Architecture specific uIP functions
[The uIP TCP/IP stack]

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Detailed Description

The functions in the architecture specific module implement the IP check sum and 32-bit additions.

The IP checksum calculation is the most computationally expensive operation in the TCP/IP stack and it therefore pays off to implement this in efficient assembler. The purpose of the uip-arch module is to let the checksum functions to be implemented in architecture specific assembler.

Files
file	uip_arch.h
	Declarations of architecture specific functions.
Functions
void	uip_add32 (u8_t *op32, u16_t op16)
	Carry out a 32-bit addition.
u16_t	uip_chksum (u16_t *buf, u16_t len)
	Calculate the Internet checksum over a buffer.
u16_t	uip_ipchksum (void)
	Calculate the IP header checksum of the packet header in uip_buf.
u16_t	uip_tcpchksum (void)
	Calculate the TCP checksum of the packet in uip_buf and uip_appdata.
Variables
u8_t	uip_acc32 [4]
	4-byte array used for the 32-bit sequence number calculations.

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Function Documentation

void uip_add32 (  u8_t *  op32, u16_t  op16 )

Carry out a 32-bit addition. Because not all architectures for which uIP is intended has native 32-bit arithmetic, uIP uses an external C function for doing the required 32-bit additions in the TCP protocol processing. This function should add the two arguments and place the result in the global variable uip_acc32. Note: The 32-bit integer pointed to by the op32 parameter and the result in the uip_acc32 variable are in network byte order (big endian). Parameters: op32  A pointer to a 4-byte array representing a 32-bit integer in network byte order (big endian). op16  A 16-bit integer in host byte order. Definition at line 249 of file uip.c. Referenced by uip_split_output().

u16_t uip_chksum (  u16_t *  buf, u16_t  len )

Calculate the Internet checksum over a buffer. The Internet checksum is the one's complement of the one's complement sum of all 16-bit words in the buffer. See RFC1071. Note: This function is not called in the current version of uIP, but future versions might make use of it. Parameters: buf  A pointer to the buffer over which the checksum is to be computed. len  The length of the buffer over which the checksum is to be computed. Returns: The Internet checksum of the buffer.

u16_t uip_ipchksum (  void   )

Calculate the IP header checksum of the packet header in uip_buf. The IP header checksum is the Internet checksum of the 20 bytes of the IP header. Returns: The IP header checksum of the IP header in the uip_buf buffer.

u16_t uip_tcpchksum (  void   )

Calculate the TCP checksum of the packet in uip_buf and uip_appdata. The TCP checksum is the Internet checksum of data contents of the TCP segment, and a pseudo-header as defined in RFC793. Note: The uip_appdata pointer that points to the packet data may point anywhere in memory, so it is not possible to simply calculate the Internet checksum of the contents of the uip_buf buffer. Returns: The TCP checksum of the TCP segment in uip_buf and pointed to by uip_appdata.

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