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/* a macro that defines a context variable that is stored in thread local | |
storage. It's implemented as a module that exports a `get`, `set` and | |
`set_to` function. `set_to` acts as a stack. */ | |
macro_rules! _context_var_impl (($name:ident : $t:ty, $primer:expr, $is_primed:expr) => ( | |
mod $name { | |
/* internal tls key helper */ | |
fn key(_x: @$t) {} | |
/* primes a context variable from a callback */ | |
fn prime(f: fn() -> @$t) -> @$t { | |
assert $is_primed; | |
let x = move f(); | |
set(x); | |
move x | |
} | |
/* checks if the variable is set. Primed context vars are always set. */ | |
pub fn is_set() -> bool { unsafe { | |
match task::local_data::local_data_get(key) { | |
Some(ref _x) => true, | |
None => $is_primed | |
} | |
} } | |
/* returns the current value of that variable or fails with an error */ | |
pub fn get() -> @$t { unsafe { | |
match move task::local_data::local_data_get(key) { | |
None => move prime(match $primer { | |
Some(move f) => f, | |
None => die!(fmt!("%s::get() tried to return value \ | |
but no value was set", | |
stringify!($name))) | |
}), | |
Some(move x) => move x | |
} | |
} } | |
/* sets the variable to a new value */ | |
pub fn set(value: @$t) { unsafe { | |
task::local_data::local_data_set(key, value); | |
} } | |
/* unsets the value. If the context variable is primed it will be | |
primed again next call. */ | |
pub fn unset() { unsafe { | |
task::local_data::local_data_pop(key); | |
}} | |
/* temporarily overrides the variable with a new value */ | |
pub fn set_to(value: @$t, cb: fn()) { unsafe { | |
let old = move task::local_data::local_data_pop(key); | |
task::local_data::local_data_set(key, value); | |
cb(); | |
match (old) { | |
None => {} | |
Some(move x) => { | |
task::local_data::local_data_set(key, move x); | |
} | |
} | |
} } | |
} | |
)) | |
/* creates a regular context var */ | |
macro_rules! context_var (($name:ident : $t:ty) => ( | |
_context_var_impl!($name : $t, None, false) | |
)) | |
/* creates a context var that is primed from a stack closure */ | |
macro_rules! context_var_primed(($name:ident : $t:ty, $primer:expr) => ( | |
_context_var_impl!($name : $t, Some($primer), true) | |
)) | |
mod llcoolj { | |
pub fn get_default_language() -> @~str { @~"de_DE" } | |
} | |
context_var_primed!(language: ~str, || { | |
::llcoolj::get_default_language() | |
}) | |
//context_var!(language: ~str) | |
fn print_language() { | |
if language::is_set() { | |
io::println(fmt!("Your language is: %s", *language::get())); | |
} else { | |
io::println("No language is set"); | |
} | |
} | |
fn main() { | |
io::print("main task before setting: "); | |
print_language(); | |
do language::set_to(@~"en_US") { | |
io::print("main task in block: "); | |
print_language(); | |
do task::spawn { | |
io::print("in another task: "); | |
print_language(); | |
} | |
} | |
} |
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