Rotate frames correctly for back camera

media/capture/video/linux/camera_facing_chromeos.cc

+// Copyright 2016 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 "camera_facing_chromeos.h"
+
+#include <base/files/file_util.h>
+#include <base/logging.h>
+#include <base/strings/stringprintf.h>
+#include <base/strings/string_number_conversions.h>
+#include <base/strings/string_piece.h>
+#include <base/strings/string_split.h>
+#include <base/strings/string_util.h>
+
+namespace media {
+
+namespace {
+
+bool GetCameraId(const base::StringPiece& sub_key, int* camera_id) {
+  const base::StringPiece camera_id_prefix = "camera";
+  if (!sub_key.starts_with(camera_id_prefix))
+    return false;
+  return base::StringToInt(sub_key.substr(camera_id_prefix.size()), camera_id);
+}
+}
+
+// /etc/camera/camera_characteristics.conf contains camera information which
+// driver cannot provide.
+static const char kCameraCharacteristicsConfigFile[] =
+    "/etc/camera/camera_characteristics.conf";
+static const char kLensFacing[] = "lens_facing";
+static const char kUsbVidPid[] = "usb_vid_pid";
+static const char kUsbPath[] = "usb_path";
+
+CameraFacingChromeOS::CameraFacingChromeOS() {
+  InitializeDeviceInfo(kCameraCharacteristicsConfigFile);
+}
+
+CameraFacingChromeOS::CameraFacingChromeOS(const char* config_file_path) {
+  InitializeDeviceInfo(config_file_path);
+}
+
+CameraFacingChromeOS::~CameraFacingChromeOS() {}
+
+CameraFacingChromeOS::LensFacing CameraFacingChromeOS::GetCameraFacing(
+    const std::string& device_id,
+    const std::string& model_id) const {
+  std::string usb_id = GetUsbId(device_id);
+  const auto& usb_id_to_camera_id_const = usb_id_to_camera_id_;
+  const auto& model_id_to_camera_id_const = model_id_to_camera_id_;
+  const auto& camera_id_to_facing_const = camera_id_to_facing_;
+  auto usb_id_iter = usb_id_to_camera_id_const.find(usb_id);
+  int camera_id;
+  if (usb_id_iter == usb_id_to_camera_id_const.end()) {
+    // Can't find Usb ID. Fall back to use model_id.
+    auto model_id_iter = model_id_to_camera_id_const.find(model_id);
+    if (model_id_iter == model_id_to_camera_id_const.end()) {
+      DLOG(ERROR) << "Can't find model ID in config file: " << model_id;
+      return kLensFacingDefault;
+    }
+    camera_id = model_id_iter->second;
+  } else {
+    camera_id = usb_id_iter->second;
+  }
+
+  auto camera_id_iter = camera_id_to_facing_const.find(camera_id);
+  if (camera_id_iter == camera_id_to_facing_const.end()) {
+    DLOG(ERROR) << "Can't find lens_facing of camera ID " << camera_id
+                << " in config file";
+    return kLensFacingDefault;
+  }
+  return camera_id_iter->second;
+}
+
+std::string CameraFacingChromeOS::GetUsbId(const std::string& device_id) const {
+  // |device_id| is of the form "/dev/video2".  We want to retrieve "video2"
+  // into |file_name|.
+  const std::string device_dir = "/dev/";
+  DCHECK(base::StartsWith(device_id, device_dir, base::CompareCase::SENSITIVE));
+  const std::string file_name = device_id.substr(device_dir.length());
+
+  // Usb ID can be obtained by "readlink /sys/class/video4linux/video2/device".
+  const std::string symlink =
+      base::StringPrintf("/sys/class/video4linux/%s/device", file_name.c_str());
+  base::FilePath symlinkTarget;
+  if (!base::ReadSymbolicLink(base::FilePath(symlink), &symlinkTarget)) {
+    DPLOG(ERROR) << "Failed to readlink: " << symlink;
+    return std::string();
+  }
+
+  // |symlinkTarget| is of the format "../../../A-B:C.D". Remove the path
+  // prefix.
+  base::StringPiece usb_part = symlinkTarget.BaseName().value();
+
+  // |usb_part| is of the format "A-B:C.D" or "A-B.C:D". We want everything
+  // before ":".
+  std::vector<base::StringPiece> usb_id_pieces = base::SplitStringPiece(
+      usb_part, ":", base::WhitespaceHandling::TRIM_WHITESPACE,
+      base::SplitResult::SPLIT_WANT_ALL);
+
+  if (usb_id_pieces.empty()) {
+    DLOG(ERROR) << "Error after split: " << usb_part;
+    return std::string();
+  }
+  return usb_id_pieces[0].as_string();
+}
+
+void CameraFacingChromeOS::InitializeDeviceInfo(const char* config_file_path) {
+  const base::FilePath path(config_file_path);
+  std::string content;
+  if (!base::ReadFileToString(path, &content)) {
+    DPLOG(ERROR) << "ReadFileToString fails";
+    return;
+  }
+  std::vector<base::StringPiece> lines = base::SplitStringPiece(

