/*

 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#ifndef SHARE_VM_CLASSFILE_IMAGEDECOMPRESSOR_HPP

#define SHARE_VM_CLASSFILE_IMAGEDECOMPRESSOR_HPP

#include "runtime/thread.inline.hpp"

#include "classfile/classLoader.hpp"

#include "classfile/imageFile.hpp"

#include "classfile/symbolTable.hpp"

#include "oops/symbol.hpp"

#include "utilities/growableArray.hpp"

/*

 * Compressed resources located in image have an header.

 * This header contains:

 * - _magic: A magic u4, required to retrieved the header in the compressed content

 * - _size: The size of the compressed resource.

 * - _uncompressed_size: The uncompressed size of the compressed resource.

 * - _decompressor_name_offset: The ImageDecompressor instance name StringsTable offset.

 * - _decompressor_config_offset: StringsTable offset of configuration that could be needed by

 *   the decompressor in order to decompress.

 * - _is_terminal: 1: the compressed content is terminal. Uncompressing it would

 *   create the actual resource. 0: the compressed content is not terminal. Uncompressing it

 *   will result in a compressed content to be decompressed (This occurs when a stack of compressors

 *   have been used to compress the resource.

 */

struct ResourceHeader {

  /* Length of header, needed to retrieve content offset */

  static const u1 resource_header_length = 21;

  /* magic bytes that identifies a compressed resource header*/

  static const u4 resource_header_magic = 0xCAFEFAFA;

  u4 _magic; // Resource header

  u4 _size;  // Resource size

  u4 _uncompressed_size;  // Expected uncompressed size

  u4 _decompressor_name_offset;  // Strings table decompressor offset

  u4 _decompressor_config_offset; // Strings table config offset

  u1 _is_terminal; // Last decompressor 1, otherwise 0.

};

/*

 * Resources located in jimage file can be compressed. Compression occurs at

 * jimage file creation time. When compressed a resource is added an header that

 * contains the name of the compressor that compressed it.

 * Various compression strategies can be applied to compress a resource.

 * The same resource can even be compressed multiple time by a stack of compressors.

 * At runtime, a resource is decompressed in a loop until there is no more header

 * meaning that the resource is equivalent to the not compressed resource.

 * In each iteration, the name of the compressor located in the current header

 * is used to retrieve the associated instance of ImageDecompressor.

 * For example “zip” is the name of the compressor that compresses resources

 * using the zip algorithm. The ZipDecompressor class name is also “zip”.

 * ImageDecompressor instances are retrieved from a static array in which

 * they are registered.

 */

class ImageDecompressor: public CHeapObj<mtClass> {

private:

  const Symbol* _name;

  /*

   * Array of concrete decompressors. This array is used to retrieve the decompressor

   * that can handle resource decompression.

   */

  static GrowableArray<ImageDecompressor*>* _decompressors;

  /*

   * Identifier of a decompressor. This name is the identification key to retrieve

   * decompressor from a resource header.

   */

  inline const Symbol* get_name() const { return _name; }

protected:

  ImageDecompressor(const Symbol* name) : _name(name) {

  }

  virtual void decompress_resource(u1* data, u1* uncompressed,

    ResourceHeader* header, const ImageStrings* strings) = 0;

public:

  inline static void add_decompressor(ImageDecompressor* decompressor) {

    _decompressors->append(decompressor);

  }

  inline static ImageDecompressor* get_decompressor(const char * decompressor_name) {

    Thread* THREAD = Thread::current();

    TempNewSymbol sym = SymbolTable::new_symbol(decompressor_name,

            (int) strlen(decompressor_name), CHECK_NULL);

    if (HAS_PENDING_EXCEPTION) {

      warning("can't create symbol\n");

      CLEAR_PENDING_EXCEPTION;

      return NULL;

    }

    for (int i = 0; i < _decompressors->length(); i++) {

      ImageDecompressor* decompressor = _decompressors->at(i);

      if (decompressor->get_name()->fast_compare(sym) == 0) {

        return decompressor;

      }

    }

    guarantee(false, "No decompressor found.");

    return NULL;

  }

  static void decompress_resource(u1* compressed, u1* uncompressed,

    u4 uncompressed_size, const ImageStrings* strings, bool is_C_heap);

};

/**

 * Zip decompressor.

 */

class ZipDecompressor : public ImageDecompressor {

public:

  ZipDecompressor(const Symbol* sym) : ImageDecompressor(sym) { }

  void decompress_resource(u1* data, u1* uncompressed, ResourceHeader* header,

    const ImageStrings* strings);

};

#endif // SHARE_VM_CLASSFILE_IMAGEDECOMPRESSOR_HPP