From ed5e7684b766a3914b30c5b449608542695fd3b8 Mon Sep 17 00:00:00 2001
From: Mike Buland <eichlan@xagasoft.com>
Date: Tue, 4 Feb 2020 09:01:45 -0800
Subject: Minor Bu::Hash updates and additions.

Bu::Hash::KeyList has been added, I thought that was always there.
Bu::Hash::rehash has been added. Rehashes can be triggered manually now.
---
 src/stable/hash.h | 40 ++++++++++++++++++++++++++++++++++------
 1 file changed, 34 insertions(+), 6 deletions(-)

(limited to 'src/stable')

diff --git a/src/stable/hash.h b/src/stable/hash.h
index 7f4066e..0c5bd9e 100644
--- a/src/stable/hash.h
+++ b/src/stable/hash.h
@@ -211,7 +211,7 @@ namespace Bu
             return 0;
         }
 
-        uint32_t probe( uint32_t hash, const key &k, bool &bFill, bool rehash=true )
+        uint32_t probe( uint32_t hash, const key &k, bool &bFill, bool bRehash=true )
         {
             init();
 
@@ -244,9 +244,9 @@ namespace Bu
 
             // This is our insurance, if the table is full, then go ahead and
             // rehash, then try again.
-            if( (isFilled( nCur ) || j == 32) && rehash == true )
+            if( (isFilled( nCur ) || j == 32) && bRehash == true )
             {
-                reHash( szCalc( nCapacity, nFilled, nDeleted ) );
+                rehash( szCalc( nCapacity, nFilled, nDeleted ) );
 
                 // This is potentially dangerous, and could cause an infinite loop.
                 // Be careful writing probe, eh?
@@ -309,7 +309,7 @@ namespace Bu
             }
         }
 
-        void reHash( uint32_t nNewSize )
+        void rehash( uint32_t nNewSize )
         {
             //printf("--rehash: %d --> %d (%d, %d)\n", nCapacity, nNewSize, nFilled, nDeleted );
             //printf("---REHASH---");
@@ -386,11 +386,13 @@ namespace Bu
             for( uint32_t j = 0; j < nCapacity; j++ )
             {
                 if( isFilled( j ) )
+                {
                     if( !isDeleted( j ) )
                     {
                         va.destroy( &aValues[j] );
                         ka.destroy( &aKeys[j] );
                     }
+                }
             }
             va.deallocate( aValues, nCapacity );
             ka.deallocate( aKeys, nCapacity );
@@ -501,6 +503,8 @@ namespace Bu
         {
         }
 
+        typedef Bu::List<key> KeyList;
+
         /**
          * Get the current hash table capacity. (Changes at re-hash)
          *@returns (uint32_t) The current capacity.
@@ -1135,9 +1139,9 @@ namespace Bu
          * Get a list of all the keys in the hash table.
          *@returns (std::list<key_type>) The list of keys in the hash table.
          */
-        Bu::List<key> getKeys() const
+        KeyList getKeys() const
         {
-            Bu::List<key> lKeys;
+            KeyList lKeys;
 
             for( uint32_t j = 0; j < core->nCapacity; j++ )
             {
@@ -1171,6 +1175,30 @@ namespace Bu
             return lValues;
         }
 
+        /**
+         * This can be a very expensive operation, but when there are a decent
+         * number of deleted entries it can be good to be able to clean them
+         * up on your own terms.
+         *
+         * This will always allocate a new table and move all non-deleted items
+         * over to it. The size of the new table depends on which resizing
+         * calculator is selected. The default resize calculator will shrink
+         * the table if it's mostly deleted/empty space.
+         *
+         * This will be done by the system whenever it deems necesarry, but
+         * only during probing operations. That means that an insert could
+         * trigger a rehash, which could be very expensive. If you know, for
+         * example, that you'll be deleting most of the entries once a night
+         * during a low-usage time, that would probably be a good time to
+         * manually trigger a rehash and save the extra time on the next insert
+         * after the cleanup.  This is partucularly true for systems like
+         * caches that need to be periodically cleaned up.
+         */
+        void rehash()
+        {
+            core->rehash( core->szCalc( core->nCapacity, core->nFilled, core->nDeleted ) );
+        }
+
         bool operator==( const MyType &rhs ) const
         {
             if( this == &rhs )
-- 
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