312 lines
9.9 KiB
C++
312 lines
9.9 KiB
C++
/* Copyright (C) 2012-2013
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Free Software Foundation
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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GCC is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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#ifndef _VTV_MAP_H
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#define _VTV_MAP_H 1
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#include <string.h>
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#include <vtv_utils.h>
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inline uint64_t
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load8bytes (const void *p)
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{
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uint64_t result;
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memcpy (&result, p, 8);
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return result;
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}
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/* Insert_only_hash_map maps keys to values. The implementation is a
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basic hash table with open addressing. The keys are not "owned" by
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the table; it only stores pointers to keys. The key type is
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specified below (see insert_only_hash_map::key_type) and is,
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roughly speaking, a string of any length with the string length and
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a hash code stored at the front. The code here does not compute
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any hash codes, but rather uses what's given. */
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template<typename T, typename Alloc>
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class insert_only_hash_map
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{
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public:
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typedef size_t size_type;
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typedef T value_type;
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typedef Alloc alloc_type;
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enum { min_capacity = 4 };
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#if HASHMAP_STATS
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enum { stats = true };
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#else
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enum { stats = false };
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#endif
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/* Keys are a byte string (up to 2^32 - 1 long) plus a uint32_t
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that's used as a hash code. The latter can encode arbitrary
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information at the client's discretion, so, e.g., multiple keys
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that are the same string still "differ" if the hash codes differ.
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Keys are equal if the first 8 bytes are equal and the next n
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bytes are equal. */
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struct key_type
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{
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uint32_t n;
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uint32_t hash;
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char bytes[0];
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bool
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equals (const key_type *k) const;
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};
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/* Create an empty map with a reasonable number of buckets for the
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expected size. Returns NULL if the allocator fails. */
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static insert_only_hash_map *
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create (size_type expected_size);
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/* The opposite of create(). Free the memory for the given map. */
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static void
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destroy (insert_only_hash_map *m)
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{ Alloc().dealloc (m, m->size_in_bytes_); }
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/* Return a map identical to this except that *k is mapped to v.
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Typcially it's done by modifying this in place, but if a resize
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is necessary then this is deallocated and a new map is returned.
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Requires k to be non-NULL. Does nothing and returns NULL if the
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allocator fails. */
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insert_only_hash_map*
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put (const key_type *k, const value_type &v)
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{ return this->put_internal (k, v, false); }
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/* If *k is a key in this then set *v to point to the corresponding
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value. Otherwise, do the equivalent of insert(k, value_type())
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and, if that succeeds, set *v to point to the inserted value.
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Requires k to be non-NULL. Does nothing and returns NULL if the
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allocator fails. Typically returns this, but will return a new
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insert_only_hash_map if a resize occurs. If the return value is
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non-NULL, *v is set and it's valid until a resize of the map that
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is the return value. */
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insert_only_hash_map *
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find_or_add_key (const key_type *k, value_type **v);
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/* Get the value corresponding to *k. Returns NULL if there is
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none. Requires k to be non-NULL. The return value is valid
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until any resize. */
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const value_type *get (const key_type *k) const;
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size_type
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size () const
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{ return num_entries_; }
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bool
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empty () const
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{ return this->size () == 0; }
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size_type
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bucket_count () const
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{ return num_buckets_; }
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private:
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typedef std::pair <const key_type *, value_type> bucket_type;
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insert_only_hash_map *put_internal (const key_type *, const value_type &,
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bool);
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/* This function determines when to resize the table. */
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bool
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is_too_full (size_type entries) const
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{ return entries > (this->bucket_count () * 0.7); }
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/* Return a copy with double the number of buckets. Returns NULL if
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the allocator fails. Otherwise, calls destroy (this). */
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insert_only_hash_map *destructive_copy ();
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/* Must be a power of 2 not less than min_capacity. */
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size_type num_buckets_;
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size_type num_entries_;
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size_type size_in_bytes_;
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bucket_type buckets[0]; /* Actual array size is num_buckets. */
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};
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template <typename T, typename Alloc>
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insert_only_hash_map <T, Alloc> *
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insert_only_hash_map <T, Alloc>::create (size_type expected_size)
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{
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size_t cap = min_capacity;
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while (expected_size >= cap)
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{
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cap *= 2;
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}
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size_t size_in_bytes = sizeof (insert_only_hash_map <T, Alloc>)
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+ cap * sizeof (bucket_type);
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insert_only_hash_map <T, Alloc>* result =
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static_cast <insert_only_hash_map <T, Alloc>*> (Alloc ()
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.alloc (size_in_bytes));
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if (result != NULL)
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{
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result->size_in_bytes_ = size_in_bytes;
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result->num_buckets_ = cap;
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result->num_entries_ = 0;
