From 9f8bf52436d3778bbc4f7caf5561f7961c8c1e08 Mon Sep 17 00:00:00 2001
From: eug-vs <eugene@eug-vs.xyz>
Date: Wed, 16 Aug 2023 02:34:03 +0300
Subject: feat: implement bitboard setwise fills

---
 src/bitboard.rs | 82 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)

(limited to 'src/bitboard.rs')

diff --git a/src/bitboard.rs b/src/bitboard.rs
index 4fb5b30..056822b 100644
--- a/src/bitboard.rs
+++ b/src/bitboard.rs
@@ -29,6 +29,21 @@ pub trait BitboardFns {
 
     /// Convert bitboard into the list of squares
     fn serialize(self) -> Vec<Square>;
+
+    /// Return bitboard shifted nort, no wrap occurs
+    fn nort_one(self) -> Self;
+    /// Return bitboard shifted sout, no wrap occurs
+    fn sout_one(self) -> Self;
+    /// Return bitboard shifted east, no wrap occurs
+    fn east_one(self) -> Self;
+    /// Return bitboard shifted west, no wrap occurs
+    fn west_one(self) -> Self;
+
+    /// Return bitboard with a nort fill
+    fn nort_fill(self) -> Self;
+    /// Return bitboard with a sout fill
+    fn sout_fill(self) -> Self;
+
 }
 
 const DE_BRUJIN_SEQUENCE: [u8; 64] = [
@@ -42,6 +57,9 @@ const DE_BRUJIN_SEQUENCE: [u8; 64] = [
    25, 14, 19,  9, 13,  8,  7,  6
 ];
 
+static NOT_A_FILE: Bitboard = 0xFEFEFEFEFEFEFEFE;
+static NOT_H_FILE: Bitboard = 0x7F7F7F7F7F7F7F7F;
+
 impl BitboardFns for Bitboard {
     fn print(self, title: &str) {
         println!("\n  {}", title);
@@ -98,6 +116,38 @@ impl BitboardFns for Bitboard {
         }
         serialized
     }
+
+    fn nort_one(self) -> Self {
+        self << 8
+    }
+
+    fn sout_one(self) -> Self {
+        self >> 8
+    }
+
+    fn east_one(self) -> Self {
+        (self << 1) & NOT_A_FILE
+    }
+
+    fn west_one(self) -> Self {
+        (self >> 1) & NOT_H_FILE
+    }
+
+    fn nort_fill(self) -> Self {
+        let mut fill = self;
+        fill |= fill << 8;
+        fill |= fill << 16;
+        fill |= fill << 32;
+        fill
+    }
+
+    fn sout_fill(self) -> Self {
+        let mut fill = self;
+        fill |= fill >> 8;
+        fill |= fill >> 16;
+        fill |= fill >> 32;
+        fill
+    }
 }
 
 #[cfg(test)]
@@ -139,4 +189,36 @@ mod tests {
         assert_eq!(serialized[1], Square::from(15));
         assert_eq!(serialized[2], Square::from(60));
     }
+
+    #[test]
+    fn shifts() {
+        let bb = Square::E4.to_bitboard();
+        assert_eq!(bb.nort_one(), Square::E5.to_bitboard());
+        assert_eq!(bb.sout_one(), Square::E3.to_bitboard());
+        assert_eq!(bb.west_one(), Square::D4.to_bitboard());
+        assert_eq!(bb.east_one(), Square::F4.to_bitboard());
+    }
+
+    #[test]
+    fn shifts_wraps() {
+        assert_eq!(Square::A1.to_bitboard().sout_one(), 0);
+        assert_eq!(Square::A1.to_bitboard().west_one(), 0);
+        assert_eq!(Square::H8.to_bitboard().nort_one(), 0);
+        assert_eq!(Square::H8.to_bitboard().east_one(), 0);
+    }
+
+    #[test]
+    fn fills() {
+        let bb = Square::A4.to_bitboard() | Square::E4.to_bitboard();
+        let nort = bb.nort_fill();
+        let sout = bb.sout_fill();
+
+        assert_eq!(nort.pop_count(), 10);
+        assert!(nort & Square::A8.to_bitboard() != 0);
+        assert!(nort & Square::E8.to_bitboard() != 0);
+
+        assert_eq!(sout.pop_count(), 8);
+        assert!(sout & Square::A1.to_bitboard() != 0);
+        assert!(sout & Square::E1.to_bitboard() != 0);
+    }
 }
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