diff --git a/.clang-format b/.clang-format
index 0f5eb6b..1a6a5b5 100644
--- a/.clang-format
+++ b/.clang-format
@@ -233,6 +233,7 @@ StatementMacros:
   - Q_UNUSED
   - QT_REQUIRE_VERSION
   - munit_void_test_decl
+  - nghttp3_ksl_search_def
   - nghttp3_max_def
   - nghttp3_min_def
   - nghttp3_objalloc_decl
diff --git a/lib/nghttp3_gaptr.c b/lib/nghttp3_gaptr.c
index 20eed5f..9ad12af 100644
--- a/lib/nghttp3_gaptr.c
+++ b/lib/nghttp3_gaptr.c
@@ -29,8 +29,8 @@
 #include <assert.h>
 
 void nghttp3_gaptr_init(nghttp3_gaptr *gaptr, const nghttp3_mem *mem) {
-  nghttp3_ksl_init(&gaptr->gap, nghttp3_ksl_range_compar, sizeof(nghttp3_range),
-                   mem);
+  nghttp3_ksl_init(&gaptr->gap, nghttp3_ksl_range_compar,
+                   nghttp3_ksl_range_search, sizeof(nghttp3_range), mem);
 
   gaptr->mem = mem;
 }
@@ -62,8 +62,8 @@ int nghttp3_gaptr_push(nghttp3_gaptr *gaptr, uint64_t offset,
     }
   }
 
-  it = nghttp3_ksl_lower_bound_compar(&gaptr->gap, &q,
-                                      nghttp3_ksl_range_exclusive_compar);
+  it = nghttp3_ksl_lower_bound_search(&gaptr->gap, &q,
+                                      nghttp3_ksl_range_exclusive_search);
 
   for (; !nghttp3_ksl_it_end(&it);) {
     k = *(nghttp3_range *)nghttp3_ksl_it_key(&it);
@@ -120,8 +120,8 @@ nghttp3_range nghttp3_gaptr_get_first_gap_after(nghttp3_gaptr *gaptr,
     return r;
   }
 
-  it = nghttp3_ksl_lower_bound_compar(&gaptr->gap, &q,
-                                      nghttp3_ksl_range_exclusive_compar);
+  it = nghttp3_ksl_lower_bound_search(&gaptr->gap, &q,
+                                      nghttp3_ksl_range_exclusive_search);
 
   assert(!nghttp3_ksl_it_end(&it));
 
@@ -138,8 +138,8 @@ int nghttp3_gaptr_is_pushed(nghttp3_gaptr *gaptr, uint64_t offset,
     return 0;
   }
 
-  it = nghttp3_ksl_lower_bound_compar(&gaptr->gap, &q,
-                                      nghttp3_ksl_range_exclusive_compar);
+  it = nghttp3_ksl_lower_bound_search(&gaptr->gap, &q,
+                                      nghttp3_ksl_range_exclusive_search);
   m = nghttp3_range_intersect(&q, (nghttp3_range *)nghttp3_ksl_it_key(&it));
 
   return nghttp3_range_len(&m) == 0;
diff --git a/lib/nghttp3_ksl.c b/lib/nghttp3_ksl.c
index b17d27c..f7bc6a3 100644
--- a/lib/nghttp3_ksl.c
+++ b/lib/nghttp3_ksl.c
@@ -59,7 +59,8 @@ static void ksl_node_set_key(nghttp3_ksl *ksl, nghttp3_ksl_node *node,
 }
 
 void nghttp3_ksl_init(nghttp3_ksl *ksl, nghttp3_ksl_compar compar,
-                      size_t keylen, const nghttp3_mem *mem) {
+                      nghttp3_ksl_search search, size_t keylen,
+                      const nghttp3_mem *mem) {
   size_t nodelen = ksl_nodelen(keylen);
 
   nghttp3_objalloc_init(&ksl->blkalloc,
@@ -68,6 +69,7 @@ void nghttp3_ksl_init(nghttp3_ksl *ksl, nghttp3_ksl_compar compar,
   ksl->head = NULL;
   ksl->front = ksl->back = NULL;
   ksl->compar = compar;
+  ksl->search = search;
   ksl->n = 0;
   ksl->keylen = keylen;
   ksl->nodelen = nodelen;
@@ -274,20 +276,6 @@ static void ksl_insert_node(nghttp3_ksl *ksl, nghttp3_ksl_blk *blk, size_t i,
   ++blk->n;
 }
 
