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Commit 7b977ea0 authored by Alex Klyubin's avatar Alex Klyubin
Browse files

Improve DataSource interface. 

1. This adds way to obtain a DataSource which represents a region of
   data contained in the DataSource.
2. This fixes a design bug in "feed" method where the size parameter
   was an int instead of long.
3. This fixes a bug in ByteBufferDataSource where its mSize field was
   a long instead of an int (ByteBuffer's length cannot be more than
   2^31).

Bug: 27461702
Change-Id: Ib0812784beb581f19d2412e667b8bd018f0a3c78
parent 8ed91b66

tools/apksigner/core/src/com/android/apksigner/core/internal/util/ByteBufferDataSource.java

+53 −21
Original line number Diff line number Diff line
@@ -28,7 +28,7 @@ import java.nio.ByteBuffer; 
public class ByteBufferDataSource implements DataSource {



    private final ByteBuffer mBuffer;

    private final long mSize;

    private final int mSize;



    /**

     * Constructs a new {@code ByteBufferDigestSource} based on the data contained in the provided
@@ -45,29 +45,39 @@ public class ByteBufferDataSource implements DataSource { 
    }



    @Override

    public void feed(long offset, int size, DataSink sink) throws IOException {

        if (offset < 0) {

            throw new IllegalArgumentException("offset: " + offset);

    public ByteBufferDataSource slice(long offset, long size) {

        if ((offset == 0) && (size == mSize)) {

            return this;

        }

        if (size < 0) {

            throw new IllegalArgumentException("size: " + size);

        }

        if (offset > mSize) {

            throw new IllegalArgumentException(

                    "offset (" + offset + ") > source size (" + mSize + ")");

        }

        long endOffset = offset + size;

        if (endOffset < offset) {

            throw new IllegalArgumentException(

                    "offset (" + offset + ") + size (" + size + ") overflow");

        checkChunkValid(offset, size);



        // checkChunkValid ensures that it's OK to cast offset and size to int.

        int chunkPosition = (int) offset;

        int chunkLimit = (int) (chunkPosition + size);

        // Creating a slice of ByteBuffer modifies the state of the source ByteBuffer (position

        // and limit fields, to be more specific). We thus use synchronization around these

        // state-changing operations to make instances of this class thread-safe.

        synchronized (mBuffer) {

            // ByteBuffer.limit(int) and .position(int) check that that the position >= limit

            // invariant is not broken. Thus, the only way to safely change position and limit

            // without caring about their current values is to first set position to 0 or set the

            // limit to capacity.

            mBuffer.position(0);



            mBuffer.limit(chunkLimit);

            mBuffer.position(chunkPosition);

            // Create a ByteBufferDataSource for the slice of the buffer between limit and position.

            return new ByteBufferDataSource(mBuffer);

        }

        if (endOffset > mSize) {

            throw new IllegalArgumentException(

                    "offset (" + offset + ") + size (" + size + ") > source size (" + mSize  +")");

    }



        int chunkPosition = (int) offset; // safe to downcast because mSize <= Integer.MAX_VALUE

        int chunkLimit = (int) endOffset; // safe to downcast because mSize <= Integer.MAX_VALUE

    @Override

    public void feed(long offset, long size, DataSink sink) throws IOException {

        checkChunkValid(offset, size);



        // checkChunkValid ensures that it's OK to cast offset and size to int.

        int chunkPosition = (int) offset;

        int chunkLimit = (int) (chunkPosition + size);

        ByteBuffer chunk;

        // Creating a slice of ByteBuffer modifies the state of the source ByteBuffer (position

        // and limit fields, to be more specific). We thus use synchronization around these
@@ -86,4 +96,26 @@ public class ByteBufferDataSource implements DataSource { 


        sink.consume(chunk);

    }



    private void checkChunkValid(long offset, long size) {

        if (offset < 0) {

            throw new IllegalArgumentException("offset: " + offset);

        }

        if (size < 0) {

            throw new IllegalArgumentException("size: " + size);

        }

        if (offset > mSize) {

            throw new IllegalArgumentException(

                    "offset (" + offset + ") > source size (" + mSize + ")");

        }

        long endOffset = offset + size;

        if (endOffset < offset) {

            throw new IllegalArgumentException(

                    "offset (" + offset + ") + size (" + size + ") overflow");

        }

        if (endOffset > mSize) {

            throw new IllegalArgumentException(

                    "offset (" + offset + ") + size (" + size + ") > source size (" + mSize  +")");

        }

    }

}

tools/apksigner/core/src/com/android/apksigner/core/util/DataSource.java

+7 −1
Original line number Diff line number Diff line
@@ -43,5 +43,11 @@ public interface DataSource { 
     * @param offset index (in bytes) at which the chunk starts inside data source

     * @param size size (in bytes) of the chunk

     */

    void feed(long offset, int size, DataSink sink) throws IOException;

    void feed(long offset, long size, DataSink sink) throws IOException;



    /**

     * Returns a data source representing the specified region of data of this data source. Changes

     * to data represented by this data source will also be visible in the returned data source.

     */

    DataSource slice(long offset, long size);

}

tools/apksigner/core/src/com/android/apksigner/core/util/DataSources.java

+2 −1
Original line number Diff line number Diff line
@@ -12,7 +12,8 @@ public abstract class DataSources { 


    /**

     * Returns a {@link DataSource} backed by the provided {@link ByteBuffer}. The data source

     * represents the data contained between the position and limit of the buffer.

     * represents the data contained between the position and limit of the buffer. Changes to the

     * buffer's contents will be visible in the data source.

     */

    public static DataSource asDataSource(ByteBuffer buffer) {

        if (buffer == null) {