Added PackedIntArray, PackedIntSlice to std #2422
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These are likely to be moved to third party packages in the std lib audit (#1629), but for now, they're very welcome, because they provide a well-encapsulated, well-tested API that helps prevent regressions in the language, as well as an experiment in solving "packed arrays" in userland. 👍 |
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PackedIntArray(comptime Int: type, comptime int_count: usize) type: Creates a bit-packed array ofint_countintegers of typeInt. Bits are packed using native endianess and without storing any meta data. PackedIntArray(i3, 8) will occupy exactly 3 bytes of memory.PackedIntSlice(comptime Int: type) type: Uses a slice as a bit-packed block of integers of type Int. Bits are packed using native endianess and without storing any meta data..len()gets the number of items the array/slice can hold..get(index: usize)and.set(index: usize, int: Int)are used for accessing the individual items..slice(start: usize, end: usize)creates a new PackedIntSlice(Int) instance covering the specified range of items (exclusive)..sliceCast(NewInt: type)returns a new PackedIntSlice(NewInt) covering the same bytes but using a different bit-width integer (which must fit evenly within the old range of bits).PackedIntArrays can be initialized from unpacked arrays or literals. PackedIntSlices initialize with a []u8 and a count of items.
.bytesRequired(int_count: usize)can be used to calculate the number of bytes required in the slice for the given count.Update: there are now also
PackedIntArrayEndian,PackedIntSliceEndian, and.sliceCastEndianwhich allow specifying the endianess of the bit packing instead of using native.