AAPT2: Fix windows unicode path issues

Mingw64 was being difficult, so instead of defining a wmain entrypoint,
the command line parameters are parsed manually using built-in Windows
methods that support Unicode. The results are converted to UTF8 and
handled just like the rest of the linux/mac version of the code.

This also removes dependencies on std::istream in favour of a
FileInputStream which calls the appropriate unicode version of
open to read a file.

No speed regressions found on Linux or MacOS.

Bug: 62336414
Bug: 63830502
Test: manual
Change-Id: I597da51e33729ed1b98bf246e7e773337fd3fee8
diff --git a/tools/aapt2/io/FileInputStream.cpp b/tools/aapt2/io/FileInputStream.cpp
new file mode 100644
index 0000000..07dbb5a
--- /dev/null
+++ b/tools/aapt2/io/FileInputStream.cpp
@@ -0,0 +1,102 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#include "io/FileInputStream.h"
+
+#include <errno.h>   // for errno
+#include <fcntl.h>   // for O_RDONLY
+#include <unistd.h>  // for read
+
+#include "android-base/errors.h"
+#include "android-base/file.h"  // for O_BINARY
+#include "android-base/macros.h"
+#include "android-base/utf8.h"
+
+using ::android::base::SystemErrorCodeToString;
+
+namespace aapt {
+namespace io {
+
+FileInputStream::FileInputStream(const std::string& path, size_t buffer_capacity)
+    : FileInputStream(::android::base::utf8::open(path.c_str(), O_RDONLY | O_BINARY),
+                      buffer_capacity) {
+}
+
+FileInputStream::FileInputStream(int fd, size_t buffer_capacity)
+    : fd_(fd),
+      buffer_capacity_(buffer_capacity),
+      buffer_offset_(0u),
+      buffer_size_(0u),
+      total_byte_count_(0u) {
+  if (fd_ == -1) {
+    error_ = SystemErrorCodeToString(errno);
+  } else {
+    buffer_.reset(new uint8_t[buffer_capacity_]);
+  }
+}
+
+bool FileInputStream::Next(const void** data, size_t* size) {
+  if (HadError()) {
+    return false;
+  }
+
+  // Deal with any remaining bytes after BackUp was called.
+  if (buffer_offset_ != buffer_size_) {
+    *data = buffer_.get() + buffer_offset_;
+    *size = buffer_size_ - buffer_offset_;
+    total_byte_count_ += buffer_size_ - buffer_offset_;
+    buffer_offset_ = buffer_size_;
+    return true;
+  }
+
+  ssize_t n = TEMP_FAILURE_RETRY(read(fd_, buffer_.get(), buffer_capacity_));
+  if (n < 0) {
+    error_ = SystemErrorCodeToString(errno);
+    fd_.reset();
+    return false;
+  }
+
+  buffer_size_ = static_cast<size_t>(n);
+  buffer_offset_ = buffer_size_;
+  total_byte_count_ += buffer_size_;
+
+  *data = buffer_.get();
+  *size = buffer_size_;
+  return buffer_size_ != 0u;
+}
+
+void FileInputStream::BackUp(size_t count) {
+  if (count > buffer_offset_) {
+    count = buffer_offset_;
+  }
+  buffer_offset_ -= count;
+  total_byte_count_ -= count;
+}
+
+size_t FileInputStream::ByteCount() const {
+  return total_byte_count_;
+}
+
+bool FileInputStream::HadError() const {
+  return !error_.empty();
+}
+
+std::string FileInputStream::GetError() const {
+  return error_;
+}
+
+}  // namespace io
+}  // namespace aapt