/*
 * 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.
 *
 */

#include "precompiled.hpp"
#include "classfile/imageDecompressor.hpp"
#include "classfile/imageFile.hpp"
#include "memory/resourceArea.hpp"
#include "runtime/mutex.hpp"
#include "runtime/mutexLocker.hpp"
#include "runtime/os.inline.hpp"
#include "utilities/endian.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.
//
// (More detailed nodes in the header.)
//

// Compute the Perfect Hashing hash code for the supplied UTF-8 string.
s4 ImageStrings::hash_code(const char* string, s4 seed) {
  // Access bytes as unsigned.
  u1* bytes = (u1*)string;
  // Compute hash code.
  for (u1 byte = *bytes++; byte; byte = *bytes++) {
    seed = (seed * HASH_MULTIPLIER) ^ byte;
  }
  // Ensure the result is not signed.
  return seed & 0x7FFFFFFF;
}

// Match up a string in a perfect hash table.  Result still needs validation
// for precise match (false positive.)
s4 ImageStrings::find(Endian* endian, const char* name, s4* redirect, u4 length) {
  // If the table is empty, then short cut.
  if (redirect == NULL || length == 0) {
    return NOT_FOUND;
  }
  // Compute the basic perfect hash for name.
  s4 hash_code = ImageStrings::hash_code(name);
  // Modulo table size.
  s4 index = hash_code % length;
  // Get redirect entry.
  //   value == 0 then not found
  //   value < 0 then -1 - value is true index
  //   value > 0 then value is seed for recomputing hash.
  s4 value = endian->get(redirect[index]);
  // if recompute is required.
  if (value > 0) {
    // Entry collision value, need to recompute hash.
    hash_code = ImageStrings::hash_code(name, value);
    // Modulo table size.
    return hash_code % length;
  } else if (value < 0) {
    // Compute direct index.
    return -1 - value;
  }
  // No entry found.
  return NOT_FOUND;
}

// 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.
const char* ImageStrings::starts_with(const char* string, const char* start) {
  char ch1, ch2;
  // Match up the strings the best we can.
  while ((ch1 = *string) && (ch2 = *start)) {
    if (ch1 != ch2) {
      // Mismatch, return NULL.
      return NULL;
    }
    // Next characters.
    string++, start++;
  }
  // Return remainder of string.
  return string;
}

// 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 (from constructor.)
void ImageLocation::set_data(u1* data) {
  // Deflate the attribute stream into an array of attributes.
  u1 byte;
  // Repeat until end header is found.
  while ((byte = *data)) {
    // Extract kind from header byte.
    u1 kind = attribute_kind(byte);
    guarantee(kind < ATTRIBUTE_COUNT, "invalid image location attribute");
    // Extract length of data (in bytes).
    u1 n = attribute_length(byte);
    // Read value (most significant first.)
    _attributes[kind] = attribute_value(data + 1, n);
    // Position to next attribute by skipping attribute header and data bytes.
    data += n + 1;
  }
}

// Zero all attribute values.
void ImageLocation::clear_data() {
  // Set defaults to zero.
  memset(_attributes, 0, sizeof(_attributes));
}

