1 files changed, 88 insertions, 0 deletions
diff --git a/nitrocli/src/crc32.rs b/nitrocli/src/crc32.rs
new file mode 100644
index 0000000..8431db5
--- /dev/null
+++ b/nitrocli/src/crc32.rs
@@ -0,0 +1,88 @@
+// crc32.rs
+
+// *************************************************************************
+// * Copyright (C) 2017 Daniel Mueller (deso@posteo.net)                   *
+// *                                                                       *
+// * This program is free software: you can redistribute it and/or modify  *
+// * it under the terms of the GNU General Public License as published by  *
+// * the Free Software Foundation, either version 3 of the License, or     *
+// * (at your option) any later version.                                   *
+// *                                                                       *
+// * This program is distributed in the hope that it will be useful,       *
+// * but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+// * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
+// * GNU General Public License for more details.                          *
+// *                                                                       *
+// * You should have received a copy of the GNU General Public License     *
+// * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
+// *************************************************************************
+
+/// Polynomial used in STM32.
+const CRC32_POLYNOMIAL: u32 = 0x04c11db7;
+
+
+fn crc32(mut crc: u32, data: u32) -> u32 {
+  crc = crc ^ data;
+
+  for _ in 0..32 {
+    if crc & 0x80000000 != 0 {
+      crc = (crc << 1) ^ CRC32_POLYNOMIAL;
+    } else {
+      crc = crc << 1;
+    }
+  }
+  return crc;
+}
+
+
+/// Retrieve a u32 slice of the 'data' part.
+///
+/// Note that the size of the supplied data has to be a multiple of 4
+/// bytes.
+fn as_slice_u32(data: &[u8]) -> &[u32] {
+  assert!(data.len() % ::std::mem::size_of::<u32>() == 0);
+
+  unsafe {
+    let ptr = data.as_ptr() as *const u32;
+    let len = data.len() / ::std::mem::size_of::<u32>();
+    return ::std::slice::from_raw_parts(ptr, len);
+  }
+}
+
+
+/// Calculate the CRC of a byte slice.
+pub fn crc(data: &[u8]) -> u32 {
+  let mut crc = 0xffffffff;
+  let data = as_slice_u32(data);
+
+  for i in 0..data.len() {
+    crc = crc32(crc, data[i]);
+  }
+  return crc;
+}
+
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  #[test]
+  fn test_crc32() {
+    let mut crc = 0;
+
+    // The expected values were computed with the original function.
+    crc = crc32(crc, 0xdeadbeef);
+    assert_eq!(crc, 0x46dec763);
+
+    crc = crc32(crc, 42);
+    assert_eq!(crc, 0x7e579b45);
+  }
+
+  #[test]
+  fn test_crc() {
+    let data = &"thisisatextthatistobecrced..".to_string().into_bytes();
+    let crc = crc(data);
+
+    assert_eq!(crc, 0x469db4ee);
+  }
+}