com.facebook.buck.android.resources.ChunkUtils.java Source code

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Here is the source code for com.facebook.buck.android.resources.ChunkUtils.java

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/*
 * Copyright 2017-present Facebook, Inc.
 *
 * 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 com.facebook.buck.android.resources;

import com.google.common.collect.ImmutableList;
import java.nio.ByteBuffer;
import java.util.List;

class ChunkUtils {
    private ChunkUtils() {
    }

    /**
     * Finds all chunks in the buffer with the requested type. This is useful for tests to find chunks
     * of a certain type without needing to understand all the other encountered chunks.
     *
     * @return A list of offsets in the buffer to chunks of the requested type.
     */
    static List<Integer> findChunks(ByteBuffer data, int wantedType) {
        ByteBuffer buf = ResChunk.slice(data, 0);
        ImmutableList.Builder<Integer> offsetsBuilder = ImmutableList.builder();
        int offset = 0;
        while (offset < buf.limit()) {
            int type = buf.getShort(offset);
            if (type == wantedType) {
                offsetsBuilder.add(offset);
            }
            int headerSize = buf.getShort(offset + 2);
            int chunkSize = buf.getInt(offset + 4);
            // These chunks consist of lists of sub-chunks after their headers.
            if (type == ResChunk.CHUNK_RESOURCE_TABLE || type == ResChunk.CHUNK_RES_TABLE_PACKAGE
                    || type == ResChunk.CHUNK_XML_TREE) {
                int subchunksStart = offset + headerSize;
                int subchunksLength = chunkSize - headerSize;
                for (int subOffset : findChunks(ResChunk.slice(buf, subchunksStart, subchunksLength), wantedType)) {
                    offsetsBuilder.add(subchunksStart + subOffset);
                }
            }
            offset += chunkSize;
        }
        return offsetsBuilder.build();
    }
}