Added utility for generating a pkg-config file

Author: harlanhaskins

utils/make-pkgconfig.swift

@@ -0,0 +1,97 @@
+#!/usr/bin/env swift
+import Foundation
+
+/// Runs the specified program at the provided path.
+/// - parameter path: The full path of the executable you
+///                   wish to run.
+/// - parameter args: The arguments you wish to pass to the
+///                   process.
+/// - returns: The standard output of the process, or nil if it was empty.
+func run(_ path: String, args: [String] = []) -> String? {
+    let pipe = Pipe()
+    let process = Process()
+    process.launchPath = path
+    process.arguments = args
+    process.standardOutput = pipe
+    process.launch()
+    process.waitUntilExit()
+
+    let data = pipe.fileHandleForReading.readDataToEndOfFile()
+    guard let result = String(data: data, encoding: .utf8)?
+                        .trimmingCharacters(in: .whitespacesAndNewlines),
+              !result.isEmpty else { return nil }
+    return result
+}
+
+/// Finds the location of the provided binary on your system.
+func which(_ name: String) -> String? {
+    return run("/usr/bin/which", args: [name])
+}
+
+extension String: Error {
+  /// Replaces all occurrences of characters in the provided set with
+  /// the provided string.
+  func replacing(charactersIn characterSet: CharacterSet,
+                 with separator: String) -> String {
+    let components = self.components(separatedBy: characterSet)
+    return components.joined(separator: separator)
+  }
+}
+
+func makeFile() throws {
+  let pkgConfigPath = "/usr/local/lib/pkgconfig"
+  let pkgConfigDir = URL(fileURLWithPath: pkgConfigPath)
+
+  // Make /usr/local/lib/pkgconfig if it doesn't already exist
+  if !FileManager.default.fileExists(atPath: pkgConfigPath) {
+    try FileManager.default.createDirectory(at: pkgConfigDir,
+                                            withIntermediateDirectories: true)
+  }
+  let cllvmPath = pkgConfigDir.appendingPathComponent("cllvm.pc")
+
+  /// Ensure we have llvm-config in the PATH
+  guard let llvmConfig = which("llvm-config") else {
+    throw "Failed to find llvm-config. Ensure llvm-config is installed and " +
+          "in your PATH"
+  }
+
+  /// Extract the info we need from llvm-config
+
+  print("Found llvm-config at \(llvmConfig)...")
+  print("Running llvm-config --libs all")
+  let ldFlags = run(llvmConfig, args: ["--libs", "all"])!
+                .replacing(charactersIn: .newlines, with: "")
+  print("Running llvm-config --version")
+  let version = run(llvmConfig, args: ["--version"])!
+                .replacing(charactersIn: .newlines, with: "")
+
+  // SwiftPM has a whitelisted set of cflags that it understands, and
+  // unfortunately that includes almost everything but the include dir.
+
+  print("Running llvm-config --cflags")
+  let cFlags = run(llvmConfig, args: ["--cflags"])!
+                .replacing(charactersIn: .newlines, with: "")
+                .components(separatedBy: " ")
+                .filter { $0.hasPrefix("-I") }
+                .joined(separator: " ")
+
+  /// Emit the pkg-config file to the path
+
+  let s = [
+    "Name: cllvm",
+    "Description: The llvm library",
+    "Version: \(version)",
+    "Libs: \(ldFlags)",
+    "Requires.private:",
+    "Cflags: \(cFlags)",
+  ].joined(separator: "\n")
+
+  try s.write(toFile: cllvmPath.path, atomically: true, encoding: .utf8)
+}
+
+do {
+  try makeFile()
+} catch {
+  print("error: \(error)")
+  exit(-1)
+}