do_csum

函数名称：do_csum

函数原型：static unsigned int do_csum(const unsigned char *buff, int len)

返回类型：unsigned int

参数：

类型	参数	名称
const unsigned char *	buff
int	len

49

result等于0

51

如果len小于等于0则转到:out

53

odd等于1按位与buff

54

如果odd则

56

result加等于buff左移8位

60

len自减

61

buff自加

63

如果len大于等于2则

64

如果2按位与buff则

65

result加等于buff

66

len减等于2

67

buff加等于2

69

如果len大于等于4则

70

end等于buff加len按位与3的反的值

71

carry等于0

72

73

w等于buff

74

buff加等于4

75

result加等于carry

76

result加等于w

77

carry等于w大于result

78

当buff小于end 循环

79

result加等于carry

80

result等于result按位与0xffff的值加result右移16位的值

82

如果len按位与2则

83

result加等于buff

84

buff加等于2

87

如果len按位与1则result加等于buff

93

result等于from32to16(result)

94

如果odd则result等于result右移8位按位与0xff按位或result按位与0xff的值左移8位

96

out :

97

返回:result

**调用者**
名称	描述
ip_fast_csum	This is a version of ip_compute_csum() optimized for IP headers,* which always checksum on 4 octet boundaries.
csum_partial	mputes the checksum of a memory block at buff, length len,* and adds in "sum" (32-bit)* returns a 32-bit number suitable for feeding into itself* or csum_tcpudp_magic* this function must be called with even lengths, except* for the last fragment, which
ip_compute_csum	IP校验

源代码转换工具开放的插件接口	X
支持：c/c++/esqlc/java Oracle/Informix/Mysql 插件可实现：逻辑报告代码生成和批量转换代码