-static size_t ksl_search(const nghttp3_ksl *ksl, nghttp3_ksl_blk *blk,
-                         const nghttp3_ksl_key *key,
-                         nghttp3_ksl_compar compar) {
-  size_t i;
-  nghttp3_ksl_node *node;
-
-  for (i = 0, node = (nghttp3_ksl_node *)(void *)blk->nodes;
-       i < blk->n && compar((nghttp3_ksl_key *)node->key, key);
-       ++i, node = (nghttp3_ksl_node *)(void *)((uint8_t *)node + ksl->nodelen))
-    ;
-
-  return i;
-}
-
 int nghttp3_ksl_insert(nghttp3_ksl *ksl, nghttp3_ksl_it *it,
                        const nghttp3_ksl_key *key, void *data) {
   nghttp3_ksl_blk *blk;
@@ -312,7 +300,7 @@ int nghttp3_ksl_insert(nghttp3_ksl *ksl, nghttp3_ksl_it *it,
   blk = ksl->head;
 
   for (;;) {
-    i = ksl_search(ksl, blk, key, ksl->compar);
+    i = ksl->search(ksl, blk, key);
 
     if (blk->leaf) {
       if (i < blk->n &&
@@ -571,7 +559,7 @@ int nghttp3_ksl_remove(nghttp3_ksl *ksl, nghttp3_ksl_it *it,
   }
 
   for (;;) {
-    i = ksl_search(ksl, blk, key, ksl->compar);
+    i = ksl->search(ksl, blk, key);
 
     if (i == blk->n) {
       if (it) {
@@ -642,12 +630,12 @@ int nghttp3_ksl_remove(nghttp3_ksl *ksl, nghttp3_ksl_it *it,
 
 nghttp3_ksl_it nghttp3_ksl_lower_bound(const nghttp3_ksl *ksl,
                                        const nghttp3_ksl_key *key) {
-  return nghttp3_ksl_lower_bound_compar(ksl, key, ksl->compar);
+  return nghttp3_ksl_lower_bound_search(ksl, key, ksl->search);
 }
 
-nghttp3_ksl_it nghttp3_ksl_lower_bound_compar(const nghttp3_ksl *ksl,
+nghttp3_ksl_it nghttp3_ksl_lower_bound_search(const nghttp3_ksl *ksl,
                                               const nghttp3_ksl_key *key,
-                                              nghttp3_ksl_compar compar) {
+                                              nghttp3_ksl_search search) {
   nghttp3_ksl_blk *blk = ksl->head;
   nghttp3_ksl_it it;
   size_t i;
@@ -658,7 +646,7 @@ nghttp3_ksl_it nghttp3_ksl_lower_bound_compar(const nghttp3_ksl *ksl,
   }
 
   for (;;) {
-    i = ksl_search(ksl, blk, key, compar);
+    i = search(ksl, blk, key);
 
     if (blk->leaf) {
       if (i == blk->n && blk->next) {
@@ -702,7 +690,7 @@ void nghttp3_ksl_update_key(nghttp3_ksl *ksl, const nghttp3_ksl_key *old_key,
   assert(ksl->head);
 
   for (;;) {
-    i = ksl_search(ksl, blk, old_key, ksl->compar);
+    i = ksl->search(ksl, blk, old_key);
 
     assert(i < blk->n);
     node = nghttp3_ksl_nth_node(ksl, blk, i);
@@ -825,9 +813,50 @@ int nghttp3_ksl_range_compar(const nghttp3_ksl_key *lhs,
   return a->begin < b->begin;
 }
 
