From 1fdcaac52f7476a51bf1c55fe6ad0f42b1b88ec9 Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benjamin.valentin@ml-pa.com>
Date: Wed, 19 Mar 2025 16:45:55 +0100
Subject: [PATCH] sys/string_utils: add reverse_buf()

---
 sys/include/string_utils.h |  8 ++++++++
 sys/libc/string.c          | 11 +++++++++++
 2 files changed, 19 insertions(+)

diff --git a/sys/include/string_utils.h b/sys/include/string_utils.h
index 32e8ee2907..69c530fbff 100644
--- a/sys/include/string_utils.h
+++ b/sys/include/string_utils.h
@@ -179,6 +179,14 @@ ssize_t strscpy(char *dest, const char *src, size_t count);
  */
 const void *memchk(const void *data, uint8_t c, size_t len);
 
+/**
+ * @brief   Reverse the order of bytes in a buffer
+ *
+ * @param[in, out]  buf     The buffer to reverse
+ * @param[in]       len     Size of the buffer
+ */
+void reverse_buf(void *buf, size_t len);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/sys/libc/string.c b/sys/libc/string.c
index 1ab18f461c..97eccbae8a 100644
--- a/sys/libc/string.c
+++ b/sys/libc/string.c
@@ -80,4 +80,15 @@ int __swprintf(string_writer_t *sw, FLASH_ATTR const char *restrict format, ...)
     return res;
 }
 
+void reverse_buf(void *buf, size_t len)
+{
+    uint8_t *cur = buf;
+    uint8_t *end = cur + len - 1;
+    while (cur < end) {
+        uint8_t tmp = *cur;
+        *cur++ = *end;
+        *end-- = tmp;
+    }
+}
+
 /** @} */