55 lines
2.4 KiB
Java
55 lines
2.4 KiB
Java
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import java.io.*;
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import java.util.*;
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import java.util.zip.*;
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/**
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* Minimal zipalign: copies a zip, padding STORED entries so their data is 4-byte aligned,
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* and appends any extra files given after the output path (compressed, at the zip root).
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*/
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public class ZipAlign {
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public static void main(String[] a) throws IOException {
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try (ZipFile in = new ZipFile(a[0]);
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CountingOut cnt = new CountingOut(new BufferedOutputStream(new FileOutputStream(a[1])));
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ZipOutputStream out = new ZipOutputStream(cnt)) {
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for (ZipEntry e : Collections.list(in.entries())) {
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ZipEntry n = new ZipEntry(e.getName());
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n.setMethod(e.getMethod());
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n.setTime(946684800000L); // 2000-01-01, inside the DOS date range (no extra timestamp field)
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if (e.getMethod() == ZipEntry.STORED) {
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n.setSize(e.getSize());
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n.setCompressedSize(e.getSize());
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n.setCrc(e.getCrc());
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out.flush();
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long dataStart = cnt.count + 30 + n.getName().getBytes("UTF-8").length;
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int pad = (int) ((4 - dataStart % 4) % 4);
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if (pad > 0) n.setExtra(padExtra(pad));
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}
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out.putNextEntry(n);
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in.getInputStream(e).transferTo(out);
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out.closeEntry();
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}
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for (int i = 2; i < a.length; i++) {
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File f = new File(a[i]);
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ZipEntry n = new ZipEntry(f.getName());
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n.setTime(946684800000L);
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out.putNextEntry(n);
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try (InputStream fin = new FileInputStream(f)) { fin.transferTo(out); }
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out.closeEntry();
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}
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}
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}
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// An extra field needs a 4-byte header, so use one field of pad+4 bytes (Android's 0xD935 alignment tag).
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static byte[] padExtra(int pad) {
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byte[] x = new byte[pad + 4];
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x[0] = 0x35; x[1] = (byte) 0xD9; x[2] = (byte) pad;
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return x;
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}
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static class CountingOut extends FilterOutputStream {
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long count;
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CountingOut(OutputStream o) { super(o); }
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@Override public void write(int b) throws IOException { out.write(b); count++; }
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@Override public void write(byte[] b, int off, int len) throws IOException { out.write(b, off, len); count += len; }
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}
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}
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