lib/src/ioctl/decoder_cmd.rs

use crate::bindings;
use crate::bindings::v4l2_decoder_cmd;
use nix::errno::Errno;
use std::{
    convert::{Infallible, TryFrom},
    mem,
    os::unix::io::AsRawFd,
};
use thiserror::Error;

#[doc(hidden)]
mod ioctl {
    use crate::bindings::v4l2_decoder_cmd;
    nix::ioctl_readwrite!(vidioc_decoder_cmd, b'V', 96, v4l2_decoder_cmd);
    nix::ioctl_readwrite!(vidioc_try_decoder_cmd, b'V', 97, v4l2_decoder_cmd);
}

#[derive(Debug, Clone, Copy)]
pub enum DecoderCommand {
    // TODO: support extra data
    Start,
    // TODO: support extra data
    Stop,
    Pause,
    Resume,
}

#[derive(Debug, Error)]
pub enum DecoderCmdError {
    #[error("error while converting from v4l2_decoder_cmd")]
    FromV4L2CommandConversionError,
    #[error("drain already in progress")]
    DrainInProgress,
    #[error("command not supported by device")]
    UnsupportedCommand,
    #[error("ioctl error: {0}")]
    IoctlError(Errno),
}

impl From<DecoderCmdError> for Errno {
    fn from(err: DecoderCmdError) -> Self {
        match err {
            DecoderCmdError::FromV4L2CommandConversionError => Errno::EINVAL,
            DecoderCmdError::DrainInProgress => Errno::EBUSY,
            DecoderCmdError::UnsupportedCommand => Errno::EINVAL,
            DecoderCmdError::IoctlError(e) => e,
        }
    }
}

impl From<Errno> for DecoderCmdError {
    fn from(error: Errno) -> Self {
        match error {
            Errno::EBUSY => DecoderCmdError::DrainInProgress,
            Errno::EINVAL => DecoderCmdError::UnsupportedCommand,
            e => DecoderCmdError::IoctlError(e),
        }
    }
}

impl From<DecoderCommand> for v4l2_decoder_cmd {
    fn from(command: DecoderCommand) -> Self {
        v4l2_decoder_cmd {
            cmd: match &command {
                DecoderCommand::Start => bindings::V4L2_DEC_CMD_START,
                DecoderCommand::Stop => bindings::V4L2_DEC_CMD_STOP,
                DecoderCommand::Pause => bindings::V4L2_DEC_CMD_PAUSE,
                DecoderCommand::Resume => bindings::V4L2_DEC_CMD_RESUME,
            },
            ..unsafe { mem::zeroed() }
        }
    }
}

impl TryFrom<v4l2_decoder_cmd> for () {
    type Error = Infallible;

    fn try_from(_: v4l2_decoder_cmd) -> Result<Self, Self::Error> {
        Ok(())
    }
}

/// Safe wrapper around the `VIDIOC_DECODER_CMD` ioctl.
pub fn decoder_cmd<I: Into<v4l2_decoder_cmd>, O: TryFrom<v4l2_decoder_cmd>>(
    fd: &impl AsRawFd,
    command: I,
) -> Result<O, DecoderCmdError> {
    let mut dec_cmd = command.into();

    match unsafe { ioctl::vidioc_decoder_cmd(fd.as_raw_fd(), &mut dec_cmd) } {
        Ok(_) => Ok(
            O::try_from(dec_cmd).map_err(|_| DecoderCmdError::FromV4L2CommandConversionError)?
        ),
        Err(e) => Err(e.into()),
    }
}

/// Safe wrapper around the `VIDIOC_TRY_DECODER_CMD` ioctl.
pub fn try_decoder_cmd<I: Into<v4l2_decoder_cmd>, O: TryFrom<v4l2_decoder_cmd>>(
    fd: &impl AsRawFd,
    command: I,
) -> Result<O, DecoderCmdError> {
    let mut dec_cmd = command.into();

    match unsafe { ioctl::vidioc_try_decoder_cmd(fd.as_raw_fd(), &mut dec_cmd) } {
        Ok(_) => Ok(
            O::try_from(dec_cmd).map_err(|_| DecoderCmdError::FromV4L2CommandConversionError)?
        ),
        Err(e) => Err(e.into()),
    }
}