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core: Add private global data interface. rust-lang#3915
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/*! | ||
Global data | ||
An interface for creating and retrieving values with global | ||
(per-runtime) scope. | ||
Global values are stored in a map and protected by a single global | ||
mutex. Operations are provided for accessing and cloning the value | ||
under the mutex. | ||
Because all globals go through a single mutex, they should be used | ||
sparingly. The interface is intended to be used with clonable, | ||
atomically reference counted synchronization types, like ARCs, in | ||
which case the value should be cached locally whenever possible to | ||
avoid hitting the mutex. | ||
*/ | ||
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use cast::{transmute, reinterpret_cast}; | ||
use clone::Clone; | ||
use kinds::Owned; | ||
use libc::{c_void, uintptr_t}; | ||
use option::{Option, Some, None}; | ||
use ops::Drop; | ||
use pipes; | ||
use private::{Exclusive, exclusive}; | ||
use private::{SharedMutableState, shared_mutable_state}; | ||
use private::{get_shared_immutable_state}; | ||
use private::at_exit::at_exit; | ||
use send_map::linear::LinearMap; | ||
use sys::Closure; | ||
use task::spawn; | ||
use uint; | ||
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pub type GlobalDataKey<T: Owned> = &fn(v: T); | ||
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pub unsafe fn global_data_clone_create<T: Owned Clone>( | ||
key: GlobalDataKey<T>, create: &fn() -> ~T) -> T { | ||
/*! | ||
* Clone a global value or, if it has not been created, | ||
* first construct the value then return a clone. | ||
* | ||
* # Safety note | ||
* | ||
* Both the clone operation and the constructor are | ||
* called while the global lock is held. Recursive | ||
* use of the global interface in either of these | ||
* operations will result in deadlock. | ||
*/ | ||
global_data_clone_create_(key_ptr(key), create) | ||
} | ||
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unsafe fn global_data_clone_create_<T: Owned Clone>( | ||
key: uint, create: &fn() -> ~T) -> T { | ||
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let mut clone_value: Option<T> = None; | ||
do global_data_modify_(key) |value: Option<~T>| { | ||
match value { | ||
None => { | ||
let value = create(); | ||
clone_value = Some(value.clone()); | ||
Some(value) | ||
} | ||
Some(value) => { | ||
clone_value = Some(value.clone()); | ||
Some(value) | ||
} | ||
} | ||
} | ||
return clone_value.unwrap(); | ||
} | ||
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unsafe fn global_data_modify<T: Owned>( | ||
key: GlobalDataKey<T>, op: &fn(Option<~T>) -> Option<~T>) { | ||
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global_data_modify_(key_ptr(key), op) | ||
} | ||
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unsafe fn global_data_modify_<T: Owned>( | ||
key: uint, op: &fn(Option<~T>) -> Option<~T>) { | ||
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let mut old_dtor = None; | ||
do get_global_state().with |gs| unsafe { | ||
let (maybe_new_value, maybe_dtor) = match gs.map.pop(&key) { | ||
Some((ptr, dtor)) => { | ||
let value: ~T = transmute(ptr); | ||
(op(Some(value)), Some(dtor)) | ||
} | ||
None => { | ||
(op(None), None) | ||
} | ||
}; | ||
match maybe_new_value { | ||
Some(value) => { | ||
let data: *c_void = transmute(value); | ||
let dtor: ~fn() = match maybe_dtor { | ||
Some(dtor) => dtor, | ||
None => { | ||
let dtor: ~fn() = || unsafe { | ||
let _destroy_value: ~T = transmute(data); | ||
}; | ||
dtor | ||
} | ||
}; | ||
let value = (data, dtor); | ||
gs.map.insert(key, value); | ||
} | ||
None => { | ||
match maybe_dtor { | ||
Some(dtor) => old_dtor = Some(dtor), | ||
None => () | ||
} | ||
} | ||
} | ||
} | ||
} | ||
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// GlobalState is a map from keys to unique pointers and a | ||
// destructor. Keys are pointers derived from the type of the | ||
// global value. There is a single GlobalState instance per runtime. | ||
struct GlobalState { | ||
map: LinearMap<uint, (*c_void, ~fn())> | ||
} | ||
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impl GlobalState: Drop { | ||
fn finalize(&self) { | ||
for self.map.each_value |v| { | ||
match v { | ||
&(_, ref dtor) => (*dtor)() | ||
} | ||
} | ||
} | ||
} | ||
