Let API user pass ownership of potentially big strings

User will need to create a copy if the memory is static!
Otherwise he can pass the string to libsass and we will
take care to free the memory when the context is destroyed.

parser.cpp

@@ -167,17 +167,19 @@ namespace Sass {
             while (*includes) {
               struct Sass_Import* include = *includes;
               const char *file = sass_import_get_path(include);
-              const char *source = sass_import_get_source(include);
-              // const char *srcmap = sass_import_get_srcmap[include];
+              char *source = sass_import_get_source(include);
+              // char *srcmap = sass_import_get_srcmap(include);
               if (source) {
                 string inc_path = unquote(import_path);
                 if (file) {
-                  ctx.add_source(file, import_path, strdup(source));
+                  ctx.add_source(file, import_path, source);
                   imp->files().push_back(file);
                 } else {
-                  ctx.add_source(import_path, import_path, strdup(source));
+                  ctx.add_source(import_path, import_path, source);
                   imp->files().push_back(import_path);
                 }
+                // we passed ownership to context
+                sass_import_forget_source(include);
               } else if(file) {
                 add_single_file(imp, file);
               }

sass_functions.cpp

@@ -38,7 +38,7 @@ extern "C" {
   struct Sass_Import {
     const char* path;
     char*       source;
-    const char* srcmap;
+    char*       srcmap;
   };
 
   struct Sass_C_Import_Descriptor {
@@ -64,7 +64,8 @@ extern "C" {
   }
 
   // Creator for a single import entry returned by the custom importer inside the list
-  struct Sass_Import* sass_make_import_entry(const char* path, char* source, const char* srcmap)
+  // We take ownership of the memory for source and srcmap (freed when context is destroyd)
+  struct Sass_Import* sass_make_import_entry(const char* path, char* source, char* srcmap)
   {
     Sass_Import* v = (Sass_Import*) calloc(1, sizeof(Sass_Import));
     v->path = path;
@@ -82,6 +83,8 @@ extern "C" {
   {
     struct Sass_Import** it = list;
     while(*list) {
+      free((*list)->source);
+      free((*list)->srcmap);
       free(*list);
       ++list;
     }
@@ -90,7 +93,11 @@ extern "C" {
 
   // Getter for import entry
   const char*sass_import_get_path(struct Sass_Import* entry) { return entry->path; }
-  const char*sass_import_get_source(struct Sass_Import* entry) { return entry->source; }
-  const char*sass_import_get_srcmap(struct Sass_Import* entry) { return entry->srcmap; }
+  char* sass_import_get_source(struct Sass_Import* entry) { return entry->source; }
+  char* sass_import_get_srcmap(struct Sass_Import* entry) { return entry->srcmap; }
+
+  // Explicit functions once the ownership is passed on
+  void sass_import_forget_source (struct Sass_Import* entry) { entry->source = 0; }
+  void sass_import_forget_srcmap (struct Sass_Import* entry) { entry->srcmap = 0; }
 
 }

sass_functions.h

@@ -29,7 +29,7 @@ void* sass_import_get_cookie (Sass_C_Import_Callback fn);
 // Creator for sass custom importer return argument list
 struct Sass_Import** sass_make_import_list (size_t length);
 // Creator for a single import entry returned by the custom importer inside the list
-struct Sass_Import* sass_make_import_entry (const char* path, char* source, const char* srcmap);
+struct Sass_Import* sass_make_import_entry (const char* path, char* source, char* srcmap);
 
 // Setters to insert an entry into the import list (you may also use [] access directly)
 // Since we are dealing with pointers they should have a guaranteed and fixed size
@@ -38,8 +38,11 @@ struct Sass_Import* sass_import_get_list_entry (struct Sass_Import** list, size_
 
 // Getters for import entry
 const char*sass_import_get_path (struct Sass_Import*);
-const char*sass_import_get_source (struct Sass_Import*);
-const char*sass_import_get_srcmap (struct Sass_Import*);
+char* sass_import_get_source (struct Sass_Import*);
+char* sass_import_get_srcmap (struct Sass_Import*);
+// Explicit functions once the ownership is passed on
+void sass_import_forget_source (struct Sass_Import*);
+void sass_import_forget_srcmap (struct Sass_Import*);
 
 // Deallocator for associated memory (incl. entries)
 void sass_delete_import_list (struct Sass_Import**);