Initial project import

tools/v/vlib/goroutines/context_nix.c.v

@@ -0,0 +1,47 @@
+// Copyright (c) 2019-2024 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+//
+// Platform-specific context switching using ucontext (Linux, macOS, BSDs).
+// This provides the low-level mechanism for goroutine context switches,
+// analogous to Go's gogo/gosave assembly routines.
+module goroutines
+
+#flag -D_XOPEN_SOURCE=700
+#flag darwin -D_DARWIN_C_SOURCE
+#include "@VMODROOT/vlib/goroutines/context_nix.h"
+
+fn C.goroutines_context_alloc() voidptr
+fn C.goroutines_context_init(ctx voidptr, stack voidptr, stack_size int, entry_fn voidptr, arg voidptr)
+fn C.goroutines_context_switch(from voidptr, to voidptr)
+fn C.goroutines_context_set(to voidptr)
+
+// Context wraps ucontext_t for goroutine context switching.
+// The actual ucontext_t is heap-allocated in C to avoid issues with
+// ucontext_t being a typedef rather than a struct tag.
+pub struct Context {
+pub mut:
+	uctx voidptr // heap-allocated ucontext_t
+}
+
+// context_init initializes a context for a new goroutine.
+// Sets up the context to run `entry_fn` with `arg` on the given stack.
+pub fn context_init(mut ctx Context, stack voidptr, stack_size int, entry_fn fn (voidptr), arg voidptr) {
+	if ctx.uctx == unsafe { nil } {
+		ctx.uctx = C.goroutines_context_alloc()
+	}
+	C.goroutines_context_init(ctx.uctx, stack, stack_size, voidptr(entry_fn), arg)
+}
+
+// context_switch saves the current context into `from` and switches to `to`.
+pub fn context_switch(mut from Context, to &Context) {
+	if from.uctx == unsafe { nil } {
+		from.uctx = C.goroutines_context_alloc()
+	}
+	C.goroutines_context_switch(from.uctx, to.uctx)
+}
+
+// context_set switches to the given context without saving.
+pub fn context_set(to &Context) {
+	C.goroutines_context_set(to.uctx)
+}