// ImageModuleData constructor maps out sub-tables for faster access.
ImageModuleData::ImageModuleData(const ImageFileReader* image_file,
        const char* module_data_name) :
    _image_file(image_file),
    _endian(image_file->endian()),
    _strings(image_file->get_strings()) {
  // Retrieve the resource containing the module data for the image file.
  ImageLocation location;
  bool found = image_file->find_location(module_data_name, location);
  guarantee(found, "missing module data");
  u8 data_size = location.get_attribute(ImageLocation::ATTRIBUTE_UNCOMPRESSED);
  _data = (u1*)NEW_C_HEAP_ARRAY(char, data_size, mtClass);
  _image_file->get_resource(location, _data);
  // Map out the header.
  _header = (Header*)_data;
  // Get the package to module entry count.
  u4 ptm_count = _header->ptm_count(_endian);
  // Get the module to package entry count.
  u4 mtp_count = _header->mtp_count(_endian);
  // Compute the offset of the package to module perfect hash redirect.
  u4 ptm_redirect_offset = sizeof(Header);
  // Compute the offset of the package to module data.
  u4 ptm_data_offset = ptm_redirect_offset + ptm_count * sizeof(s4);
  // Compute the offset of the module to package perfect hash redirect.
  u4 mtp_redirect_offset = ptm_data_offset + ptm_count * sizeof(PTMData);
  // Compute the offset of the module to package data.
  u4 mtp_data_offset = mtp_redirect_offset + mtp_count * sizeof(s4);
  // Compute the offset of the module to package tables.
  u4 mtp_packages_offset = mtp_data_offset + mtp_count * sizeof(MTPData);
  // Compute the address of the package to module perfect hash redirect.
  _ptm_redirect = (s4*)(_data + ptm_redirect_offset);
  // Compute the address of the package to module data.
  _ptm_data = (PTMData*)(_data + ptm_data_offset);
  // Compute the address of the module to package perfect hash redirect.
  _mtp_redirect = (s4*)(_data + mtp_redirect_offset);
  // Compute the address of the module to package data.
  _mtp_data = (MTPData*)(_data + mtp_data_offset);
  // Compute the address of the module to package tables.
  _mtp_packages = (s4*)(_data + mtp_packages_offset);
}

// Release module data resource.
ImageModuleData::~ImageModuleData() {
  if (_data != NULL) {
    FREE_C_HEAP_ARRAY(u1, _data);
  }
}

// Return the name of the module data resource.  Ex. "./lib/modules/file.jimage"
// yields "file.jdata"
void ImageModuleData::module_data_name(char* buffer, const char* image_file_name) {
  // Locate the last slash in the file name path.
  const char* slash = strrchr(image_file_name, os::file_separator()[0]);
  // Trim the path to name and extension.
  const char* name = slash != NULL ? slash + 1 : (char *)image_file_name;
  // Locate the extension period.
  const char* dot = strrchr(name, '.');
  guarantee(dot, "missing extension on jimage name");
  // Trim to only base name.
  int length = dot - name;
  strncpy(buffer, name, length);
  buffer[length] = '\0';
  // Append extension.
  strcat(buffer, ".jdata");
}

// Return the module in which a package resides.  Returns NULL if not found.
const char* ImageModuleData::package_to_module(const char* package_name) {
  // Search the package to module table.
  s4 index = ImageStrings::find(_endian, package_name, _ptm_redirect,
                                  _header->ptm_count(_endian));
  // If entry is found.
  if (index != ImageStrings::NOT_FOUND) {
    // Retrieve the package to module entry.
    PTMData* data = _ptm_data + index;
    // Verify that it is the correct data.
    if (strcmp(package_name, get_string(data->name_offset(_endian))) != 0) {
      return NULL;
    }
    // Return the module name.
    return get_string(data->module_name_offset(_endian));
  }
  return NULL;
}

// Returns all the package names in a module.  Returns NULL if module not found.
GrowableArray<const char*>* ImageModuleData::module_to_packages(const char* module_name) {
  // Search the module to package table.
  s4 index = ImageStrings::find(_endian, module_name, _mtp_redirect,
                                  _header->mtp_count(_endian));
  // If entry is found.
  if (index != ImageStrings::NOT_FOUND) {
    // Retrieve the module to package entry.
    MTPData* data = _mtp_data + index;
    // Verify that it is the correct data.
    if (strcmp(module_name, get_string(data->name_offset(_endian))) != 0) {
      return NULL;
    }
    // Construct an array of all the package entries.
    GrowableArray<const char*>* packages = new GrowableArray<const char*>();
    s4 package_offset = data->package_offset(_endian);
    for (u4 i = 0; i < data->package_count(_endian); i++) {
      u4 package_name_offset = mtp_package(package_offset + i);
      const char* package_name = get_string(package_name_offset);
      packages->append(package_name);
    }
    return packages;
  }
  return NULL;
}

