mirror of
https://github.com/Ed94/Odin.git
synced 2026-06-13 09:22:22 -07:00
Jeroen van Rijn
124 lines
2.9 KiB
Odin
124 lines
2.9 KiB
Odin
package dynamic_bit_array
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import "core:intrinsics"
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/*
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Note that these constants are dependent on the backing being a u64.
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*/
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@(private="file")
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INDEX_SHIFT :: 6
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@(private="file")
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INDEX_MASK :: 63
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Bit_Array :: struct {
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bits: [dynamic]u64,
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bias: int,
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}
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/*
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In:
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- ba: ^Bit_Array - a pointer to the Bit Array
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- index: The bit index. Can be an enum member.
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Out:
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- res: The bit you're interested in.
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- ok: Whether the index was valid. Returns `false` if the index is smaller than the bias.
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The `ok` return value may be ignored.
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*/
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get :: proc(ba: ^Bit_Array, #any_int index: uint, allocator := context.allocator) -> (res: bool, ok: bool) {
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idx := int(index) - ba.bias
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if ba == nil || int(index) < ba.bias { return false, false }
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context.allocator = allocator
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leg_index := idx >> INDEX_SHIFT
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bit_index := idx & INDEX_MASK
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/*
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If we `get` a bit that doesn't fit in the Bit Array, it's naturally `false`.
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This early-out prevents unnecessary resizing.
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*/
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if leg_index + 1 > len(ba.bits) { return false, true }
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val := u64(1 << uint(bit_index))
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res = ba.bits[leg_index] & val == val
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return res, true
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}
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/*
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In:
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- ba: ^Bit_Array - a pointer to the Bit Array
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- index: The bit index. Can be an enum member.
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Out:
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- ok: Whether or not we managed to set requested bit.
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`set` automatically resizes the Bit Array to accommodate the requested index if needed.
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*/
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set :: proc(ba: ^Bit_Array, #any_int index: uint, allocator := context.allocator) -> (ok: bool) {
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idx := int(index) - ba.bias
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if ba == nil || int(index) < ba.bias { return false }
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context.allocator = allocator
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leg_index := idx >> INDEX_SHIFT
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bit_index := idx & INDEX_MASK
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resize_if_needed(ba, leg_index) or_return
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ba.bits[leg_index] |= 1 << uint(bit_index)
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return true
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}
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/*
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A helper function to create a Bit Array with optional bias, in case your smallest index is non-zero (including negative).
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*/
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create :: proc(max_index: int, min_index := 0, allocator := context.allocator) -> (res: Bit_Array, ok: bool) #optional_ok {
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context.allocator = allocator
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size_in_bits := max_index - min_index
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if size_in_bits < 1 { return {}, false }
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legs := size_in_bits >> INDEX_SHIFT
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res = Bit_Array{
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bias = min_index,
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}
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return res, resize_if_needed(&res, size_in_bits)
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}
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/*
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Sets all bits to `false`.
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*/
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clear :: proc(ba: ^Bit_Array) {
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if ba == nil { return }
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ba.bits = {}
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}
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/*
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Releases the memory used by the Bit Array.
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*/
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destroy :: proc(ba: ^Bit_Array) {
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if ba == nil { return }
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delete(ba.bits)
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}
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/*
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Resizes the Bit Array. For internal use.
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If you want to reserve the memory for a given-sized Bit Array up front, you can use `create`.
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*/
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@(private="file")
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resize_if_needed :: proc(ba: ^Bit_Array, legs: int, allocator := context.allocator) -> (ok: bool) {
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if ba == nil { return false }
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context.allocator = allocator
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if legs + 1 > len(ba.bits) {
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resize(&ba.bits, legs + 1)
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}
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return len(ba.bits) > legs
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} |