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fix calculation of max_io_bits in PackedIntIo

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Matthew Borkowski
2021-05-14 23:18:43 -04:00
committed by Andrew Kelley
parent 3845c264a6
commit 510f858143
1 changed files with 14 additions and 6 deletions
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20
lib/std/packed_int_array.zig
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@@ -30,13 +30,13 @@ pub fn PackedIntIo(comptime Int: type, comptime endian: Endian) type {
const min_io_bits = ((int_bits + 7) / 8) * 8;
//in the worst case, this is the number of bytes we need to touch
// to read or write a value, as bits
// to read or write a value, as bits. To calculate for int_bits > 1,
// set aside 2 bits to touch the first and last bytes, then divide
// by 8 to see how many bytes can be filled up inbetween.
const max_io_bits = switch (int_bits) {
0 => 0,
1 => 8,
2...9 => 16,
10...65535 => ((int_bits / 8) + 2) * 8,
else => unreachable,
else => ((int_bits - 2) / 8 + 2) * 8,
};
//we bitcast the desired Int type to an unsigned version of itself
@@ -378,12 +378,20 @@ test "PackedIntArray" {
}
}
test "PackedIntIo" {
const bytes = [_]u8 { 0b01101_000, 0b01011_110, 0b00011_101 };
try testing.expectEqual(@as(u15, 0x2bcd), PackedIntIo(u15, .Little).get(&bytes, 0, 3));
try testing.expectEqual(@as(u16, 0xabcd), PackedIntIo(u16, .Little).get(&bytes, 0, 3));
try testing.expectEqual(@as(u17, 0x1abcd), PackedIntIo(u17, .Little).get(&bytes, 0, 3));
try testing.expectEqual(@as(u18, 0x3abcd), PackedIntIo(u18, .Little).get(&bytes, 0, 3));
}
test "PackedIntArray init" {
if (we_are_testing_this_with_stage1_which_leaks_comptime_memory) return error.SkipZigTest;
const PackedArray = PackedIntArray(u3, 8);
var packed_array = PackedArray.init([_]u3{ 0, 1, 2, 3, 4, 5, 6, 7 });
var i = @as(usize, 0);
while (i < packed_array.len()) : (i += 1) testing.expectEqual(@intCast(u3, i), packed_array.get(i));
while (i < packed_array.len()) : (i += 1) try testing.expectEqual(@intCast(u3, i), packed_array.get(i));
}
test "PackedIntArray initAllTo" {
@@ -391,7 +399,7 @@ test "PackedIntArray initAllTo" {
const PackedArray = PackedIntArray(u3, 8);
var packed_array = PackedArray.initAllTo(5);
var i = @as(usize, 0);
while (i < packed_array.len()) : (i += 1) testing.expectEqual(@as(u3, 5), packed_array.get(i));
while (i < packed_array.len()) : (i += 1) try testing.expectEqual(@as(u3, 5), packed_array.get(i));
}
test "PackedIntSlice" {