// Table to manage multiple opens of an image file.
GrowableArray<ImageFileReader*>* ImageFileReader::_reader_table =
  new(ResourceObj::C_HEAP, mtInternal) GrowableArray<ImageFileReader*>(2, true);

// Open an image file, reuse structure if file already open.
ImageFileReader* ImageFileReader::open(const char* name, bool big_endian) {
  // Lock out _reader_table.
  MutexLocker ml(ImageFileReaderTable_lock);
  ImageFileReader* reader;
  // Search for an exist image file.
  for (int i = 0; i < _reader_table->length(); i++) {
    // Retrieve table entry.
    reader = _reader_table->at(i);
    // If name matches, then reuse (bump up use count.)
    if (strcmp(reader->name(), name) == 0) {
      reader->inc_use();
      return reader;
    }
  }
  // Need a new image reader.
  reader = new ImageFileReader(name, big_endian);
  bool opened = reader->open();
  // If failed to open.
  if (!opened) {
    delete reader;
    return NULL;
  }
  // Bump use count and add to table.
  reader->inc_use();
  _reader_table->append(reader);
  return reader;
}

// Close an image file if the file is not in use elsewhere.
void ImageFileReader::close(ImageFileReader *reader) {
  // Lock out _reader_table.
  MutexLocker ml(ImageFileReaderTable_lock);
  // If last use then remove from table and then close.
  if (reader->dec_use()) {
    _reader_table->remove(reader);
    delete reader;
  }
}

// Return an id for the specifed ImageFileReader.
u8 ImageFileReader::readerToID(ImageFileReader *reader) {
  // ID is just the cloaked reader address.
  return (u8)reader;
}

// Validate the image id.
bool ImageFileReader::idCheck(u8 id) {
  // Make sure the ID is a managed (_reader_table) reader.
  MutexLocker ml(ImageFileReaderTable_lock);
  return _reader_table->contains((ImageFileReader*)id);
}

// Return an id for the specifed ImageFileReader.
ImageFileReader* ImageFileReader::idToReader(u8 id) {
#ifdef PRODUCT
  // Fast convert.
  return (ImageFileReader*)id;
#else
  // Do a slow check before fast convert.
  return idCheck(id) ? (ImageFileReader*)id : NULL;
#endif
}

// Constructor intializes to a closed state.
ImageFileReader::ImageFileReader(const char* name, bool big_endian) {
  // Copy the image file name.
  _name = NEW_C_HEAP_ARRAY(char, strlen(name) + 1, mtClass);
  strcpy(_name, name);
  // Initialize for a closed file.
  _fd = -1;
  _endian = Endian::get_handler(big_endian);
  _index_data = NULL;
}

// Close image and free up data structures.
ImageFileReader::~ImageFileReader() {
  // Ensure file is closed.
  close();
  // Free up name.
  if (_name != NULL) {
    FREE_C_HEAP_ARRAY(char, _name);
    _name = NULL;
  }
}

