/*
 * Copyright (c) 2014, 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
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#ifndef SHARE_VM_CLASSFILE_IMAGEFILE_HPP
#define SHARE_VM_CLASSFILE_IMAGEFILE_HPP

#include "classfile/classLoader.hpp"
#include "memory/allocation.hpp"
#include "memory/allocation.inline.hpp"
#include "utilities/endian.hpp"
#include "utilities/globalDefinitions.hpp"
#include "utilities/growableArray.hpp"

// Image files are an alternate file format for storing classes and resources. The
// goal is to supply file access which is faster and smaller than the jar format.
// It should be noted that unlike jars, information stored in an image is in native
// endian format. This allows the image to be mapped into memory without endian
// translation.  This also means that images are platform dependent.
//
// Image files are structured as three sections;
//
//         +-----------+
//         |  Header   |
//         +-----------+
//         |           |
//         |   Index   |
//         |           |
//         +-----------+
//         |           |
//         |           |
//         | Resources |
//         |           |
//         |           |
//         +-----------+
//
// The header contains information related to identification and description of
// contents.
//
//         +-------------------------+
//         |   Magic (0xCAFEDADA)    |
//         +------------+------------+
//         | Major Vers | Minor Vers |
//         +------------+------------+
//         |          Flags          |
//         +-------------------------+
//         |      Resource Count     |
//         +-------------------------+
//         |       Table Length      |
//         +-------------------------+
//         |      Attributes Size    |
//         +-------------------------+
//         |       Strings Size      |
//         +-------------------------+
//
// Magic - means of identifying validity of the file.  This avoids requiring a
//         special file extension.
// Major vers, minor vers - differences in version numbers indicate structural
//                          changes in the image.
// Flags - various image wide flags (future).
// Resource count - number of resources in the file.
// Table length - the length of lookup tables used in the index.
// Attributes size - number of bytes in the region used to store location attribute
//                   streams.
// Strings size - the size of the region used to store strings used by the
//                index and meta data.
//
// The index contains information related to resource lookup. The algorithm
// used for lookup is "A Practical Minimal Perfect Hashing Method"
// (http://homepages.dcc.ufmg.br/~nivio/papers/wea05.pdf). Given a path string
// in the form /<module>/<package>/<base>.<extension>  return the resource location
// information;
//
//     redirectIndex = hash(path, DEFAULT_SEED) % table_length;
//     redirect = redirectTable[redirectIndex];
//     if (redirect == 0) return not found;
//     locationIndex = redirect < 0 ? -1 - redirect : hash(path, redirect) % table_length;
//     location = locationTable[locationIndex];
//     if (!verify(location, path)) return not found;
//     return location;
//
// Note: The hash function takes an initial seed value.  A different seed value
// usually returns a different result for strings that would otherwise collide with
// other seeds. The verify function guarantees the found resource location is
// indeed the resource we are looking for.
//
// The following is the format of the index;
//
//         +-------------------+
//         |   Redirect Table  |
//         +-------------------+
//         | Attribute Offsets |
//         +-------------------+
//         |   Attribute Data  |
//         +-------------------+
//         |      Strings      |
//         +-------------------+
//
// Redirect Table - Array of 32-bit signed values representing actions that
//                  should take place for hashed strings that map to that
//                  value.  Negative values indicate no hash collision and can be
//                  quickly converted to indices into attribute offsets.  Positive
//                  values represent a new seed for hashing an index into attribute
//                  offsets.  Zero indicates not found.
// Attribute Offsets - Array of 32-bit unsigned values representing offsets into
//                     attribute data.  Attribute offsets can be iterated to do a
//                     full survey of resources in the image.  Offset of zero
//                     indicates no attributes.
// Attribute Data - Bytes representing compact attribute data for locations. (See
//                  comments in ImageLocation.)
// Strings - Collection of zero terminated UTF-8 strings used by the index and
//           image meta data.  Each string is accessed by offset.  Each string is
//           unique.  Offset zero is reserved for the empty string.
//
// Note that the memory mapped index assumes 32 bit alignment of each component
// in the index.
//
// Endianness of an image.
// An image booted by hotspot is always in native endian.  However, it is possible
// to read (by the JDK) in alternate endian format.  Primarily, this is during
// cross platform scenarios.  Ex, where javac needs to read an embedded image
// to access classes for crossing compilation.
//

class ImageFileReader; // forward declaration

// Manage image file string table.
class ImageStrings VALUE_OBJ_CLASS_SPEC {
private:
  u1* _data; // Data bytes for strings.
  u4 _size; // Number of bytes in the string table.
public:
  enum {
    // Not found result from find routine.
    NOT_FOUND = -1,
    // Prime used to generate hash for Perfect Hashing.
    HASH_MULTIPLIER = 0x01000193
  };

