From bbefd9daf54ff7e3d32f8d1b708833723b3318bc Mon Sep 17 00:00:00 2001
From: Henrik Hautakoski <henrik@fiktivkod.org>
Date: Thu, 3 Nov 2011 13:10:30 +0100
Subject: [PATCH] dlhist.c: calculate initial size when read table from file.

Now that records are fixed size, it's easy to calculate the number of
entries in the file. use that to calculate how large the hash table
should be.
---
 dlhist.c | 31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)

diff --git a/dlhist.c b/dlhist.c
index 47aedaf..0411a21 100644
--- a/dlhist.c
+++ b/dlhist.c
@@ -50,6 +50,10 @@ union hash {
 	unsigned char sha1[20];
 };
 
+/*
+ * NOTE: be sure to change this constant if the struct's size changes.
+ */
+#define HE_SZ (sizeof(union hash) + sizeof(unsigned))
 struct hash_entry {
 	union hash   hash;
 	unsigned int time;
@@ -126,6 +130,18 @@ static void he_remove(struct hash_entry *he) {
 	table_count--;
 }
 
+static unsigned calculate_size(unsigned count) {
+
+	/*
+	 * set size to a load factor that is in the
+	 * middle in the valid range.
+	 */
+	unsigned size = count / 0.625;
+	if (size < TABLE_MIN_SIZE)
+		size = TABLE_MIN_SIZE;
+	return size;
+}
+
 static void resize_table() {
 
 	double load;
@@ -139,13 +155,7 @@ static void resize_table() {
 		(load >= 0.5 && load <= 0.75))
 		return;
 
-	/*
-	 * set size to a load factor that is in the
-	 * middle in the valid range.
-	 */
-	table_size = table_count / 0.625;
-	if (table_size < TABLE_MIN_SIZE)
-		table_size = TABLE_MIN_SIZE;
+	table_size = calculate_size(table_count);
 
 	table_count = 0;
 	table = calloc(sizeof(*table), table_size);
@@ -162,6 +172,7 @@ static void build_table(const char *buf, size_t len) {
 
 	size_t offset = 0;
 
+	table_size = calculate_size(len / HE_SZ);
 	table = calloc(sizeof(*table), table_size);
 
 	while(offset < len) {
@@ -217,15 +228,9 @@ int dlhist_open() {
 			goto error;
 		}
 
-		/* Get current table size */
-		table_size = htonl(hdr->size);
-
 		offset = sizeof(*hdr);
 	}
 
-	if (table_size < 1)
-		table_size = TABLE_MIN_SIZE;
-
 	build_table(buf + offset, st.st_size - offset);
 
 	ret = 0;