From 501ca7e34d24a375aff5bf25bc0c8bf94acd7239 Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benjamin.valentin@ml-pa.com>
Date: Mon, 2 May 2022 22:48:21 +0200
Subject: [PATCH] sys/iolist: introduce iolist_to_buffer()

---
 sys/include/iolist.h | 12 ++++++++++++
 sys/iolist/iolist.c  | 20 ++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/sys/include/iolist.h b/sys/include/iolist.h
index ff6c27f23d..a5617b4e1f 100644
--- a/sys/include/iolist.h
+++ b/sys/include/iolist.h
@@ -82,6 +82,18 @@ struct iovec;
  */
 size_t iolist_to_iovec(const iolist_t *iolist, struct iovec *iov, unsigned *count);
 
+/**
+ * @brief   Copies the bytes of the iolist to a buffer
+ *
+ * @param[in]   iolist  iolist to read from
+ * @param[out]  dst     Destination buffer
+ * @param[in]   len     Size of the destination buffer
+ *
+ * @returns iolist_size(iolist) on success
+ *          -ENOBUFS if the buffer is too small
+ */
+ssize_t iolist_to_buffer(const iolist_t *iolist, void *dst, size_t len);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/sys/iolist/iolist.c b/sys/iolist/iolist.c
index b10e4e982c..cbc9b32b7b 100644
--- a/sys/iolist/iolist.c
+++ b/sys/iolist/iolist.c
@@ -18,6 +18,9 @@
  * @}
  */
 
+#include <errno.h>
+#include <stdint.h>
+#include <string.h>
 #include <sys/uio.h>
 
 #include "iolist.h"
@@ -60,3 +63,20 @@ size_t iolist_to_iovec(const iolist_t *iolist, struct iovec *iov, unsigned *coun
 
     return bytes;
 }
+
+ssize_t iolist_to_buffer(const iolist_t *iolist, void *buf, size_t len)
+{
+    char *dst = buf;
+
+    while (iolist) {
+        if (iolist->iol_len > len) {
+            return -ENOBUFS;
+        }
+        memcpy(dst, iolist->iol_base, iolist->iol_len);
+        len -= iolist->iol_len;
+        dst += iolist->iol_len;
+        iolist = iolist->iol_next;
+    }
+
+    return (uintptr_t)dst - (uintptr_t)buf;
+}