1 files changed, 55 insertions, 8 deletions

diff --git a/core/upb_string.c b/core/upb_string.c
index 91ab9ae..f9af9e9 100644
--- a/core/upb_string.c
+++ b/core/upb_string.c
@@ -7,8 +7,11 @@
 #include "upb_string.h"
 
 #include <stdlib.h>
-
-#define UPB_STRING_UNFINALIZED -1
+#ifdef __GLIBC__
+#include <malloc.h>
+#elif defined(__APPLE__)
+#include <malloc/malloc.h>
+#endif
 
 static uint32_t upb_round_up_pow2(uint32_t v) {
   // http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
@@ -25,23 +28,67 @@ static uint32_t upb_round_up_pow2(uint32_t v) {
 upb_string *upb_string_new() {
   upb_string *str = malloc(sizeof(*str));
   str->ptr = NULL;
+  str->cached_mem = NULL;
+#ifndef UPB_HAVE_MSIZE
   str->size = 0;
-  str->len = UPB_STRING_UNFINALIZED;
+#endif
+  str->src = NULL;
   upb_atomic_refcount_init(&str->refcount, 1);
   return str;
 }
 
+uint32_t upb_string_size(upb_string *str) {
+#ifdef __GLIBC__
+  return malloc_usable_size(str->cached_mem);
+#elif defined(__APPLE__)
+  return malloc_size(str->cached_mem);
+#else
+  return str->size;
+#endif
+}
+
+static void upb_string_release(upb_string *str) {
+  if(str->src) {
+    upb_string_unref(str->src);
+    str->src = NULL;
+  }
+}
+
 void _upb_string_free(upb_string *str) {
-  if(str->ptr) free(str->ptr);
+  if(str->cached_mem) free(str->cached_mem);
+  upb_string_release(str);
   free(str);
 }
 
+upb_string *upb_string_tryrecycle(upb_string *str) {
+  if(str == NULL || upb_atomic_read(&str->refcount) > 1) {
+    return upb_string_new();
+  } else {
+    str->ptr = NULL;
+    upb_string_release(str);
+    return str;
+  }
+}
+
 char *upb_string_getrwbuf(upb_string *str, upb_strlen_t len) {
-  assert(str->len == UPB_STRING_UNFINALIZED);
-  if (str->size < len) {
-    str->size = upb_round_up_pow2(len);
-    str->ptr = realloc(str->ptr, str->size);
+  assert(str->ptr == NULL);
+  uint32_t size = upb_string_size(str);
+  if (size < len) {
+    size = upb_round_up_pow2(len);
+    str->cached_mem = realloc(str->cached_mem, size);
+#ifndef UPB_HAVE_MSIZE
+    str->size = size;
+#endif
   }
   str->len = len;
+  str->ptr = str->cached_mem;
   return str->ptr;
 }
+
+void upb_string_substr(upb_string *str, upb_string *target_str,
+                       upb_strlen_t start, upb_strlen_t len) {
+  assert(str->ptr == NULL);
+  str->src = upb_string_getref(target_str);
+  str->ptr = upb_string_getrobuf(target_str) + start;
+  str->len = len;
+}