AAPT2: Add a daemon mode

Gradle and other build tools that need to frequently interact with aapt2
can use the daemon mode to issue regular CLI commands without paying
the process start cost for each invocation.

Test: manual
Change-Id: I543858ed46496278bad643f0dae688c924ec6c3f

3 files changed, 106 insertions, 38 deletions

diff --git a/tools/aapt2/Main.cpp b/tools/aapt2/Main.cpp
index 89cce5ffca53..e4ca7a463df1 100644
--- a/tools/aapt2/Main.cpp
+++ b/tools/aapt2/Main.cpp
@@ -24,10 +24,16 @@
 #include <iostream>
 #include <vector>
 
+#include "android-base/stringprintf.h"
 #include "android-base/utf8.h"
 #include "androidfw/StringPiece.h"
 
 #include "Diagnostics.h"
+#include "util/Files.h"
+#include "util/Util.h"
+
+using ::android::StringPiece;
+using ::android::base::StringPrintf;
 
 namespace aapt {
 
@@ -37,53 +43,103 @@ static const char* sMajorVersion = "2";
 // Update minor version whenever a feature or flag is added.
 static const char* sMinorVersion = "18";
 
-int PrintVersion() {
-  std::cerr << "Android Asset Packaging Tool (aapt) " << sMajorVersion << "."
-            << sMinorVersion << std::endl;
-  return 0;
+static void PrintVersion() {
+  std::cerr << StringPrintf("Android Asset Packaging Tool (aapt) %s:%s", sMajorVersion,
+                            sMinorVersion)
+            << std::endl;
 }
 
-extern int Compile(const std::vector<android::StringPiece>& args, IDiagnostics* diagnostics);
-extern int Link(const std::vector<android::StringPiece>& args, IDiagnostics* diagnostics);
-extern int Dump(const std::vector<android::StringPiece>& args);
-extern int Diff(const std::vector<android::StringPiece>& args);
-extern int Optimize(const std::vector<android::StringPiece>& args);
+static void PrintUsage() {
+  std::cerr << "\nusage: aapt2 [compile|link|dump|diff|optimize|version] ..." << std::endl;
+}
+
+extern int Compile(const std::vector<StringPiece>& args, IDiagnostics* diagnostics);
+extern int Link(const std::vector<StringPiece>& args, IDiagnostics* diagnostics);
+extern int Dump(const std::vector<StringPiece>& args);
+extern int Diff(const std::vector<StringPiece>& args);
+extern int Optimize(const std::vector<StringPiece>& args);
+
+static int ExecuteCommand(const StringPiece& command, const std::vector<StringPiece>& args,
+                          IDiagnostics* diagnostics) {
+  if (command == "compile" || command == "c") {
+    return Compile(args, diagnostics);
+  } else if (command == "link" || command == "l") {
+    return Link(args, diagnostics);
+  } else if (command == "dump" || command == "d") {
+    return Dump(args);
+  } else if (command == "diff") {
+    return Diff(args);
+  } else if (command == "optimize") {
+    return Optimize(args);
+  } else if (command == "version") {
+    PrintVersion();
+    return 0;
+  }
+  diagnostics->Error(DiagMessage() << "unknown command '" << command << "'");
+  return -1;
+}
+
+static void RunDaemon(IDiagnostics* diagnostics) {
+  std::cout << "Ready" << std::endl;
+
+  // Run in daemon mode. Each line of input from stdin is treated as a command line argument
+  // invocation. This means we need to split the line into a vector of args.
+  for (std::string line; std::getline(std::cin, line);) {
+    const util::Tokenizer tokenizer = util::Tokenize(line, file::sPathSep);
+    auto token_iter = tokenizer.begin();
+    if (token_iter == tokenizer.end()) {
+      diagnostics->Error(DiagMessage() << "no command");
+      continue;
+    }
+
+    const StringPiece command(*token_iter);
+    if (command == "quit") {
+      break;
+    }
+
+    ++token_iter;
+
+    std::vector<StringPiece> args;
+    args.insert(args.end(), token_iter, tokenizer.end());
+    ExecuteCommand(command, args, diagnostics);
+    std::cout << "Done" << std::endl;
+  }
+
+  std::cout << "Exiting daemon" << std::endl;
+}
 
