48 lines
1.9 KiB
Zig
48 lines
1.9 KiB
Zig
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const std = @import("std");
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/// default EntityTraitsDefinition with reasonable sizes suitable for most situations
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pub const EntityTraits = EntityTraitsType(.medium);
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pub const EntityTraitsSize = enum { small, medium, large };
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pub fn EntityTraitsType(comptime size: EntityTraitsSize) type {
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return switch (size) {
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.small => EntityTraitsDefinition(u16, u12, u4),
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.medium => EntityTraitsDefinition(u32, u20, u12),
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.large => EntityTraitsDefinition(u64, u32, u32),
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};
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}
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fn EntityTraitsDefinition(comptime EntityType: type, comptime IndexType: type, comptime VersionType: type) type {
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std.debug.assert(@typeInfo(EntityType) == .Int and !EntityType.is_signed);
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std.debug.assert(@typeInfo(IndexType) == .Int and !IndexType.is_signed);
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std.debug.assert(@typeInfo(VersionType) == .Int and !VersionType.is_signed);
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if (@bitSizeOf(IndexType) + @bitSizeOf(VersionType) != @bitSizeOf(EntityType))
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@compileError("IndexType and VersionType must sum to EntityType's bit count");
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return struct {
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entity_type: type = EntityType,
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index_type: type = IndexType,
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version_type: type = VersionType,
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/// Mask to use to get the entity index number out of an identifier
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entity_mask: EntityType = std.math.maxInt(IndexType),
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/// Mask to use to get the version out of an identifier
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version_mask: EntityType = std.math.maxInt(VersionType),
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pub fn init() @This() {
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return @This(){};
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}
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};
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}
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test "entity traits" {
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const sm = EntityTraitsType(.small).init();
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const m = EntityTraitsType(.medium).init();
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const l = EntityTraitsType(.large).init();
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std.testing.expectEqual(sm.entity_mask, std.math.maxInt(sm.index_type));
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std.testing.expectEqual(m.entity_mask, std.math.maxInt(m.index_type));
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std.testing.expectEqual(l.entity_mask, std.math.maxInt(l.index_type));
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}
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