Rotate frames correctly for back camera

media/capture/video/linux/camera_characteristics.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_characteristics.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>
+
+namespace media {
+
+// /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";
+static const int kUsbIdFullSize = 128;
+
+CameraCharacteristics::CameraCharacteristics() {
+  const base::FilePath path(kCameraCharacteristicsConfigFile);
+  if (!base::ReadFileToString(path, &content_)) {

[kcwu, 2016/11/24 10:16:08]

Don't have non-trivial code in ctor.

[shenghao, 2016/11/24 14:13:24]

Done.

+    DVLOG(1) << "ReadFileToString fails";
+    content_.erase();
+  } else {
+    InitializeDeviceInfo();
+  }
+}
+
+CameraCharacteristics::~CameraCharacteristics() {}
+
+int CameraCharacteristics::GetCameraFacing(const std::string& model_id,
+                                           const std::string& device_id) {
+  std::string usb_id = GetUsbId(device_id);
+  auto usb_id_iter = usb_id_to_camera_id_.find(usb_id);
+  int camera_id;
+  if (usb_id_iter == usb_id_to_camera_id_.end()) {
+    // Can't find Usb ID. Fall back to use model_id.
+    auto model_id_iter = model_id_to_camera_id_.find(model_id);
+    if (model_id_iter == model_id_to_camera_id_.end()) {
+      LOG(ERROR) << "Can't find model ID in config file: " << model_id;
+      return CameraDeviceInfo::LENS_FACING_FRONT;
+    }
+    camera_id = model_id_iter->second;
+  } else {
+    camera_id = usb_id_iter->second;
+  }
+
+  auto camera_id_iter = camera_id_to_facing_.find(camera_id);
+  if (camera_id_iter == camera_id_to_facing_.end()) {
+    LOG(ERROR) << "Can't find camera ID in config file: " << camera_id;
+    return CameraDeviceInfo::LENS_FACING_FRONT;
+  }
+  return camera_id_iter->second;
+}
+
+std::string CameraCharacteristics::GetUsbId(const std::string& device_id) {
+  // |device_id| is of the form "/dev/video2".  We want to retrieve "video2"
+  // into |file_name|.
+  const std::string device_dir = "/dev/";
+  DCHECK_EQ(0, device_id.compare(0, device_dir.length(), device_dir));

[kcwu, 2016/11/24 10:16:08]

DCHECK(base::StartsWith(device_id, device_dir, base::CompareCase::SENSITIVE));

if device_id is StringPiece, it has stars_with().

[shenghao, 2016/11/24 14:13:24]

Done.

+  const std::string file_name =
+      device_id.substr(device_dir.length(), device_id.length());

[kcwu, 2016/11/24 10:16:08]

device_id.substr(device_dir.length());
the second argument could be skip.

[shenghao, 2016/11/24 14:13:24]

Done.

+
+  // 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());
+  char usb_full[kUsbIdFullSize] = {0};
+  if (readlink(symlink.c_str(), usb_full, kUsbIdFullSize) == -1) {

[kcwu, 2016/11/24 10:16:08]

base::ReadSymbolicLink() then we can get rid of kUsbIdFullSize.

[shenghao, 2016/11/24 14:13:24]

Done.

+    LOG(ERROR) << "Failed to readlink: " << symlink;
+    return std::string();
+  }
+
+  // |usb_full| is of the format "../../../A-B:C.D". Remove the path prefix.
+  base::StringPiece usb_part = usb_full;

[kcwu, 2016/11/24 10:16:08]

If usb_full is base::FilePath, it has BaseName()

[shenghao, 2016/11/24 14:13:24]

Done.

+  usb_part.remove_prefix(usb_part.find_last_of("/") + 1);
+
+  // |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);
+  return usb_id_pieces[0].as_string();

[kcwu, 2016/11/24 10:16:08]

Check usb_id_pieces.size(), otherwise access usb_id_pieces[0] will crash.

[shenghao, 2016/11/24 14:13:24]

Done.

+}
+
+bool CameraCharacteristics::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);
+}
+
+void CameraCharacteristics::InitializeDeviceInfo() {
+  if (content_.empty()) {

[kcwu, 2016/11/24 10:16:08]

No need to keep |content_| in memory after parse.

[shenghao, 2016/11/24 14:13:24]

Done.

+    // The config file was not read successfully. Return early.
+    return;
+  }
+  std::vector<base::StringPiece> lines = base::SplitStringPiece(
+      content_, "\n", base::WhitespaceHandling::TRIM_WHITESPACE,
+      base::SplitResult::SPLIT_WANT_NONEMPTY);
+
+  for (base::StringPiece line : lines) {
+    if (line.starts_with(base::StringPiece("#"))) {

[kcwu, 2016/11/24 10:16:08]

line.starts_with("#")
IIUC, the good of StringPiece is that it will cast automatically.

[shenghao, 2016/11/24 14:13:25]

Done.

+      // Ignore the comments that starts with "#".
+      continue;
+    }
+    std::vector<base::StringPiece> key_value = base::SplitStringPiece(
+        line, "=", base::WhitespaceHandling::TRIM_WHITESPACE,
+        base::SplitResult::SPLIT_WANT_ALL);
+    if (key_value.size() != 2) {
+      LOG(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() == 2 && sub_keys[1] == kLensFacing) {
+      int lens_facing = CameraDeviceInfo::LENS_FACING_FRONT;
+      if (!base::StringToInt(value, &lens_facing)) {
+        LOG(ERROR) << "Invalid value for lens_facing: " << value;
+        continue;
+      }
+      int camera_id = 0;
+      if (!GetCameraId(sub_keys[0], &camera_id)) {
+        LOG(ERROR) << "Invalid sub key for camera id: " << sub_keys[0];
+        continue;
+      }
+      camera_id_to_facing_[camera_id] = lens_facing;
+    } else if (sub_keys.size() == 3 && sub_keys[2] == kUsbVidPid) {
+      int camera_id = 0;

[kcwu, 2016/11/24 10:16:08]

sub_keys[1] is not used?

[shenghao, 2016/11/24 14:13:24]

Yeah, the module number is not needed for our case

[kcwu, 2016/11/24 15:48:52]

What if the line is
camera0.helloworld.usb_vid_pid=0123:4567 ?

+      if (!GetCameraId(sub_keys[0], &camera_id)) {
+        LOG(ERROR) << "Invalid sub key for camera id: " << sub_keys[0];
+        continue;
+      }
+      if (value.empty()) {
+        LOG(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) {
+      int camera_id = 0;

[kcwu, 2016/11/24 10:16:08]

sub_keys[1] is not used?

[shenghao, 2016/11/24 14:13:24]

Yeah, the module number is not needed for our case

+      if (!GetCameraId(sub_keys[0], &camera_id)) {
+        LOG(ERROR) << "Invalid sub key for camera id: " << sub_keys[0];
+        continue;
+      }
+      if (value.empty()) {
+        LOG(ERROR) << "usb_path is empty";
+        continue;
+      }
+      usb_id_to_camera_id_[value] = camera_id;
+    }
+  }
+}
+
+}  // namespace media