zba/src/util.zig

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const std = @import("std");
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pub fn u32SignExtend(comptime bits: usize, value: u32) u32 {
return @bitCast(u32, signExtend(i32, bits, @bitCast(i32, value)));
}
fn signExtend(comptime T: type, comptime bits: usize, value: anytype) T {
const ValT = comptime @TypeOf(value);
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comptime std.debug.assert(isInteger(ValT));
comptime std.debug.assert(isSigned(ValT));
const value_bits = @typeInfo(ValT).Int.bits;
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comptime std.debug.assert(value_bits >= bits);
const bit_diff = value_bits - bits;
// (1 << bits) -1 is a mask that will take values like 0x100 and make them 0xFF
// value & mask so that only the relevant bits are sign extended
// therefore, value & ((1 << bits) - 1) is the isolation of the relevant bits
return ((value & ((1 << bits) - 1)) << bit_diff) >> bit_diff;
}
fn isInteger(comptime T: type) bool {
return @typeInfo(T) == .Int;
}
fn isSigned(comptime T: type) bool {
return @typeInfo(T).Int.signedness == .signed;
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}