Java example source code file (Fixups.java)
The Fixups.java Java example source code/*
* Copyright (c) 2003, 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.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package com.sun.java.util.jar.pack;
import com.sun.java.util.jar.pack.ConstantPool.Entry;
import java.util.AbstractCollection;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.Objects;
/**
* Collection of relocatable constant pool references.
* It operates with respect to a particular byte array,
* and stores some of its state in the bytes themselves.
* <p>
* As a Collection, it can be iterated over, but it is not a List,
* since it does not natively support indexed access.
* <p>
*
* @author John Rose
*/
final class Fixups extends AbstractCollection<Fixups.Fixup> {
byte[] bytes; // the subject of the relocations
int head; // desc locating first reloc
int tail; // desc locating last reloc
int size; // number of relocations
Entry[] entries; // [0..size-1] relocations
int[] bigDescs; // descs which cannot be stored in the bytes
// A "desc" (descriptor) is a bit-encoded pair of a location
// and format. Every fixup occurs at a "desc". Until final
// patching, bytes addressed by descs may also be used to
// link this data structure together. If the bytes are missing,
// or if the "desc" is too large to encode in the bytes,
// it is kept in the bigDescs array.
Fixups(byte[] bytes) {
this.bytes = bytes;
entries = new Entry[3];
bigDescs = noBigDescs;
}
Fixups() {
// If there are no bytes, all descs are kept in bigDescs.
this((byte[])null);
}
Fixups(byte[] bytes, Collection<Fixup> fixups) {
this(bytes);
addAll(fixups);
}
Fixups(Collection<Fixup> fixups) {
this((byte[])null);
addAll(fixups);
}
private static final int MINBIGSIZE = 1;
// cleverly share empty bigDescs:
private static final int[] noBigDescs = {MINBIGSIZE};
@Override
public int size() {
return size;
}
public void trimToSize() {
if (size != entries.length) {
Entry[] oldEntries = entries;
entries = new Entry[size];
System.arraycopy(oldEntries, 0, entries, 0, size);
}
int bigSize = bigDescs[BIGSIZE];
if (bigSize == MINBIGSIZE) {
bigDescs = noBigDescs;
} else if (bigSize != bigDescs.length) {
int[] oldBigDescs = bigDescs;
bigDescs = new int[bigSize];
System.arraycopy(oldBigDescs, 0, bigDescs, 0, bigSize);
}
}
public void visitRefs(Collection<Entry> refs) {
for (int i = 0; i < size; i++) {
refs.add(entries[i]);
}
}
@Override
public void clear() {
if (bytes != null) {
// Clean the bytes:
for (Fixup fx : this) {
//System.out.println("clean "+fx);
storeIndex(fx.location(), fx.format(), 0);
}
}
size = 0;
if (bigDescs != noBigDescs)
bigDescs[BIGSIZE] = MINBIGSIZE;
// do not trim to size, however
}
public byte[] getBytes() {
return bytes;
}
public void setBytes(byte[] newBytes) {
if (bytes == newBytes) return;
ArrayList<Fixup> old = null;
assert((old = new ArrayList<>(this)) != null);
if (bytes == null || newBytes == null) {
// One or the other representations is deficient.
// Construct a checkpoint.
ArrayList<Fixup> save = new ArrayList<>(this);
clear();
bytes = newBytes;
addAll(save);
} else {
// assume newBytes is some sort of bitwise copy of the old bytes
bytes = newBytes;
}
assert(old.equals(new ArrayList<>(this)));
}
private static final int LOC_SHIFT = 1;
private static final int FMT_MASK = 0x1;
private static final byte UNUSED_BYTE = 0;
private static final byte OVERFLOW_BYTE = -1;
// fill pointer of bigDescs array is in element [0]
private static final int BIGSIZE = 0;
// Format values:
private static final int U2_FORMAT = 0;
private static final int U1_FORMAT = 1;
// Special values for the static methods.
