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const std = @import("std");
/// Maps each field of a struct `S` to the enum value in `E`
pub fn StructFieldsMap(
comptime S: type,
comptime E: type,
) type {
const KV = struct { []const u8, E };
var slice: []const KV = &[_]KV{};
var idx: usize = 0;
for (std.meta.fields(S)) |field| {
slice = slice ++ &[_]KV{.{ field.name, @intToEnum(E, idx) }};
idx += 1;
}
return std.ComptimeStringMap(E, slice);
}
/// Creates an enum with fields matching each field in struct `S`.
/// Runs `F` for each field in `S` to modify the names in the resulting enum.
// sort of opposite to the included EnumFieldStruct in std
pub fn StructFieldsEnum(
comptime S: type,
comptime F: ?fn (comptime []const u8) []const u8,
) type {
const EnumField = std.builtin.Type.EnumField;
var fields: []const EnumField = &[_]EnumField{};
var idx: usize = 0;
for (std.meta.fields(S)) |field| {
fields = fields ++ &[_]EnumField{.{
.name = blk: {
if (F) |f| break :blk f(field.name);
break :blk field.name;
},
.value = idx,
}};
idx += 1;
}
return @Type(.{ .Enum = .{
.tag_type = usize,
.fields = fields,
.decls = &.{},
.is_exhaustive = true,
} });
}
const TestStruct = struct {
a_a: bool,
b_b: bool,
};
fn replaceUnderscores(comptime o: []const u8) []const u8 {
var name: [o.len]u8 = undefined;
_ = std.mem.replace(u8, o, &[_]u8{'_'}, &[_]u8{'-'}, &name);
return &name;
}
test "StructFieldsEnum" {
{
const e = StructFieldsEnum(TestStruct, null);
try std.testing.expect(std.mem.eql(u8, std.meta.fields(e)[0].name, "a_a"));
try std.testing.expect(std.mem.eql(u8, std.meta.fields(e)[1].name, "b_b"));
}
{
const e = StructFieldsEnum(TestStruct, replaceUnderscores);
try std.testing.expect(std.mem.eql(u8, std.meta.fields(e)[0].name, "a-a"));
try std.testing.expect(std.mem.eql(u8, std.meta.fields(e)[1].name, "b-b"));
}
}
test "StructFieldsMap" {
{
const e = StructFieldsEnum(TestStruct, null);
const map = StructFieldsMap(TestStruct, e);
try std.testing.expect(std.mem.eql(u8, @tagName(map.get("a_a").?), "a_a"));
try std.testing.expect(std.mem.eql(u8, @tagName(map.get("b_b").?), "b_b"));
}
{
const e = StructFieldsEnum(TestStruct, replaceUnderscores);
const map = StructFieldsMap(TestStruct, e);
try std.testing.expect(std.mem.eql(u8, @tagName(map.get("a_a").?), "a-a"));
try std.testing.expect(std.mem.eql(u8, @tagName(map.get("b_b").?), "b-b"));
}
}
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