Zig 0.17.0-dev (Split by item)

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writeSignedFixed

This is an "advanced" function. It allows one to use a fixed amount of memory to store an ILEB128. This defeats the entire purpose of using this data encoding; it will no longer use fewer bytes to store smaller numbers. The advantage of using a fixed width is that it makes fields have a predictable size and so depending on the use case this tradeoff can be worthwhile. An example use case of this is in emitting DWARF info where one wants to make a ILEB128 field "relocatable", meaning that it becomes possible to later go back and patch the number to be a different value without shifting all the following code.

leb128.writeSignedFixed

pub fn writeSignedFixed(comptime l: usize, ptr: *[l]u8, int: @Int(.signed, l * 7)) void

File

lib/std/leb128.zig:68

Code

pub fn writeSignedFixed(comptime l: usize, ptr: *[l]u8, int: @Int(.signed, l * 7)) void {
    const T = @TypeOf(int);
    const U = if (@typeInfo(T).int.bits < 8) u8 else T;
    var value: U = @intCast(int);

    comptime var i = 0;
    inline while (i < (l - 1)) : (i += 1) {
        const byte: u8 = @bitCast(@as(i8, @truncate(value)) | -0b1000_0000);
        value >>= 7;
        ptr[i] = byte;
    }
    ptr[i] = @as(u7, @bitCast(@as(i7, @truncate(value))));
}