From: Nathael Pajani <nathael.pajani@ed3l.fr>
Date: Thu, 19 Nov 2020 18:48:38 +0000 (+0100)
Subject: Add reverse_byte()
X-Git-Url: http://git.techno-innov.fr/?a=commitdiff_plain;h=6c09a47ce436531cb5d60a86b9f3dd812907697f;p=soft%2Flpc122x%2Fcore

Add reverse_byte()
---

diff --git a/lib/utils.c b/lib/utils.c
index 96ab676..5b02434 100644
--- a/lib/utils.c
+++ b/lib/utils.c
@@ -100,3 +100,26 @@ uint8_t bits_set(uint32_t x)
 	return r;
 }
 
+
+#if 0
+/*
+ * Reverse bits (order) in a single byte
+ */
+uint8_t reverse_byte(uint8_t b) {
+   b = (b & 0xF0) >> 4 | (b & 0x0F) << 4;
+   b = (b & 0xCC) >> 2 | (b & 0x33) << 2;
+   b = (b & 0xAA) >> 1 | (b & 0x55) << 1;
+   return b;
+}
+
+/*
+ * Another method to reverse bits order, using a lookup table
+ */
+uint8_t reverse_byte(uint8_t b) {
+	static const uint8_t rev_half[] = { 0x0, 0x8, 0x4, 0xc, 0x2, 0xa, 0x6, 0xe,
+									  0x1, 0x9, 0x5, 0xd, 0x3, 0xb, 0x7, 0xf, };
+	/* Reverse the top and bottom nibble then swap them. */
+	return (rev_half[b & 0x0F] << 4) | rev_half[b >> 4];
+}
+#endif
+