net/nanocoap: add block init helper function

sys/include/net/nanocoap.h

@@ -540,6 +540,19 @@ static inline ssize_t coap_get_uri_query(const coap_pkt_t *pkt, uint8_t *target)
  * generally useful functions to write block options.
  */
 /**@{*/
+/**
+ * @brief Initialize a block struct from content information
+ *
+ * @param[out]   block      block struct to initialize
+ * @param[in]    blknum     offset from the beginning of content, in terms of
+                            @p blksize byte blocks
+ * @param[in]    blksize    size of each block; must be a power of 2 between 16
+ *                          and 2 raised to #NANOCOAP_BLOCK_SIZE_EXP_MAX
+ * @param[in]    more       more blocks? use 1 if yes; 0 if no or unknown
+ */
+void coap_block_object_init(coap_block1_t *block, size_t blknum, size_t blksize,
+                            int more);
+
 /**
  * @brief Finish a block2 response
  *

sys/net/application_layer/nanocoap/nanocoap.c

@@ -875,6 +875,14 @@ ssize_t coap_opt_finish(coap_pkt_t *pkt, uint16_t flags)
     return pkt->payload - (uint8_t *)pkt->hdr;
 }
 
+void coap_block_object_init(coap_block1_t *block, size_t blknum, size_t blksize,
+                            int more)
+{
+    block->szx = _size2szx(blksize);
+    block->blknum = blknum;
+    block->more = more;
+}
+
 void coap_block2_init(coap_pkt_t *pkt, coap_block_slicer_t *slicer)
 {
     uint32_t blknum;