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Dynamic scripting for the JVM
/*
* Copyright (C) 2007 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.snapscript.dx.dex.file;
import java.util.Collection;
import org.snapscript.dx.util.AnnotatedOutput;
/**
* A section of a {@code .dex} file. Each section consists of a list
* of items of some sort or other.
*/
public abstract class Section {
/** {@code null-ok;} name of this part, for annotation purposes */
private final String name;
/** {@code non-null;} file that this instance is part of */
private final DexFile file;
/** {@code > 0;} alignment requirement for the final output;
* must be a power of 2 */
private final int alignment;
/** {@code >= -1;} offset from the start of the file to this part, or
* {@code -1} if not yet known */
private int fileOffset;
/** whether {@link #prepare} has been called successfully on this
* instance */
private boolean prepared;
/**
* Validates an alignment.
*
* @param alignment the alignment
* @throws IllegalArgumentException thrown if {@code alignment}
* isn't a positive power of 2
*/
public static void validateAlignment(int alignment) {
if ((alignment <= 0) ||
(alignment & (alignment - 1)) != 0) {
throw new IllegalArgumentException("invalid alignment");
}
}
/**
* Constructs an instance. The file offset is initially unknown.
*
* @param name {@code null-ok;} the name of this instance, for annotation
* purposes
* @param file {@code non-null;} file that this instance is part of
* @param alignment {@code > 0;} alignment requirement for the final output;
* must be a power of 2
*/
public Section(String name, DexFile file, int alignment) {
if (file == null) {
throw new NullPointerException("file == null");
}
validateAlignment(alignment);
this.name = name;
this.file = file;
this.alignment = alignment;
this.fileOffset = -1;
this.prepared = false;
}
/**
* Gets the file that this instance is part of.
*
* @return {@code non-null;} the file
*/
public final DexFile getFile() {
return file;
}
/**
* Gets the alignment for this instance's final output.
*
* @return {@code > 0;} the alignment
*/
public final int getAlignment() {
return alignment;
}
/**
* Gets the offset from the start of the file to this part. This
* throws an exception if the offset has not yet been set.
*
* @return {@code >= 0;} the file offset
*/
public final int getFileOffset() {
if (fileOffset < 0) {
throw new RuntimeException("fileOffset not set");
}
return fileOffset;
}
/**
* Sets the file offset. It is only valid to call this method once
* once per instance.
*
* @param fileOffset {@code >= 0;} the desired offset from the start of the
* file where this for this instance
* @return {@code >= 0;} the offset that this instance should be placed at
* in order to meet its alignment constraint
*/
public final int setFileOffset(int fileOffset) {
if (fileOffset < 0) {
throw new IllegalArgumentException("fileOffset < 0");
}
if (this.fileOffset >= 0) {
throw new RuntimeException("fileOffset already set");
}
int mask = alignment - 1;
fileOffset = (fileOffset + mask) & ~mask;
this.fileOffset = fileOffset;
return fileOffset;
}
/**
* Writes this instance to the given raw data object.
*
* @param out {@code non-null;} where to write to
*/
public final void writeTo(AnnotatedOutput out) {
throwIfNotPrepared();
align(out);
int cursor = out.getCursor();
if (fileOffset < 0) {
fileOffset = cursor;
} else if (fileOffset != cursor) {
throw new RuntimeException("alignment mismatch: for " + this +
", at " + cursor +
", but expected " + fileOffset);
}
if (out.annotates()) {
if (name != null) {
out.annotate(0, "\n" + name + ":");
} else if (cursor != 0) {
out.annotate(0, "\n");
}
}
writeTo0(out);
}
/**
* Returns the absolute file offset, given an offset from the
* start of this instance's output. This is only valid to call
* once this instance has been assigned a file offset (via {@link
* #setFileOffset}).
*
* @param relative {@code >= 0;} the relative offset
* @return {@code >= 0;} the corresponding absolute file offset
*/
public final int getAbsoluteOffset(int relative) {
if (relative < 0) {
throw new IllegalArgumentException("relative < 0");
}
if (fileOffset < 0) {
throw new RuntimeException("fileOffset not yet set");
}
return fileOffset + relative;
}
/**
* Returns the absolute file offset of the given item which must
* be contained in this section. This is only valid to call
* once this instance has been assigned a file offset (via {@link
* #setFileOffset}).
*
* Note: Subclasses must implement this as appropriate for
* their contents.
*
* @param item {@code non-null;} the item in question
* @return {@code >= 0;} the item's absolute file offset
*/
public abstract int getAbsoluteItemOffset(Item item);
/**
* Prepares this instance for writing. This performs any necessary
* prerequisites, including particularly adding stuff to other
* sections. This method may only be called once per instance;
* subsequent calls will throw an exception.
*/
public final void prepare() {
throwIfPrepared();
prepare0();
prepared = true;
}
/**
* Gets the collection of all the items in this section.
* It is not valid to attempt to change the returned list.
*
* @return {@code non-null;} the items
*/
public abstract Collection items();
/**
* Does the main work of {@link #prepare}.
*/
protected abstract void prepare0();
/**
* Gets the size of this instance when output, in bytes.
*
* @return {@code >= 0;} the size of this instance, in bytes
*/
public abstract int writeSize();
/**
* Throws an exception if {@link #prepare} has not been
* called on this instance.
*/
protected final void throwIfNotPrepared() {
if (!prepared) {
throw new RuntimeException("not prepared");
}
}
/**
* Throws an exception if {@link #prepare} has already been called
* on this instance.
*/
protected final void throwIfPrepared() {
if (prepared) {
throw new RuntimeException("already prepared");
}
}
/**
* Aligns the output of the given data to the alignment of this instance.
*
* @param out {@code non-null;} the output to align
*/
protected final void align(AnnotatedOutput out) {
out.alignTo(alignment);
}
/**
* Writes this instance to the given raw data object. This gets
* called by {@link #writeTo} after aligning the cursor of
* {@code out} and verifying that either the assigned file
* offset matches the actual cursor {@code out} or that the
* file offset was not previously assigned, in which case it gets
* assigned to {@code out}'s cursor.
*
* @param out {@code non-null;} where to write to
*/
protected abstract void writeTo0(AnnotatedOutput out);
/**
* Returns the name of this section, for annotation purposes.
*
* @return {@code null-ok;} name of this part, for annotation purposes
*/
protected final String getName() {
return name;
}
}