diff --git a/BUILD b/BUILD
index 3136a19106..b8358297e9 100644
--- a/BUILD
+++ b/BUILD
@@ -109,6 +109,8 @@ cc_library(
         "upb/encode.c",
         "upb/internal/table.h",
         "upb/internal/unicode.h",
+        "upb/map_sorter.c",
+        "upb/map_sorter.h",
         "upb/msg.c",
         "upb/msg_internal.h",
         "upb/status.c",
@@ -375,6 +377,7 @@ cc_library(
     hdrs = [
         "upb/collections.h",
         "upb/map.h",
+        "upb/map_sorter.h",
         "upb/message_value.h",
     ],
     copts = UPB_DEFAULT_COPTS,
diff --git a/upb/encode.c b/upb/encode.c
index 05f4736c11..a9a1a1094d 100644
--- a/upb/encode.c
+++ b/upb/encode.c
@@ -33,6 +33,7 @@
 
 #include "upb/extension_registry.h"
 #include "upb/internal/array.h"
+#include "upb/map_sorter.h"
 #include "upb/msg_internal.h"
 #include "upb/upb.h"
 
diff --git a/upb/map_sorter.c b/upb/map_sorter.c
new file mode 100644
index 0000000000..561981a6bc
--- /dev/null
+++ b/upb/map_sorter.c
@@ -0,0 +1,136 @@
+/*
+ * Copyright (c) 2009-2021, Google LLC
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of Google LLC nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL Google LLC BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "upb/map_sorter.h"
+
+// Must be last.
+#include "upb/port_def.inc"
+
+static void _upb_mapsorter_getkeys(const void* _a, const void* _b, void* a_key,
+                                   void* b_key, size_t size) {
+  const upb_tabent* const* a = _a;
+  const upb_tabent* const* b = _b;
+  upb_StringView a_tabkey = upb_tabstrview((*a)->key);
+  upb_StringView b_tabkey = upb_tabstrview((*b)->key);
+  _upb_map_fromkey(a_tabkey, a_key, size);
+  _upb_map_fromkey(b_tabkey, b_key, size);
+}
+
+static int _upb_mapsorter_cmpi64(const void* _a, const void* _b) {
+  int64_t a, b;
+  _upb_mapsorter_getkeys(_a, _b, &a, &b, 8);
+  return a < b ? -1 : a > b;
+}
+
+static int _upb_mapsorter_cmpu64(const void* _a, const void* _b) {
+  uint64_t a, b;
+  _upb_mapsorter_getkeys(_a, _b, &a, &b, 8);
+  return a < b ? -1 : a > b;
+}
+
+static int _upb_mapsorter_cmpi32(const void* _a, const void* _b) {
+  int32_t a, b;
+  _upb_mapsorter_getkeys(_a, _b, &a, &b, 4);
+  return a < b ? -1 : a > b;
+}
+
+static int _upb_mapsorter_cmpu32(const void* _a, const void* _b) {
+  uint32_t a, b;
+  _upb_mapsorter_getkeys(_a, _b, &a, &b, 4);
+  return a < b ? -1 : a > b;
+}
+
+static int _upb_mapsorter_cmpbool(const void* _a, const void* _b) {
+  bool a, b;
+  _upb_mapsorter_getkeys(_a, _b, &a, &b, 1);
+  return a < b ? -1 : a > b;
+}
+
+static int _upb_mapsorter_cmpstr(const void* _a, const void* _b) {
+  upb_StringView a, b;
+  _upb_mapsorter_getkeys(_a, _b, &a, &b, UPB_MAPTYPE_STRING);
+  size_t common_size = UPB_MIN(a.size, b.size);
+  int cmp = memcmp(a.data, b.data, common_size);
+  if (cmp) return -cmp;
+  return a.size < b.size ? -1 : a.size > b.size;
+}
+
+static int (*const compar[kUpb_FieldType_SizeOf])(const void*, const void*) = {
+    [kUpb_FieldType_Int64] = _upb_mapsorter_cmpi64,
+    [kUpb_FieldType_SFixed64] = _upb_mapsorter_cmpi64,
+    [kUpb_FieldType_SInt64] = _upb_mapsorter_cmpi64,
+
+    [kUpb_FieldType_UInt64] = _upb_mapsorter_cmpu64,
+    [kUpb_FieldType_Fixed64] = _upb_mapsorter_cmpu64,
+
+    [kUpb_FieldType_Int32] = _upb_mapsorter_cmpi32,
+    [kUpb_FieldType_SInt32] = _upb_mapsorter_cmpi32,
+    [kUpb_FieldType_SFixed32] = _upb_mapsorter_cmpi32,
+    [kUpb_FieldType_Enum] = _upb_mapsorter_cmpi32,
+
+    [kUpb_FieldType_UInt32] = _upb_mapsorter_cmpu32,
+    [kUpb_FieldType_Fixed32] = _upb_mapsorter_cmpu32,
+
+    [kUpb_FieldType_Bool] = _upb_mapsorter_cmpbool,
