ndef: Add near_ndef_record_length function

This function returns the length of a NDEF record.

diff --git a/include/ndef.h b/include/ndef.h
index c21e86e..0d23a85 100644 (file)
--- a/include/ndef.h
+++ b/include/ndef.h
@@ -32,6 +32,8 @@ struct near_ndef_message {
        uint8_t *data;
 };
 
+int near_ndef_record_length(uint8_t *ndef_in, size_t ndef_in_length);
+
 GList *near_ndef_parse(uint8_t *ndef_data, size_t ndef_length);
 
 struct near_ndef_message *near_ndef_prepare_text_record(char *encoding,

diff --git a/src/ndef.c b/src/ndef.c
index 35a42c4..cfd3919 100644 (file)
--- a/src/ndef.c
+++ b/src/ndef.c
@@ -1334,6 +1334,64 @@ fail:
        return records;
 }
 
+/*
+ * @brief Compute an NDEF record length
+ *
+ * Would compute ndef records length, even though the submitted frame
+ * is incomplete. This code is used in the handover read function, as
+ * we have to "guess" the final frame size.
+ *
+ * Message size for SR=1 is:
+ *  1 : ndef rec header (offset 0)
+ *  x : record type length (offset 1)
+ *  y : payload length (offset 2) 1 byte ONLY if SR=1
+ *     if SR=0: (4bytes) 32 bits
+ *  z : payload id length (offset 3) ONLY if il_length=1
+ * */
+int near_ndef_record_length(uint8_t *ndef_in, size_t ndef_in_length)
+{
+       int ndef_size;   /* default size for NDEF hdr + rec typ len + payl */
+       size_t offset;
+       uint8_t hdr;
+
+       DBG("");
+
+       if (ndef_in_length < 3)
+               return -EINVAL;
+
+       ndef_size = 3;
+       offset = 0;
+
+       /* save header byte */
+       hdr = ndef_in[offset];
+       offset++;
+
+       /* header->type_len */
+       ndef_size += ndef_in[offset++];
+
+       /* header->payload_len */
+       if (RECORD_SR_BIT(hdr) == 1) {
+               ndef_size += ndef_in[offset++];
+       } else {
+               ndef_size += g_ntohl(*((uint32_t *)(ndef_in + offset)));
+               offset += 4;
+
+               if (offset >= ndef_in_length)
+                       return -ERANGE;
+       }
+
+       /* header->il */
+       ndef_size += RECORD_IL_BIT(hdr);
+
+       /* header->il_length */
+       if (RECORD_IL_BIT(hdr) == 1)
+               ndef_size += ndef_in[offset++];
+
+       DBG("near_ndef_message_length is %d", ndef_size);
+
+       return ndef_size;
+}
+
 /**
  * @brief Allocates ndef message struture
  *