Avoid oom situations

Author: qarmin

.gitignore

@@ -4,3 +4,4 @@ Cargo.lock
 .DS_Store
 /image.png
 /.vscode
+/.idea

src/pixmap.rs

@@ -44,13 +44,11 @@ impl Pixmap {
         let size = IntSize::from_wh(width, height)?;
         let data_len = data_len_for_size(size)?;
 
-        // We cannot check that allocation was successful yet.
-        // We have to wait for https://github.com/rust-lang/rust/issues/48043
+        let mut data = Vec::new();
+        data.try_reserve_exact(data_len).ok()?;
+        data.resize(data_len, 0);
 
-        Some(Pixmap {
-            data: vec![0; data_len],
-            size,
-        })
+        Some(Pixmap { data, size })
     }
 
     /// Creates a new pixmap by taking ownership over an image buffer
@@ -81,7 +79,10 @@ impl Pixmap {
         let mut decoder = png::Decoder::new(data);
         decoder.set_transformations(png::Transformations::normalize_to_color8());
         let mut reader = decoder.read_info()?;
-        let mut img_data = vec![0; reader.output_buffer_size()];
+        let mut img_data = Vec::new();
+        img_data.try_reserve_exact(reader.output_buffer_size())
+            .map_err(|_| make_custom_png_error("failed to reserve output buffer"))?;
+        img_data.resize(reader.output_buffer_size(), 0);
         let info = reader.next_frame(&mut img_data)?;
 
         if info.bit_depth != png::BitDepth::Eight {