From 4a50be27de9c142c9944ac77c082aa25afb2bd6a Mon Sep 17 00:00:00 2001
From: Romuald Conty <romuald@libnfc.org>
Date: Thu, 14 Oct 2010 17:32:15 +0000
Subject: [PATCH] Add a iso14443a function to extract Historical Bytes from ATS

---
 libnfc/iso14443-subr.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/libnfc/iso14443-subr.c b/libnfc/iso14443-subr.c
index 0f64f57..4035da9 100644
--- a/libnfc/iso14443-subr.c
+++ b/libnfc/iso14443-subr.c
@@ -52,3 +52,26 @@ append_iso14443a_crc (byte_t * pbtData, size_t szLen)
 {
   iso14443a_crc (pbtData, szLen, pbtData + szLen);
 }
+
+byte_t *
+extract_historical_bytes(byte_t * pbtAts, size_t szAts, size_t * pszHB)
+{
+  if (szAts) {
+    size_t offset = 1;
+    if (pbtAts[0] & 0x10) { // TA
+      offset++;
+    }
+    if (pbtAts[0] & 0x20) { // TB
+      offset++;
+    }
+    if (pbtAts[0] & 0x40) { // TC
+      offset++;
+    }
+    if (szAts > offset) {
+      *pszHB = (szAts-offset);
+      return (pbtAts+offset);
+    }
+  }
+  *pszHB = 0;
+  return NULL;
+}