private static final int SPECIAL_LOC = 0;
private static final int SPECIAL_FMT = U2_FORMAT;
static int fmtLen(int fmt) { return 1+(fmt-U1_FORMAT)/(U2_FORMAT-U1_FORMAT); }
static int descLoc(int desc) { return desc >>> LOC_SHIFT; }
static int descFmt(int desc) { return desc & FMT_MASK; }
static int descEnd(int desc) { return descLoc(desc) + fmtLen(descFmt(desc)); }
static int makeDesc(int loc, int fmt) {
int desc = (loc << LOC_SHIFT) | fmt;
assert(descLoc(desc) == loc);
assert(descFmt(desc) == fmt);
return desc;
}
int fetchDesc(int loc, int fmt) {
byte b1 = bytes[loc];
assert(b1 != OVERFLOW_BYTE);
int value;
if (fmt == U2_FORMAT) {
byte b2 = bytes[loc+1];
value = ((b1 & 0xFF) << 8) + (b2 & 0xFF);
} else {
value = (b1 & 0xFF);
}
// Stored loc field is difference between its own loc and next loc.
return value + (loc << LOC_SHIFT);
}
boolean storeDesc(int loc, int fmt, int desc) {
if (bytes == null)
return false;
int value = desc - (loc << LOC_SHIFT);
byte b1, b2;
switch (fmt) {
case U2_FORMAT:
assert(bytes[loc+0] == UNUSED_BYTE);
assert(bytes[loc+1] == UNUSED_BYTE);
b1 = (byte)(value >> 8);
b2 = (byte)(value >> 0);
if (value == (value & 0xFFFF) && b1 != OVERFLOW_BYTE) {
bytes[loc+0] = b1;
bytes[loc+1] = b2;
assert(fetchDesc(loc, fmt) == desc);
return true;
}
break;
case U1_FORMAT:
assert(bytes[loc] == UNUSED_BYTE);
b1 = (byte)value;
if (value == (value & 0xFF) && b1 != OVERFLOW_BYTE) {
bytes[loc] = b1;
assert(fetchDesc(loc, fmt) == desc);
return true;
}
break;
default: assert(false);
}
// Failure. Caller must allocate a bigDesc.
bytes[loc] = OVERFLOW_BYTE;
assert(fmt==U1_FORMAT || (bytes[loc+1]=(byte)bigDescs[BIGSIZE])!=999);
return false;
}
void storeIndex(int loc, int fmt, int value) {
storeIndex(bytes, loc, fmt, value);
}
static
void storeIndex(byte[] bytes, int loc, int fmt, int value) {
switch (fmt) {
case U2_FORMAT:
assert(value == (value & 0xFFFF)) : (value);
bytes[loc+0] = (byte)(value >> 8);
bytes[loc+1] = (byte)(value >> 0);
break;
case U1_FORMAT:
assert(value == (value & 0xFF)) : (value);
bytes[loc] = (byte)value;
break;
default: assert(false);
}
}
void addU1(int pc, Entry ref) {
add(pc, U1_FORMAT, ref);
}
void addU2(int pc, Entry ref) {
add(pc, U2_FORMAT, ref);
}
/** Simple and necessary tuple to present each fixup. */
public static
class Fixup implements Comparable<Fixup> {
int desc; // location and format of reloc
Entry entry; // which entry to plug into the bytes
Fixup(int desc, Entry entry) {
this.desc = desc;
this.entry = entry;
}
public Fixup(int loc, int fmt, Entry entry) {
this.desc = makeDesc(loc, fmt);
this.entry = entry;
}
public int location() { return descLoc(desc); }
public int format() { return descFmt(desc); }
public Entry entry() { return entry; }
@Override
public int compareTo(Fixup that) {
// Ordering depends only on location.
return this.location() - that.location();
}
@Override
public boolean equals(Object x) {
if (!(x instanceof Fixup)) return false;
Fixup that = (Fixup) x;
return this.desc == that.desc && this.entry == that.entry;
}
@Override
public int hashCode() {
int hash = 7;
hash = 59 * hash + this.desc;
hash = 59 * hash + Objects.hashCode(this.entry);
return hash;
}
@Override
public String toString() {
return "@"+location()+(format()==U1_FORMAT?".1":"")+"="+entry;
}
}
private
class Itr implements Iterator<Fixup> {
int index = 0; // index into entries
int bigIndex = BIGSIZE+1; // index into bigDescs
int next = head; // desc pointing to next fixup
@Override
public boolean hasNext() { return index < size; }
@Override
public void remove() { throw new UnsupportedOperationException(); }
@Override
public Fixup next() {
int thisIndex = index;
return new Fixup(nextDesc(), entries[thisIndex]);
}
int nextDesc() {
index++;
int thisDesc = next;
if (index < size) {
// Fetch next desc eagerly, in case this fixup gets finalized.
int loc = descLoc(thisDesc);
int fmt = descFmt(thisDesc);
if (bytes != null && bytes[loc] != OVERFLOW_BYTE) {
next = fetchDesc(loc, fmt);
} else {
// The unused extra byte is "asserted" to be equal to BI.