+nghttp3_ksl_search_def(range, nghttp3_ksl_range_compar)
+
+size_t nghttp3_ksl_range_search(const nghttp3_ksl *ksl, nghttp3_ksl_blk *blk,
+                                const nghttp3_ksl_key *key) {
+  return ksl_range_search(ksl, blk, key);
+}
+
 int nghttp3_ksl_range_exclusive_compar(const nghttp3_ksl_key *lhs,
                                        const nghttp3_ksl_key *rhs) {
   const nghttp3_range *a = lhs, *b = rhs;
   return a->begin < b->begin && !(nghttp3_max_uint64(a->begin, b->begin) <
                                   nghttp3_min_uint64(a->end, b->end));
 }
+
+nghttp3_ksl_search_def(range_exclusive, nghttp3_ksl_range_exclusive_compar)
+
+size_t nghttp3_ksl_range_exclusive_search(const nghttp3_ksl *ksl,
+                                          nghttp3_ksl_blk *blk,
+                                          const nghttp3_ksl_key *key) {
+  return ksl_range_exclusive_search(ksl, blk, key);
+}
+
+int nghttp3_ksl_uint64_less(const nghttp3_ksl_key *lhs,
+                            const nghttp3_ksl_key *rhs) {
+  return *(uint64_t *)lhs < *(uint64_t *)rhs;
+}
+
+nghttp3_ksl_search_def(uint64_less, nghttp3_ksl_uint64_less)
+
+size_t nghttp3_ksl_uint64_less_search(const nghttp3_ksl *ksl,
+                                      nghttp3_ksl_blk *blk,
+                                      const nghttp3_ksl_key *key) {
+  return ksl_uint64_less_search(ksl, blk, key);
+}
+
+int nghttp3_ksl_int64_greater(const nghttp3_ksl_key *lhs,
+                              const nghttp3_ksl_key *rhs) {
+  return *(int64_t *)lhs > *(int64_t *)rhs;
+}
+
+nghttp3_ksl_search_def(int64_greater, nghttp3_ksl_int64_greater)
+
+size_t nghttp3_ksl_int64_greater_search(const nghttp3_ksl *ksl,
+                                        nghttp3_ksl_blk *blk,
+                                        const nghttp3_ksl_key *key) {
+  return ksl_int64_greater_search(ksl, blk, key);
+}
diff --git a/lib/nghttp3_ksl.h b/lib/nghttp3_ksl.h
index 49e27c3..d0ce8cd 100644
--- a/lib/nghttp3_ksl.h
+++ b/lib/nghttp3_ksl.h
@@ -115,6 +115,35 @@ typedef int (*nghttp3_ksl_compar)(const nghttp3_ksl_key *lhs,
 
 typedef struct nghttp3_ksl nghttp3_ksl;
 
+/*
+ * nghttp3_ksl_search is a function to search for the first element in
+ * |blk|->nodes which is not ordered before |key|.  It returns the
+ * index of such element.  It returns |blk|->n if there is no such
+ * element.
+ */
+typedef size_t (*nghttp3_ksl_search)(const nghttp3_ksl *ksl,
+                                     nghttp3_ksl_blk *blk,
+                                     const nghttp3_ksl_key *key);
+
+/*
+ * nghttp3_ksl_search_def is a macro to implement nghttp3_ksl_search
+ * with COMPAR which is supposed to be nghttp3_ksl_compar.
+ */
+#define nghttp3_ksl_search_def(NAME, COMPAR)                                   \
+  static size_t ksl_##NAME##_search(const nghttp3_ksl *ksl,                    \
+                                    nghttp3_ksl_blk *blk,                      \
+                                    const nghttp3_ksl_key *key) {              \
+    size_t i;                                                                  \
+    nghttp3_ksl_node *node;                                                    \
+                                                                               \
+    for (i = 0, node = (nghttp3_ksl_node *)(void *)blk->nodes;                 \
+         i < blk->n && COMPAR((nghttp3_ksl_key *)node->key, key); ++i,         \
+        node = (nghttp3_ksl_node *)(void *)((uint8_t *)node + ksl->nodelen))   \
+      ;                                                                        \
+                                                                               \
+    return i;                                                                  \
+  }
+
 typedef struct nghttp3_ksl_it nghttp3_ksl_it;
 
