make copyBytes allocate its own buffer

examples/middle_amp.scri

@@ -1,8 +1,3 @@
 load :0;
-amp 80 70 10;
-amp 80 73 20;
-amp 80 75 20;
-amp 80 76 20;
-amp 7 4 2;
-amp 5 1 8;
+amp 3 1 10;
 quicksave;

src/image.zig

@@ -54,12 +54,6 @@ fn swrite(file: *c.SNDFILE, buf: [*]f32, frames: i64) !void {
     }
 }
 
-fn getEndPos(path: []const u8) !usize {
-    var file = try std.fs.File.openRead(path);
-    defer file.close();
-    return file.getEndPos();
-}
-
 fn temporaryName(allocator: *std.mem.Allocator) ![]u8 {
     const template_start = "/temp/temp_";
     const template = "/tmp/temp_XXXXXXXX";
@@ -108,24 +102,31 @@ pub const Image = struct {
     /// Pointer to the underlying libsndfile's SNDFILE struct.
     sndfile: *c.SNDFILE,
 
+    /// Current sound file's framecount.
+    frames: usize,
+
     /// The original image file path.
     path: []const u8,
 
     /// Represents the current path being worked on.
     curpath: []const u8,
 
-    /// Open a BMP file.
+    /// Open a BMP image for later.
     pub fn open(allocator: *std.mem.Allocator, path: []const u8) !*Image {
         var in_fmt = mkSfInfo();
 
         var sndfile = try sopen(allocator, path, c.SFM_READ, &in_fmt);
         var image = try allocator.create(Image);
 
+        std.debug.assert(in_fmt.frames > i64(0));
+        std.debug.assert(in_fmt.seekable == i32(1));
+
         image.* = Image{
             .allocator = allocator,
             .sndfile = sndfile,
             .path = path,
             .curpath = path,
+            .frames = @intCast(usize, in_fmt.frames),
         };
 
         return image;
@@ -161,10 +162,12 @@ pub const Image = struct {
     fn copyBytes(
         self: *Image,
         out_file: *c.SNDFILE,
-        buf: []f32,
         start: usize,
         end: usize,
     ) !void {
+        var buf = try self.allocator.alloc(f32, BufferSize);
+        defer self.allocator.free(buf);
+
         const total_bytes = end - start;
         var i: usize = start;
 
@@ -197,6 +200,13 @@ pub const Image = struct {
         _ = c.sf_seek(self.sndfile, @intCast(i64, end), c.SEEK_SET);
     }
 
+    fn getSeekPos(self: *Image, position: plugins.Position) plugins.SeekPos {
+        const file_end = self.frames;
+        var seek_pos = position.seekPos(file_end);
+        std.debug.warn("\tstart {} end {}\n", seek_pos.start, seek_pos.end);
+        return seek_pos;
+    }
+
     /// Run a plugin over the image.
     /// This setups a new lilv world/plugin among other things.
     /// The internal SNDFILE pointer is modified to point to the output of the
@@ -263,9 +273,7 @@ pub const Image = struct {
         // just copy the original image and the part where we run the plugin
         // over the image.
 
-        const file_end = try getEndPos(self.curpath);
-        const seek_pos = position.seekPos(file_end);
-        std.debug.warn("\tstart {} end {}\n", seek_pos.start, seek_pos.end);
+        const seek_pos = self.getSeekPos(position);
 
         // make sure we start from 0
         _ = c.sf_seek(self.sndfile, 0, c.SEEK_SET);
@@ -276,15 +284,11 @@ pub const Image = struct {
         // - plugin
         // - post-plugin
 
-        var file_copy_buf = try self.allocator.alloc(f32, BufferSize);
-        defer self.allocator.free(file_copy_buf);
-
         // pre-plugin copy, merged with bmp header copy
         try self.copyBytes(
             out_file,
-            file_copy_buf,
             usize(0),
-            seek_pos.start + @mod(seek_pos.start, BufferSize),
+            seek_pos.start,
         );
 
         _ = c.sf_seek(self.sndfile, @intCast(i64, seek_pos.start), c.SEEK_SET);
@@ -311,9 +315,8 @@ pub const Image = struct {
         // post-plugin copy
         try self.copyBytes(
             out_file,
-            file_copy_buf,
             seek_pos.end + 1,
-            file_end + @mod(file_end, BufferSize),
+            self.frames,
         );
 
         c.sf_write_sync(out_file);
@@ -349,9 +352,7 @@ pub const Image = struct {
         var bufs = try plugins.RunBuffers.init(self.allocator);
         defer bufs.deinit();
 
-        const file_end = try getEndPos(self.curpath);
-        const seek_pos = position.seekPos(file_end);
-        std.debug.warn("\tstart {} end {}\n", seek_pos.start, seek_pos.end);
+        const seek_pos = self.getSeekPos(position);
 
         // make sure we start from 0
         _ = c.sf_seek(self.sndfile, 0, c.SEEK_SET);
@@ -362,15 +363,11 @@ pub const Image = struct {
         // - CUSTOM plugin
         // - post-plugin
 
-        var file_copy_buf = try self.allocator.alloc(f32, BufferSize);
-        defer self.allocator.free(file_copy_buf);
-
         // pre-plugin copy, merged with bmp header copy
         try self.copyBytes(
             out_file,
-            file_copy_buf,
             usize(0),
-            seek_pos.start + @mod(seek_pos.start, BufferSize),
+            seek_pos.start,
         );
 
         _ = c.sf_seek(self.sndfile, @intCast(i64, seek_pos.start), c.SEEK_SET);
@@ -397,9 +394,8 @@ pub const Image = struct {
         // post-plugin copy
         try self.copyBytes(
             out_file,
-            file_copy_buf,
             seek_pos.end + 1,
-            file_end + @mod(file_end, BufferSize),
+            self.frames,
         );
 
         c.sf_write_sync(out_file);