/*

 * Copyright (c) 1997, 2018, 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_COMPACTHASHTABLE_HPP

#define SHARE_VM_CLASSFILE_COMPACTHASHTABLE_HPP

#include "oops/array.hpp"

#include "oops/symbol.hpp"

#include "utilities/hashtable.hpp"

template <

  typename K,

  typename V,

  V (*DECODE)(address base_address, u4 offset),

  bool (*EQUALS)(V value, K key, int len)

  >

class CompactHashtable;

class NumberSeq;

class SimpleCompactHashtable;

class SerializeClosure;

// Stats for symbol tables in the CDS archive

class CompactHashtableStats {

public:

  int hashentry_count;

  int hashentry_bytes;

  int bucket_count;

  int bucket_bytes;

};

#if INCLUDE_CDS

/////////////////////////////////////////////////////////////////////////

//

// The compact hash table writer. Used at dump time for writing out

// the compact table to the shared archive.

//

// At dump time, the CompactHashtableWriter obtains all entries from the

// symbol/string table and adds them to a new temporary hash table. The hash

// table size (number of buckets) is calculated using

// '(num_entries + bucket_size - 1) / bucket_size'. The default bucket

// size is 4 and can be changed by -XX:SharedSymbolTableBucketSize option.

// 4 is chosen because it produces smaller sized bucket on average for

// faster lookup. It also has relatively small number of empty buckets and

// good distribution of the entries.

//

// We use a simple hash function (hash % num_bucket) for the table.

// The new table is compacted when written out. Please see comments

// above the CompactHashtable class for the table layout detail. The bucket

// offsets are written to the archive as part of the compact table. The

// bucket offset is encoded in the low 30-bit (0-29) and the bucket type

// (regular or compact) are encoded in bit[31, 30]. For buckets with more

// than one entry, both hash and entry offset are written to the

// table. For buckets with only one entry, only the entry offset is written

// to the table and the buckets are tagged as compact in their type bits.

// Buckets without entry are skipped from the table. Their offsets are

// still written out for faster lookup.

//

class CompactHashtableWriter: public StackObj {

public:

  class Entry {

    unsigned int _hash;

    u4 _value;

  public:

    Entry() {}

    Entry(unsigned int hash, u4 val) : _hash(hash), _value(val) {}

    u4 value() {

      return _value;

    }

    unsigned int hash() {

      return _hash;

    }

    bool operator==(const CompactHashtableWriter::Entry& other) {

      return (_value == other._value && _hash == other._hash);

    }

  }; // class CompactHashtableWriter::Entry

private:

  int _num_entries;

  int _num_buckets;

  int _num_empty_buckets;

  int _num_value_only_buckets;

  int _num_other_buckets;

  GrowableArray<Entry>** _buckets;

  CompactHashtableStats* _stats;

  Array<u4>* _compact_buckets;

  Array<u4>* _compact_entries;

public:

  // This is called at dump-time only

  CompactHashtableWriter(int num_buckets, CompactHashtableStats* stats);

  ~CompactHashtableWriter();

  void add(unsigned int hash, u4 value);

private:

  void allocate_table();

  void dump_table(NumberSeq* summary);

public:

  void dump(SimpleCompactHashtable *cht, const char* table_name);

  static int default_num_buckets(size_t num_entries) {

    return default_num_buckets((int)num_entries);

  }

  static int default_num_buckets(int num_entries) {

    int num_buckets = num_entries / SharedSymbolTableBucketSize;

    // calculation of num_buckets can result in zero buckets, we need at least one

    return (num_buckets < 1) ? 1 : num_buckets;

  }

};

#endif // INCLUDE_CDS

#define REGULAR_BUCKET_TYPE       0

#define VALUE_ONLY_BUCKET_TYPE    1

#define TABLEEND_BUCKET_TYPE      3

#define BUCKET_OFFSET_MASK        0x3FFFFFFF

#define BUCKET_OFFSET(info)       ((info) & BUCKET_OFFSET_MASK)

#define BUCKET_TYPE_SHIFT         30

#define BUCKET_TYPE(info)         (((info) & ~BUCKET_OFFSET_MASK) >> BUCKET_TYPE_SHIFT)

#define BUCKET_INFO(offset, type) (((type) << BUCKET_TYPE_SHIFT) | ((offset) & BUCKET_OFFSET_MASK))

/////////////////////////////////////////////////////////////////////////////

//

// CompactHashtable is used to store the CDS archive's symbol/string tables.

//

// Because these tables are read-only (no entries can be added/deleted) at run-time

// and tend to have large number of entries, we try to minimize the footprint

// cost per entry.

//

// The CompactHashtable is split into two arrays

//

//   u4 buckets[num_buckets+1]; // bit[31,30]: type; bit[29-0]: offset

//   u4 entries[<variable size>]

//

// The size of buckets[] is 'num_buckets + 1'. Each entry of

// buckets[] is a 32-bit encoding of the bucket type and bucket offset,

// with the type in the left-most 2-bit and offset in the remaining 30-bit.

// The last entry is a special type. It contains the end of the last

// bucket.

//

// There are two types of buckets, regular buckets and value_only buckets. The

// value_only buckets have '01' in their highest 2-bit, and regular buckets have

// '00' in their highest 2-bit.

//

// For normal buckets, each entry is 8 bytes in the entries[]:

//   u4 hash;    /* symbol/string hash */

//   union {

//     u4 offset;  /* Symbol* sym = (Symbol*)(base_address + offset) */

//     narrowOop str; /* String narrowOop encoding */

//   }

//

//

// For value_only buckets, each entry has only the 4-byte 'offset' in the entries[].

//

// Example -- note that the second bucket is a VALUE_ONLY_BUCKET_TYPE so the hash code

//            is skipped.