+
+    [kUpb_FieldType_String] = _upb_mapsorter_cmpstr,
+    [kUpb_FieldType_Bytes] = _upb_mapsorter_cmpstr,
+};
+
+bool _upb_mapsorter_pushmap(_upb_mapsorter* s, upb_FieldType key_type,
+                            const upb_Map* map, _upb_sortedmap* sorted) {
+  int map_size = _upb_Map_Size(map);
+  sorted->start = s->size;
+  sorted->pos = sorted->start;
+  sorted->end = sorted->start + map_size;
+
+  // Grow s->entries if necessary.
+  if (sorted->end > s->cap) {
+    s->cap = _upb_Log2CeilingSize(sorted->end);
+    s->entries = realloc(s->entries, s->cap * sizeof(*s->entries));
+    if (!s->entries) return false;
+  }
+
+  s->size = sorted->end;
+
+  // Copy non-empty entries from the table to s->entries.
+  upb_tabent const** dst = &s->entries[sorted->start];
+  const upb_tabent* src = map->table.t.entries;
+  const upb_tabent* end = src + upb_table_size(&map->table.t);
+  for (; src < end; src++) {
+    if (!upb_tabent_isempty(src)) {
+      *dst = src;
+      dst++;
+    }
+  }
+  UPB_ASSERT(dst == &s->entries[sorted->end]);
+
+  // Sort entries according to the key type.
+  qsort(&s->entries[sorted->start], map_size, sizeof(*s->entries),
+        compar[key_type]);
+  return true;
+}
diff --git a/upb/map_sorter.h b/upb/map_sorter.h
new file mode 100644
index 0000000000..07c0bcafcf
--- /dev/null
+++ b/upb/map_sorter.h
@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2009-2021, Google LLC
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of Google LLC nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL Google LLC BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+// EVERYTHING BELOW THIS LINE IS INTERNAL - DO NOT USE /////////////////////////
+
+#ifndef UPB_MAP_SORTER_H_
+#define UPB_MAP_SORTER_H_
+
+#include "upb/msg_internal.h"
+
+// Must be last.
+#include "upb/port_def.inc"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// _upb_mapsorter sorts maps and provides ordered iteration over the entries.
+// Since maps can be recursive (map values can be messages which contain other
+// maps), _upb_mapsorter can contain a stack of maps.
+
+typedef struct {
+  upb_tabent const** entries;
+  int size;
+  int cap;
+} _upb_mapsorter;
+
+typedef struct {
+  int start;
+  int pos;
+  int end;
+} _upb_sortedmap;
+
+UPB_INLINE void _upb_mapsorter_init(_upb_mapsorter* s) {
+  s->entries = NULL;
+  s->size = 0;
+  s->cap = 0;
+}
+
+UPB_INLINE void _upb_mapsorter_destroy(_upb_mapsorter* s) {
+  if (s->entries) free(s->entries);
+}
+
+UPB_INLINE bool _upb_sortedmap_next(_upb_mapsorter* s, const upb_Map* map,
+                                    _upb_sortedmap* sorted, upb_MapEntry* ent) {
+  if (sorted->pos == sorted->end) return false;
+  const upb_tabent* tabent = s->entries[sorted->pos++];
+  upb_StringView key = upb_tabstrview(tabent->key);
+  _upb_map_fromkey(key, &ent->k, map->key_size);
+  upb_value val = {tabent->val.val};
+  _upb_map_fromvalue(val, &ent->v, map->val_size);
+  return true;
+}
+
+UPB_INLINE void _upb_mapsorter_popmap(_upb_mapsorter* s,
+                                      _upb_sortedmap* sorted) {
+  s->size = sorted->start;
+}
+
+bool _upb_mapsorter_pushmap(_upb_mapsorter* s, upb_FieldType key_type,
+                            const upb_Map* map, _upb_sortedmap* sorted);
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#include "upb/port_undef.inc"
+
+#endif /* UPB_MAP_SORTER_H_ */
diff --git a/upb/msg.c b/upb/msg.c
index 714cc79208..53ea32217b 100644
--- a/upb/msg.c
+++ b/upb/msg.c
@@ -192,125 +192,5 @@ upb_Map* _upb_Map_New(upb_Arena* a, size_t key_size, size_t value_size) {
   return map;
 }
 
