100 lines
3.8 KiB
Plaintext
100 lines
3.8 KiB
Plaintext
// Obj-C blocks bridged to sx closures.
|
|
//
|
|
// Apple's block ABI (clang's "Block Implementation Specification"): a block
|
|
// pointer is a struct whose first five fields are { isa, flags, reserved,
|
|
// invoke, descriptor } followed by per-block captured state. When an API
|
|
// like `[UIView animateWithDuration:animations:]` receives a block, the
|
|
// runtime reads `invoke` and calls it with the block pointer as the first
|
|
// argument. UIKit / Foundation callers always `_Block_copy` synchronously
|
|
// before returning, so a stack-allocated block is safe to pass directly.
|
|
//
|
|
// We layer the sx closure onto Apple's layout by appending two pointer
|
|
// fields to the standard 32-byte header: `sx_env` (the closure's captured
|
|
// environment pointer) and `sx_fn` (the closure trampoline). The per-
|
|
// signature `__block_invoke_*` C-ABI fn knows the offsets and calls
|
|
// through to `sx_fn(sx_env, args...)`.
|
|
//
|
|
// ── Lifetime contract ───────────────────────────────────────────────────
|
|
// `xx <closure> : *Block` returns a pointer into the surrounding sx
|
|
// function's stack frame. Same rule as `&local_var`: pass it directly to
|
|
// a callee that consumes it immediately or `_Block_copy`s internally
|
|
// (UIKit/Foundation always do). Don't store the pointer to use after the
|
|
// caller returns. If you need that, ship a `Block_copy`-backed sibling
|
|
// API and use it instead.
|
|
|
|
// Standard 32-byte block header plus two trailing slots for the sx closure
|
|
// it wraps. Total = 48 bytes.
|
|
Block :: struct {
|
|
isa: *void;
|
|
flags: s32;
|
|
reserved: s32;
|
|
invoke: *void;
|
|
descriptor: *void;
|
|
sx_env: *void;
|
|
sx_fn: *void;
|
|
}
|
|
|
|
// Per-block-shape metadata. The runtime reads `size` when copying the
|
|
// block to the heap, so it must equal the actual instance size.
|
|
BlockDescriptor :: struct {
|
|
reserved: u64;
|
|
size: u64;
|
|
}
|
|
|
|
// libSystem isa pointer for stack-allocated blocks. Resolved at link time
|
|
// (auto-linked on every Apple target via libSystem).
|
|
_NSConcreteStackBlock : *void #foreign;
|
|
|
|
// Shared descriptor for the 48-byte sx-block layout. All Into impls below
|
|
// point their `descriptor` field at this.
|
|
__sx_block_descriptor : BlockDescriptor = .{
|
|
reserved = 0,
|
|
size = 48,
|
|
};
|
|
|
|
// Per-signature invoke trampolines. Each one reads sx_env + sx_fn from
|
|
// its block_self argument and tail-calls the closure through a typed
|
|
// fn-ptr cast. One per Apple block signature we support.
|
|
//
|
|
// Signature: `void (^)(void)` — no args, no return. The single most
|
|
// common Apple block shape (UIView animation bodies, dispatch_async, etc).
|
|
__block_invoke_void :: (block_self: *Block) callconv(.c) {
|
|
typed_fn : (*void) -> void = xx block_self.sx_fn;
|
|
typed_fn(block_self.sx_env);
|
|
}
|
|
|
|
impl Into(Block) for Closure() -> void {
|
|
convert :: (self: Closure() -> void) -> Block {
|
|
.{
|
|
isa = @_NSConcreteStackBlock,
|
|
flags = 0,
|
|
reserved = 0,
|
|
invoke = xx @__block_invoke_void,
|
|
descriptor = xx @__sx_block_descriptor,
|
|
sx_env = self.env,
|
|
sx_fn = self.fn_ptr,
|
|
};
|
|
}
|
|
}
|
|
|
|
// Signature: `void (^)(BOOL)` — UIView animation completion handlers and
|
|
// similar one-arg-bool callbacks.
|
|
__block_invoke_bool :: (block_self: *Block, arg0: bool) callconv(.c) {
|
|
typed_fn : (*void, bool) -> void = xx block_self.sx_fn;
|
|
typed_fn(block_self.sx_env, arg0);
|
|
}
|
|
|
|
impl Into(Block) for Closure(bool) -> void {
|
|
convert :: (self: Closure(bool) -> void) -> Block {
|
|
.{
|
|
isa = @_NSConcreteStackBlock,
|
|
flags = 0,
|
|
reserved = 0,
|
|
invoke = xx @__block_invoke_bool,
|
|
descriptor = xx @__sx_block_descriptor,
|
|
sx_env = self.env,
|
|
sx_fn = self.fn_ptr,
|
|
};
|
|
}
|
|
}
|