sizeof

pub fn sizeof(target: anytype) usize

File

Code

pub fn sizeof(target: anytype) usize {
    const T: type = if (@TypeOf(target) == type) target else @TypeOf(target);
    switch (@typeInfo(T)) {
        .float, .int, .@"struct", .@"union", .array, .bool, .vector => return @sizeOf(T),
        .@"fn" => {
            // sizeof(main) in C returns 1
            return 1;
        },
        .null => return @sizeOf(*anyopaque),
        .void => {
            // Note: sizeof(void) is 1 on clang/gcc and 0 on MSVC.
            return 1;
        },
        .@"opaque" => {
            if (T == anyopaque) {
                // Note: sizeof(void) is 1 on clang/gcc and 0 on MSVC.
                return 1;
            } else {
                @compileError("Cannot use C sizeof on opaque type " ++ @typeName(T));
            }
        },
        .optional => |opt| {
            if (@typeInfo(opt.child) == .pointer) {
                return sizeof(opt.child);
            } else {
                @compileError("Cannot use C sizeof on non-pointer optional " ++ @typeName(T));
            }
        },
        .pointer => |ptr| {
            if (ptr.size == .slice) {
                @compileError("Cannot use C sizeof on slice type " ++ @typeName(T));
            }

            // for strings, sizeof("a") returns 2.
            // normal pointer decay scenarios from C are handled
            // in the .array case above, but strings remain literals
            // and are therefore always pointers, so they need to be
            // specially handled here.
            if (ptr.size == .one and ptr.is_const and @typeInfo(ptr.child) == .array) {
                const array_info = @typeInfo(ptr.child).array;
                if ((array_info.child == u8 or array_info.child == u16) and array_info.sentinel() == 0) {
                    // length of the string plus one for the null terminator.
                    return (array_info.len + 1) * @sizeOf(array_info.child);
                }
            }

            // When zero sized pointers are removed, this case will no
            // longer be reachable and can be deleted.
            if (@sizeOf(T) == 0) {
                return @sizeOf(*anyopaque);
            }

            return @sizeOf(T);
        },
        .comptime_float => return @sizeOf(f64), // TODO c_double #3999
        .comptime_int => {
            // TODO to get the correct result we have to translate
            // `1073741824 * 4` as `int(1073741824) *% int(4)` since
            // sizeof(1073741824 * 4) != sizeof(4294967296).

            // TODO test if target fits in int, long or long long
            return @sizeOf(c_int);
        },
        else => @compileError("__helpers.sizeof does not support type " ++ @typeName(T)),
    }
}