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fn get_global_state() -> Exclusive<GlobalState> unsafe { | ||
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const POISON: int = -1; | ||
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// XXX: Doing atomic_cxchg to initialize the global state | ||
// lazily, which wouldn't be necessary with a runtime written | ||
// in Rust | ||
let global_ptr = rust_get_global_data_ptr(); | ||
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if *global_ptr == 0 { | ||
// Global state doesn't exist yet, probably | ||
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// The global state object | ||
let state = GlobalState { | ||
map: LinearMap() | ||
}; | ||
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// It's under a reference-counted mutex | ||
let state = ~exclusive(state); | ||
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// Convert it to an integer | ||
let state_ptr: &Exclusive<GlobalState> = state; | ||
let state_i: int = transmute(state_ptr); | ||
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// Swap our structure into the global pointer | ||
let prev_i = atomic_cxchg(&mut *global_ptr, 0, state_i); | ||
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// Sanity check that we're not trying to reinitialize after shutdown | ||
assert prev_i != POISON; | ||
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if prev_i == 0 { | ||
// Successfully installed the global pointer | ||
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// Take a handle to return | ||
let clone = state.clone(); | ||
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// Install a runtime exit function to destroy the global object | ||
do at_exit || unsafe { | ||
// Poison the global pointer | ||
let prev_i = atomic_cxchg(&mut *global_ptr, state_i, POISON); | ||
assert prev_i == state_i; | ||
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// Capture the global state object in the at_exit closure | ||
// so that it is destroyed at the right time | ||
let _capture_global_state = &state; | ||
}; | ||
return clone; | ||
} else { | ||
// Somebody else initialized the globals first | ||
let state: &Exclusive<GlobalState> = transmute(prev_i); | ||
return state.clone(); | ||
} | ||
} else { | ||
let state: &Exclusive<GlobalState> = transmute(*global_ptr); | ||
return state.clone(); | ||
} | ||
} | ||
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fn key_ptr<T: Owned>(key: GlobalDataKey<T>) -> uint unsafe { | ||
let closure: Closure = reinterpret_cast(&key); | ||
return transmute(closure.code); | ||
} | ||
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extern { | ||
fn rust_get_global_data_ptr() -> *mut int; | ||
} | ||
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#[abi = "rust-intrinsic"] | ||
extern { | ||
fn atomic_cxchg(dst: &mut int, old: int, src: int) -> int; | ||
} | ||
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#[test] | ||
fn test_clone_rc() unsafe { | ||
type MyType = SharedMutableState<int>; | ||
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fn key(_v: SharedMutableState<int>) { } | ||
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for uint::range(0, 100) |_| { | ||
do spawn unsafe { | ||
let val = do global_data_clone_create(key) { | ||
~shared_mutable_state(10) | ||
}; | ||
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assert get_shared_immutable_state(&val) == &10; | ||
} | ||
} | ||
} | ||
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#[test] | ||
fn test_modify() unsafe { | ||
type MyType = SharedMutableState<int>; | ||
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fn key(_v: SharedMutableState<int>) { } | ||
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do global_data_modify(key) |v| unsafe { | ||
match v { | ||
None => { | ||
Some(~shared_mutable_state(10)) | ||
} | ||
_ => fail | ||
} | ||
} | ||
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do global_data_modify(key) |v| { | ||
match v { | ||
Some(sms) => { | ||
let v = get_shared_immutable_state(sms); | ||
assert *v == 10; | ||
None | ||
}, | ||
_ => fail | ||
} | ||
} | ||
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do global_data_modify(key) |v| unsafe { | ||
match v { | ||
None => { | ||
Some(~shared_mutable_state(10)) | ||
} | ||
_ => fail | ||
} | ||
} | ||
} |
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