Remove swift-function-caller-generator's dependency on Foundation

Building Foundation seems to be optional in the Linux build script,
which makes it tricky to link against outside of Darwin platforms. This
removes the dependency on Foundation and calls libc for I/O instead.

Author: hnrklssn

tools/swift-function-caller-generator/Package.swift

@@ -4,7 +4,7 @@ import PackageDescription
 
 let package = Package(
   name: "swift-function-caller-generator",
-  platforms: [.macOS(.v11)],
+  platforms: [.macOS(.v13)],
   products: [
     .executable(name: "swift-function-caller-generator", targets: ["swift-function-caller-generator"]),
   ],

tools/swift-function-caller-generator/Sources/swift-function-caller-generator/swift-function-caller-generator.swift

@@ -1,21 +1,34 @@
-import Foundation
 import SwiftParser
 import SwiftSyntax
 import SwiftSyntaxMacros
 
+#if canImport(Darwin)
+import Darwin
+#elseif canImport(Glibc)
+import Glibc
+#elseif canImport(Musl)
+import Musl
+#elseif canImport(Android)
+import Android
+#elseif os(WASI)
+import WASILibc
+#elseif os(Windows)
+import CRT
+import WinSDK
+#endif
+
 @main
 class SwiftMacroTestGen: SyntaxVisitor {
   static func main() {
     if CommandLine.argc < 2 {
-      print("error: missing module name (passed 1 argument, expected 2)")
+      printError("missing module name (passed 0 arguments, expected 2)")
       exit(1)
     }
-    let contents =
-      if CommandLine.argc > 2 {
-        read(file: CommandLine.arguments[2])
-      } else {
-        readStdin()
-      }
+    if CommandLine.argc < 3 {
+      printError("missing module name (passed 1 argument, expected 2)")
+      exit(1)
+    }
+    let contents = read(file: CommandLine.arguments[2])
     let syntaxTree = Parser.parse(source: contents)
     print("import \(CommandLine.arguments[1])\n")
     let visitor = SwiftMacroTestGen(viewMode: .all)
@@ -101,23 +114,27 @@ class TypeAliasReplacer: SyntaxRewriter {
 }
 
 func read(file path: String) -> String {
-  do {
-    return try String(contentsOfFile: path, encoding: .utf8)
-  } catch {
-    print("Error reading file \(path): \(error.localizedDescription)")
+  guard let f = fopen(path, "r") else {
+    printError("could not open file \(path)")
     exit(1)
   }
-}
-
-func readStdin() -> String {
-  if let data = try? FileHandle.standardInput.readToEnd(),
-    let input = String(data: data, encoding: .utf8)
-  {
-    return input
-  } else {
-    print("Error reading stdin)")
+  if fseek(f, 0, SEEK_END) != 0 {
+    printError("could not read file \(path)")
+    exit(1)
+  }
+  let len = Int(ftell(f))
+  if len < 0 {
+    printError("could not read size of file \(path)")
     exit(1)
   }
+  rewind(f)
+  let contents = String(
+    unsafeUninitializedCapacity: len,
+    initializingUTF8With: { stringBuffer in
+      fread(UnsafeMutableRawPointer(stringBuffer.baseAddress!), 1, len, f)
+    })
+  fclose(f)
+  return contents
 }
 
 func createBody(_ f: FunctionDeclSyntax, selfParam: TokenSyntax?) -> CodeBlockSyntax {
@@ -190,6 +207,17 @@ extension TypeSyntax {
   }
 }
 
+// String.contains is not available without Foundation
+extension String {
+  public func contains(_ other: String) -> Bool {
+    return self.withCString({ this in
+      return other.withCString({ that in
+        return strstr(this, that) != nil
+      })
+    })
+  }
+}
+
 func addSelfParam(_ params: FunctionParameterListSyntax, _ type: TokenSyntax, _ name: TokenSyntax)
   -> FunctionParameterListSyntax
 {
@@ -282,3 +310,7 @@ extension AttributeListSyntax.Element {
     }
   }
 }
+
+func printError(_ s: String) {
+  fputs("error: \(s)\n", stderr)
+}