Add c_vec library to std.

This commit is contained in:
Joshua Wise 2011-11-23 05:15:04 -05:00 committed by Niko Matsakis
parent 9aa6e5750e
commit c2eb084b4c
2 changed files with 100 additions and 1 deletions

98
src/lib/c_vec.rs Normal file
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@ -0,0 +1,98 @@
/*
Module: c_vec
Library to interface with chunks of memory allocated in C.
It is often desirable to safely interface with memory allocated from C,
encapsulating the unsafety into allocation and destruction time. Indeed,
allocating memory externally is currently the only way to give Rust shared
mutable state with C programs that keep their own references; vectors are
unsuitable because they could be reallocated or moved at any time, and
importing C memory into a vector takes a one-time snapshot of the memory.
This module simplifies the usage of such external blocks of memory. Memory
is encapsulated into an opaque object after creation; the lifecycle of the
memory can be optionally managed by Rust, if an appropriate destructor
closure is provided. Safety is ensured by bounds-checking accesses, which
are marshalled through get and set functions.
There are three unsafe functions: the two introduction forms, and the
pointer elimination form. The introduction forms are unsafe for the obvious
reason (they act on a pointer that cannot be checked inside the method), but
the elimination form is somewhat more subtle in its unsafety. By using a
pointer taken from a c_vec::t without keeping a reference to the c_vec::t
itself around, the c_vec could be garbage collected, and the memory within
could be destroyed. There are legitimate uses for the pointer elimination
form -- for instance, to pass memory back into C -- but great care must be
taken to ensure that a reference to the c_vec::t is still held if needed.
*/
export t;
export create, create_with_dtor;
export get, set;
export size;
export ptr;
/*
Type: t
The type representing a native chunk of memory. Wrapped in a tag for
opacity; FIXME #818 when it is possible to have truly opaque types, this
should be revisited.
*/
tag t<T> {
t({ base: *T, size: uint, rsrc: @dtor_res});
}
resource dtor_res(dtor: option::t<fn@()>) {
alt dtor {
option::none. { }
option::some(f) { f(); }
}
}
/*
Section: Introduction forms
*/
unsafe fn create<T>(base: *T, size: uint) -> t<T> {
ret t({base: base,
size: size,
rsrc: @dtor_res(option::none)
});
}
unsafe fn create_with_dtor<T>(base: *T, size: uint, dtor: fn@()) -> t<T> {
ret t({base: base,
size: size,
rsrc: @dtor_res(option::some(dtor))
});
}
/*
Section: Operations
*/
fn get<copy T>(t: t<T>, ofs: uint) -> T {
assert ofs < (*t).size;
ret unsafe { *ptr::offset((*t).base, ofs) };
}
fn set<copy T>(t: t<T>, ofs: uint, v: T) {
assert ofs < (*t).size;
unsafe { *(ptr::offset((*t).base, ofs) as *mutable T) = v };
}
/*
Section: Elimination forms
*/
fn size<T>(t: t<T>) -> uint {
ret (*t).size;
}
unsafe fn ptr<T>(t: t<T>) -> *T {
ret (*t).base;
}

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@ -10,7 +10,7 @@
export box, char, float, int, str, ptr;
export uint, u8, u32, u64, vec, bool;
export comm, fs, io, net, run, sys, task;
export ctypes, either, option, result, four, tri, util;
export c_vec, ctypes, either, option, result, four, tri, util;
export bitv, deque, fun_treemap, list, map, smallintmap, sort, treemap, ufind;
export rope;
export math, math_f32, math_f64;
@ -50,6 +50,7 @@ mod task;
// Utility modules
mod c_vec;
mod ctypes;
mod cmath; /* unexported */
mod either;