-static void _upb_mapsorter_getkeys(const void* _a, const void* _b, void* a_key,
-                                   void* b_key, size_t size) {
-  const upb_tabent* const* a = _a;
-  const upb_tabent* const* b = _b;
-  upb_StringView a_tabkey = upb_tabstrview((*a)->key);
-  upb_StringView b_tabkey = upb_tabstrview((*b)->key);
-  _upb_map_fromkey(a_tabkey, a_key, size);
-  _upb_map_fromkey(b_tabkey, b_key, size);
-}
-
-#define UPB_COMPARE_INTEGERS(a, b) ((a) < (b) ? -1 : ((a) == (b) ? 0 : 1))
-
-static int _upb_mapsorter_cmpi64(const void* _a, const void* _b) {
-  int64_t a, b;
-  _upb_mapsorter_getkeys(_a, _b, &a, &b, 8);
-  return UPB_COMPARE_INTEGERS(a, b);
-}
-
-static int _upb_mapsorter_cmpu64(const void* _a, const void* _b) {
-  uint64_t a, b;
-  _upb_mapsorter_getkeys(_a, _b, &a, &b, 8);
-  return UPB_COMPARE_INTEGERS(a, b);
-}
-
-static int _upb_mapsorter_cmpi32(const void* _a, const void* _b) {
-  int32_t a, b;
-  _upb_mapsorter_getkeys(_a, _b, &a, &b, 4);
-  return UPB_COMPARE_INTEGERS(a, b);
-}
-
-static int _upb_mapsorter_cmpu32(const void* _a, const void* _b) {
-  uint32_t a, b;
-  _upb_mapsorter_getkeys(_a, _b, &a, &b, 4);
-  return UPB_COMPARE_INTEGERS(a, b);
-}
-
-static int _upb_mapsorter_cmpbool(const void* _a, const void* _b) {
-  bool a, b;
-  _upb_mapsorter_getkeys(_a, _b, &a, &b, 1);
-  return UPB_COMPARE_INTEGERS(a, b);
-}
-
-static int _upb_mapsorter_cmpstr(const void* _a, const void* _b) {
-  upb_StringView a, b;
-  _upb_mapsorter_getkeys(_a, _b, &a, &b, UPB_MAPTYPE_STRING);
-  size_t common_size = UPB_MIN(a.size, b.size);
-  int cmp = memcmp(a.data, b.data, common_size);
-  if (cmp) return -cmp;
-  return UPB_COMPARE_INTEGERS(a.size, b.size);
-}
-
-#undef UPB_COMPARE_INTEGERS
-
-bool _upb_mapsorter_pushmap(_upb_mapsorter* s, upb_FieldType key_type,
-                            const upb_Map* map, _upb_sortedmap* sorted) {
-  int map_size = _upb_Map_Size(map);
-  sorted->start = s->size;
-  sorted->pos = sorted->start;
-  sorted->end = sorted->start + map_size;
-
-  /* Grow s->entries if necessary. */
-  if (sorted->end > s->cap) {
-    s->cap = _upb_Log2CeilingSize(sorted->end);
-    s->entries = realloc(s->entries, s->cap * sizeof(*s->entries));
-    if (!s->entries) return false;
-  }
-
-  s->size = sorted->end;
-
-  /* Copy non-empty entries from the table to s->entries. */
-  upb_tabent const** dst = &s->entries[sorted->start];
-  const upb_tabent* src = map->table.t.entries;
-  const upb_tabent* end = src + upb_table_size(&map->table.t);
-  for (; src < end; src++) {
-    if (!upb_tabent_isempty(src)) {
-      *dst = src;
-      dst++;
-    }
-  }
-  UPB_ASSERT(dst == &s->entries[sorted->end]);
-
-  /* Sort entries according to the key type. */
-
-  int (*compar)(const void*, const void*);
-
-  switch (key_type) {
-    case kUpb_FieldType_Int64:
-    case kUpb_FieldType_SFixed64:
-    case kUpb_FieldType_SInt64:
-      compar = _upb_mapsorter_cmpi64;
-      break;
-    case kUpb_FieldType_UInt64:
-    case kUpb_FieldType_Fixed64:
-      compar = _upb_mapsorter_cmpu64;
-      break;
-    case kUpb_FieldType_Int32:
-    case kUpb_FieldType_SInt32:
-    case kUpb_FieldType_SFixed32:
-    case kUpb_FieldType_Enum:
-      compar = _upb_mapsorter_cmpi32;
-      break;
-    case kUpb_FieldType_UInt32:
-    case kUpb_FieldType_Fixed32:
-      compar = _upb_mapsorter_cmpu32;
-      break;
-    case kUpb_FieldType_Bool:
-      compar = _upb_mapsorter_cmpbool;
-      break;
-    case kUpb_FieldType_String:
-    case kUpb_FieldType_Bytes:
-      compar = _upb_mapsorter_cmpstr;
-      break;
-    default:
-      UPB_UNREACHABLE();
-  }
-
-  qsort(&s->entries[sorted->start], map_size, sizeof(*s->entries), compar);
-  return true;
-}
-
 const float kUpb_FltInfinity = INFINITY;
 const double kUpb_Infinity = INFINITY;
diff --git a/upb/msg_internal.h b/upb/msg_internal.h
index 85bac968a1..ccf44ac113 100644
--- a/upb/msg_internal.h
+++ b/upb/msg_internal.h
@@ -650,53 +650,6 @@ UPB_INLINE void _upb_msg_map_set_value(void* msg, const void* val,
   }
 }
 
