Optimise json malloc strategy to minimise memory allocations and avoid unnecessary strdups

src/jansson-2.6/src/dump.c

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2009-2013 Petri Lehtinen <petri@digip.org>
+ * Copyright (c) 2015 Con Kolivas <kernel@kolivas.org>
  *
  * Jansson is free software; you can redistribute it and/or modify
  * it under the terms of the MIT license. See LICENSE for details.
@@ -427,13 +428,6 @@ static int do_dump(const json_t *json, size_t flags, int depth,
     }
 }
 
-char *json_dump_dup(const char *str, size_t flags)
-{
-	if (flags & JSON_EOL)
-		return jsonp_eolstrdup(str);
-	return jsonp_strdup(str);
-}
-
 char *json_dumps(const json_t *json, size_t flags)
 {
     strbuffer_t strbuff;
@@ -444,10 +438,11 @@ char *json_dumps(const json_t *json, size_t flags)
 
     if(json_dump_callback(json, dump_to_strbuffer, (void *)&strbuff, flags))
         result = NULL;
+    else if (flags & JSON_EOL)
+	result = jsonp_eolstrsteal(&strbuff);
     else
-        result = json_dump_dup(strbuffer_value(&strbuff), flags);
+	result = jsonp_strsteal(&strbuff);
 
-    strbuffer_close(&strbuff);
     return result;
 }
 

src/jansson-2.6/src/jansson_private.h

@@ -86,7 +86,8 @@ void _jsonp_free(void **ptr);
 
 char *jsonp_strndup(const char *str, size_t length);
 char *jsonp_strdup(const char *str);
-char *jsonp_eolstrdup(const char *str);
+char *jsonp_strsteal(strbuffer_t *strbuff);
+char *jsonp_eolstrsteal(strbuffer_t *strbuff);
 
 /* Windows compatibility */
 #ifdef _WIN32

src/jansson-2.6/src/memory.c

@@ -51,23 +51,22 @@ char *jsonp_strdup(const char *str)
     return new_str;
 }
 
-char *jsonp_eolstrdup(const char *str)
+char *jsonp_strsteal(strbuffer_t *strbuff)
 {
-    char *new_str;
-    size_t len;
+	size_t len = strbuff->length + 1;
+	char *ret = realloc(strbuff->value, len);
 
-    len = strlen(str);
-    if(len == (size_t)-1)
-        return NULL;
+	return ret;
+}
 
-    new_str = jsonp_malloc(len + 2);
-    if(!new_str)
-        return NULL;
+char *jsonp_eolstrsteal(strbuffer_t *strbuff)
+{
+	size_t len = strbuff->length + 2;
+	char *ret = realloc(strbuff->value, len);
 
-    memcpy(new_str, str, len);
-    new_str[len] = '\n';
-    new_str[len + 1] = '\0';
-    return new_str;
+	ret[strbuff->length] = '\n';
+	ret[strbuff->length + 1] = '\0';
+	return ret;
 }
 
 void json_set_alloc_funcs(json_malloc_t malloc_fn, json_free_t free_fn)

src/jansson-2.6/src/strbuffer.c

@@ -16,7 +16,7 @@
 #include "jansson_private.h"
 #include "strbuffer.h"
 
-#define STRBUFFER_MIN_SIZE  16
+#define STRBUFFER_MIN_SIZE  4096
 #define STRBUFFER_FACTOR    2
 #define STRBUFFER_SIZE_MAX  ((size_t)-1)
 
@@ -74,7 +74,8 @@ int strbuffer_append_byte(strbuffer_t *strbuff, char byte)
 
 int strbuffer_append_bytes(strbuffer_t *strbuff, const char *data, size_t size)
 {
-    if(size >= strbuff->size - strbuff->length)
+    /* Leave room for EOL and NULL bytes */
+    if(size + 2 > strbuff->size - strbuff->length)
     {
 	int backoff = 1;
         size_t new_size;