  ImageStrings(u1* data, u4 size) : _data(data), _size(size) {}

  // Return the UTF-8 string beginning at offset.
  inline const char* get(u4 offset) const {
    guarantee(offset < _size, "offset exceeds string table size");
    return (const char*)(_data + offset);
  }

  // Compute the Perfect Hashing hash code for the supplied UTF-8 string.
  inline static u4 hash_code(const char* string) {
    return hash_code(string, HASH_MULTIPLIER);
  }

  // Compute the Perfect Hashing hash code for the supplied string, starting at seed.
  static s4 hash_code(const char* string, s4 seed);

  // Match up a string in a perfect hash table.  Result still needs validation
  // for precise match.
  static s4 find(Endian* endian, const char* name, s4* redirect, u4 length);

  // Test to see if UTF-8 string begins with the start UTF-8 string.  If so,
  // return non-NULL address of remaining portion of string.  Otherwise, return
  // NULL.  Used to test sections of a path without copying from image string
  // table.
  static const char* starts_with(const char* string, const char* start);

  // Test to see if UTF-8 string begins with start char.  If so, return non-NULL
  // address of remaining portion of string.  Otherwise, return NULL.  Used
  // to test a character of a path without copying.
  inline static const char* starts_with(const char* string, const char ch) {
    return *string == ch ? string + 1 : NULL;
  }
};

// Manage image file location attribute data.  Within an image, a location's
// attributes are compressed into a stream of bytes.  An attribute stream is
// composed of individual attribute sequences.  Each attribute sequence begins with
// a header byte containing the attribute 'kind' (upper 5 bits of header) and the
// 'length' less 1 (lower 3 bits of header) of bytes that follow containing the
// attribute value.  Attribute values present as most significant byte first.
//
// Ex. Container offset (ATTRIBUTE_OFFSET) 0x33562 would be represented as 0x22
// (kind = 4, length = 3), 0x03, 0x35, 0x62.
//
// An attribute stream is terminated with a header kind of ATTRIBUTE_END (header
// byte of zero.)
//
// ImageLocation inflates the stream into individual values stored in the long
// array _attributes. This allows an attribute value can be quickly accessed by
// direct indexing. Unspecified values default to zero.
//
// Notes:
//  - Even though ATTRIBUTE_END is used to mark the end of the attribute stream,
//    streams will contain zero byte values to represent lesser significant bits.
//    Thus, detecting a zero byte is not sufficient to detect the end of an attribute
//    stream.
//  - ATTRIBUTE_OFFSET represents the number of bytes from the beginning of the region
//    storing the resources.  Thus, in an image this represents the number of bytes
//    after the index.
//  - Currently, compressed resources are represented by having a non-zero
//    ATTRIBUTE_COMPRESSED value.  This represents the number of bytes stored in the
//    image, and the value of ATTRIBUTE_UNCOMPRESSED represents number of bytes of the
//    inflated resource in memory. If the ATTRIBUTE_COMPRESSED is zero then the value
//    of ATTRIBUTE_UNCOMPRESSED represents both the number of bytes in the image and
//    in memory.  In the future, additional compression techniques will be used and
//    represented differently.
//  - Package strings include trailing slash and extensions include prefix period.
//
class ImageLocation VALUE_OBJ_CLASS_SPEC {
public:
  enum {
    ATTRIBUTE_END,          // End of attribute stream marker
    ATTRIBUTE_MODULE,       // String table offset of module name
    ATTRIBUTE_PARENT,       // String table offset of resource path parent
    ATTRIBUTE_BASE,         // String table offset of resource path base
    ATTRIBUTE_EXTENSION,    // String table offset of resource path extension
    ATTRIBUTE_OFFSET,       // Container byte offset of resource
    ATTRIBUTE_COMPRESSED,   // In image byte size of the compressed resource
    ATTRIBUTE_UNCOMPRESSED, // In memory byte size of the uncompressed resource
    ATTRIBUTE_COUNT         // Number of attribute kinds
  };

private:
  // Values of inflated attributes.
  u8 _attributes[ATTRIBUTE_COUNT];