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memset (result->buckets, 0, cap * sizeof (bucket_type));
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}
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return result;
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}
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template <typename T, typename Alloc>
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insert_only_hash_map <T, Alloc>*
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insert_only_hash_map <T, Alloc>::destructive_copy ()
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{
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insert_only_hash_map* copy = create (this->bucket_count ());
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if (copy == NULL)
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return NULL;
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VTV_DEBUG_ASSERT (copy->bucket_count () == 2 * this->bucket_count ());
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for (size_type i = 0; i < this->bucket_count (); i++)
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if (this->buckets[i].first != NULL)
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copy->put_internal (this->buckets[i].first, this->buckets[i].second,
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true);
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VTV_DEBUG_ASSERT (copy->size () == this->size ());
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destroy (this);
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return copy;
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}
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template <typename T, typename Alloc>
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insert_only_hash_map <T, Alloc>*
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insert_only_hash_map <T, Alloc>::find_or_add_key (const key_type *k,
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value_type **v)
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{
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/* Table size is always a power of 2. */
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const size_type mask = this->bucket_count () - 1;
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size_type bucket_index = k->hash & mask;
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size_type step = 1;
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for (;;)
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{
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bucket_type &bucket = this->buckets[bucket_index];
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if (bucket.first == NULL)
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{
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/* Key was not present. */
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if (this->is_too_full (this->size () + 1))
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{
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insert_only_hash_map <T, Alloc>* result =
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this->destructive_copy ();
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return result == NULL
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? NULL
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: result->find_or_add_key (k, v);
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}
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else
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{
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bucket.first = k;
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bucket.second = T ();
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this->num_entries_++;
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*v = &bucket.second;
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return this;
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}
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}
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else if (bucket.first->equals (k))
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{
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/* Key was present. */
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*v = &bucket.second;
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return this;
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}
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else
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bucket_index = (bucket_index + step++) & mask;
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}
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}
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template <typename T, typename Alloc>
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insert_only_hash_map <T, Alloc>*
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insert_only_hash_map <T, Alloc>::put_internal (
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const insert_only_hash_map::key_type *k,
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const insert_only_hash_map::value_type &v,
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bool unique_key_and_resize_not_needed)
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{
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/* Table size is always a power of 2. */
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const size_type mask = this->bucket_count () - 1;
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size_type bucket_index = k->hash & mask;
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size_type step = 1;
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for (;;)
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{
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bucket_type &bucket = this->buckets[bucket_index];
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if (bucket.first == NULL)
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{
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/* Key was not present. */
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if (!unique_key_and_resize_not_needed
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&& this->is_too_full (this->size () + 1))
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{
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insert_only_hash_map <T, Alloc>* result =
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this->destructive_copy ();
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return result == NULL
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? NULL
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: result->put_internal (k, v, true);
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}
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else
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{
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bucket.first = k;
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bucket.second = v;
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this->num_entries_++;
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return this;
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}
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}
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else if (!unique_key_and_resize_not_needed && bucket.first->equals (k))
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{
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/* Key was present. Just change the value. */
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bucket.second = v;
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return this;
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}
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else
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bucket_index = (bucket_index + step++) & mask;
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}
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}
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template <typename T, typename Alloc>
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inline const typename insert_only_hash_map <T, Alloc>::value_type*
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insert_only_hash_map <T, Alloc>::get (const insert_only_hash_map::key_type *k)
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const
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{
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/* Table size is always a power of 2. */
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const size_type mask = this->bucket_count () - 1;
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size_type bucket_index = k->hash & mask;
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size_type step = 1;
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for (;;)
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{
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const bucket_type &bucket = this->buckets[bucket_index];
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if (bucket.first == NULL)
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return NULL;
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else if (bucket.first->equals (k))
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return &bucket.second;
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else
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bucket_index = (bucket_index + step++) & mask;
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}
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}
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template <typename T, typename Alloc>
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inline bool
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insert_only_hash_map <T, Alloc>::key_type::equals (
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const typename insert_only_hash_map <T, Alloc>::key_type *k) const
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{
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const char* x = reinterpret_cast <const char *> (k);
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const char* y = reinterpret_cast <const char *> (this);
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return (load8bytes (x) == load8bytes (y)
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&& memcmp (x + 8, y + 8, this->n) == 0);
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}
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#endif /* _VTV_MAP_H */
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