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std.mem.reverseIterator: add nextPtr()

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This commit is contained in:
Carl Åstholm
2023-03-31 22:50:31 +02:00
parent 0bbc1ec206
commit 3cd72951c0
1 changed files with 30 additions and 0 deletions
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30
lib/std/mem.zig
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@@ -3014,6 +3014,7 @@ fn ReverseIterator(comptime T: type) type {
@compileError("expected slice or pointer to array, found '" ++ @typeName(T) ++ "'");
};
const Element = std.meta.Elem(Pointer);
const ElementPointer = @TypeOf(&@as(Pointer, undefined)[0]);
return struct {
ptr: Pointer,
index: usize,
@@ -3022,6 +3023,11 @@ fn ReverseIterator(comptime T: type) type {
self.index -= 1;
return self.ptr[self.index];
}
pub fn nextPtr(self: *@This()) ?ElementPointer {
if (self.index == 0) return null;
self.index -= 1;
return &self.ptr[self.index];
}
};
}
@@ -3051,6 +3057,18 @@ test "reverseIterator" {
try testing.expectEqual(@as(?i32, 7), it.next());
try testing.expectEqual(@as(?i32, 3), it.next());
try testing.expectEqual(@as(?i32, null), it.next());
it = reverseIterator(slice);
try testing.expect(trait.isConstPtr(@TypeOf(it.nextPtr().?)));
try testing.expectEqual(@as(?i32, 7), it.nextPtr().?.*);
try testing.expectEqual(@as(?i32, 3), it.nextPtr().?.*);
try testing.expectEqual(@as(?*const i32, null), it.nextPtr());
var mut_slice: []i32 = &array;
var mut_it = reverseIterator(mut_slice);
mut_it.nextPtr().?.* += 1;
mut_it.nextPtr().?.* += 2;
try testing.expectEqual([2]i32{ 5, 8 }, array);
}
{
var array = [2]i32{ 3, 7 };
@@ -3059,6 +3077,18 @@ test "reverseIterator" {
try testing.expectEqual(@as(?i32, 7), it.next());
try testing.expectEqual(@as(?i32, 3), it.next());
try testing.expectEqual(@as(?i32, null), it.next());
it = reverseIterator(ptr_to_array);
try testing.expect(trait.isConstPtr(@TypeOf(it.nextPtr().?)));
try testing.expectEqual(@as(?i32, 7), it.nextPtr().?.*);
try testing.expectEqual(@as(?i32, 3), it.nextPtr().?.*);
try testing.expectEqual(@as(?*const i32, null), it.nextPtr());
var mut_ptr_to_array: *[2]i32 = &array;
var mut_it = reverseIterator(mut_ptr_to_array);
mut_it.nextPtr().?.* += 1;
mut_it.nextPtr().?.* += 2;
try testing.expectEqual([2]i32{ 5, 8 }, array);
}
}