chore: vendor trimmed v4l2r capture crate

libs/v4l2r/src/ioctl/enum_fmt.rs

@@ -0,0 +1,137 @@
+//! Safe wrapper for the `VIDIOC_ENUM_FMT` ioctl.
+use super::string_from_cstr;
+use crate::bindings;
+use crate::bindings::v4l2_fmtdesc;
+use crate::{PixelFormat, QueueType};
+use bitflags::bitflags;
+use log::error;
+use nix::errno::Errno;
+use std::fmt;
+use std::os::unix::io::AsRawFd;
+use thiserror::Error;
+
+bitflags! {
+    /// Flags returned by the `VIDIOC_ENUM_FMT` ioctl into the `flags` field of
+    /// `struct v4l2_fmtdesc`.
+    #[derive(Clone, Copy, Debug)]
+    pub struct FormatFlags: u32 {
+        const COMPRESSED = bindings::V4L2_FMT_FLAG_COMPRESSED;
+        const EMULATED = bindings::V4L2_FMT_FLAG_EMULATED;
+    }
+}
+/// Quickly get the Fourcc code of a format.
+impl From<v4l2_fmtdesc> for PixelFormat {
+    fn from(fmtdesc: v4l2_fmtdesc) -> Self {
+        fmtdesc.pixelformat.into()
+    }
+}
+
+/// Safe variant of the `v4l2_fmtdesc` struct, to be used with `enum_fmt`.
+#[derive(Debug)]
+pub struct FmtDesc {
+    pub flags: FormatFlags,
+    pub description: String,
+    pub pixelformat: PixelFormat,
+}
+
+impl fmt::Display for FmtDesc {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "{}: {} {}",
+            self.pixelformat,
+            self.description,
+            if self.flags.is_empty() {
+                "".into()
+            } else {
+                format!("({:?})", self.flags)
+            }
+        )
+    }
+}
+
+impl From<v4l2_fmtdesc> for FmtDesc {
+    fn from(fmtdesc: v4l2_fmtdesc) -> Self {
+        FmtDesc {
+            flags: FormatFlags::from_bits_truncate(fmtdesc.flags),
+            description: string_from_cstr(&fmtdesc.description).unwrap_or_else(|_| "".into()),
+            pixelformat: fmtdesc.pixelformat.into(),
+        }
+    }
+}
+
+#[doc(hidden)]
+mod ioctl {
+    use crate::bindings::v4l2_fmtdesc;
+    nix::ioctl_readwrite!(vidioc_enum_fmt, b'V', 2, v4l2_fmtdesc);
+}
+
+#[derive(Debug, Error)]
+pub enum EnumFmtError {
+    #[error("ioctl error: {0}")]
+    IoctlError(#[from] nix::Error),
+}
+
+impl From<EnumFmtError> for Errno {
+    fn from(err: EnumFmtError) -> Self {
+        match err {
+            EnumFmtError::IoctlError(e) => e,
+        }
+    }
+}
+
+/// Safe wrapper around the `VIDIOC_ENUM_FMT` ioctl.
+pub fn enum_fmt<T: From<v4l2_fmtdesc>>(
+    fd: &impl AsRawFd,
+    queue: QueueType,
+    index: u32,
+) -> Result<T, EnumFmtError> {
+    let mut fmtdesc = v4l2_fmtdesc {
+        type_: queue as u32,
+        index,
+        ..Default::default()
+    };
+    unsafe { ioctl::vidioc_enum_fmt(fd.as_raw_fd(), &mut fmtdesc) }?;
+
+    Ok(T::from(fmtdesc))
+}
+
+/// Iterator over the formats of the given queue. This takes a reference to the
+/// device's file descriptor so no operation that could affect the format
+/// enumeration can take place while the iterator exists.
+pub struct FormatIterator<'a, F: AsRawFd> {
+    fd: &'a F,
+    queue: QueueType,
+    index: u32,
+}
+
+impl<'a, F: AsRawFd> FormatIterator<'a, F> {
+    /// Create a new iterator listing all the currently valid formats on
+    /// `queue`.
+    pub fn new(fd: &'a F, queue: QueueType) -> Self {
+        FormatIterator {
+            fd,
+            queue,
+            index: 0,
+        }
+    }
+}
+
+impl<'a, F: AsRawFd> Iterator for FormatIterator<'a, F> {
+    type Item = FmtDesc;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match enum_fmt(self.fd, self.queue, self.index) {
+            Ok(fmtdesc) => {
+                self.index += 1;
+                Some(fmtdesc)
+            }
+            // EINVAL means we have reached the last format.
+            Err(EnumFmtError::IoctlError(Errno::EINVAL)) => None,
+            _ => {
+                error!("Unexpected return value for VIDIOC_ENUM_FMT!");
+                None
+            }
+        }
+    }
+}