Swift: transfer TrapArena

swift/extractor/SwiftExtractor.cpp

@@ -13,6 +13,7 @@
 #include <llvm/Support/Path.h>
 
 #include "swift/extractor/trap/TrapClasses.h"
+#include "swift/extractor/trap/TrapArena.h"
 
 using namespace codeql;
 
@@ -75,10 +76,12 @@ static void extractFile(const SwiftExtractorConfiguration& config, swift::Source
   }
   trap << "\n\n";
 
+  TrapArena arena{trap};
+  // arena will be passed to another class in a later PR, the next block of code is only an example
   File f;
-  f.id = TrapLabel<FileTag>{};
+  f.id = arena.getLabel<FileTag>();
   f.name = srcFilePath.str().str();
-  trap << f.id << "=*\n" << f;
+  arena.emit(f);
 
   // TODO: Pick a better name to avoid collisions
   std::string trapName = file.getFilename().str() + ".trap";

swift/extractor/trap/TrapArena.h

@@ -0,0 +1,70 @@
+//
+// Created by redsun82 on 18.01.22.
+//
+
+#pragma once
+
+#include <iostream>
+#include <sstream>
+#include <vector>
+
+#include "swift/extractor/trap/TrapLabel.h"
+
+namespace codeql {
+
+// TrapArena has the responsibilities to
+// * allocate distinct trap #-labels outputting their assignment to '*' or a @-keys to a trap output
+// * forwarding trap entries to said output
+// TODO: split or move these responsibilities into separate classes
+class TrapArena {
+ public:
+  explicit TrapArena(std::ostream& out) : out_{out} {}
+
+  // get a new label for *
+  template <typename Tag>
+  TrapLabel<Tag> getLabel() {
+    auto ret = allocateLabel<Tag>();
+    print(ret, "=*");
+    return ret;
+  }
+
+  // get a new label for an @-key
+  template <typename Tag>
+  TrapLabel<Tag> getLabel(const std::string& key) {
+    auto ret = allocateLabel<Tag>();
+    // prefix the key with the id to guarantee the same key is not used wrongly with different tags
+    auto prefixed = std::string(Tag::prefix) + '_' + key;
+    print(ret, "=@", quoted(prefixed));
+    return ret;
+  }
+
+  // same as getLabel(const std::string&) above, concatenating keyParts
+  template <typename Tag, typename... Args>
+  TrapLabel<Tag> getLabel(const Args&... keyParts) {
+    std::ostringstream oss;
+    (oss << ... << keyParts);
+    return getLabel<Tag>(oss.str());
+  }
+
+  // emit a trap entry
+  template <typename Entry>
+  void emit(const Entry& e) {
+    print(e);
+  }
+
+ private:
+  template <typename... Args>
+  void print(const Args&... args) {
+    (out_ << ... << args) << '\n';
+  }
+
+  template <typename Tag>
+  TrapLabel<Tag> allocateLabel() {
+    return {id_++};
+  }
+
+  uint64_t id_{0};
+  std::ostream& out_;
+};
+
+}  // namespace codeql

swift/extractor/trap/TrapLabel.h

@@ -34,6 +34,9 @@ class TrapLabel : public UntypedTrapLabel {
 
   using UntypedTrapLabel::UntypedTrapLabel;
 
+  // we want only TrapArena to create non-default labels
+  friend class TrapArena;
+
  public:
   using Tag = TagParam;