add file "saving" to quicksave cmd

examples/middle_echo.scri

@@ -1,4 +1,4 @@
 load :0;
-amp 3 1 10;
+amp 3 1 20;
 # echo 3 0 1 0.2;
 quicksave;

src/image.zig

@@ -109,9 +109,16 @@ fn mkSfInfo() c.SF_INFO {
 
 pub const Image = struct {
     allocator: *std.mem.Allocator,
+
+    /// Pointer to the underlying libsndfile's SNDFILE struct.
     sndfile: *c.SNDFILE,
+
+    /// The original image file path.
     path: []const u8,
 
+    /// Represents the current path being worked on.
+    curpath: []const u8,
+
     /// Open a BMP file.
     pub fn open(allocator: *std.mem.Allocator, path: []const u8) !*Image {
         var in_fmt = mkSfInfo();
@@ -123,6 +130,7 @@ pub const Image = struct {
             .allocator = allocator,
             .sndfile = sndfile,
             .path = path,
+            .curpath = path,
         };
 
         return image;
@@ -251,6 +259,13 @@ pub const Image = struct {
             }
         }
 
-        _ = c.sf_close(out_file);
+        _ = c.sf_close(self.sndfile);
+        self.sndfile = out_file;
+        self.curpath = tmpnam;
+    }
+
+    pub fn saveTo(self: *Image, out_path: []const u8) !void {
+        std.debug.warn("saved to '{}'\n", out_path);
+        try std.fs.copyFile(self.curpath, out_path);
     }
 };

src/runner.zig

@@ -136,8 +136,16 @@ pub const Runner = struct {
             }
         }
 
-        const out_path = try std.fmt.allocPrint(self.allocator, "{}_g{}{}", starts_with, max + 1, extension);
-        std.debug.warn("out path: {}\n", out_path);
+        const out_path = try std.fmt.allocPrint(
+            self.allocator,
+            "{}/{}{}{}",
+            dirname,
+            starts_with,
+            max + 1,
+            extension,
+        );
+
+        try image.saveTo(out_path);
     }
 
     /// Run the http://lv2plug.in/plugins/eg-amp plugin over the file.