Rotate implementation in Rust

codecs/rotate/Dockerfile

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+FROM ubuntu
+RUN apt-get update && \
+  apt-get install -qqy git build-essential cmake python2.7
+RUN git clone --recursive https://github.com/WebAssembly/wabt /usr/src/wabt
+RUN mkdir -p /usr/src/wabt/build
+WORKDIR /usr/src/wabt/build
+RUN cmake .. -DCMAKE_INSTALL_PREFIX=/opt/wabt && \
+  make && \
+  make install
+
+FROM rust
+RUN rustup install nightly && \
+  rustup target add --toolchain nightly wasm32-unknown-unknown
+
+COPY --from=0 /opt/wabt /opt/wabt
+ENV PATH="/opt/wabt/bin:${PATH}"
+WORKDIR /src

codecs/rotate/build.sh

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+#!/bin/bash
+
+set -e
+
+echo "============================================="
+echo "Compiling wasm"
+echo "============================================="
+(
+  rustup run nightly \
+    rustc \
+    --target=wasm32-unknown-unknown \
+    -C opt-level=3 \
+    -o rotate.wasm \
+    rotate.rs
+    wasm-strip rotate.wasm
+)
+echo "============================================="
+echo "Compiling wasm  done"
+echo "============================================="
+
+echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
+echo "Did you update your docker image?"
+echo "Run \`docker build -t squoosh-rotate .\`"
+echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"

codecs/rotate/package.json

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+{
+  "name": "rotate",
+  "scripts": {
+    "build:image": "docker build -t squoosh-rotate .",
+    "build": "docker run --rm -v $(pwd):/src squoosh-rotate ./build.sh"
+  }
+}

codecs/rotate/rotate.rs

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+#![no_std]
+#![no_main]
+
+use core::panic::PanicInfo;
+use core::slice::from_raw_parts_mut;
+
+#[no_mangle]
+fn rotate(input_width: isize, input_height: isize, rotate: isize) {
+  let mut i = 0isize;
+
+  // In the straight-copy case, d1 is x, d2 is y.
+  // x starts at 0 and increases.
+  // y starts at 0 and increases.
+  let mut d1_start: isize = 0;
+  let mut d1_limit: isize = input_width;
+  let mut d1_advance: isize = 1;
+  let mut d1_multiplier: isize = 1;
+  let mut d2_start: isize = 0;
+  let mut d2_limit: isize = input_height;
+  let mut d2_advance: isize = 1;
+  let mut d2_multiplier: isize = input_width;
+
+  if rotate == 90 {
+    // d1 is y, d2 is x.
+    // y starts at its max value and decreases.
+    // x starts at 0 and increases.
+    d1_start = input_height - 1;
+    d1_limit = input_height;
+    d1_advance = -1;
+    d1_multiplier = input_width;
+    d2_start = 0;
+    d2_limit = input_width;
+    d2_advance = 1;
+    d2_multiplier = 1;
+  } else if rotate == 180 {
+    // d1 is x, d2 is y.
+    // x starts at its max and decreases.
+    // y starts at its max and decreases.
+    d1_start = input_width - 1;
+    d1_limit = input_width;
+    d1_advance = -1;
+    d1_multiplier = 1;
+    d2_start = input_height - 1;
+    d2_limit = input_height;
+    d2_advance = -1;
+    d2_multiplier = input_width;
+  } else if rotate == 270 {
+    // d1 is y, d2 is x.
+    // y starts at 0 and increases.
+    // x starts at its max and decreases.
+    d1_start = 0;
+    d1_limit = input_height;
+    d1_advance = 1;
+    d1_multiplier = input_width;
+    d2_start = input_width - 1;
+    d2_limit = input_width;
+    d2_advance = -1;
+    d2_multiplier = 1;
+  }
+
+  let num_pixels = (input_width * input_height) as usize;
+  let in_b: &mut [u32];
+  let out_b: &mut [u32];
+  unsafe {
+    in_b = from_raw_parts_mut::<u32>(4 as *mut u32, num_pixels);
+    out_b = from_raw_parts_mut::<u32>((input_width * input_height * 4 + 4) as *mut u32, num_pixels);
+  }
+
+  for d2 in 0..d2_limit {
+    for d1 in 0..d1_limit {
+      let in_idx = (d1_start + d1 * d1_advance) * d1_multiplier + (d2_start + d2 * d2_advance) * d2_multiplier;
+      out_b[i as usize] = in_b[in_idx as usize];
+      i += 1;
+    }
+  }
+}
+
+#[panic_handler]
+fn panic(_info: &PanicInfo) -> ! {
+  loop {}
+}