1 files changed, 92 insertions, 0 deletions
diff --git a/src/shifter/extract.rs b/src/shifter/extract.rs
new file mode 100644
index 0000000..d4ff6e0
--- /dev/null
+++ b/src/shifter/extract.rs
@@ -0,0 +1,92 @@
+/*
+	Copyright 2021-2023 Gabriel Jensen.
+
+	This file is part of Luma.
+
+	Luma is free software: you can redistribute it
+	and/or modify it under the terms of the GNU
+	Affero General Public License as published by
+	the Free Software Foundation, either version 3
+	of the License, or (at your option) any later
+	version.
+
+	Luma 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
+	Affero General Public License for more details.
+
+	You should have received a copy of the GNU
+	Affero General Public License along with Luma.
+	If not, see <https://www.gnu.org/licenses/>.
+*/
+
+use crate::shifter::Shifter;
+
+use std::hint::unreachable_unchecked;
+
+impl Shifter {
+	pub fn extract(opcode: u32) -> Self {
+		use Shifter::*;
+
+		match opcode & 0b00000010000000000000000000000000 != 0x0 {
+			false => {
+				let rm = (opcode & 0b00000000000000000000000000001111) as u8;
+
+				let shift          = (opcode & 0b00000000000000000000000001100000).wrapping_shr(0x5) as u8;
+				let register_shift = opcode & 0b00000000000000000000000000010000 != 0x0;
+
+				match register_shift {
+					false => {
+						let imm = (opcode & 0b00000000000000000000111110000000).wrapping_shr(0x7) as u8;
+
+						return match shift {
+							0b11 => match imm {
+								0x0 => RotateRightExtend(   rm),
+								imm => RotateRightImmediate(rm, imm),
+							},
+
+							shift => {
+								match shift {
+									0b00 => LogicalShiftLeftImmediate(rm, imm),
+
+									0b01 => LogicalShiftRightImmediate(rm, match imm {
+										0x0 => 0x20,
+										imm => imm,
+									}),
+
+									0b10 => ArithmeticShiftRightImmediate(rm, match imm {
+										0x0 => 0x20,
+										imm => imm,
+									}),
+
+									_ => unsafe { unreachable_unchecked() },
+								}
+							},
+						};
+					},
+
+					true => {
+						let rs = (opcode & 0b0000000000000000000111100000000).wrapping_shr(0x8) as u8;
+
+						return match shift {
+							0b00 => LogicalShiftLeftRegister(    rm, rs),
+							0b01 => LogicalShiftRightRegister(   rm, rs),
+							0b10 => ArithmeticShiftRightRegister(rm, rs),
+							0b11 => RotateRightRegister(         rm, rs),
+
+							_ => unsafe { unreachable_unchecked() },
+						};
+					},
+				};
+			},
+
+			true => {
+				let imm = (opcode & 0b00000000000000000000000011111111) as u8;
+				let rot = (opcode & 0b00000000000000000000111100000000).wrapping_shr(0x7) as u8;
+
+				return Immediate(imm, rot);
+			},
+		};
+	}
+}