Separate mojo/shell into a runner and the application manager (shell)

mojo/shell/application_manager/data_pipe_peek.cc

-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "mojo/shell/application_manager/data_pipe_peek.h"
-
-#include <stdint.h>
-
-#include "base/bind.h"
-#include "base/macros.h"
-
-namespace mojo {
-namespace shell {
-
-namespace {
-
-// Sleep for as long as max_sleep_micros if the deadline hasn't been reached
-// and the number of bytes read is still increasing. Returns true if sleep
-// was actually called.
-//
-// This class is a substitute for being able to wait until N bytes are available
-// from a data pipe. The MaybeSleep method is called when num_bytes_read are
-// available but more are needed by the Peek operation. If a second
-// Peek operation finds the same number of bytes after sleeping we assume
-// that there's no point in trying again.
-// TODO(hansmuller): this heuristic is weak. crbug.com/429377
-class PeekSleeper {
- public:
-  explicit PeekSleeper(MojoTimeTicks deadline)
-      : deadline_(deadline),
-        last_number_bytes_read_(0) {}
-
-  bool MaybeSleep(uint32_t num_bytes_read) {
-    if (num_bytes_read > 0 && last_number_bytes_read_ >= num_bytes_read)
-      return false;
-    last_number_bytes_read_ = num_bytes_read;
-
-    MojoTimeTicks now(GetTimeTicksNow());
-    if (now > deadline_)
-      return false;
-
-    MojoTimeTicks sleep_time =
-        (deadline_ == 0) ? kMaxSleepMicros
-                         : std::min<int64>(deadline_ - now, kMaxSleepMicros);
-    base::PlatformThread::Sleep(base::TimeDelta::FromMicroseconds(sleep_time));
-    return true;
-  }
-
- private:
-  static const MojoTimeTicks kMaxSleepMicros = 1000 * 10;  // 10 ms
-
-  const MojoTimeTicks deadline_;  // 0 => MOJO_DEADLINE_INDEFINITE
-  uint32_t last_number_bytes_read_;
-
-  DISALLOW_COPY_AND_ASSIGN(PeekSleeper);
-};
-
-const MojoTimeTicks PeekSleeper::kMaxSleepMicros;
-
-enum PeekStatus { kSuccess, kFail, kKeepReading };
-typedef const base::Callback<PeekStatus(const void*, uint32_t, std::string*)>&
-    PeekFunc;
-
-// When data is available on source, call peek_func and then either return true
-// and value, continue waiting for enough data to satisfy peek_func, or fail
-// and return false. Fail if the timeout is exceeded.
-// This function is not guaranteed to work correctly if applied to a data pipe
-// that's already been read from.
-bool BlockingPeekHelper(DataPipeConsumerHandle source,
-                        std::string* value,
-                        MojoDeadline timeout,
-                        PeekFunc peek_func) {
-  DCHECK(value);
-  value->clear();
-
-  MojoTimeTicks deadline =
-      (timeout == MOJO_DEADLINE_INDEFINITE)
-          ? 0
-          : 1 + GetTimeTicksNow() + static_cast<MojoTimeTicks>(timeout);
-  PeekSleeper sleeper(deadline);
-
-  MojoResult result;
-  do {
-    const void* buffer;
-    uint32_t num_bytes;
-    result =
-        BeginReadDataRaw(source, &buffer, &num_bytes, MOJO_READ_DATA_FLAG_NONE);
-
-    if (result == MOJO_RESULT_OK) {
-      PeekStatus status = peek_func.Run(buffer, num_bytes, value);
-      CHECK_EQ(EndReadDataRaw(source, 0), MOJO_RESULT_OK);
-      switch (status) {
-        case PeekStatus::kSuccess:
-          return true;
-        case PeekStatus::kFail:
-          return false;
-        case PeekStatus::kKeepReading:
-          break;
-      }
-      if (!sleeper.MaybeSleep(num_bytes))
-        return false;
-    } else if (result == MOJO_RESULT_SHOULD_WAIT) {
-      MojoTimeTicks now(GetTimeTicksNow());
-      if (timeout == MOJO_DEADLINE_INDEFINITE || now < deadline)
-        result =
-            Wait(source, MOJO_HANDLE_SIGNAL_READABLE, deadline - now, nullptr);
-    }
-  } while (result == MOJO_RESULT_OK);
-
-  return false;
-}
-
-PeekStatus PeekLine(size_t max_line_length,
-                    const void* buffer,
-                    uint32_t buffer_num_bytes,
-                    std::string* line) {
-  const char* p = static_cast<const char*>(buffer);
-  size_t max_p_index = std::min<size_t>(buffer_num_bytes, max_line_length);
-  for (size_t i = 0; i < max_p_index; i++) {
-    if (p[i] == '\n') {
-      *line = std::string(p, i + 1);  // Include the trailing newline.
-      return PeekStatus::kSuccess;
-    }
-  }
-  return (buffer_num_bytes >= max_line_length) ? PeekStatus::kFail
-                                               : PeekStatus::kKeepReading;
-}
-
-PeekStatus PeekNBytes(size_t bytes_length,
-                      const void* buffer,
-                      uint32_t buffer_num_bytes,
-                      std::string* bytes) {
-  if (buffer_num_bytes >= bytes_length) {
-    const char* p = static_cast<const char*>(buffer);
-    *bytes = std::string(p, bytes_length);
-    return PeekStatus::kSuccess;
-  }
-  return PeekStatus::kKeepReading;
-}
-
-}  // namespace
-
-bool BlockingPeekNBytes(DataPipeConsumerHandle source,
-                        std::string* bytes,
-                        size_t bytes_length,
-                        MojoDeadline timeout) {
-  PeekFunc peek_nbytes = base::Bind(PeekNBytes, bytes_length);
-  return BlockingPeekHelper(source, bytes, timeout, peek_nbytes);
-}
-
-bool BlockingPeekLine(DataPipeConsumerHandle source,
-                      std::string* line,
-                      size_t max_line_length,
-                      MojoDeadline timeout) {
-  PeekFunc peek_line = base::Bind(PeekLine, max_line_length);
-  return BlockingPeekHelper(source, line, timeout, peek_line);
-}
-
-}  // namespace shell
-}  // namespace mojo