[committed] Add emulate_htab

[committed] Add emulate_htab

[Tom de Vries]

Hi,

Add a function emulate_htab that emulates how the hash tables in hashtab.c
grow in size.

Committed to trunk.

Thanks,
- Tom

Add emulate_htab

2019-11-20  Tom de Vries  <tdevries@suse.de>

	* hashtab.c (higher_prime_number): Remove static.
	* hashtab.h (higher_prime_number): Declare.
	* dwz.c (emulate_htab): New function.

---
 dwz.c     | 30 ++++++++++++++++++++++++++++++
 hashtab.c |  3 +--
 hashtab.h |  3 +++
 3 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/dwz.c b/dwz.c
index 846e42f..db134ab 100644
--- a/dwz.c
+++ b/dwz.c
@@ -1197,6 +1197,36 @@ estimate_nr_dies (void)
   return nr_dies;
 }
 
+static size_t UNUSED
+emulate_htab (size_t initial, size_t final_nr_elements)
+{
+  size_t size = initial;
+
+  /* Emulate creation.  */
+  size = higher_prime_number (size);
+
+  /* Emulate growing till htab contains find_nr_elements.  */
+  while (1)
+    {
+      /* Emulate expansion trigger.  */
+      size_t nr_elements = size * 3 / 4;
+      while (!(size * 3 <= nr_elements * 4))
+	nr_elements++;
+
+      if (nr_elements > final_nr_elements)
+	{
+	  nr_elements = final_nr_elements;
+	  break;
+	}
+
+      /* Emulate expansion.  */
+      size = size * 2;
+      size = higher_prime_number (size);
+    }
+
+  return size;
+}
+
 /* Hash function for off_htab hash table.  */
 static hashval_t
 off_hash (const void *p)
diff --git a/hashtab.c b/hashtab.c
index 5d98451..41eab30 100644
--- a/hashtab.c
+++ b/hashtab.c
@@ -51,7 +51,6 @@ Boston, MA 02110-1301, USA.  */
 
 #define DELETED_ENTRY  ((void *) 1)
 
-static unsigned long higher_prime_number (unsigned long);
 static hashval_t hash_pointer (const void *);
 static int eq_pointer (const void *, const void *);
 static int htab_expand (htab_t);
@@ -66,7 +65,7 @@ htab_eq htab_eq_pointer = eq_pointer;
 /* The following function returns a nearest prime number which is
    greater than N, and near a power of two. */
 
-static unsigned long
+unsigned long
 higher_prime_number (n)
      unsigned long n;
 {
diff --git a/hashtab.h b/hashtab.h
index f1cc743..cb3da01 100644
--- a/hashtab.h
+++ b/hashtab.h
@@ -132,6 +132,9 @@ extern size_t	htab_size	(htab_t);
 extern size_t	htab_elements	(htab_t);
 extern double	htab_collisions	(htab_t);
 
+/* Utility function.  */
+unsigned long higher_prime_number (unsigned long);
+
 /* A hash function for pointers.  */
 extern htab_hash htab_hash_pointer;