diff --git a/tools/ijar/ijar.cc b/tools/ijar/ijar.cc
new file mode 100644
index 0000000..1925b48
--- /dev/null
+++ b/tools/ijar/ijar.cc
@@ -0,0 +1,182 @@
+// Copyright 2001,2007 Alan Donovan. All rights reserved.
+//
+// Author: Alan Donovan <adonovan@google.com>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// ijar.cpp -- .jar -> _interface.jar tool.
+//
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <errno.h>
+#include <memory>
+
+#include "zip.h"
+
+namespace devtools_ijar {
+
+bool verbose = false;
+
+// Reads a JVM class from classdata_in (of the specified length), and
+// writes out a simplified class to classdata_out, advancing the
+// pointer.
+void StripClass(u1 *&classdata_out, const u1 *classdata_in, size_t in_length);
+
+const char* CLASS_EXTENSION = ".class";
+const size_t CLASS_EXTENSION_LENGTH = strlen(CLASS_EXTENSION);
+
+// ZipExtractorProcessor that select only .class file and use
+// StripClass to generate an interface class, storing as a new file
+// in the specified ZipBuilder.
+class JarStripperProcessor : public ZipExtractorProcessor {
+ public:
+  JarStripperProcessor() {}
+  virtual ~JarStripperProcessor() {}
+
+  virtual void Process(const char* filename, const u4 attr,
+                       const u1* data, const size_t size);
+  virtual bool Accept(const char* filename, const u4 attr);
+
+ private:
+  // Not owned by JarStripperProcessor, see SetZipBuilder().
+  ZipBuilder* builder;
+
+ public:
+  // Set the ZipBuilder to add the ijar class to the output zip file.
+  // This pointer should not be deleted while this class is still in use and
+  // it should be set before any call to the Process() method.
+  void SetZipBuilder(ZipBuilder* builder) {
+    this->builder = builder;
+  }
+};
+
+bool JarStripperProcessor::Accept(const char* filename, const u4) {
+  ssize_t offset = strlen(filename) - CLASS_EXTENSION_LENGTH;
+  if (offset >= 0) {
+    return strcmp(filename + offset, CLASS_EXTENSION) == 0;
+  }
+  return false;
+}
+
+void JarStripperProcessor::Process(const char* filename, const u4,
+                                   const u1* data, const size_t size) {
+  if (verbose) {
+    fprintf(stderr, "INFO: StripClass: %s\n", filename);
+  }
+  u1 *q = builder->NewFile(filename, 0);
+  u1 *classdata_out = q;
+  StripClass(q, data, size);  // actually process it
+  size_t out_length = q - classdata_out;
+  builder->FinishFile(out_length);
+}
+
+// Opens "file_in" (a .jar file) for reading, and writes an interface
+// .jar to "file_out".
+void OpenFilesAndProcessJar(const char *file_out, const char *file_in) {
+  JarStripperProcessor processor;
+  std::unique_ptr<ZipExtractor> in(ZipExtractor::Create(file_in, &processor));
+  if (in.get() == NULL) {
+    fprintf(stderr, "Unable to open Zip file %s: %s\n", file_in,
+            strerror(errno));
+    abort();
+  }
+  u8 output_length = in->CalculateOutputLength();
+  std::unique_ptr<ZipBuilder> out(ZipBuilder::Create(file_out, output_length));
+  if (out.get() == NULL) {
+    fprintf(stderr, "Unable to open output file %s: %s\n", file_out,
+            strerror(errno));
+    abort();
+  }
+  processor.SetZipBuilder(out.get());
+
+  // Process all files in the zip
+  if (in->ProcessAll() < 0) {
+    fprintf(stderr, "%s\n", in->GetError());
+    abort();
+  }
+
+  // Add dummy file, since javac doesn't like truly empty jars.
+  if (out->GetNumberFiles() == 0) {
+    out->WriteEmptyFile("dummy");
+  }
+  // Finish writing the output file
+  if (out->Finish() < 0) {
+    fprintf(stderr, "%s\n", out->GetError());
+    abort();
+  }
+  // Get all file size
+  size_t in_length = in->GetSize();
+  size_t out_length = out->GetSize();
+  if (verbose) {
+    fprintf(stderr, "INFO: produced interface jar: %s -> %s (%d%%).\n",
+            file_in, file_out,
+            static_cast<int>(100.0 * out_length / in_length));
+  }
+}
+
+}  // namespace devtools_ijar
+
+//
+// main method
+//
+static void usage() {
+  fprintf(stderr, "Usage: ijar [-v] x.jar [x_interface.jar>]\n");
+  fprintf(stderr, "Creates an interface jar from the specified jar file.\n");
+  exit(1);
+}
+
+int main(int argc, char **argv) {
+  const char *filename_in = NULL;
+  const char *filename_out = NULL;
+
+  for (int ii = 1; ii < argc; ++ii) {
+    if (strcmp(argv[ii], "-v") == 0) {
+      devtools_ijar::verbose = true;
+    } else if (filename_in == NULL) {
+      filename_in = argv[ii];
+    } else if (filename_out == NULL) {
+      filename_out = argv[ii];
+    } else {
+      usage();
+    }
+  }
+
+  if (filename_in == NULL) {
+    usage();
+  }
+
+  // Guess output filename from input:
+  char filename_out_buf[PATH_MAX];
+  if (filename_out == NULL) {
+    size_t len = strlen(filename_in);
+    if (len > 4 && strncmp(filename_in + len - 4, ".jar", 4) == 0) {
+      strcpy(filename_out_buf, filename_in);
+      strcpy(filename_out_buf + len - 4, "-interface.jar");
+      filename_out = filename_out_buf;
+    } else {
+      fprintf(stderr, "Can't determine output filename since input filename "
+              "doesn't end with '.jar'.\n");
+      return 1;
+    }
+  }
+
+  if (devtools_ijar::verbose) {
+    fprintf(stderr, "INFO: writing to '%s'.\n", filename_out);
+  }
+
+  devtools_ijar::OpenFilesAndProcessJar(filename_out, filename_in);
+  return 0;
+}