// buckets[0, 4, 5, ....]

//         |  |  |

//         |  |  +---+

//         |  |      |

//         |  +----+ |

//         v       v v

// entries[H,O,H,O,O,H,O,H,O.....]

//

// See CompactHashtable::lookup() for how the table is searched at runtime.

// See CompactHashtableWriter::dump() for how the table is written at CDS

// dump time.

//

class SimpleCompactHashtable {

protected:

  address  _base_address;

  u4  _bucket_count;

  u4  _entry_count;

  u4* _buckets;

  u4* _entries;

public:

  SimpleCompactHashtable() {

    _entry_count = 0;

    _bucket_count = 0;

    _buckets = 0;

    _entries = 0;

  }

  void reset() {

    _bucket_count = 0;

    _entry_count = 0;

    _buckets = 0;

    _entries = 0;

  }

  void init(address base_address, u4 entry_count, u4 bucket_count, u4* buckets, u4* entries) {

    _base_address = base_address;

    _bucket_count = bucket_count;

    _entry_count = entry_count;

    _buckets = buckets;

    _entries = entries;

  }

  // Read/Write the table's header from/to the CDS archive

  void serialize_header(SerializeClosure* soc) NOT_CDS_RETURN;

  inline bool empty() {

    return (_entry_count == 0);

  }

};

template <

  typename K,

  typename V,

  V (*DECODE)(address base_address, u4 offset),

  bool (*EQUALS)(V value, K key, int len)

  >

class CompactHashtable : public SimpleCompactHashtable {

  friend class VMStructs;

  V decode(u4 offset) const {

    return DECODE(_base_address, offset);

  }

public:

  CompactHashtable() : SimpleCompactHashtable() {}

  // Lookup a value V from the compact table using key K

  inline V lookup(K key, unsigned int hash, int len) const {

    if (_entry_count > 0) {

      int index = hash % _bucket_count;

      u4 bucket_info = _buckets[index];

      u4 bucket_offset = BUCKET_OFFSET(bucket_info);

      int bucket_type = BUCKET_TYPE(bucket_info);

      u4* entry = _entries + bucket_offset;

      if (bucket_type == VALUE_ONLY_BUCKET_TYPE) {

        V value = decode(entry[0]);

        if (EQUALS(value, key, len)) {

          return value;

        }

      } else {

        // This is a regular bucket, which has more than one

        // entries. Each entry is a pair of entry (hash, offset).

        // Seek until the end of the bucket.

        u4* entry_max = _entries + BUCKET_OFFSET(_buckets[index + 1]);

        while (entry < entry_max) {

          unsigned int h = (unsigned int)(entry[0]);

          if (h == hash) {

            V value = decode(entry[1]);

            if (EQUALS(value, key, len)) {

              return value;

            }

          }

          entry += 2;

        }

      }

    }

    return NULL;

  }

  template <class ITER>

  inline void iterate(ITER* iter) const {

    for (u4 i = 0; i < _bucket_count; i++) {

      u4 bucket_info = _buckets[i];

      u4 bucket_offset = BUCKET_OFFSET(bucket_info);

      int bucket_type = BUCKET_TYPE(bucket_info);

      u4* entry = _entries + bucket_offset;

      if (bucket_type == VALUE_ONLY_BUCKET_TYPE) {

        iter->do_value(decode(entry[0]));

      } else {

        u4*entry_max = _entries + BUCKET_OFFSET(_buckets[i + 1]);

        while (entry < entry_max) {

          iter->do_value(decode(entry[1]));

          entry += 2;

        }

      }

    }

  }

};

////////////////////////////////////////////////////////////////////////

//

// Read/Write the contents of a hashtable textual dump (created by

// SymbolTable::dump and StringTable::dump).

// Because the dump file may be big (hundred of MB in extreme cases),

// we use mmap for fast access when reading it.

//

class HashtableTextDump {

  int _fd;

  const char* _base;

  const char* _p;

  const char* _end;

  const char* _filename;

  size_t      _size;

  int         _prefix_type;

  int         _line_no;

public:

  HashtableTextDump(const char* filename);

  ~HashtableTextDump();

  enum {

    SymbolPrefix = 1 << 0,

    StringPrefix = 1 << 1,

    Unknown = 1 << 2

  };

  void quit(const char* err, const char* msg);

  inline int remain() {

    return (int)(_end - _p);

  }

  void corrupted(const char *p, const char *msg);

  inline void corrupted_if(bool cond, const char *msg) {

    if (cond) {

      corrupted(_p, msg);

    }

  }

  bool skip_newline();

  int skip(char must_be_char);

  void skip_past(char c);

  void check_version(const char* ver);

  inline void get_num(char delim, int *num) {

    const char* p   = _p;

    const char* end = _end;

    u8 n = 0;

    while (p < end) {

      char c = *p++;

      if ('0' <= c && c <= '9') {

        n = n * 10 + (c - '0');

        if (n > (u8)INT_MAX) {

          corrupted(_p, "Num overflow");

        }

      } else if (c == delim) {

        _p = p;

        *num = (int)n;

        return;

      } else {

        // Not [0-9], not 'delim'

        corrupted(_p, "Unrecognized format");;

      }

    }

    corrupted(_end, "Incorrect format");

    ShouldNotReachHere();

  }

  void scan_prefix_type();

  int scan_prefix(int* utf8_length);

  int scan_string_prefix();

  int scan_symbol_prefix();

  jchar unescape(const char* from, const char* end, int count);

  void get_utf8(char* utf8_buffer, int utf8_length);

  static void put_utf8(outputStream* st, const char* utf8_string, int utf8_length);

};

#endif // SHARE_VM_CLASSFILE_COMPACTHASHTABLE_HPP