xref: /dalvik/dexgen/src/com/android/dexgen/dex/file/HeaderItem.java

/*
 * 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 com.android.dexgen.dex.file;

import com.android.dexgen.rop.cst.CstUtf8;
import com.android.dexgen.util.AnnotatedOutput;
import com.android.dexgen.util.Hex;

/**
 * File header section of a {@code .dex} file.
 */
public final class HeaderItem extends IndexedItem {
    /**
     * {@code non-null;} the file format magic number, represented as the
     * low-order bytes of a string
     */
    private static final String MAGIC = "dex\n035\0";

    /** size of this section, in bytes */
    private static final int HEADER_SIZE = 0x70;

    /** the endianness tag */
    private static final int ENDIAN_TAG = 0x12345678;

    /**
     * Constructs an instance.
     */
    public HeaderItem() {
        // This space intentionally left blank.
    }

    /** {@inheritDoc} */
    @Override
    public ItemType itemType() {
        return ItemType.TYPE_HEADER_ITEM;
    }

    /** {@inheritDoc} */
    @Override
    public int writeSize() {
        return HEADER_SIZE;
    }

    /** {@inheritDoc} */
    @Override
    public void addContents(DexFile file) {
        // Nothing to do here.
    }

    /** {@inheritDoc} */
    @Override
    public void writeTo(DexFile file, AnnotatedOutput out) {
        int mapOff = file.getMap().getFileOffset();
        Section firstDataSection = file.getFirstDataSection();
        Section lastDataSection = file.getLastDataSection();
        int dataOff = firstDataSection.getFileOffset();
        int dataSize = lastDataSection.getFileOffset() +
            lastDataSection.writeSize() - dataOff;

        if (out.annotates()) {
            out.annotate(8, "magic: " + new CstUtf8(MAGIC).toQuoted());
            out.annotate(4, "checksum");
            out.annotate(20, "signature");
            out.annotate(4, "file_size:       " +
                         Hex.u4(file.getFileSize()));
            out.annotate(4, "header_size:     " + Hex.u4(HEADER_SIZE));
            out.annotate(4, "endian_tag:      " + Hex.u4(ENDIAN_TAG));
            out.annotate(4, "link_size:       0");
            out.annotate(4, "link_off:        0");
            out.annotate(4, "map_off:         " + Hex.u4(mapOff));
        }

        // Write the magic number.
        for (int i = 0; i < 8; i++) {
            out.writeByte(MAGIC.charAt(i));
        }

        // Leave space for the checksum and signature.
        out.writeZeroes(24);

        out.writeInt(file.getFileSize());
        out.writeInt(HEADER_SIZE);
        out.writeInt(ENDIAN_TAG);

        /*
         * Write zeroes for the link size and data, as the output
         * isn't a staticly linked file.
         */
        out.writeZeroes(8);

        out.writeInt(mapOff);

        // Write out each section's respective header part.
        file.getStringIds().writeHeaderPart(out);
        file.getTypeIds().writeHeaderPart(out);
        file.getProtoIds().writeHeaderPart(out);
        file.getFieldIds().writeHeaderPart(out);
        file.getMethodIds().writeHeaderPart(out);
        file.getClassDefs().writeHeaderPart(out);

        if (out.annotates()) {
            out.annotate(4, "data_size:       " + Hex.u4(dataSize));
            out.annotate(4, "data_off:        " + Hex.u4(dataOff));
        }

        out.writeInt(dataSize);
        out.writeInt(dataOff);
    }
}