From 60ead7c24466f0da3f97f331cd4e647d8b819295 Mon Sep 17 00:00:00 2001
From: Eduardo Silva <eduardo@treasure-data.com>
Date: Fri, 17 Nov 2017 14:31:21 -0800
Subject: [PATCH] hash_table: new structure to support counters and eviction
 modes

Signed-off-by: Eduardo Silva <eduardo@treasure-data.com>
---
 include/fluent-bit/flb_hash.h | 16 ++++++++++++++--
 src/flb_hash.c                | 27 ++++++++++++++++++++++++++-
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/include/fluent-bit/flb_hash.h b/include/fluent-bit/flb_hash.h
index d8f3b4c6961..ecc6b861af5 100644
--- a/include/fluent-bit/flb_hash.h
+++ b/include/fluent-bit/flb_hash.h
@@ -26,12 +26,20 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+/* Eviction modes when the table reach full capacity (if any) */
+#define FLB_HASH_EVICT_NONE       0
+#define FLB_HASH_EVICT_OLDER      1
+#define FLB_HASH_EVICT_LESS_USED  2
+
 struct flb_hash_entry {
+    time_t created;
+    uint64_t hits;
     char *key;
     size_t key_len;
     char *val;
     size_t val_size;
-    struct mk_list _head;
+    struct mk_list _head;         /* link to flb_hash_table->chains */
+    struct mk_list _head_parent;  /* link to flb_hash->entries */
 };
 
 struct flb_hash_table {
@@ -40,11 +48,15 @@ struct flb_hash_table {
 };
 
 struct flb_hash {
+    int evict_mode;
+    int max_entries;
+    int total_count;
     size_t size;
+    struct mk_list entries;
     struct flb_hash_table *table;
 };
 
-struct flb_hash *flb_hash_create(size_t size);
+struct flb_hash *flb_hash_create(int evict_mode, size_t size, int max_entries);
 void flb_hash_destroy(struct flb_hash *ht);
 
 int flb_hash_add(struct flb_hash *ht, char *key, int key_len,
diff --git a/src/flb_hash.c b/src/flb_hash.c
index a3124fe598b..68591afbc61 100644
--- a/src/flb_hash.c
+++ b/src/flb_hash.c
@@ -87,12 +87,13 @@ static unsigned int gen_hash(const void *key, int len)
 static inline void flb_hash_entry_free(struct flb_hash_entry *entry)
 {
     mk_list_del(&entry->_head);
+    mk_list_del(&entry->_head_parent);
     flb_free(entry->key);
     flb_free(entry->val);
     flb_free(entry);
 }
 
-struct flb_hash *flb_hash_create(size_t size)
+struct flb_hash *flb_hash_create(int evict_mode, size_t size, int max_entries)
 {
     int i;
     struct flb_hash_table *tmp;
@@ -108,6 +109,10 @@ struct flb_hash *flb_hash_create(size_t size)
         return NULL;
     }
 
+    mk_list_init(&ht->entries);
+    ht->evict_mode = evict_mode;
+    ht->max_entries = max_entries;
+    ht->total_count = 0;
     ht->size = size;
     ht->table = flb_calloc(1, sizeof(struct flb_hash_table) * size);
     if (!ht->table) {
@@ -162,6 +167,20 @@ int flb_hash_add(struct flb_hash *ht, char *key, int key_len,
         return -1;
     }
 
+    /* Check capacity */
+    if (ht->max_entries > 0 && ht->total_count >= ht->max_entries) {
+        /* FIXME: handle eviction mode */
+        if (ht->evict_mode == FLB_HASH_EVICT_NONE) {
+
+        }
+        else if (ht->evict_mode == FLB_HASH_EVICT_OLDER) {
+
+        }
+        else if (ht->evict_mode == FLB_HASH_EVICT_LESS_USED) {
+
+        }
+    }
+
     /* Generate hash number */
     hash = gen_hash(key, key_len);
     id = (hash % ht->size);
@@ -172,6 +191,8 @@ int flb_hash_add(struct flb_hash *ht, char *key, int key_len,
         flb_errno();
         return -1;
     }
+    entry->created = time(NULL);
+    entry->hits = 0;
 
     /* Store the key and value as a new memory region */
     entry->key = flb_strdup(key);
@@ -183,6 +204,7 @@ int flb_hash_add(struct flb_hash *ht, char *key, int key_len,
         flb_free(entry);
         return -1;
     }
+
     /*
      * Copy the buffer and append a NULL byte in case the caller set and
      * expects a string.
@@ -197,6 +219,7 @@ int flb_hash_add(struct flb_hash *ht, char *key, int key_len,
     /* Check if the new key already exists */
     if (table->count == 0) {
         mk_list_add(&entry->_head, &table->chains);
+        mk_list_add(&entry->_head_parent, &ht->entries);
     }
     else {
         mk_list_foreach_safe(head, tmp, &table->chains) {
@@ -208,6 +231,7 @@ int flb_hash_add(struct flb_hash *ht, char *key, int key_len,
             }
         }
         mk_list_add(&entry->_head, &table->chains);
+        mk_list_add(&entry->_head_parent, &ht->entries);
     }
 
     table->count++;
@@ -270,6 +294,7 @@ int flb_hash_get(struct flb_hash *ht, char *key, int key_len,
         return -1;
     }
 
+    entry->hits++;
     *out_buf = entry->val;
     *out_size = entry->val_size;