  // Return the attribute value number of bytes.
  inline static u1 attribute_length(u1 data) {
    return (data & 0x7) + 1;
  }

  // Return the attribute kind.
  inline static u1 attribute_kind(u1 data) {
    u1 kind = data >> 3;
    guarantee(kind < ATTRIBUTE_COUNT, "invalid attribute kind");
    return kind;
  }

  // Return the attribute length.
  inline static u8 attribute_value(u1* data, u1 n) {
    guarantee(0 < n && n <= 8, "invalid attribute value length");
    u8 value = 0;
    // Most significant bytes first.
    for (u1 i = 0; i < n; i++) {
      value <<= 8;
      value |= data[i];
    }
    return value;
  }

public:
  ImageLocation() {
    clear_data();
  }

  ImageLocation(u1* data) {
    clear_data();
    set_data(data);
  }

  // Inflates the attribute stream into individual values stored in the long
  // array _attributes. This allows an attribute value to be quickly accessed by
  // direct indexing. Unspecified values default to zero.
  void set_data(u1* data);

  // Zero all attribute values.
  void clear_data();

  // Retrieve an attribute value from the inflated array.
  inline u8 get_attribute(u1 kind) const {
    guarantee(ATTRIBUTE_END < kind && kind < ATTRIBUTE_COUNT, "invalid attribute kind");
    return _attributes[kind];
  }

  // Retrieve an attribute string value from the inflated array.
  inline const char* get_attribute(u4 kind, const ImageStrings& strings) const {
    return strings.get((u4)get_attribute(kind));
  }
};

//
// NOTE: needs revision.
// Each loader requires set of module meta data to identify which modules and
// packages are managed by that loader.  Currently, there is one image file per
// builtin loader, so only one  module meta data resource per file.
//
// Each element in the module meta data is a native endian 4 byte integer.  Note
// that entries with zero offsets for string table entries should be ignored (
// padding for hash table lookup.)
//
// Format:
//    Count of package to module entries
//    Count of module to package entries
//    Perfect Hash redirect table[Count of package to module entries]
//    Package to module entries[Count of package to module entries]
//        Offset to package name in string table
//        Offset to module name in string table
//    Perfect Hash redirect table[Count of module to package entries]
//    Module to package entries[Count of module to package entries]
//        Offset to module name in string table
//        Count of packages in module
//        Offset to first package in packages table
//    Packages[]
//        Offset to package name in string table
//
// Manage the image module meta data.
class ImageModuleData : public CHeapObj<mtClass> {
  class Header VALUE_OBJ_CLASS_SPEC {
  private:
    u4 _ptm_count;      // Count of package to module entries
    u4 _mtp_count;      // Count of module to package entries
  public:
    inline u4 ptm_count(Endian* endian) const { return endian->get(_ptm_count); }
    inline u4 mtp_count(Endian* endian) const { return endian->get(_mtp_count); }
  };

  // Hashtable entry
  class HashData VALUE_OBJ_CLASS_SPEC {
  private:
    u4 _name_offset;    // Name offset in string table
  public:
    inline s4 name_offset(Endian* endian) const { return endian->get(_name_offset); }
  };

  // Package to module hashtable entry
  class PTMData : public HashData {
  private:
    u4 _module_name_offset; // Module name offset in string table
  public:
    inline s4 module_name_offset(Endian* endian) const { return endian->get(_module_name_offset); }
  };