 /*
@@ -138,6 +167,7 @@ struct nghttp3_ksl {
   /* back points to the last leaf block. */
   nghttp3_ksl_blk *back;
   nghttp3_ksl_compar compar;
+  nghttp3_ksl_search search;
   /* n is the number of elements stored. */
   size_t n;
   /* keylen is the size of key */
@@ -149,11 +179,13 @@ struct nghttp3_ksl {
 
 /*
  * nghttp3_ksl_init initializes |ksl|.  |compar| specifies compare
- * function.  |keylen| is the length of key and must be at least
+ * function.  |search| is a search function which must use |compar|.
+ * |keylen| is the length of key and must be at least
  * sizeof(uint64_t).
  */
 void nghttp3_ksl_init(nghttp3_ksl *ksl, nghttp3_ksl_compar compar,
-                      size_t keylen, const nghttp3_mem *mem);
+                      nghttp3_ksl_search search, size_t keylen,
+                      const nghttp3_mem *mem);
 
 /*
  * nghttp3_ksl_free frees resources allocated for |ksl|.  If |ksl| is
@@ -218,12 +250,12 @@ nghttp3_ksl_it nghttp3_ksl_lower_bound(const nghttp3_ksl *ksl,
                                        const nghttp3_ksl_key *key);
 
 /*
- * nghttp3_ksl_lower_bound_compar works like nghttp3_ksl_lower_bound,
- * but it takes custom function |compar| to do lower bound search.
+ * nghttp3_ksl_lower_bound_search works like nghttp3_ksl_lower_bound,
+ * but it takes custom function |search| to do lower bound search.
  */
-nghttp3_ksl_it nghttp3_ksl_lower_bound_compar(const nghttp3_ksl *ksl,
+nghttp3_ksl_it nghttp3_ksl_lower_bound_search(const nghttp3_ksl *ksl,
                                               const nghttp3_ksl_key *key,
-                                              nghttp3_ksl_compar compar);
+                                              nghttp3_ksl_search search);
 
 /*
  * nghttp3_ksl_update_key replaces the key of nodes which has
@@ -330,22 +362,69 @@ int nghttp3_ksl_it_begin(const nghttp3_ksl_it *it);
 
 /*
  * nghttp3_ksl_range_compar is an implementation of
- * nghttp3_ksl_compar.  lhs->ptr and rhs->ptr must point to
- * nghttp3_range object and the function returns nonzero if (const
- * nghttp3_range *)(lhs->ptr)->begin < (const nghttp3_range
- * *)(rhs->ptr)->begin.
+ * nghttp3_ksl_compar.  |lhs| and |rhs| must point to nghttp3_range
+ * object, and the function returns nonzero if ((const nghttp3_range
+ * *)lhs)->begin < ((const nghttp3_range *)rhs)->begin.
  */
 int nghttp3_ksl_range_compar(const nghttp3_ksl_key *lhs,
                              const nghttp3_ksl_key *rhs);
 
