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This is an example of documentation generated by ZigDoc, an alternative to Zig's built-in Auto Doc feature. See also examples in other modes/formats. The project being documented here (as the example) is the Zig standard library. Public Function

writePackedTwosComplement

Doc Source

Public Function

std.math.big.int.Const.writePackedTwosComplement

pub fn writePackedTwosComplement(x: Const, buffer: []u8, bit_offset: usize, bit_count: usize, endian: Endian) void

Write the value of x to a packed memory buffer. Asserts that buffer is large enough to contain a value of bit-size bit_count at offset bit_offset.

This is equivalent to storing the value of an integer with bit_count bits as if it were a field in packed memory at the provided bit offset.

Params

x: Const
buffer: []u8
bit_offset: usize
bit_count: usize
endian: Endian

File

math/big/int.zig:2600

    pub fn writePackedTwosComplement(x: Const, buffer: []u8, bit_offset: usize, bit_count: usize, endian: Endian) void {
        assert(x.fitsInTwosComp(if (x.positive) .unsigned else .signed, bit_count));

        // Copy all complete limbs
        var carry: u1 = 1;
        var limb_index: usize = 0;
        var bit_index: usize = 0;
        while (limb_index < bit_count / @bitSizeOf(Limb)) : (limb_index += 1) {
            var limb: Limb = if (limb_index < x.limbs.len) x.limbs[limb_index] else 0;

            // 2's complement (bitwise not, then add carry bit)
            if (!x.positive) {
                const ov = @addWithOverflow(~limb, carry);
                limb = ov[0];
                carry = ov[1];
            }

            // Write one Limb of bits
            mem.writePackedInt(Limb, buffer, bit_index + bit_offset, limb, endian);
            bit_index += @bitSizeOf(Limb);
        }

        // Copy the remaining bits
        if (bit_count != bit_index) {
            var limb: Limb = if (limb_index < x.limbs.len) x.limbs[limb_index] else 0;

            // 2's complement (bitwise not, then add carry bit)
            if (!x.positive) limb = ~limb +% carry;

            // Write all remaining bits
            mem.writeVarPackedInt(buffer, bit_index + bit_offset, bit_count - bit_index, limb, endian);
        }
    }