From ac809c4a9f0bb4b4b22a5be7dbb2e0f16d0008e0 Mon Sep 17 00:00:00 2001
From: iceman1001 <iceman@iuse.se>
Date: Mon, 22 Apr 2024 09:29:38 +0200
Subject: [PATCH] support function

---
 common/commonutil.c | 10 ++++++++++
 common/commonutil.h |  1 +
 2 files changed, 11 insertions(+)

diff --git a/common/commonutil.c b/common/commonutil.c
index c9ae5981c..79985099c 100644
--- a/common/commonutil.c
+++ b/common/commonutil.c
@@ -144,6 +144,16 @@ uint32_t reflect32(uint32_t b) {
     return v;
 }
 
+uint64_t reflect64(uint64_t b) {
+    // https://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
+    uint64_t v = b; // 32-bit word to reverse bit order
+    // swap 2-byte long pairs
+    uint64_t v1 = reflect32(v >> 32);
+    uint64_t v2 = reflect32(v);
+    v = (v1 << 32) | (v2 & 0xFFFFFFFF);
+    return v;
+}
+
 void num_to_bytes(uint64_t n, size_t len, uint8_t *dest) {
     while (len--) {
         dest[len] = (uint8_t) n;
diff --git a/common/commonutil.h b/common/commonutil.h
index a31c6c64e..a6dc243da 100644
--- a/common/commonutil.h
+++ b/common/commonutil.h
@@ -74,6 +74,7 @@ uint32_t reflect(uint32_t v, int b); // used in crc.c ...
 uint8_t reflect8(uint8_t b);         // dedicated 8bit reversal
 uint16_t reflect16(uint16_t b);      // dedicated 16bit reversal
 uint32_t reflect32(uint32_t b);      // dedicated 32bit reversal
+uint64_t reflect64(uint64_t b);      // dedicated 64bit reversal
 
 void num_to_bytes(uint64_t n, size_t len, uint8_t *dest);
 uint64_t bytes_to_num(const uint8_t *src, size_t len);