Add the Base128OutputStream class

Test: later
Bug: N/A
Change-Id: I4271f6e05cfccc603d25f558c468bd02d632c647

3 files changed, 175 insertions, 0 deletions

diff --git a/emulator/screen-sharing-agent/app/src/main/cpp/CMakeLists.txt b/emulator/screen-sharing-agent/app/src/main/cpp/CMakeLists.txt
index ac076ec4bc2..7802a31464d 100644
--- a/emulator/screen-sharing-agent/app/src/main/cpp/CMakeLists.txt
+++ b/emulator/screen-sharing-agent/app/src/main/cpp/CMakeLists.txt
@@ -26,6 +26,7 @@ add_library(
         accessors/window_manager.cc
         agent.cc
         base128_input_stream.cc
+        base128_output_stream.cc
         control_messages.cc
         controller.cc
         display_streamer.cc
diff --git a/emulator/screen-sharing-agent/app/src/main/cpp/base128_output_stream.cc b/emulator/screen-sharing-agent/app/src/main/cpp/base128_output_stream.cc
new file mode 100644
index 00000000000..6b08c898e2b
--- /dev/null
+++ b/emulator/screen-sharing-agent/app/src/main/cpp/base128_output_stream.cc
@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2022 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 "base128_output_stream.h"
+
+#include <unistd.h>
+
+#include <memory>
+
+#include "io_exception.h"
+
+namespace screensharing {
+
+using namespace std;
+
+Base128OutputStream::Base128OutputStream(int fd, size_t buffer_size)
+    : fd_(fd),
+      buffer_(new uint8_t[buffer_size]),
+      buffer_capacity_(buffer_size),
+      offset_(0),
+      data_end_(0) {
+}
+
+Base128OutputStream::~Base128OutputStream() {
+  close(fd_);
+  delete [] buffer_;
+}
+
+int Base128OutputStream::Close() {
+  Flush();
+  return close(fd_);
+}
+
+void Base128OutputStream::Flush() {
+  while (offset_ > 0) {
+    auto n = write(fd_, buffer_, offset_);
+    if (n < 0) {
+      if (errno == EBADFD || errno == EPIPE) {
+        throw EndOfFile();
+      }
+      throw IoException();
+    }
+    assert(n <= offset_);  // By contract of the write function.
+    offset_ -= n;
+    if (offset_ > 0) {
+      memcpy(buffer_, buffer_ + n, offset_);
+    }
+  }
+}
+
+void Base128OutputStream::WriteByte(uint8_t byte) {
+  if (offset_ == buffer_capacity_) {
+    Flush();
+  }
+  buffer_[offset_++] = byte;
+}
+
+void Base128OutputStream::WriteBytes(const string& bytes) {
+  WriteInt32(bytes.size());
+  for (auto b : bytes) {
+    WriteByte(b);
+  }
+}
+
+void Base128OutputStream::WriteUInt16(uint16_t value) {
+  do {
+    uint8_t b = value & 0x7F;
+    value >>= 7;
+    if (value != 0) {
+      b |= 0x80;
+    }
+    WriteByte(b);
+  } while (value != 0);
+}
+
+void Base128OutputStream::WriteUInt32(uint32_t value) {
+  do {
+    uint8_t b = value & 0x7F;
+    value >>= 7;
+    if (value != 0) {
+      b |= 0x80;
+    }
+    WriteByte(b);
+  } while (value != 0);
+}
+
+void Base128OutputStream::WriteUInt64(uint64_t value) {
+  do {
+    uint8_t b = value & 0x7F;
+    value >>= 7;
+    if (value != 0) {
+      b |= 0x80;
+    }
+    WriteByte(b);
+  } while (value != 0);
+}
+
+void Base128OutputStream::WriteBool(bool value) {
+  WriteByte(value ? 1 : 0);
+}
+
+}  // namespace screensharing
diff --git a/emulator/screen-sharing-agent/app/src/main/cpp/base128_output_stream.h b/emulator/screen-sharing-agent/app/src/main/cpp/base128_output_stream.h
new file mode 100644
index 00000000000..4babbf04cb1
--- /dev/null
+++ b/emulator/screen-sharing-agent/app/src/main/cpp/base128_output_stream.h
@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2022 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.
+ */
+
+#pragma once
+
+#include <cerrno>
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+#include <string>
+
+#include "common.h"
+
+namespace screensharing {
+
+// An output stream that uses the unsigned little endian base 128 (<a xref="https://en.wikipedia.org/wiki/LEB128">LEB128</a>)
+// variable-length encoding for integer values.
+// See Base128InputStream.
+class Base128OutputStream {
+public:
+  Base128OutputStream(int fd, size_t buffer_size);
+  ~Base128OutputStream();
+
+  int Close();
+  void Flush();
+  void WriteByte(uint8_t byte);
+  void WriteBytes(const std::string& bytes);
+  void WriteUInt16(uint16_t value);
+  void WriteInt16(int16_t value) { WriteUInt16(value); }
+  void WriteUInt32(uint32_t value);
+  void WriteInt32(int32_t value) { WriteUInt32(value); }
+  void WriteUInt64(uint64_t value);
+  void WriteInt64(int64_t value) { WriteUInt64(value); }
+  void WriteBool(bool value);
+
+private:
+  int fd_;
+  uint8_t* buffer_;
+  size_t buffer_capacity_;
+  size_t offset_;
+  size_t data_end_;
+
+  DISALLOW_COPY_AND_ASSIGN(Base128OutputStream);
+};
+
+}  // namespace screensharing