How Can Boolean Values Be Efficiently Encoded and Decoded into Bytes?

Decoding and Encoding Boolean Values into and out of Bytes

Decoding and encoding boolean values into and out of bytes can be achieved through various methods. This article will explore two approaches:

Hard Way:

Utilizing a direct bit manipulation approach, the following functions are used:

unsigned char ToByte(bool b[8]) {
    unsigned char c = 0;
    for (int i = 0; i < 8; ++i) {
        if (b[i]) {
            c |= 1 << i;
        }
    }
    return c;
}

void FromByte(unsigned char c, bool b[8]) {
    for (int i = 0; i < 8; ++i) {
        b[i] = (c & (1 << i)) != 0;
    }
}

In this method, each boolean value is represented by a bit, with a byte (8 bits) being able to hold 8 boolean values.

Cool Way:

An alternative approach leverages bitfields within a structure and a union to provide flexible data manipulation:

struct Bits {
    unsigned b0 : 1, b1 : 1, b2 : 1, b3 : 1, b4 : 1, b5 : 1, b6 : 1, b7 : 1;
};

union CBits {
    Bits bits;
    unsigned char byte;
};

Here, the Bits structure holds 8 boolean values as bitfields. The CBits union shares the same memory space, allowing access to the boolean values through the bits member or the byte value through the byte member.

Implementation Notes:

• Bitfield order and padding are implementation-defined.
• Reading from one union member after writing to another is well-defined in C99 and some C implementations (including MSVC and GCC), but it's Undefined Behavior in standard C .
• For portable C , consider using memcpy or C 20's std::bit_cast for type-pun casting.

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