// This helps keep the overflow descs in sync.
assert(fmt==U1_FORMAT || bytes == null || bytes[loc+1]==(byte)bigIndex);
next = bigDescs[bigIndex++];
}
}
return thisDesc;
}
}
@Override
public Iterator<Fixup> iterator() {
return new Itr();
}
public void add(int location, int format, Entry entry) {
addDesc(makeDesc(location, format), entry);
}
@Override
public boolean add(Fixup f) {
addDesc(f.desc, f.entry);
return true;
}
@Override
public boolean addAll(Collection<? extends Fixup> c) {
if (c instanceof Fixups) {
// Use knowledge of Itr structure to avoid building little structs.
Fixups that = (Fixups) c;
if (that.size == 0) return false;
if (this.size == 0 && entries.length < that.size)
growEntries(that.size); // presize exactly
Entry[] thatEntries = that.entries;
for (Itr i = that.new Itr(); i.hasNext(); ) {
int ni = i.index;
addDesc(i.nextDesc(), thatEntries[ni]);
}
return true;
} else {
return super.addAll(c);
}
}
// Here is how things get added:
private void addDesc(int thisDesc, Entry entry) {
if (entries.length == size)
growEntries(size * 2);
entries[size] = entry;
if (size == 0) {
head = tail = thisDesc;
} else {
int prevDesc = tail;
// Store new desc in previous tail.
int prevLoc = descLoc(prevDesc);
int prevFmt = descFmt(prevDesc);
int prevLen = fmtLen(prevFmt);
int thisLoc = descLoc(thisDesc);
// The collection must go in ascending order, and not overlap.
if (thisLoc < prevLoc + prevLen)
badOverlap(thisLoc);
tail = thisDesc;
if (!storeDesc(prevLoc, prevFmt, thisDesc)) {
// overflow
int bigSize = bigDescs[BIGSIZE];
if (bigDescs.length == bigSize)
growBigDescs();
//System.out.println("bigDescs["+bigSize+"] = "+thisDesc);
bigDescs[bigSize++] = thisDesc;
bigDescs[BIGSIZE] = bigSize;
}
}
size += 1;
}
private void badOverlap(int thisLoc) {
throw new IllegalArgumentException("locs must be ascending and must not overlap: "+thisLoc+" >> "+this);
}
private void growEntries(int newSize) {
Entry[] oldEntries = entries;
entries = new Entry[Math.max(3, newSize)];
System.arraycopy(oldEntries, 0, entries, 0, oldEntries.length);
}
private void growBigDescs() {
int[] oldBigDescs = bigDescs;
bigDescs = new int[oldBigDescs.length * 2];
System.arraycopy(oldBigDescs, 0, bigDescs, 0, oldBigDescs.length);
}
/// Static methods that optimize the use of this class.
static Object addRefWithBytes(Object f, byte[] bytes, Entry e) {
return add(f, bytes, 0, U2_FORMAT, e);
}
static Object addRefWithLoc(Object f, int loc, Entry entry) {
return add(f, null, loc, U2_FORMAT, entry);
}
private static
Object add(Object prevFixups,
byte[] bytes, int loc, int fmt,
Entry e) {
Fixups f;
if (prevFixups == null) {
if (loc == SPECIAL_LOC && fmt == SPECIAL_FMT) {
// Special convention: If the attribute has a
// U2 relocation at position zero, store the Entry
// rather than building a Fixups structure.
return e;
}
f = new Fixups(bytes);
} else if (!(prevFixups instanceof Fixups)) {
// Recognize the special convention:
Entry firstEntry = (Entry) prevFixups;
f = new Fixups(bytes);
f.add(SPECIAL_LOC, SPECIAL_FMT, firstEntry);
} else {
f = (Fixups) prevFixups;
assert(f.bytes == bytes);
}
f.add(loc, fmt, e);
return f;
}
public static
void setBytes(Object fixups, byte[] bytes) {
if (fixups instanceof Fixups) {
Fixups f = (Fixups) fixups;
f.setBytes(bytes);
}
}
public static
Object trimToSize(Object fixups) {
if (fixups instanceof Fixups) {
Fixups f = (Fixups) fixups;
f.trimToSize();
if (f.size() == 0)
fixups = null;
}
return fixups;
}
// Iterate over all the references in this set of fixups.
