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Commit 924a6837 authored by Alex Klyubin's avatar Alex Klyubin
Browse files

Make signapk align .so entries to 4096 bytes. 

This makes signapk align uncompressed .so entries to memory page
boundary (4096 bytes) to enable such libraries to be loaded at runtime
through memory-mapping the APK.

With this change in place, there should no longer be a need to run
zipalign after (or before) signapk.

Bug: 25794543
Change-Id: I74775af15a683791f57fcbd3497a79951b3f63a1
parent 88ca8aff

tools/signapk/SignApk.java

+20 −1
Original line number Diff line number Diff line
@@ -476,7 +476,7 @@ class SignApk { 
     * more efficient.

     */

    private static void copyFiles(Manifest manifest, JarFile in, JarOutputStream out,

                                  long timestamp, int alignment) throws IOException {

                                  long timestamp, int defaultAlignment) throws IOException {

        byte[] buffer = new byte[4096];

        int num;
@@ -515,6 +515,7 @@ class SignApk { 
                offset += 4;

                firstEntry = false;

            }

            int alignment = getStoredEntryDataAlignment(name, defaultAlignment);

            if (alignment > 0 && (offset % alignment != 0)) {

                // Set the "extra data" of the entry to between 1 and

                // alignment-1 bytes, to make the file data begin at
@@ -555,6 +556,24 @@ class SignApk { 
        }

    }



    /**

     * Returns the multiple (in bytes) at which the provided {@code STORED} entry's data must start

     * relative to start of file or {@code 0} if alignment of this entry's data is not important.

     */

    private static int getStoredEntryDataAlignment(String entryName, int defaultAlignment) {

        if (defaultAlignment <= 0) {

            return 0;

        }



        if (entryName.endsWith(".so")) {

            // Align .so contents to memory page boundary to enable memory-mapped

            // execution.

            return 4096;

        } else {

            return defaultAlignment;

        }

    }



    private static class WholeFileSignerOutputStream extends FilterOutputStream {

        private boolean closing = false;

        private ByteArrayOutputStream footer = new ByteArrayOutputStream();