From ffafcf9633eae1c679b8835a31e9b00dca740dde Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Wed, 4 Jan 2023 12:55:59 -0700
Subject: [PATCH] [map] Add hb_map_next()

---
 docs/harfbuzz-sections.txt |  1 +
 src/hb-map.cc              | 25 ++++++++++++++++++++++++-
 src/hb-map.h               |  6 ++++++
 src/hb-map.hh              | 24 ++++++++++++++++++++++++
 src/test-map.cc            | 27 +++++++++++++++++++++++++++
 5 files changed, 82 insertions(+), 1 deletion(-)

diff --git a/docs/harfbuzz-sections.txt b/docs/harfbuzz-sections.txt
index f697157ae..e30590f59 100644
--- a/docs/harfbuzz-sections.txt
+++ b/docs/harfbuzz-sections.txt
@@ -546,6 +546,7 @@ hb_map_get_population
 hb_map_is_empty
 hb_map_is_equal
 hb_map_hash
+hb_map_next
 HB_MAP_VALUE_INVALID
 hb_map_t
 </SECTION>
diff --git a/src/hb-map.cc b/src/hb-map.cc
index 5c5f5de59..fd7f3e371 100644
--- a/src/hb-map.cc
+++ b/src/hb-map.cc
@@ -335,9 +335,32 @@ hb_map_is_equal (const hb_map_t *map,
  *
  * Since: 4.4.0
  **/
-HB_EXTERN unsigned int
+unsigned int
 hb_map_hash (const hb_map_t *map)
 {
   return map->hash ();
 }
 
+/**
+ * hb_map_next:
+ * @map: A map
+ * @idx: (inout): Iterator internal state
+ * @key: (out): Key retrieved
+ * @value: (out): Value retrieved
+ *
+ * Fetches the next key/value paire in @map.
+ *
+ * Set @idx to -1 to get started.
+ *
+ * Return value: `true` if there was a next value, `false` otherwise
+ *
+ * Since: REPLACEME
+ **/
+hb_bool_t
+hb_map_next (const hb_map_t *map,
+	     int *idx,
+	     hb_codepoint_t *key,
+	     hb_codepoint_t *value)
+{
+  return map->next (idx, key, value);
+}
diff --git a/src/hb-map.h b/src/hb-map.h
index 3a067c5c7..9387ec2ce 100644
--- a/src/hb-map.h
+++ b/src/hb-map.h
@@ -118,6 +118,12 @@ HB_EXTERN hb_bool_t
 hb_map_has (const hb_map_t *map,
 	    hb_codepoint_t  key);
 
+/* Pass -1 in for idx to get started. */
+HB_EXTERN hb_bool_t
+hb_map_next (const hb_map_t *map,
+	     int *idx,
+	     hb_codepoint_t *key,
+	     hb_codepoint_t *value);
 
 HB_END_DECLS
 
diff --git a/src/hb-map.hh b/src/hb-map.hh
index bfb1b3f76..9d6fbec8b 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -348,6 +348,30 @@ struct hb_hashmap_t
     | hb_map (hb_ridentity)
   )
 
+  /* C iterator. */
+  bool next (int *idx,
+	     K *key,
+	     V *value) const
+  {
+    unsigned i = (unsigned) (*idx + 1);
+
+    unsigned count = size ();
+    while (i <= count && !items[i].is_real ())
+      i++;
+
+    if (i >= count)
+    {
+      *idx = -1;
+      return false;
+    }
+
+    *key = items[i].key;
+    *value = items[i].value;
+
+    *idx = (signed) i;
+    return true;
+  }
+
   /* Sink interface. */
   hb_hashmap_t& operator << (const hb_pair_t<K, V>& v)
   { set (v.first, v.second); return *this; }
diff --git a/src/test-map.cc b/src/test-map.cc
index da77a2f6c..bda3548e8 100644
--- a/src/test-map.cc
+++ b/src/test-map.cc
@@ -301,6 +301,33 @@ main (int argc, char **argv)
     m.set (1, hb_set_t {1, 2, 3});
     m.reset ();
   }
+  /* Test iteration. */
+  {
+    hb_map_t m;
+    m.set (1, 1);
+    m.set (4, 3);
+    m.set (5, 5);
+    m.set (2, 1);
+    m.set (3, 2);
+    m.set (6, 8);
+
+    hb_codepoint_t k;
+    hb_codepoint_t v;
+    unsigned pop = 0;
+    for (signed i;
+	 m.next (&i, &k, &v);)
+    {
+      pop++;
+           if (k == 1) assert (v == 1);
+      else if (k == 2) assert (v == 1);
+      else if (k == 3) assert (v == 2);
+      else if (k == 4) assert (v == 3);
+      else if (k == 5) assert (v == 5);
+      else if (k == 6) assert (v == 8);
+      else assert (false);
+    }
+    assert (pop = m.get_population ());
+  }
 
   return 0;
 }