  // Module to package hashtable entry
  class MTPData : public HashData {
  private:
    u4 _package_count;     // Number of packages in module
    u4 _package_offset;    // Offset in package list
  public:
    inline u4 package_count(Endian* endian)  const { return endian->get(_package_count); }
    inline u4 package_offset(Endian* endian) const { return endian->get(_package_offset); }
  };

  const ImageFileReader* _image_file; // Source image file
  Endian* _endian;                    // Endian handler
  ImageStrings _strings;              // Image file strings
  u1* _data;                          // Module data resource data
  u8 _data_size;                      // Size of resource data
  Header* _header;                    // Module data header
  s4* _ptm_redirect;                  // Package to module hashtable redirect
  PTMData* _ptm_data;                 // Package to module data
  s4* _mtp_redirect;                  // Module to packages hashtable redirect
  MTPData* _mtp_data;                 // Module to packages data
  s4* _mtp_packages;                  // Package data (name offsets)

  // Return a string from the string table.
  inline const char* get_string(u4 offset) {
    return _strings.get(offset);
  }

  inline u4 mtp_package(u4 index) {
    return _endian->get(_mtp_packages[index]);
  }

public:
  ImageModuleData(const ImageFileReader* image_file, const char* module_data_name);
  ~ImageModuleData();

  // Return the name of the module data resource.
  static void module_data_name(char* buffer, const char* image_file_name);

  // Return the module in which a package resides.  Returns NULL if not found.
  const char* package_to_module(const char* package_name);

  // Returns all the package names in a module.  Returns NULL if module not found.
  GrowableArray<const char*>* module_to_packages(const char* module_name);
};

// Image file header, starting at offset 0.
class ImageHeader VALUE_OBJ_CLASS_SPEC {
private:
  u4 _magic;           // Image file marker
  u4 _version;         // Image file major version number
  u4 _flags;           // Image file flags
  u4 _resource_count;  // Number of resources in file
  u4 _table_length;    // Number of slots in index tables
  u4 _locations_size;  // Number of bytes in attribute table
  u4 _strings_size;    // Number of bytes in string table

public:
  u4 magic() const { return _magic; }
  u4 magic(Endian* endian) const { return endian->get(_magic); }
  void set_magic(Endian* endian, u4 magic) { return endian->set(_magic, magic); }

  u4 major_version(Endian* endian) const { return endian->get(_version) >> 16; }
  u4 minor_version(Endian* endian) const { return endian->get(_version) & 0xFFFF; }
  void set_version(Endian* endian, u4 major_version, u4 minor_version) {
    return endian->set(_version, major_version << 16 | minor_version);
  }

  u4 flags(Endian* endian) const { return endian->get(_flags); }
  void set_flags(Endian* endian, u4 value) { return endian->set(_flags, value); }

  u4 resource_count(Endian* endian) const { return endian->get(_resource_count); }
  void set_resource_count(Endian* endian, u4 count) { return endian->set(_resource_count, count); }

  u4 table_length(Endian* endian) const { return endian->get(_table_length); }
  void set_table_length(Endian* endian, u4 count) { return endian->set(_table_length, count); }

  u4 locations_size(Endian* endian) const { return endian->get(_locations_size); }
  void set_locations_size(Endian* endian, u4 size) { return endian->set(_locations_size, size); }

  u4 strings_size(Endian* endian) const { return endian->get(_strings_size); }
  void set_strings_size(Endian* endian, u4 size) { return endian->set(_strings_size, size); }
};

// Max path length limit independent of platform.  Windows max path is 1024,
// other platforms use 4096.  The JCK fails several tests when 1024 is used.
#define IMAGE_MAX_PATH 4096

// Manage the image file.
// ImageFileReader manages the content of an image file.
// Initially, the header of the image file is read for validation.  If valid,
// values in the header are used calculate the size of the image index.  The
// index is then memory mapped to allow load on demand and sharing.  The
// -XX:+MemoryMapImage flag determines if the entire file is loaded (server use.)
// An image can be used by Hotspot and multiple reference points in the JDK, thus
// it is desirable to share a reader.  To accomodate sharing, a share table is
// defined (see ImageFileReaderTable in imageFile.cpp)  To track the number of
// uses, ImageFileReader keeps a use count (_use).  Use is incremented when
// 'opened' by reference point and decremented when 'closed'.  Use of zero
// leads the ImageFileReader to be actually closed and discarded.
class ImageFileReader : public CHeapObj<mtClass> {
private:
  // Manage a number of image files such that an image can be shared across
  // multiple uses (ex. loader.)
  static GrowableArray<ImageFileReader*>* _reader_table;

