1 files changed, 29 insertions, 2 deletions

diff --git a/src/Storage.cpp b/src/Storage.cpp
index c9dfb17..a1dc777 100644
--- a/src/Storage.cpp
+++ b/src/Storage.cpp
@@ -5,6 +5,8 @@
 #include <assert.h>
 #include <json/reader.h>
 #include <json/writer.h>
+#include <rapidjson/writer.h>
+#include <rapidjson/stringbuffer.h>
 #include <unordered_set>
 
 #if OS_FAMILY == OS_FAMILY_POSIX
@@ -137,12 +139,12 @@ namespace QuickMedia {
         return -1;
     }
 
-    int file_overwrite(const Path &path, const std::string &data) {
+    static int file_overwrite(const Path &path, const char *str, size_t size) {
         FILE *file = fopen(path.data.c_str(), "wb");
         if(!file)
             return -1;
         
-        if(fwrite(data.data(), 1, data.size(), file) != data.size()) {
+        if(fwrite(str, 1, size, file) != size) {
             fclose(file);
             return -1;
         }
@@ -150,6 +152,10 @@ namespace QuickMedia {
         return fclose(file);
     }
 
+    int file_overwrite(const Path &path, const std::string &data) {
+        return file_overwrite(path, data.c_str(), data.size());
+    }
+
     void for_files_in_dir(const Path &path, FileIteratorCallback callback) {
         try {
             for(auto &p : std::filesystem::directory_iterator(path.data)) {
@@ -226,6 +232,27 @@ namespace QuickMedia {
         return true;
     }
 
+    bool save_json_to_file_atomic(const Path &path, const rapidjson::Value &json) {
+        Path tmp_path = path;
+        tmp_path.append(".tmp");
+
+        rapidjson::StringBuffer buffer;
+        rapidjson::Writer<rapidjson::StringBuffer> writer(buffer);
+        json.Accept(writer);
+
+        Json::StreamWriterBuilder json_builder;
+        if(file_overwrite(tmp_path, buffer.GetString(), buffer.GetSize()) != 0)
+            return false;
+
+        // Rename is atomic under posix!
+        if(rename(tmp_path.data.c_str(), path.data.c_str()) != 0) {
+            perror("save_json_to_file_atomic rename");
+            return false;
+        }
+
+        return true;
+    }
+
     bool is_program_executable_by_name(const char *name) {
         // TODO: Implement for Windows. Windows also uses semicolon instead of colon as a separator
         char *env = getenv("PATH");