 1);
} else {
cln = a;
}
}
}
if (verbose)
err.println("pkg=" + pkg + ", cln=" + cln);
}
// Read keys and values
//
Hasher load() throws IOException {
BufferedReader br
= new BufferedReader(new InputStreamReader(System.in));
for (String ln; (ln = br.readLine()) != null;) {
String[] ws = ln.split(",?\\s+", 2);
String w = ws[0].replaceAll("\"", "");
if (keys.contains(w))
throw new RuntimeException("Duplicate word in input: " + w);
keys.add(w);
if (ws.length < 2)
throw new RuntimeException("Missing expression for key " + w);
values.add(ws[1]);
}
return this;
}
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
out.flush();
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, PrintWriter pw) {
Object v = empty ? null : a[1];
pw.print("new Object[] { \"" + a[0] + "\", " + v);
if (a.length < 3) {
pw.print(" }");
return;
}
pw.println(",");
pw.print(ind + " ");
for (int i = 0; i < depth; i++)
pw.print(" ");
genEntry((Object[])a[2], depth + 1, pw);
pw.print(" }");
}
// Generate a PreHashedMap subclass from the computed hash table
//
Hasher generate() throws IOException {
if (cln == null)
return this;
PrintWriter pw
= new PrintWriter(new BufferedWriter(new OutputStreamWriter(out)));
if (inner)
ind = " ";
if (!inner && pkg != null) {
pw.println();
pw.println("package " + pkg + ";");
pw.println();
}
if (inner) {
pw.println(ind + "private static final class " + cln);
} else {
pw.println();
pw.println("public final class " + cln);
}
pw.println(ind + " extends sun.util.PreHashedMap<" + vtype +">");
pw.println(ind + "{");
pw.println();
pw.println(ind + " private static final int ROWS = "
+ ht.length + ";");
pw.println(ind + " private static final int SIZE = "
+ keys.size() + ";");
pw.println(ind + " private static final int SHIFT = "
+ shift + ";");
pw.println(ind + " private static final int MASK = 0x"
+ Integer.toHexString(mask) + ";");
pw.println();
pw.println(ind + " " + (inner ? "private " : "public ")
+ cln + "() {");
pw.println(ind + " super(ROWS, SIZE, SHIFT, MASK);");
pw.println(ind + " }");
pw.println();
pw.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];
pw.print(ind + " ht[" + i + "] = ");
genEntry(a, 0, pw);
pw.println(";");
}
pw.println(ind + " }");
pw.println();
pw.println(ind + "}");
if (inner)
pw.println();
pw.close();
return this;
}
public static void main(String[] args) throws IOException {
new Hasher(args)
.load()
.build()
.test()
.generate();
}
}