  char* _name;         // Name of image
  s4 _use;             // Use count
  int _fd;             // File descriptor
  Endian* _endian;     // Endian handler
  u8 _file_size;       // File size in bytes
  ImageHeader _header; // Image header
  size_t _index_size;  // Total size of index
  u1* _index_data;     // Raw index data
  s4* _redirect_table; // Perfect hash redirect table
  u4* _offsets_table;  // Location offset table
  u1* _location_bytes; // Location attributes
  u1* _string_bytes;   // String table

  ImageFileReader(const char* name, bool big_endian);
  ~ImageFileReader();

  // Compute number of bytes in image file index.
  inline u8 index_size() {
    return sizeof(ImageHeader) +
      table_length() * sizeof(u4) * 2 + locations_size() + strings_size();
  }

public:
  enum {
    // Image file marker.
    IMAGE_MAGIC = 0xCAFEDADA,
    // Endian inverted Image file marker.
    IMAGE_MAGIC_INVERT = 0xDADAFECA,
    // Image file major version number.
    MAJOR_VERSION = 1,
    // Image file minor version number.
    MINOR_VERSION = 0
  };

  // Open an image file, reuse structure if file already open.
  static ImageFileReader* open(const char* name, bool big_endian = Endian::is_big_endian());

  // Close an image file if the file is not in use elsewhere.
  static void close(ImageFileReader *reader);

  // Return an id for the specifed ImageFileReader.
  static u8 readerToID(ImageFileReader *reader);

  // Validate the image id.
  static bool idCheck(u8 id);

  // Return an id for the specifed ImageFileReader.
  static ImageFileReader* idToReader(u8 id);

  // Open image file for read access.
  bool open();

  // Close image file.
  void close();

  // Read directly from the file.
  bool read_at(u1* data, u8 size, u8 offset) const;

  inline Endian* endian() const { return _endian; }

  // Retrieve name of image file.
  inline const char* name() const {
    return _name;
  }

  // Retrieve size of image file.
  inline u8 file_size() const {
    return _file_size;
  }

  // Return first address of index data.
  inline u1* get_index_address() const {
    return _index_data;
  }

  // Return first address of resource data.
  inline u1* get_data_address() const {
    return _index_data + _index_size;
  }

  // Get the size of the index data.
  size_t get_index_size() const {
    return _index_size;
  }

  inline u4 table_length() const {
    return _header.table_length(_endian);
  }

  inline u4 locations_size() const {
    return _header.locations_size(_endian);
  }

  inline u4 strings_size()const  {
    return _header.strings_size(_endian);
  }

  inline u4* offsets_table() const {
    return _offsets_table;
  }

  // Increment use count.
  inline void inc_use() {
    _use++;
  }

  // Decrement use count.
  inline bool dec_use() {
    return --_use == 0;
  }

  // Return a string table accessor.
  inline const ImageStrings get_strings() const {
    return ImageStrings(_string_bytes, _header.strings_size(_endian));
  }

  // Return location attribute stream at offset.
  inline u1* get_location_offset_data(u4 offset) const {
    guarantee((u4)offset < _header.locations_size(_endian),
              "offset exceeds location attributes size");
    return offset != 0 ? _location_bytes + offset : NULL;
  }

  // Return location attribute stream for location i.
  inline u1* get_location_data(u4 index) const {
    guarantee((u4)index < _header.table_length(_endian),
              "index exceeds location count");
    u4 offset = _endian->get(_offsets_table[index]);

    return get_location_offset_data(offset);
  }

  // Find the location attributes associated with the path.  Returns true if
  // the location is found, false otherwise.
  bool find_location(const char* path, ImageLocation& location) const;

  // Assemble the location path.
  void location_path(ImageLocation& location, char* path, size_t max) const;

  // Verify that a found location matches the supplied path.
  bool verify_location(ImageLocation& location, const char* path) const;

  // Return the resource for the supplied path.
  void get_resource(ImageLocation& location, u1* uncompressed_data) const;
};
#endif // SHARE_VM_CLASSFILE_IMAGEFILE_HPP