public static
void visitRefs(Object fixups, Collection<Entry> refs) {
if (fixups == null) {
} else if (!(fixups instanceof Fixups)) {
// Special convention; see above.
refs.add((Entry) fixups);
} else {
Fixups f = (Fixups) fixups;
f.visitRefs(refs);
}
}
// Clear out this set of fixups by replacing each reference
// by a hardcoded coding of its reference, drawn from ix.
public static
void finishRefs(Object fixups, byte[] bytes, ConstantPool.Index ix) {
if (fixups == null)
return;
if (!(fixups instanceof Fixups)) {
// Special convention; see above.
int index = ix.indexOf((Entry) fixups);
storeIndex(bytes, SPECIAL_LOC, SPECIAL_FMT, index);
return;
}
Fixups f = (Fixups) fixups;
assert(f.bytes == bytes);
f.finishRefs(ix);
}
void finishRefs(ConstantPool.Index ix) {
if (isEmpty())
return;
for (Fixup fx : this) {
int index = ix.indexOf(fx.entry);
//System.out.println("finish "+fx+" = "+index);
// Note that the iterator has already fetched the
// bytes we are about to overwrite.
storeIndex(fx.location(), fx.format(), index);
}
// Further iterations should do nothing:
bytes = null; // do not clean them
clear();
}
/*
/// Testing.
public static void main(String[] av) {
byte[] bytes = new byte[1 << 20];
ConstantPool cp = new ConstantPool();
Fixups f = new Fixups(bytes);
boolean isU1 = false;
int span = 3;
int nextLoc = 0;
int[] locs = new int[100];
final int[] indexes = new int[100];
int iptr = 1;
for (int loc = 0; loc < bytes.length; loc++) {
if (loc == nextLoc && loc+1 < bytes.length) {
int fmt = (isU1 ? U1_FORMAT : U2_FORMAT);
Entry e = ConstantPool.getUtf8Entry("L"+loc);
f.add(loc, fmt, e);
isU1 ^= true;
if (iptr < 10) {
// Make it close in.
nextLoc += fmtLen(fmt) + (iptr < 5 ? 0 : 1);
} else {
nextLoc += span;
span = (int)(span * 1.77);
}
// Here are the bytes that would have gone here:
locs[iptr] = loc;
if (fmt == U1_FORMAT) {
indexes[iptr++] = (loc & 0xFF);
} else {
indexes[iptr++] = ((loc & 0xFF) << 8) | ((loc+1) & 0xFF);
++loc; // skip a byte
}
continue;
}
bytes[loc] = (byte)loc;
}
System.out.println("size="+f.size()
+" overflow="+(f.bigDescs[BIGSIZE]-1));
System.out.println("Fixups: "+f);
// Test collection contents.
assert(iptr == 1+f.size());
List l = new ArrayList(f);
Collections.sort(l); // should not change the order
if (!l.equals(new ArrayList(f))) System.out.println("** disordered");
f.setBytes(null);
if (!l.equals(new ArrayList(f))) System.out.println("** bad set 1");
f.setBytes(bytes);
if (!l.equals(new ArrayList(f))) System.out.println("** bad set 2");
Fixups f3 = new Fixups(f);
if (!l.equals(new ArrayList(f3))) System.out.println("** bad set 3");
Iterator fi = f.iterator();
for (int i = 1; i < iptr; i++) {
Fixup fx = (Fixup) fi.next();
if (fx.location() != locs[i]) {
System.out.println("** "+fx+" != "+locs[i]);
}
if (fx.format() == U1_FORMAT)
System.out.println(fx+" -> "+bytes[locs[i]]);
else
System.out.println(fx+" -> "+bytes[locs[i]]+" "+bytes[locs[i]+1]);
}
assert(!fi.hasNext());
indexes[0] = 1; // like iptr
Index ix = new Index("ix") {
public int indexOf(Entry e) {
return indexes[indexes[0]++];
}
};
f.finishRefs(ix);
for (int loc = 0; loc < bytes.length; loc++) {
if (bytes[loc] != (byte)loc) {
System.out.println("** ["+loc+"] = "+bytes[loc]+" != "+(byte)loc);
}
}
}
//*/
}
Other Java examples (source code examples)Here is a short list of links related to this Java Fixups.java source code file: |
The search page
Other Java source code examples at this package level
Click here to learn more about this project
