[英]How do you validate that a string is a valid MAC address in C?
例:
12:45:ff:ab:aa:cd is valid 45:jj:jj:kk:ui>cd is not valid
以下代碼檢查有效的MAC地址(帶或不帶“:”分隔符):
#include <ctype.h>
int isValidMacAddress(const char* mac) {
int i = 0;
int s = 0;
while (*mac) {
if (isxdigit(*mac)) {
i++;
}
else if (*mac == ':' || *mac == '-') {
if (i == 0 || i / 2 - 1 != s)
break;
++s;
}
else {
s = -1;
}
++mac;
}
return (i == 12 && (s == 5 || s == 0));
}
該代碼檢查以下內容:
mac
恰好包含12個十六進制數字。 :
,則僅在偶數個十六進制數字之后出現。 它是這樣的:
i
( mac
的十六進制數字)被初始化為0。 while
循環輸入字符串中的每個字符,直到字符串結尾或檢測到12個十六進制數字。
*mac
)是有效的十六進制數字,則i
遞增,並且循環將檢查下一個字符。 如果您不想接受分隔符,只需將return語句更改為:
return (i == 12 && s == 0);
我需要在ANSI C中驗證和解析MAC地址,所以這里是函數。 如果mac地址已經過驗證,則返回1(它將接受12個十六進制字符,小寫或大寫字母,帶或不帶冒號,包括部分正確的輸入,如b3:0a:23:48fad3
)。 它在cortex m3控制器上的嵌入式應用程序中為我完成了工作。
該功能還將接受來自網頁的直接輸入(這實際上是我的用法),因此它將接受冒號作為%3A
字符。
結果是一個六個字節的數組。 您必須為此#include <cctype>
。
輸入字符串( *mac
)必須以零結尾,函數才能正常工作。
int parse_mac_address(char* mac, unsigned char *mac_address) {
int index=0;
char temp_mac[12]={0,0,0,0,0,0,0,0,0,0,0,0};
memset(mac_address, 0, 6); // Clear the 6 needed bytes in target array (which should be defined as "unsigned char mac_address[6]")
while(*mac) { // Repeat while we have something in the string
if(index>11) { // The string may be longer than our 12 digits
return 0; // If it has too many digits, break out and return an error (zero)
}
if(isxdigit(*mac)) { // If this is a hex digit
if(isdigit(*mac)) { // If the digit is 0 to 9
temp_mac[index]=*mac-0x30; // Convert to a number
}
else { // If the digit is A to F
temp_mac[index]=toupper(*mac)-0x37; // Make sure it is an upper case letter and convert to a number
}
++mac; // Go further on the mac string
++index; // Promote the index to the next value in our array
}
else {
if(!(index%2) && *mac==':') { // If it was not a digit, it can be a colon, but only on an odd locations in the array
++mac;
}
else {
if(!(index%2) && *mac=='%' && *(mac+1)=='3' && toupper(*(mac+2))=='A') { // In case of web colon sign we receive '%3A' instead, so we have to jump 3 characters to the next digit
mac+=3;
}
else { // If we discovered anything else, this is not a valid mac address - break out and return an error (zero)
return 0;
}
}
}
}
if(index!=11) { // Last check - the index must be exactly 11, to indicate we have filled in 12 digits
return 0; // If not - return with error (zero)
}
for(index=0;index<6;index++) { // Now, when we have 12 digits in an array, we will convert them in to two-digit bytes
*(mac_address+5-index)=temp_mac[index*2+1]+temp_mac[index*2]*0x10; // Taking pairs of digits and converting them in to a byte
// This operation will make mac_address[0] the LSB and mac_address[5] the MSB
// If you need it the other way round, replace *(mac_address+5-index) with *(mac_address+index)
}
return 1; // Return OK (one)
}
這是檢查MAC地址是否正常的另一個簡單功能
#include <stdio.h>
#include <string.h>
typedef unsigned char byte;
#define ETH_ADDR_LEN 6
#define FALSE 0
#define TRUE 1
#define MAC_STR_LEN 18
#define SEPERATOR ':'
int isMacValid(char *MacAddress) {
char mac_part[3] = {0};
byte mac_byte = 0;
byte mac_idx = 0;
while(MacAddress[mac_idx] != 0 && mac_idx < MAC_STR_LEN){
if(mac_idx != 15 && MacAddress[mac_idx + 2] != SEPERATOR)
return FALSE;
strncpy(mac_part, MacAddress+mac_idx,2);
mac_byte = (byte)strtol(mac_part, NULL, 16);
if(mac_byte == 0 && strcmp(mac_part,"00"))
return FALSE;
mac_idx += 3;
}
if(mac_idx == MAC_STR_LEN)
return TRUE;
return FALSE;
}
您可以依靠sscanf來檢查所提供的MAC地址的格式和內容,例如
bool checkMacAddr(const char * mac) noexcept
{
if(nullptr == mac) return false;
printf("[%s] strlen(%s)=%lu\n", __func__, mac, strlen(mac));
if(strlen(mac) != 17) return false;
uint32_t bytes[6]={0};
return (6 == sscanf(mac, "%02X:%02X:%02X:%02X:%02X:%02X"
, &bytes[5]
, &bytes[4]
, &bytes[3]
, &bytes[2]
, &bytes[1]
, &bytes[0]));
}
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