-/** _upb_mapsorter ************************************************************/
-
-/* _upb_mapsorter sorts maps and provides ordered iteration over the entries.
- * Since maps can be recursive (map values can be messages which contain other
- * maps). _upb_mapsorter can contain a stack of maps. */
-
-typedef struct {
-  upb_tabent const** entries;
-  int size;
-  int cap;
-} _upb_mapsorter;
-
-typedef struct {
-  int start;
-  int pos;
-  int end;
-} _upb_sortedmap;
-
-UPB_INLINE void _upb_mapsorter_init(_upb_mapsorter* s) {
-  s->entries = NULL;
-  s->size = 0;
-  s->cap = 0;
-}
-
-UPB_INLINE void _upb_mapsorter_destroy(_upb_mapsorter* s) {
-  if (s->entries) free(s->entries);
-}
-
-bool _upb_mapsorter_pushmap(_upb_mapsorter* s, upb_FieldType key_type,
-                            const upb_Map* map, _upb_sortedmap* sorted);
-
-UPB_INLINE void _upb_mapsorter_popmap(_upb_mapsorter* s,
-                                      _upb_sortedmap* sorted) {
-  s->size = sorted->start;
-}
-
-UPB_INLINE bool _upb_sortedmap_next(_upb_mapsorter* s, const upb_Map* map,
-                                    _upb_sortedmap* sorted, upb_MapEntry* ent) {
-  if (sorted->pos == sorted->end) return false;
-  const upb_tabent* tabent = s->entries[sorted->pos++];
-  upb_StringView key = upb_tabstrview(tabent->key);
-  _upb_map_fromkey(key, &ent->k, map->key_size);
-  upb_value val = {tabent->val.val};
-  _upb_map_fromvalue(val, &ent->v, map->val_size);
-  return true;
-}
-
 #ifdef __cplusplus
 } /* extern "C" */
 #endif
diff --git a/upb/text_encode.c b/upb/text_encode.c
index d3e9f0145c..45acc34f5b 100644
--- a/upb/text_encode.c
+++ b/upb/text_encode.c
@@ -37,6 +37,7 @@
 #include "upb/internal/encode.h"
 #include "upb/internal/vsnprintf_compat.h"
 #include "upb/map.h"
+#include "upb/map_sorter.h"
 #include "upb/reflection/message.h"
 
 // Must be last.
diff --git a/upb/upb.h b/upb/upb.h
index e77fd40bdb..c6c3275759 100644
--- a/upb/upb.h
+++ b/upb/upb.h
@@ -111,9 +111,11 @@ typedef enum {
   kUpb_FieldType_SFixed32 = 15,
   kUpb_FieldType_SFixed64 = 16,
   kUpb_FieldType_SInt32 = 17,
-  kUpb_FieldType_SInt64 = 18
+  kUpb_FieldType_SInt64 = 18,
 } upb_FieldType;
 
+#define kUpb_FieldType_SizeOf 19
+
 #define kUpb_Map_Begin ((size_t)-1)
 
 UPB_INLINE bool _upb_IsLittleEndian(void) {