63 lines
1.5 KiB
Rust
63 lines
1.5 KiB
Rust
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/*!
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Module for wrapping freezable data structures in managed boxes.
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Normally freezable data structures require an unaliased reference,
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such as `T` or `~T`, so that the compiler can track when they are
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being mutated. The `rw<T>` type converts these static checks into
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dynamic checks: your program will fail if you attempt to perform
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mutation when the data structure should be immutable.
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*/
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#[forbid(non_camel_case_types)];
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#[forbid(deprecated_mode)];
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#[forbid(deprecated_pattern)];
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import util::with;
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import unsafe::transmute_immut;
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export Managed;
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enum Mode { ReadOnly, Mutable, Immutable }
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struct Data<T> {
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mut value: T;
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mut mode: Mode;
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}
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type Managed<T> = @Data<T>;
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fn Managed<T>(+t: T) -> Managed<T> {
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@Data {value: t, mode: ReadOnly}
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}
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impl<T> Data<T> {
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fn borrow_mut<R>(op: &fn(t: &mut T) -> R) -> R {
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match self.mode {
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Immutable => fail fmt!("%? currently immutable",
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self.value),
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ReadOnly | Mutable => {}
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}
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do with(&mut self.mode, Mutable) {
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op(&mut self.value)
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}
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}
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fn borrow_const<R>(op: &fn(t: &const T) -> R) -> R {
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op(&const self.value)
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}
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fn borrow_imm<R>(op: &fn(t: &T) -> R) -> R {
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match self.mode {
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Mutable => fail fmt!("%? currently mutable",
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self.value),
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ReadOnly | Immutable => {}
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}
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do with(&mut self.mode, Immutable) {
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op(unsafe{transmute_immut(&mut self.value)})
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}
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}
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}
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