// Open image file for read access.
bool ImageFileReader::open() {
  // If file exists open for reading.
  struct stat st;
  if (os::stat(_name, &st) != 0 ||
    (st.st_mode & S_IFREG) != S_IFREG ||
    (_fd = os::open(_name, 0, O_RDONLY)) == -1) {
    return false;
  }
  // Retrieve the file size.
  _file_size = (u8)st.st_size;
  // Read image file header and verify it has a valid header.
  size_t header_size = sizeof(ImageHeader);
  if (_file_size < header_size ||
    !read_at((u1*)&_header, header_size, 0) ||
    _header.magic(_endian) != IMAGE_MAGIC ||
    _header.major_version(_endian) != MAJOR_VERSION ||
    _header.minor_version(_endian) != MINOR_VERSION) {
    close();
    return false;
  }
  // Size of image index.
  _index_size = index_size();
  // Make sure file is large enough to contain the index.
  if (_file_size < _index_size) {
    return false;
  }
  // Determine how much of the image is memory mapped.
  off_t map_size = (off_t)(MemoryMapImage ? _file_size : _index_size);
  // Memory map image (minimally the index.)
  _index_data = (u1*)os::map_memory(_fd, _name, 0, NULL, map_size, true, false);
  guarantee(_index_data, "image file not memory mapped");
  // Retrieve length of index perfect hash table.
  u4 length = table_length();
  // Compute offset of the perfect hash table redirect table.
  u4 redirect_table_offset = (u4)header_size;
  // Compute offset of index attribute offsets.
  u4 offsets_table_offset = redirect_table_offset + length * sizeof(s4);
  // Compute offset of index location attribute data.
  u4 location_bytes_offset = offsets_table_offset + length * sizeof(u4);
  // Compute offset of index string table.
  u4 string_bytes_offset = location_bytes_offset + locations_size();
  // Compute address of the perfect hash table redirect table.
  _redirect_table = (s4*)(_index_data + redirect_table_offset);
  // Compute address of index attribute offsets.
  _offsets_table = (u4*)(_index_data + offsets_table_offset);
  // Compute address of index location attribute data.
  _location_bytes = _index_data + location_bytes_offset;
  // Compute address of index string table.
  _string_bytes = _index_data + string_bytes_offset;
  // Successful open.
  return true;
}

// Close image file.
void ImageFileReader::close() {
  // Dealllocate the index.
  if (_index_data != NULL) {
    os::unmap_memory((char*)_index_data, _index_size);
    _index_data = NULL;
  }
  // Close file.
  if (_fd != -1) {
    os::close(_fd);
    _fd = -1;
  }
}

// Read directly from the file.
bool ImageFileReader::read_at(u1* data, u8 size, u8 offset) const {
  return os::read_at(_fd, data, size, offset) == size;
}

// Find the location attributes associated with the path.  Returns true if
// the location is found, false otherwise.
bool ImageFileReader::find_location(const char* path, ImageLocation& location) const {
  // Locate the entry in the index perfect hash table.
  s4 index = ImageStrings::find(_endian, path, _redirect_table, table_length());
  // If is found.
  if (index != ImageStrings::NOT_FOUND) {
    // Get address of first byte of location attribute stream.
    u1* data = get_location_data(index);
    // Expand location attributes.
    location.set_data(data);
    // Make sure result is not a false positive.
    return verify_location(location, path);
  }
  return false;
}

// Assemble the location path from the string fragments indicated in the location attributes.
void ImageFileReader::location_path(ImageLocation& location, char* path, size_t max) const {
  // Manage the image string table.
  ImageStrings strings(_string_bytes, _header.strings_size(_endian));
  // Position to first character of the path buffer.
  char* next = path;
  // Temp for string length.
  size_t length;
  // Get module string.
  const char* module = location.get_attribute(ImageLocation::ATTRIBUTE_MODULE, strings);
  // If module string is not empty string.
  if (*module != '\0') {
    // Get length of module name.
    length = strlen(module);
    // Make sure there is no buffer overflow.
    guarantee(next - path + length + 2 < max, "buffer overflow");
    // Append '/module/'.
    *next++ = '/';
    strcpy(next, module); next += length;
    *next++ = '/';
  }
  // Get parent (package) string.
  const char* parent = location.get_attribute(ImageLocation::ATTRIBUTE_PARENT, strings);
  // If parent string is not empty string.
  if (*parent != '\0') {
    // Get length of module string.
    length = strlen(parent);
    // Make sure there is no buffer overflow.
    guarantee(next - path + length + 1 < max, "buffer overflow");
    // Append 'patent/' .
    strcpy(next, parent); next += length;
    *next++ = '/';
  }
  // Get base name string.
  const char* base = location.get_attribute(ImageLocation::ATTRIBUTE_BASE, strings);
  // Get length of base name.
  length = strlen(base);
  // Make sure there is no buffer overflow.
  guarantee(next - path + length < max, "buffer overflow");
  // Append base name.
  strcpy(next, base); next += length;
  // Get extension string.
  const char* extension = location.get_attribute(ImageLocation::ATTRIBUTE_EXTENSION, strings);
  // If extension string is not empty string.
  if (*extension != '\0') {
    // Get length of extension string.
    length = strlen(extension);
    // Make sure there is no buffer overflow.
    guarantee(next - path + length + 1 < max, "buffer overflow");
    // Append '.extension' .
    *next++ = '.';
    strcpy(next, extension); next += length;
  }
  // Make sure there is no buffer overflow.
  guarantee((size_t)(next - path) < max, "buffer overflow");
  // Terminate string.
  *next = '\0';
}

