Construct a vga buffer for testing

Cargo.lock

@@ -1,3 +1,11 @@
+[[package]]
+name = "array-init"
+version = "0.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "nodrop 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "bit_field"
 version = "0.9.0"
@@ -12,6 +20,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 name = "blog_os"
 version = "0.1.0"
 dependencies = [
+ "array-init 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "bootloader 0.3.12 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "spin 0.4.10 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -78,6 +87,11 @@ name = "libc"
 version = "0.2.48"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "nodrop"
+version = "0.1.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "os_bootinfo"
 version = "0.2.1"
@@ -220,6 +234,7 @@ version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [metadata]
+"checksum array-init 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "c3cc8456d0ae81a8c76f59e384683a601548c38949a4bfcb65dd31ded5c75ff3"
 "checksum bit_field 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ed8765909f9009617974ab6b7d332625b320b33c326b1e9321382ef1999b5d56"
 "checksum bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "228047a76f468627ca71776ecdebd732a3423081fcf5125585bcd7c49886ce12"
 "checksum bootloader 0.3.12 (registry+https://github.com/rust-lang/crates.io-index)" = "2b498d7168288f3667f80aee93b4894e355dfce867803e1ccd5d9ee42a0b0e1a"
@@ -230,6 +245,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum getopts 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)" = "0a7292d30132fb5424b354f5dc02512a86e4c516fe544bb7a25e7f266951b797"
 "checksum lazy_static 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "a374c89b9db55895453a74c1e38861d9deec0b01b405a82516e9d5de4820dea1"
 "checksum libc 0.2.48 (registry+https://github.com/rust-lang/crates.io-index)" = "e962c7641008ac010fa60a7dfdc1712449f29c44ef2d4702394aea943ee75047"
+"checksum nodrop 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)" = "2f9667ddcc6cc8a43afc9b7917599d7216aa09c463919ea32c59ed6cac8bc945"
 "checksum os_bootinfo 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "66481dbeb5e773e7bd85b63cd6042c30786f834338288c5ec4f3742673db360a"
 "checksum pulldown-cmark 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "8361e81576d2e02643b04950e487ec172b687180da65c731c03cf336784e6c07"
 "checksum rand 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)" = "dee497e66d8d76bf08ce20c8d36e16f93749ab0bf89975b4f8ae5cee660c2da2"

Cargo.toml

@@ -8,6 +8,7 @@ edition = "2018"
 bootloader = "0.3.12"
 volatile = "0.2.3"
 spin = "0.4.9"
+array-init = "0.0.3"
 
 [dependencies.lazy_static]
 version = "1.0"

src/vga_buffer.rs

@@ -140,3 +140,34 @@ pub fn _print(args: fmt::Arguments) {
     use core::fmt::Write;
     WRITER.lock().write_fmt(args).unwrap();
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    fn construct_writer() -> Writer {
+        use std::boxed::Box;
+
+        let buffer = construct_buffer();
+        Writer {
+            column_position: 0,
+            color_code: ColorCode::new(Color::Blue, Color::Magenta),
+            buffer: Box::leak(Box::new(buffer)),
+        }
+    }
+
+    fn construct_buffer() -> Buffer {
+        use array_init::array_init;
+
+        Buffer {
+            chars: array_init(|_| array_init(|_| Volatile::new(empty_char()))),
+        }
+    }
+
+    fn empty_char() -> ScreenChar {
+        ScreenChar {
+            ascii_character: b' ',
+            color_code: ColorCode::new(Color::Green, Color::Brown),
+        }
+    }
+}