 }  // namespace aapt
 
 int MainImpl(int argc, char** argv) {
-  if (argc >= 2) {
-    argv += 1;
-    argc -= 1;
+  if (argc < 2) {
+    std::cerr << "no command specified\n";
+    aapt::PrintUsage();
+    return -1;
+  }
 
-    std::vector<android::StringPiece> args;
-    for (int i = 1; i < argc; i++) {
-      args.push_back(argv[i]);
-    }
+  argv += 1;
+  argc -= 1;
 
-    android::StringPiece command(argv[0]);
-    if (command == "compile" || command == "c") {
-      aapt::StdErrDiagnostics diagnostics;
-      return aapt::Compile(args, &diagnostics);
-    } else if (command == "link" || command == "l") {
-      aapt::StdErrDiagnostics diagnostics;
-      return aapt::Link(args, &diagnostics);
-    } else if (command == "dump" || command == "d") {
-      return aapt::Dump(args);
-    } else if (command == "diff") {
-      return aapt::Diff(args);
-    } else if (command == "optimize") {
-      return aapt::Optimize(args);
-    } else if (command == "version") {
-      return aapt::PrintVersion();
+  aapt::StdErrDiagnostics diagnostics;
+
+  // Collect the arguments starting after the program name and command name.
+  std::vector<StringPiece> args;
+  for (int i = 1; i < argc; i++) {
+    args.push_back(argv[i]);
+  }
+
+  const StringPiece command(argv[0]);
+  if (command != "daemon" && command != "m") {
+    // Single execution.
+    const int result = aapt::ExecuteCommand(command, args, &diagnostics);
+    if (result < 0) {
+      aapt::PrintUsage();
     }
-    std::cerr << "unknown command '" << command << "'\n";
-  } else {
-    std::cerr << "no command specified\n";
+    return result;
   }
 
-  std::cerr << "\nusage: aapt2 [compile|link|dump|diff|optimize|version] ..." << std::endl;
-  return 1;
+  aapt::RunDaemon(&diagnostics);
+  return 0;
 }
 
 int main(int argc, char** argv) {
diff --git a/tools/aapt2/util/Files.h b/tools/aapt2/util/Files.h
index b6aa410f9421..b26e4fa26de6 100644
--- a/tools/aapt2/util/Files.h
+++ b/tools/aapt2/util/Files.h
@@ -34,8 +34,10 @@ namespace file {
 
 #ifdef _WIN32
 constexpr const char sDirSep = '\\';
+constexpr const char sPathSep = ';';
 #else
 constexpr const char sDirSep = '/';
+constexpr const char sPathSep = ':';
 #endif
 
 enum class FileType {
diff --git a/tools/aapt2/util/Util.h b/tools/aapt2/util/Util.h
index f89f8bf9dc44..c928458786e4 100644
--- a/tools/aapt2/util/Util.h
+++ b/tools/aapt2/util/Util.h
@@ -228,6 +228,12 @@ class Tokenizer {
  public:
   class iterator {
    public:
+    using reference = android::StringPiece&;
+    using value_type = android::StringPiece;
+    using difference_type = size_t;
+    using pointer = android::StringPiece*;
+    using iterator_category = std::forward_iterator_tag;
+
     iterator(const iterator&) = default;
     iterator& operator=(const iterator&) = default;
 
@@ -250,9 +256,13 @@ class Tokenizer {
 
   Tokenizer(const android::StringPiece& str, char sep);
 
-  iterator begin() { return begin_; }
+  iterator begin() const {
+    return begin_;
+  }
 
-  iterator end() { return end_; }
+  iterator end() const {
+    return end_;
+  }
 
  private:
   const iterator begin_;