From 7b6356dfd243858a2d810f43e133b995fb89276f Mon Sep 17 00:00:00 2001
From: Jordan Gong <jordan.gong@protonmail.com>
Date: Mon, 21 Sep 2020 20:12:02 +0800
Subject: Play around WebAssembly

---
 wasm-game-of-life/src/lib.rs | 132 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)
 create mode 100644 wasm-game-of-life/src/lib.rs

(limited to 'wasm-game-of-life/src/lib.rs')

diff --git a/wasm-game-of-life/src/lib.rs b/wasm-game-of-life/src/lib.rs
new file mode 100644
index 0000000..fe82d2c
--- /dev/null
+++ b/wasm-game-of-life/src/lib.rs
@@ -0,0 +1,132 @@
+mod utils;
+
+use wasm_bindgen::prelude::*;
+use wasm_bindgen::__rt::core::fmt::Alignment::Center;
+use wasm_bindgen::__rt::core::fmt::Formatter;
+
+// When the `wee_alloc` feature is enabled, use `wee_alloc` as the global
+// allocator.
+#[cfg(feature = "wee_alloc")]
+#[global_allocator]
+static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
+
+fn main() {
+    #[wasm_bindgen]
+    #[repr(u8)]
+    #[derive(Clone, Copy, Debug, PartialEq, Eq)]
+    pub enum Cell {
+        Dead = 0,
+        Alive = 1,
+    }
+
+    #[wasm_bindgen]
+    pub struct Universe {
+        width: u32,
+        height: u32,
+        cells: Vec<Cell>,
+    }
+
+    #[wasm_bindgen]
+    impl Universe {
+        fn get_index(&self, row: u32, column: u32) -> usize {
+            (row * self.width + column) as usize
+        }
+
+        fn live_neighbor_count(&self, row: u32, column: u32) -> u8 {
+            let mut count = 0;
+            for delta_row in [self.height - 1, 0, 1].iter().cloned() {
+                for delta_column in [self.width - 1, 0, 1].iter().cloned() {
+                    if delta_row == 0 && delta_column == 0 {
+                        continue;
+                    }
+
+                    let neighbor_row = (row + delta_row) % self.height;
+                    let neighbor_column = (column + delta_column) % self.width;
+                    let idx = self.get_index(neighbor_row, neighbor_column);
+                    count += self.cells[idx] as u8;
+                }
+            }
+            count
+        }
+        pub fn new() -> Universe {
+            let width = 64;
+            let height = 64;
+
+            let cells = (0..width * height)
+                .map(|x| {
+                    if x % 2 == 0 || x % 7 == 0 {
+                        Cell::Alive
+                    } else {
+                        Cell::Dead
+                    }
+                })
+                .collect();
+
+            Universe {
+                width,
+                height,
+                cells,
+            }
+        }
+
+        pub fn render(&self) -> String {
+            self.to_string()
+        }
+
+        pub fn tick(&mut self) {
+            let mut next = self.cells.clone();
+
+            for row in 0..self.height {
+                for col in 0..self.width {
+                    let idx = self.get_index(row, col);
+                    let cell = self.cells[idx];
+                    let live_neighbors = self.live_neighbor_count(row, col);
+
+                    let next_cell = match (cell, live_neighbors) {
+                        // 1. Underpopulation
+                        (Cell::Alive, x) if x < 2 => Cell::Dead,
+                        // 2. OK
+                        (Cell::Alive, 2) | (Cell::Alive, 3) => Cell::Alive,
+                        // 3. Overpopulation
+                        (Cell::Alive, x) if x > 3 => Cell::Dead,
+                        // 4. Reproduction
+                        (Cell::Dead, 3) => Cell::Alive,
+                        (otherwise, _) => otherwise,
+                    };
+
+                    next[idx] = next_cell;
+                }
+            }
+
+            self.cells = next;
+        }
+
+        pub fn width(&self) -> u32 {
+            self.width
+        }
+
+        pub fn height(&self) -> u32 {
+            self.height
+        }
+
+        pub fn cells(&self) -> *const Cell {
+            self.cells.as_ptr()
+        }
+    }
+
+    use std::fmt;
+
+    impl fmt::Display for Universe {
+        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+            for line in self.cells.as_slice().chunks(self.width as usize) {
+                for &cell in line {
+                    let symbol = if cell == Cell::Dead { '◻' } else { '◼' };
+                    write!(f, "{}", symbol)?;
+                }
+                write!(f, "\n")?;
+            }
+
+            Ok(())
+        }
+    }
+}
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