Revert "remove dispatch declarations; use CLinuxGCD"

This reverts commit 919bc67.

Package.resolved

@@ -9,15 +9,6 @@
         "version" : "0.9.0"
       }
     },
-    {
-      "identity" : "clinuxgcd",
-      "kind" : "remoteSourceControl",
-      "location" : "https://github.com/PADL/CLinuxGCD.git",
-      "state" : {
-        "revision" : "75635d354c4ef14675803e2d6c5dd08026e7b61a",
-        "version" : "6.0.2"
-      }
-    },
     {
       "identity" : "ioringswift",
       "kind" : "remoteSourceControl",

Package.swift

@@ -44,7 +44,6 @@ let package = Package(
     // Dependencies declare other packages that this package depends on.
     .package(url: "https://github.com/madmachineio/SwiftIO", from: "0.1.0"),
     .package(url: "https://github.com/PADL/IORingSwift.git", from: "0.1.2"),
-    .package(url: "https://github.com/PADL/CLinuxGCD.git", from: "6.0.2"),
     .package(url: "https://github.com/apple/swift-async-algorithms", from: "1.0.0"),
     .package(url: "https://github.com/lhoward/AsyncExtensions", from: "0.9.0"),
     .package(url: "https://github.com/apple/swift-system", from: "1.0.0"),
@@ -54,8 +53,6 @@ let package = Package(
       name: "LinuxHalSwiftIO",
       dependencies: [
         .product(name: "CSwiftIO", package: "SwiftIO"),
-                     .product(name: "CBlockHeaders", package: "CLinuxGCD"),
-                     .product(name: "CDispatchHeaders", package: "CLinuxGCD")
       ],
       linkerSettings: [
         .linkedLibrary("gpiod", .when(platforms: [.linux])),

Sources/LinuxHalSwiftIO/swift_hal_internal.h

@@ -16,6 +16,12 @@
 
 #pragma once
 
+#include <inttypes.h>
+#include <string.h>
+#include <fcntl.h>
+
+#include <sys/param.h>
+
 #if __has_include(<Block.h>)
 #include <Block.h>
 #elif __has_include(<Block/Block.h>)
@@ -25,7 +31,51 @@ void *_Block_copy(const void *);
 void _Block_release(const void *);
 #endif
 
+#if __has_include(<dispatch/dispatch.h>)
 #include <dispatch/dispatch.h>
+#else
+// on Linux dispatch/dispatch.h is only available with unsafe Swift flags,
+// which preclude the use of this package as a versioned dependency
+struct dispatch_source_type_s {} __attribute__((aligned(sizeof(uintptr_t))));
+
+typedef struct dispatch_source_s *dispatch_source_t;
+typedef struct dispatch_queue_s *dispatch_queue_t;
+typedef const struct dispatch_source_type_s *dispatch_source_type_t;
+
+typedef void (^dispatch_block_t)(void);
+
+extern const struct dispatch_source_type_s _dispatch_source_type_read;
+extern const struct dispatch_source_type_s _dispatch_source_type_write;
+extern const struct dispatch_source_type_s _dispatch_source_type_timer;
+
+void dispatch_release(void *object);
+void dispatch_resume(void *object);
+void dispatch_suspend(void *object);
+
+void *dispatch_get_context(void *object);
+void dispatch_set_context(void *object, void *context);
+
+void dispatch_source_cancel(void *object);
+void dispatch_source_set_event_handler(dispatch_source_t source, dispatch_block_t handler);
+void dispatch_source_set_cancel_handler(dispatch_source_t source, dispatch_block_t handler);
+
+typedef uint64_t dispatch_time_t;
+
+uintptr_t dispatch_source_get_handle(dispatch_source_t source);
+
+dispatch_queue_t dispatch_get_global_queue(intptr_t identifier, uintptr_t flags);
+dispatch_source_t dispatch_source_create(dispatch_source_type_t type, uintptr_t handle, uintptr_t mask, dispatch_queue_t queue);
+void dispatch_source_set_timer(dispatch_source_t source, dispatch_time_t start, uint64_t interval, uint64_t leeway);
+dispatch_time_t dispatch_time(dispatch_time_t when, int64_t delta);
+
+#define dispatch_cancel dispatch_source_cancel
+#define DISPATCH_QUEUE_PRIORITY_DEFAULT 0
+#define DISPATCH_SOURCE_TYPE_READ (&_dispatch_source_type_read)
+#define DISPATCH_SOURCE_TYPE_WRITE (&_dispatch_source_type_write)
+#define DISPATCH_SOURCE_TYPE_TIMER (&_dispatch_source_type_timer)
+#define DISPATCH_TIME_NOW (0ull)
+#define DISPATCH_TIME_FOREVER (~0ull)
+#endif
 
 #include <syslog.h>