Auto merge of #8503 - craftytrickster:8406/limit-suppported-format, r=mbrubeck

Adding method to detect if image formats should be supported by servo

https://github.com/servo/servo/issues/8406

Please let me know if I need to make any changes.

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/8503)
<!-- Reviewable:end -->

tests/unit/net_traits/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "net_traits_tests"
+version = "0.0.1"
+authors = ["The Servo Project Developers"]
+
+[lib]
+name = "net_traits_tests"
+path = "lib.rs"
+doctest = false
+
+[dependencies.net_traits]
+path = "../../../components/net_traits"

tests/unit/net_traits/image.rs

@@ -0,0 +1,24 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use net_traits::image::base::detect_image_format;
+
+#[test]
+fn test_supported_images() {
+    let gif1 = [b'G', b'I', b'F', b'8', b'7', b'a'];
+    let gif2 = [b'G', b'I', b'F', b'8', b'9', b'a'];
+    let jpeg = [0xff, 0xd8, 0xff];
+    let png = [0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A];
+    let bmp = [0x42, 0x4D];
+    let ico = [0x00, 0x00, 0x01, 0x00];
+    let junk_format = [0x01, 0x02, 0x03, 0x04, 0x05];
+
+    assert!(detect_image_format(&gif1).is_ok());
+    assert!(detect_image_format(&gif2).is_ok());
+    assert!(detect_image_format(&jpeg).is_ok());
+    assert!(detect_image_format(&png).is_ok());
+    assert!(detect_image_format(&bmp).is_ok());
+    assert!(detect_image_format(&ico).is_ok());
+    assert!(detect_image_format(&junk_format).is_err());
+}

tests/unit/net_traits/lib.rs

@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+extern crate net_traits;
+
+#[cfg(test)] mod image;