From 448a7c81fb0d7cda298c7faad8e407aa4cb70315 Mon Sep 17 00:00:00 2001
From: guowenxue <guowenxue@gmail.com>
Date: Wed, 26 Jun 2019 02:07:39 +0800
Subject: [PATCH] Merge branch 'master' of ssh://master.iot-yun.com:2280/apue
---
ch8_tlv/crc-itu-t.h | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 55 insertions(+), 0 deletions(-)
diff --git a/ch8_tlv/crc-itu-t.h b/ch8_tlv/crc-itu-t.h
new file mode 100644
index 0000000..e054724
--- /dev/null
+++ b/ch8_tlv/crc-itu-t.h
@@ -0,0 +1,55 @@
+/*
+ * crc-itu-t.h - CRC ITU-T V.41 routine
+ *
+ * Implements the standard CRC ITU-T V.41:
+ * Width 16
+ * Poly 0x0x1021 (x^16 + x^12 + x^15 + 1)
+ * Init 0
+ *
+ * This source code is licensed under the GNU General Public License,
+ * Version 2. See the file COPYING for more details.
+ */
+
+#ifndef CRC_ITU_T_H
+#define CRC_ITU_T_H
+
+#define MAGIC_CRC 0x1E50
+
+extern const unsigned short crc_itu_t_table[256];
+
+
+/**
+ * crc_itu_t - Compute the CRC-ITU-T for the data buffer
+ *
+ * @crc: previous CRC value, we use $IoT_MAGIC_CRC
+ * @buffer: data pointer
+ * @len: number of bytes in the buffer
+ *
+ * Returns the updated CRC value
+ */
+extern unsigned short crc_itu_t(unsigned short magic_crc, const unsigned char *buffer, unsigned int len);
+
+
+/*
+ * ushort_to_bytes - Convert unsigned short CRC16 value to two bytes
+ * @bytes: two bytes CRC16 value saving buffer, buffer size must more than 2 bytes
+ * @crc: crc_itu_t() compute returnd value( unsigned short CRC16 checksum)
+ */
+extern int ushort_to_bytes(unsigned char *bytes, unsigned short val);
+
+
+/*
+ * bytes_to_ushort - Convert two bytes mode CRC value into unsigned short CRC16 value
+ * @bytes: bytes mode CRC value first byte position
+ * @len: bytes mode CRC value length
+ */
+extern unsigned short bytes_to_ushort(unsigned char *bytes, int len);
+
+
+static inline unsigned short crc_itu_t_byte(unsigned short crc, const unsigned char data)
+{
+ return (crc << 8) ^ crc_itu_t_table[((crc >> 8) ^ data) & 0xff];
+}
+
+#endif /* CRC_ITU_T_H */
+
--
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