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Add getSentinel helper to Pointer and Array builtin.Types #21993

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Add getSentinel helper to Pointer and Array builtin.Types #21993

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16 changes: 16 additions & 0 deletions lib/std/builtin.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -607,6 +607,7 @@ pub const Type = union(enum) {
/// The type of the sentinel is the element type of the pointer, which is
/// the value of the `child` field in this struct. However there is no way
/// to refer to that type here, so we use pointer to `anyopaque`.
/// See `getSentinel` for an easier way to access this value.
sentinel: ?*const anyopaque,

/// This data structure is used by the Zig language code generation and
Expand All @@ -617,6 +618,14 @@ pub const Type = union(enum) {
Slice,
C,
};

/// Returns the sentinel value casted to the child type
/// Asserts that `pointer.size` is `.Many` or `.Slice`
/// and that `pointer.sentinel` is non-null
pub fn getSentinel(pointer: Pointer) pointer.child {
std.debug.assert(pointer.size == .Many or pointer.size == .Slice);
return @as(*const pointer.child, @ptrCast(@alignCast(pointer.sentinel.?))).*;
}
};

/// This data structure is used by the Zig language code generation and
Expand All @@ -628,7 +637,14 @@ pub const Type = union(enum) {
/// The type of the sentinel is the element type of the array, which is
/// the value of the `child` field in this struct. However there is no way
/// to refer to that type here, so we use pointer to `anyopaque`.
/// See `getSentinel` for an easier way to access this value.
sentinel: ?*const anyopaque,

/// Returns the sentinel value casted to the child type
/// Asserts that `array.sentinel` is non-null
pub fn getSentinel(array: Array) array.child {
return @as(*const array.child, @ptrCast(@alignCast(array.sentinel.?))).*;
}
};

/// This data structure is used by the Zig language code generation and
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