// Verify that a found location matches the supplied path (without copying.)
bool ImageFileReader::verify_location(ImageLocation& location, const char* path) const {
  // Manage the image string table.
  ImageStrings strings(_string_bytes, _header.strings_size(_endian));
  // Position to first character of the path string.
  const char* next = path;
  // Get module name string.
  const char* module = location.get_attribute(ImageLocation::ATTRIBUTE_MODULE, strings);
  // If module string is not empty.
  if (*module != '\0') {
    // Compare '/module/' .
    if (*next++ != '/') return false;
    if (!(next = ImageStrings::starts_with(next, module))) return false;
    if (*next++ != '/') return false;
  }
  // Get parent (package) string
  const char* parent = location.get_attribute(ImageLocation::ATTRIBUTE_PARENT, strings);
  // If parent string is not empty string.
  if (*parent != '\0') {
    // Compare 'parent/' .
    if (!(next = ImageStrings::starts_with(next, parent))) return false;
    if (*next++ != '/') return false;
  }
  // Get base name string.
  const char* base = location.get_attribute(ImageLocation::ATTRIBUTE_BASE, strings);
  // Compare with basne name.
  if (!(next = ImageStrings::starts_with(next, base))) return false;
  // Get extension string.
  const char* extension = location.get_attribute(ImageLocation::ATTRIBUTE_EXTENSION, strings);
  // If extension is not empty.
  if (*extension != '\0') {
    // Compare '.extension' .
    if (*next++ != '.') return false;
    if (!(next = ImageStrings::starts_with(next, extension))) return false;
  }
  // True only if complete match and no more characters.
  return *next == '\0';
}

// Return the resource data for the supplied location.
void ImageFileReader::get_resource(ImageLocation& location, u1* uncompressed_data) const {
  // Retrieve the byte offset and size of the resource.
  u8 offset = location.get_attribute(ImageLocation::ATTRIBUTE_OFFSET);
  u8 uncompressed_size = location.get_attribute(ImageLocation::ATTRIBUTE_UNCOMPRESSED);
  u8 compressed_size = location.get_attribute(ImageLocation::ATTRIBUTE_COMPRESSED);
  if (compressed_size != 0) {
    ResourceMark rm;
    u1* compressed_data;
    // If not memory mapped read in bytes.
    if (!MemoryMapImage) {
      // Allocate buffer for compression.
      compressed_data = NEW_RESOURCE_ARRAY(u1, compressed_size);
      // Read bytes from offset beyond the image index.
      bool is_read = read_at(compressed_data, compressed_size, _index_size + offset);
      guarantee(is_read, "error reading from image or short read");
    } else {
      compressed_data = get_data_address() + offset;
    }
    // Get image string table.
    const ImageStrings strings = get_strings();
    // Decompress resource.
    ImageDecompressor::decompress_resource(compressed_data, uncompressed_data, uncompressed_size,
            &strings, false);
  } else {
    // Read bytes from offset beyond the image index.
    bool is_read = read_at(uncompressed_data, uncompressed_size, _index_size + offset);
    guarantee(is_read, "error reading from image or short read");
  }
}