+/*
+ * nghttp3_ksl_range_search is an implementation of nghttp3_ksl_search
+ * that uses nghttp3_ksl_range_compar.
+ */
+size_t nghttp3_ksl_range_search(const nghttp3_ksl *ksl, nghttp3_ksl_blk *blk,
+                                const nghttp3_ksl_key *key);
+
 /*
  * nghttp3_ksl_range_exclusive_compar is an implementation of
- * nghttp3_ksl_compar.  lhs->ptr and rhs->ptr must point to
- * nghttp3_range object and the function returns nonzero if (const
- * nghttp3_range *)(lhs->ptr)->begin < (const nghttp3_range
- * *)(rhs->ptr)->begin and the 2 ranges do not intersect.
+ * nghttp3_ksl_compar.  |lhs| and |rhs| must point to nghttp3_range
+ * object, and the function returns nonzero if ((const nghttp3_range
+ * *)lhs)->begin < ((const nghttp3_range *)rhs)->begin, and the 2
+ * ranges do not intersect.
  */
 int nghttp3_ksl_range_exclusive_compar(const nghttp3_ksl_key *lhs,
                                        const nghttp3_ksl_key *rhs);
 
+/*
+ * nghttp3_ksl_range_exclusive_search is an implementation of
+ * nghttp3_ksl_search that uses nghttp3_ksl_range_exclusive_compar.
+ */
+size_t nghttp3_ksl_range_exclusive_search(const nghttp3_ksl *ksl,
+                                          nghttp3_ksl_blk *blk,
+                                          const nghttp3_ksl_key *key);
+
+/*
+ * nghttp3_ksl_uint64_less is an implementation of nghttp3_ksl_compar.
+ * |lhs| and |rhs| must point to uint64_t objects, and the function
+ * returns nonzero if *(uint64_t *)|lhs| < *(uint64_t *)|rhs|.
+ */
+int nghttp3_ksl_uint64_less(const nghttp3_ksl_key *lhs,
+                            const nghttp3_ksl_key *rhs);
+
+/*
+ * nghttp3_ksl_uint64_less_search is an implementation of
+ * nghttp3_ksl_search that uses nghttp3_ksl_uint64_less.
+ */
+size_t nghttp3_ksl_uint64_less_search(const nghttp3_ksl *ksl,
+                                      nghttp3_ksl_blk *blk,
+                                      const nghttp3_ksl_key *key);
+
+/*
+ * nghttp3_ksl_int64_greater is an implementation of
+ * nghttp3_ksl_compar.  |lhs| and |rhs| must point to int64_t objects,
+ * and the function returns nonzero if *(int64_t *)|lhs| > *(int64_t
+ * *)|rhs|.
+ */
+int nghttp3_ksl_int64_greater(const nghttp3_ksl_key *lhs,
+                              const nghttp3_ksl_key *rhs);
+
+/*
+ * nghttp3_ksl_int64_greater_search is an implementation of
+ * nghttp3_ksl_search that uses nghttp3_ksl_int64_greater.
+ */
+size_t nghttp3_ksl_int64_greater_search(const nghttp3_ksl *ksl,
+                                        nghttp3_ksl_blk *blk,
+                                        const nghttp3_ksl_key *key);
+
 #endif /* !defined(NGHTTP3_KSL_H) */
diff --git a/lib/nghttp3_qpack.c b/lib/nghttp3_qpack.c
index a1c7e74..26e8594 100644
--- a/lib/nghttp3_qpack.c
+++ b/lib/nghttp3_qpack.c
@@ -898,6 +898,8 @@ static int max_cnt_greater(const nghttp3_ksl_key *lhs,
   return a->max_cnt > b->max_cnt || (a->max_cnt == b->max_cnt && a->id < b->id);
 }
 
+nghttp3_ksl_search_def(max_cnt_greater, max_cnt_greater)
+
 int nghttp3_qpack_encoder_init(nghttp3_qpack_encoder *encoder,
                                size_t hard_max_dtable_capacity,
                                const nghttp3_mem *mem) {
@@ -911,6 +913,7 @@ int nghttp3_qpack_encoder_init(nghttp3_qpack_encoder *encoder,
   nghttp3_map_init(&encoder->streams, mem);
 
   nghttp3_ksl_init(&encoder->blocked_streams, max_cnt_greater,
+                   ksl_max_cnt_greater_search,
                    sizeof(nghttp3_blocked_streams_key), mem);
 
   qpack_map_init(&encoder->dtable_map);