问题
I have an array with 16 elements. I would like to evaluate these to a boolean 0 or 1 and then store this in 2 bytes so i can write to a binary file. How do I do this?
回答1:
Something like this you mean?
unsigned short binary = 0, i;
for ( i = 0; i < 16; ++i )
if ( array[i] )
binary |= 1 << i;
// the i-th bit of binary is 1 if array[i] is true and 0 otherwise.
回答2:
You have to use bitwise operators.
Here's an example:
int firstBit = 0x1;
int secondBit = 0x2;
int thirdBit = 0x4;
int fourthBit = 0x8;
int x = firstBit | fourthBit; /*both the 1st and 4th bit are set */
int isFirstBitSet = x & firstBit; /* Check if at least the first bit is set */
回答3:
int values[16];
int i;
unsigned short word = 0;
unsigned short bit = 1;
for (i = 0; i < 16; i++)
{
if (values[i])
{
word |= bit;
}
bit <<= 1;
}
回答4:
This solution avoid the use of the if inside the loop:
unsigned short binary = 0, i;
for ( i = 0; i < 16; ++i )
binary |= (array[i] != 0) << i;
回答5:
Declare an array result
with two bytes, then you loop through the source array:
for (int i = 0; i < 16; i++) {
// calclurate index in result array
int index = i >> 3;
// shift value in result
result[index] <<= 1;
// check array value
if (theArray[i]) {
// true, so set lowest bit in result byte
result[index]++;
}
}
回答6:
Something like this.
int values[16];
int bits = 0;
for (int ii = 0; ii < 16; ++ii)
{
bits |= (!!values[ii]) << ii;
}
unsigned short output = (unsigned short)bits;
the expression (!!values[ii]) forces the value to be 0 or 1, if you know for sure that the values array already contains either a 0 or a 1 and nothing else, you can leave of the !!
You could also do this if you don't like the !! syntax.
int values[16];
int bits = 0;
for (int ii = 0; ii < 16; ++ii)
{
bits |= (values[ii] != 0) << ii;
}
unsigned short output = (unsigned short)bits;
来源:https://stackoverflow.com/questions/2393914/c-building-a-byte