Add Linux support

.github/workflows/build-test.yaml

@@ -8,12 +8,25 @@ on:
 
 jobs:
   build-and-test:
-    runs-on: macOS-15
+    strategy:
+      matrix:
+        include:
+          - os: macOS-15
+            swift: '6.2'
+          - os: ubuntu-24.04
+            swift: '6.2'
+    runs-on: ${{ matrix.os }}
 
     steps:
     - uses: SwiftyLab/setup-swift@v1
       with:
-        swift-version: '6.1'
+        swift-version: ${{ matrix.swift }}
+
+    - name: Install ZeroMQ dependencies
+      if: runner.os == 'Linux'
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y libzmq3-dev libsodium-dev
 
     - name: Checkout
       uses: actions/checkout@v4

Package.swift

@@ -2,6 +2,29 @@
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 import PackageDescription
 
+#if os(Linux)
+  let zmqDependency: Target.Dependency = .target(name: "ZeroMQ")
+  let zmqTargets: [Target] = [
+    .systemLibrary(
+      name: "ZeroMQ",
+      pkgConfig: "libzmq",
+      providers: [
+        .apt(["libzmq3-dev", "libsodium-dev"])
+      ]
+    )
+  ]
+#else
+  let zmqDependency: Target.Dependency = .target(name: "zmq")
+  let zmqTargets: [Target] = [
+    .binaryTarget(
+      name: "zmq",
+      url:
+        "https://github.com/a4z/libzmq-xcf/releases/download/v4.3.5-250103_1/libzmq.xcframework.zip",
+      checksum: "34bf6c91c7151bfd9e0bea70fdea3b375246520677e0b6aa9b36184315aa0ec9"
+    )
+  ]
+#endif
+
 let package = Package(
   name: "szq",
   // other/older might be possible, but not tested
@@ -16,19 +39,14 @@ let package = Package(
       name: "szq",
       targets: ["szq"])
   ],
-  targets: [
-    .binaryTarget(
-      name: "zmq",
-      url:
-        "https://github.com/a4z/libzmq-xcf/releases/download/v4.3.5-250103_1/libzmq.xcframework.zip",
-      checksum: "34bf6c91c7151bfd9e0bea70fdea3b375246520677e0b6aa9b36184315aa0ec9"
-    ),
+  targets: zmqTargets + [
     .target(
       name: "szq",
-      dependencies: ["zmq"],
+      dependencies: [zmqDependency],
       cxxSettings: [],
       linkerSettings: [
-        .linkedLibrary("c++")
+        .linkedLibrary("c++", .when(platforms: [.macOS, .iOS, .watchOS, .tvOS])),
+        .linkedLibrary("stdc++", .when(platforms: [.linux])),
       ]
     ),
     .testTarget(

Sources/ZeroMQ/module.modulemap

@@ -0,0 +1,5 @@
+module ZeroMQ [system] {
+  header "shim.h"
+  link "zmq"
+  export *
+}

Sources/ZeroMQ/shim.h

@@ -0,0 +1 @@
+#include <zmq.h>

Sources/szq/ZmqStreamable.swift

@@ -10,13 +10,18 @@ extension String: ZmqStreamable {
 
   public static func pack(value: String) throws -> zmq_msg_t {
     var msg = zmq_msg_t()
-    let zrc = zmq_msg_init_size(&msg, value.utf8.count)
+    let count = value.utf8.count
+    let zrc = zmq_msg_init_size(&msg, count)
     if zrc != 0 {
       throw currentZmqError()
     }
-    let data = zmq_msg_data(&msg)
-    _ = value.withCString { cStr in
-      memcpy(data, cStr, value.utf8.count)
+    if count > 0 {
+      guard let data = zmq_msg_data(&msg) else {
+        throw currentZmqError()
+      }
+      _ = value.withCString { cStr in
+        memcpy(data, cStr, count)
+      }
     }
     return msg
   }
@@ -41,7 +46,7 @@ extension ZmqStreamable where Self: BitwiseCopyable {
     return dataPtr.withMemoryRebound(to: Self.self, capacity: 1) { pointer in
       return pointer.pointee
     }
-  }
+    }
 
   public static func pack(value: Self) throws -> zmq_msg_t {
     var msg = zmq_msg_t()
@@ -50,9 +55,16 @@ extension ZmqStreamable where Self: BitwiseCopyable {
     if zrc != 0 {
       throw currentZmqError()
     }
-    let data = zmq_msg_data(&msg)
-    _ = withUnsafeBytes(of: value) { bytes in
-      memcpy(data, bytes.baseAddress, size)
+    if size > 0 {
+      guard let data = zmq_msg_data(&msg) else {
+        throw currentZmqError()
+      }
+      withUnsafeBytes(of: value) { bytes in
+        guard let base = bytes.baseAddress else {
+          return
+        }
+        memcpy(data, base, size)
+      }
     }
     return msg
   }