[libcamera-devel] [PATCH v5 2/4] libcamera: V4L2Device: Use std::vector for v4l2_ext_control in getControls()

[Hirokazu Honda]

The original code uses Variable-Length-Array, which is not
officially supported in C++. This replaces the array with
std::vector.

Signed-off-by: Hirokazu Honda <hiroh at chromium.org>
---
 src/libcamera/v4l2_device.cpp | 41 +++++++++++++++++------------------
 1 file changed, 20 insertions(+), 21 deletions(-)

diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
index ce2860c4..bbe8f154 100644
--- a/src/libcamera/v4l2_device.cpp
+++ b/src/libcamera/v4l2_device.cpp
@@ -173,13 +173,18 @@ void V4L2Device::close()
  */
 ControlList V4L2Device::getControls(const std::vector<uint32_t> &ids)
 {
-	unsigned int count = ids.size();
-	if (count == 0)
+	if (ids.empty())
 		return {};
 
 	ControlList ctrls{ controls_ };
+	std::vector<v4l2_ext_control> v4l2Ctrls(ids.size());
+	memset(v4l2Ctrls.data(), 0, sizeof(v4l2_ext_control) * ctrls.size());
+
+	for (size_t i = 0, j = 0; j < ids.size(); ++j) {
+		const unsigned int id = ids[j];
+		if (ctrls.contains(id))
+			continue;
 
-	for (uint32_t id : ids) {
 		const auto iter = controls_.find(id);
 		if (iter == controls_.end()) {
 			LOG(V4L2, Error)
@@ -187,20 +192,12 @@ ControlList V4L2Device::getControls(const std::vector<uint32_t> &ids)
 			return {};
 		}
 
-		ctrls.set(id, {});
-	}
-
-	struct v4l2_ext_control v4l2Ctrls[count];
-	memset(v4l2Ctrls, 0, sizeof(v4l2Ctrls));
-
-	unsigned int i = 0;
-	for (auto &ctrl : ctrls) {
-		unsigned int id = ctrl.first;
+		v4l2_ext_control &v4l2Ctrl = v4l2Ctrls[i++];
 		const struct v4l2_query_ext_ctrl &info = controlInfo_[id];
+		ControlValue value{};
 
 		if (info.flags & V4L2_CTRL_FLAG_HAS_PAYLOAD) {
 			ControlType type;
-
 			switch (info.type) {
 			case V4L2_CTRL_TYPE_U8:
 				type = ControlTypeByte;
@@ -213,7 +210,6 @@ ControlList V4L2Device::getControls(const std::vector<uint32_t> &ids)
 				return {};
 			}
 
-			ControlValue &value = ctrl.second;
 			value.reserve(type, true, info.elems);
 			Span<uint8_t> data = value.data();
 
@@ -221,21 +217,23 @@ ControlList V4L2Device::getControls(const std::vector<uint32_t> &ids)
 			v4l2Ctrls[i].size = data.size();
 		}
 
-		v4l2Ctrls[i].id = id;
-		i++;
+		v4l2Ctrl.id = id;
+		ctrls.set(id, std::move(value));
 	}
 
+	v4l2Ctrls.resize(ctrls.size());
+
 	struct v4l2_ext_controls v4l2ExtCtrls = {};
 	v4l2ExtCtrls.which = V4L2_CTRL_WHICH_CUR_VAL;
-	v4l2ExtCtrls.controls = v4l2Ctrls;
-	v4l2ExtCtrls.count = count;
+	v4l2ExtCtrls.controls = v4l2Ctrls.data();
+	v4l2ExtCtrls.count = v4l2Ctrls.size();
 
 	int ret = ioctl(VIDIOC_G_EXT_CTRLS, &v4l2ExtCtrls);
 	if (ret) {
 		unsigned int errorIdx = v4l2ExtCtrls.error_idx;
 
 		/* Generic validation error. */
-		if (errorIdx == 0 || errorIdx >= count) {
+		if (errorIdx == 0 || errorIdx >= v4l2Ctrls.size()) {
 			LOG(V4L2, Error) << "Unable to read controls: "
 					 << strerror(-ret);
 			return {};
@@ -244,10 +242,11 @@ ControlList V4L2Device::getControls(const std::vector<uint32_t> &ids)
 		/* A specific control failed. */
 		LOG(V4L2, Error) << "Unable to read control " << errorIdx
 				 << ": " << strerror(-ret);
-		count = errorIdx - 1;
+
+		v4l2Ctrls.resize(errorIdx);
 	}
 
-	updateControls(&ctrls, v4l2Ctrls, count);
+	updateControls(&ctrls, v4l2Ctrls.data(), v4l2Ctrls.size());
 
 	return ctrls;
 }
-- 
2.31.1.498.g6c1eba8ee3d-goog