From b95809e372216b7f4d51fbd5176359c73e36b605 Mon Sep 17 00:00:00 2001
From: sergeych <real.sergeych@gmail.com>
Date: Tue, 17 Oct 2023 00:17:42 +0100
Subject: [PATCH] added compatible crc8 implementation

---
 src/crc.rs | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs |  1 +
 2 files changed, 74 insertions(+)
 create mode 100644 src/crc.rs

diff --git a/src/crc.rs b/src/crc.rs
new file mode 100644
index 0000000..8103669
--- /dev/null
+++ b/src/crc.rs
@@ -0,0 +1,73 @@
+pub struct Crc8 {
+    table : [u8; 256]
+}
+
+impl Crc8 {
+    pub fn create_msb(polynomial : u8) -> Crc8 {
+        let msbit : u8 = 0x80;
+        let mut t : u8 = msbit;
+        let mut tmp : u8;
+        let mut i : u32 = 1;
+        let mut idx : u8;
+        let mut table : [u8; 256] = [0; 256];
+
+        while i < 256 {
+            if t & msbit != 0 { tmp = polynomial; } else { tmp = 0; }
+            t = (t << 1) ^ tmp;
+            for j in 0..i {
+                idx = (i+j) as u8;
+                table[(idx) as usize] =  table[j as usize] ^ t;
+            }
+            i *= 2;
+        }
+
+        return Crc8{ table : table};
+    }
+
+    pub fn create_lsb(polynomial :u8) -> Crc8 {
+        let mut i :u32 = 0xff;
+        let mut j :u32;
+        let mut t :u8 = 1;
+        let mut tmp :u8;
+        let mut idx :u8;
+        let mut table : [u8; 256] = [0; 256];
+
+        while i != 0 {
+            if t & 1 != 0 { tmp = polynomial; } else { tmp = 0; }
+            t = (t >> 1) ^ tmp;
+            j = 0;
+            while j < 256 {
+                idx = (i+j) as u8;
+                table[idx as usize] = table[j as usize] ^ t;
+                j += 2 * i;
+            }
+            i >>= 1;
+        }
+
+        return Crc8{ table : table };
+    }
+
+    /// Update CRC using previously calculated value and return new one.
+    pub fn update(&self, buffer : &[u8], crc: u8) -> u8 {
+        let mut crc_tmp = crc;
+
+        for i in 0..buffer.len() {
+            crc_tmp = self.table[((crc_tmp ^ buffer[i])) as usize];
+        }
+        return crc_tmp;
+    }
+
+    /// Calculate crc8 with default presets compatible with defaults of mp_binary
+    /// package used in kotlin Divan interfaces (msb, polynomial=0xA7, this is
+    /// bluetooth presets btw).
+    pub fn calc(data: &[u8]) -> u8 {
+        let crc = Crc8::create_msb(0xA7);
+        crc.update(data, 0)
+    }
+}
+
+#[test]
+fn test_crc8() {
+    let a = [1,2,3,4,5];
+    assert_eq!(134, Crc8::calc(&a));
+}
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
index 510a6d0..6233b2f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -121,6 +121,7 @@ pub mod bipack;
 mod error;
 mod ser;
 mod de;
+mod crc;
 
 #[cfg(test)]
 mod tests {