From 708d50d23cc4abd35b4b87d6ec36b6754b032554 Mon Sep 17 00:00:00 2001
From: Forest Belton <65484+forestbelton@users.noreply.github.com>
Date: Tue, 6 Jul 2021 01:55:39 -0400
Subject: [PATCH] Add script for computing fixed-point constants

---
 scripts/convert_fixed_point.py | 59 ++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 scripts/convert_fixed_point.py

diff --git a/scripts/convert_fixed_point.py b/scripts/convert_fixed_point.py
new file mode 100644
index 0000000..f4fb940
--- /dev/null
+++ b/scripts/convert_fixed_point.py
@@ -0,0 +1,59 @@
+import argparse
+
+
+def convert_to(dec_str: str) -> None:
+    str_parts = dec_str.split(".")
+    assert len(str_parts) == 2
+
+    whole_str, part_str = str_parts
+    whole_dec = int(whole_str)
+    part_dec = float(f"0.{part_str}")
+    part_bits = []
+    for i in range(1, 9, 1):
+        bit = "0"
+        sub = 1 / (1 << i)
+        if part_dec > sub:
+            bit = "1"
+            part_dec = part_dec - sub
+        part_bits.append(bit)
+    part_dec = int("".join(part_bits), 2)
+
+    assert whole_dec <= 0xFF
+    assert part_dec <= 0xFF
+
+    print(f"0x{bytes([whole_dec, part_dec]).hex()}")
+
+
+def convert_from(hex_str: str) -> None:
+    assert hex_str.startswith("0x")
+    assert len(hex_str) == 6
+
+    whole_bin = int(hex_str[2:4], 16)
+    # TODO: support negatives
+    # if whole_bin & (1 << 7):
+    # whole_bin = -
+    part_bin = int(hex_str[4:6], 16)
+
+    part_dec = 0
+    for i in range(1, 9, 1):
+        mask = 1 << (8 - i)
+        if part_bin & mask:
+            part_dec += 1 / (1 << i)
+
+    print(f"{whole_bin + part_dec}")
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser("convert_fixed_point")
+    parser.add_argument("-d", "--decode", action="store_true")
+    parser.add_argument("decimal")
+
+    args = parser.parse_args()
+    if args.decode:
+        convert_from(args.decimal)
+    else:
+        convert_to(args.decimal)
+
+
+if __name__ == "__main__":
+    main()