[mcasas, 2016/12/03 03:37:11]

nit: const

[shenghao, 2016/12/05 11:17:19]

Done.

+      content, "\n", base::WhitespaceHandling::TRIM_WHITESPACE,
+      base::SplitResult::SPLIT_WANT_NONEMPTY);
+
+  for (base::StringPiece line : lines) {

[mcasas, 2016/12/03 03:37:11]

const base::StringPiece& line

[shenghao, 2016/12/05 11:17:19]

Done.

+    if (line.starts_with("#")) {
+      // Ignore the comments that starts with "#".
+      continue;
+    }

[mcasas, 2016/12/03 03:37:11]

micro nit:
if (line.starts_with("#"))  // Ignore comment lines.
  continue;

[shenghao, 2016/12/05 11:17:20]

Done.

+    std::vector<base::StringPiece> key_value = base::SplitStringPiece(

[mcasas, 2016/12/03 03:37:11]

const ? Also in l.133, etc.  Essentially, try to 
const-ify as much as possible please.

[shenghao, 2016/12/05 11:17:19]

Done.

+        line, "=", base::WhitespaceHandling::TRIM_WHITESPACE,
+        base::SplitResult::SPLIT_WANT_ALL);
+    if (key_value.size() != 2) {
+      DLOG(ERROR) << "Invalid line in config file: " << line;
+      continue;
+    }
+    const auto& key = key_value[0];
+    const auto& value = key_value[1];
+    std::vector<base::StringPiece> sub_keys = base::SplitStringPiece(
+        key, ".", base::WhitespaceHandling::TRIM_WHITESPACE,
+        base::SplitResult::SPLIT_WANT_ALL);
+
+    if (sub_keys.size() < 1) {
+      DLOG(ERROR) << "No valid sub key exists. Line format is invalid: "
+                  << line;
+      continue;
+    }
+    int camera_id = 0;
+    if (!GetCameraId(sub_keys[0], &camera_id)) {
+      DLOG(ERROR) << "Invalid sub key for camera id: " << sub_keys[0];
+      continue;
+    }
+
+    if (sub_keys.size() == 2 && sub_keys[1] == kLensFacing) {
+      int lens_facing = -1;
+      if (!base::StringToInt(value, &lens_facing)) {
+        DLOG(ERROR) << "Invalid value for lens_facing: " << value;
+        continue;
+      }
+      switch (lens_facing) {
+        case LensFacing::FRONT:
+          camera_id_to_facing_[camera_id] = LensFacing::FRONT;
+          break;
+        case LensFacing::BACK:
+          camera_id_to_facing_[camera_id] = LensFacing::BACK;
+          break;
+        default:
+          DLOG(ERROR) << "Invalid value for lens_facing: " << lens_facing;
+          continue;
+      }
+    } else if (sub_keys.size() == 3 && sub_keys[2] == kUsbVidPid) {
+      if (value.empty()) {
+        DLOG(ERROR) << "model_id is empty";
+        continue;
+      }
+      model_id_to_camera_id_[value.as_string()] = camera_id;
+    } else if (sub_keys.size() == 3 && sub_keys[2] == kUsbPath) {
+      if (value.empty()) {
+        DLOG(ERROR) << "usb_path is empty";
+        continue;
+      }
+      usb_id_to_camera_id_[value.as_string()] = camera_id;
+    }
+    // Ignore unknown or unutilized attributes.
+  }
+}
+
+}  // namespace media