这里我使用两种不同的函数来计算任何类型文件的CRC16 (.txt,.tar,.tar.gz,.bin,.scr,.sh etc)
,不同的大小也从1 KB to 5 GB
变化。对于任何类型的文件,计算CRC16时哪种数据类型更好
我想要实现这个
`cross platform
less time consuming
Have to work proper for any type of file and any size`
我得到了这两种功能的CRC值相同。但任何人都可以告诉我哪个更适合计算任何类型的文件在不同平台上的任何大小的CRC16 CRC16。
这里我们必须考虑0到255所有类型的字符。
任何机构可以请我建议我哪一个在我的要求是好的。
代码的两种功能:
其在readChar
这里int
数据类型我使用int readChar
int CRC16_int(const char* filePath) {
//Declare variable to store CRC result.
unsigned short result;
//Declare loop variables.
int intInnerLoopIndex;
result = 0xffff; //initialize result variable to perform CRC checksum calculation.
//Store message which read from file.
//char content[2000000];
//Create file pointer to open and read file.
FILE *readFile;
//Use to read character from file.
int readChar;
//open a file for Reading
readFile = fopen(filePath, "rb");
//Checking file is able to open or exists.
if (!readFile) {
fputs("Unable to open file %s", stderr);
}
/*
Here reading file and store into variable.
*/
int chCnt = 0;
while ((readChar = getc(readFile)) != EOF) {
//printf("charcater is %c\n",readChar);
//printf("charcater is %c and int is %d \n",readChar,readChar);
result ^= (short) (readChar);
for (intInnerLoopIndex = 0; intInnerLoopIndex < 8; intInnerLoopIndex++) {
if ((result & 0x0001) == 0x0001) {
result = result >> 1; //Perform bit shifting.
result = result^0xa001; //Perform XOR operation on result.
} else {
result = result >> 1; //Perform bit shifting.
}
}
//content[chCnt] = readChar;
chCnt++;
}
printf("\nCRC data length in file: %d", chCnt);
//This is final CRC value for provided message.
return (result);
}
第二个首先就是readChar
这里unsigned char
数据类型我使用unsigned char readChar
int CRC16_unchar(const char* filePath) {
unsigned int filesize;
//Declare variable to store CRC result.
unsigned short result;
//Declare loop variables.
unsigned int intOuterLoopIndex, intInnerLoopIndex;
result = 0xffff; //initialize result variable to perform CRC checksum calculation.
FILE *readFile;
//Use to read character from file.
//The problem is if you read a byte from a file with the hex value (for example) 0xfe,
//then the char value will be -2 while the unsigned char value will be 254.
//This will significantly affect your CRC
unsigned char readChar;
//open a file for Reading
readFile = fopen(filePath, "rb");
//Checking file is able to open or exists.
if (!readFile) {
fputs("Unable to open file %s", stderr);
}
fseek(readFile, 0, SEEK_END); // seek to end of file
filesize = ftell(readFile); // get current file pointer
fseek(readFile, 0, SEEK_SET); // seek back to beginning of file
/*
Here reading file and store into variable.
*/
int chCnt = 0;
for (intOuterLoopIndex = 0; intOuterLoopIndex < filesize; intOuterLoopIndex++) {
readChar = getc(readFile);
printf("charcater is %c and int is %d\n",readChar,readChar);
result ^= (short) (readChar);
for (intInnerLoopIndex = 0; intInnerLoopIndex < 8; intInnerLoopIndex++) {
if ((result & 0x0001) == 0x0001) {
result = result >> 1; //Perform bit shifting.
result = result^0xa001; //Perform XOR operation on
} else {
result = result >> 1; //Perform bit shifting.
}
}
chCnt++;
}
printf("\nCRC data length in file: %d", chCnt);
return (result);
}
请帮我看看URE出这个问题
感谢
16位CRC不足以涵盖从1K到5GB的文件。对于这样的大数据块,即使有数据错误,CRC匹配的概率也很高。 – TJD 2012-02-24 17:37:05