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mem.sliceTo on C pointers should return an optional slice #8785

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mem.sliceTo on C pointers should return an optional slice #8785

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13 changes: 8 additions & 5 deletions lib/std/mem.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -654,6 +654,7 @@ fn SliceTo(comptime T: type, comptime end: meta.Elem(T)) type {
new_ptr_info.sentinel = null;
}
}
return @Type(std.builtin.TypeInfo{ .Pointer = new_ptr_info });
},
else => {},
},
Expand All @@ -668,15 +669,16 @@ fn SliceTo(comptime T: type, comptime end: meta.Elem(T)) type {
new_ptr_info.sentinel = null;
}
}
return @Type(std.builtin.TypeInfo{ .Pointer = new_ptr_info });
},
.C => {
new_ptr_info.sentinel = end;
// C pointers are always allowzero, but we don't want the return type to be.
assert(new_ptr_info.is_allowzero);
new_ptr_info.is_allowzero = false;
return ?@Type(std.builtin.TypeInfo{ .Pointer = new_ptr_info });
},
}
return @Type(std.builtin.TypeInfo{ .Pointer = new_ptr_info });
},
else => {},
}
Expand All @@ -689,13 +691,12 @@ fn SliceTo(comptime T: type, comptime end: meta.Elem(T)) type {
/// If the pointer type is sentinel terminated and `end` matches that terminator, the
/// resulting slice is also sentinel terminated.
/// Pointer properties such as mutability and alignment are preserved.
/// C pointers are assumed to be non-null.
pub fn sliceTo(ptr: anytype, comptime end: meta.Elem(@TypeOf(ptr))) SliceTo(@TypeOf(ptr), end) {
if (@typeInfo(@TypeOf(ptr)) == .Optional) {
const Result = SliceTo(@TypeOf(ptr), end);
if (@typeInfo(Result) == .Optional) {
const non_null = ptr orelse return null;
return sliceTo(non_null, end);
}
const Result = SliceTo(@TypeOf(ptr), end);
const length = lenSliceTo(ptr, end);
if (@typeInfo(Result).Pointer.sentinel) |s| {
return ptr[0..length :s];
Expand Down Expand Up @@ -723,7 +724,9 @@ test "sliceTo" {
try testing.expectEqualSlices(u16, array[0..4], sliceTo(optional_sentinel_ptr, 99).?);

const c_ptr = @as([*c]u16, &array);
try testing.expectEqualSlices(u16, array[0..2], sliceTo(c_ptr, 3));
try testing.expectEqualSlices(u16, array[0..2], sliceTo(c_ptr, 3).?);
const null_c_ptr = @as(?[*c]u16, null);
try testing.expect(@as([]u16, null), sliceTo(null_c_ptr, 3));

const slice: []u16 = &array;
try testing.expectEqualSlices(u16, array[0..2], sliceTo(slice, 3));
Expand Down