io: Consolidate Arena types

Less maintenance burden, more visibility due to the implementations
residing in a single file again.

Signed-off-by: Christopher N. Hesse <raymanfx@gmail.com>

src/io/mmap/mod.rs

@@ -1,4 +1,2 @@
-pub(crate) mod arena;
-
 pub mod stream;
 pub use stream::Stream;

src/io/mmap/stream.rs

@@ -6,17 +6,17 @@ use v4l2_sys::v4l2_buffer;
 
 use crate::buffer::{Metadata, Type};
 use crate::device::{Device, Handle};
-use crate::io::mmap::arena::Arena;
 use crate::io::traits::{CaptureStream, OutputStream, Stream as StreamTrait};
-use crate::memory::Memory;
+use crate::io::Arena;
+use crate::memory::{Memory, Mmap};
 use crate::v4l2;
 
 /// Stream of mapped buffers
 ///
 /// An arena instance is used internally for buffer handling.
 pub struct Stream<'a> {
     handle: Arc<Handle>,
-    arena: Arena<'a>,
+    arena: Arena<Mmap<'a>>,
     arena_index: usize,
     buf_type: Type,
     buf_meta: Vec<Metadata>,
@@ -50,7 +50,7 @@ impl<'a> Stream<'a> {
     }
 
     pub fn with_buffers(dev: &Device, buf_type: Type, buf_count: u32) -> io::Result<Self> {
-        let mut arena = Arena::new(dev.handle(), buf_type);
+        let mut arena = Arena::<Mmap<'a>>::new(dev.handle(), buf_type);
         let count = arena.allocate(buf_count)?;
         let mut buf_meta = Vec::new();
         buf_meta.resize(count as usize, Metadata::default());

src/io/mod.rs

@@ -2,3 +2,174 @@ pub mod traits;
 
 pub mod mmap;
 pub mod userptr;
+
+use std::{io, mem, ptr, slice, sync::Arc};
+
+use v4l2_sys::{v4l2_buffer, v4l2_format, v4l2_requestbuffers};
+
+use crate::buffer;
+use crate::device::Handle;
+use crate::memory::{Memory, Mmap, UserPtr};
+use crate::v4l2;
+
+/// Manage mapped buffers
+///
+/// All buffers are unmapped in the Drop impl.
+/// In case of errors during unmapping, we panic because there is memory corruption going on.
+pub(crate) struct Arena<T> {
+    handle: Arc<Handle>,
+    pub bufs: Vec<T>,
+    pub buf_mem: Memory,
+    pub buf_type: buffer::Type,
+}
+
+impl<T> Arena<T> {
+    fn request(&mut self, count: u32) -> io::Result<u32> {
+        // free all buffers by requesting 0
+        let mut v4l2_reqbufs = v4l2_requestbuffers {
+            count,
+            type_: self.buf_type as u32,
+            memory: self.buf_mem as u32,
+            ..unsafe { mem::zeroed() }
+        };
+        unsafe {
+            v4l2::ioctl(
+                self.handle.fd(),
+                v4l2::vidioc::VIDIOC_REQBUFS,
+                &mut v4l2_reqbufs as *mut _ as *mut std::os::raw::c_void,
+            )?;
+        }
+
+        Ok(v4l2_reqbufs.count)
+    }
+}
+
+impl<T> Drop for Arena<T> {
+    fn drop(&mut self) {
+        if self.bufs.is_empty() {
+            // nothing to do
+            return;
+        }
+
+        // free all buffers by requesting 0
+        if let Err(e) = self.request(0) {
+            if let Some(code) = e.raw_os_error() {
+                // ENODEV means the file descriptor wrapped in the handle became invalid, most
+                // likely because the device was unplugged or the connection (USB, PCI, ..)
+                // broke down. Handle this case gracefully by ignoring it.
+                if code == 19 {
+                    /* ignore */
+                    return;
+                }
+            }
+
+            panic!("{:?}", e)
+        }
+    }
+}
+
+impl<'a> Arena<Mmap<'a>> {
+    /// Returns a new buffer manager instance
+    ///
+    /// You usually do not need to use this directly.
+    /// A MappedBufferStream creates its own manager instance by default.
+    ///
+    /// # Arguments
+    ///
+    /// * `handle` - Device handle to get its file descriptor
+    /// * `buf_type` - Type of the buffers
+    pub fn new(handle: Arc<Handle>, buf_type: buffer::Type) -> Self {
+        Arena {
+            handle,
+            bufs: Vec::new(),
+            buf_mem: Memory::Mmap,
+            buf_type,
+        }
+    }
+
+    pub fn allocate(&mut self, count: u32) -> io::Result<u32> {
+        let count = self.request(count)?;
+        for index in 0..count {
+            let mut v4l2_buf = v4l2_buffer {
+                index,
+                type_: self.buf_type as u32,
+                memory: self.buf_mem as u32,
+                ..unsafe { mem::zeroed() }
+            };
+            unsafe {
+                v4l2::ioctl(
+                    self.handle.fd(),
+                    v4l2::vidioc::VIDIOC_QUERYBUF,
+                    &mut v4l2_buf as *mut _ as *mut std::os::raw::c_void,
+                )?;
+
+                let ptr = v4l2::mmap(
+                    ptr::null_mut(),
+                    v4l2_buf.length as usize,
+                    libc::PROT_READ | libc::PROT_WRITE,
+                    libc::MAP_SHARED,
+                    self.handle.fd(),
+                    v4l2_buf.m.offset as libc::off_t,
+                )?;
+
+                let slice =
+                    slice::from_raw_parts_mut::<u8>(ptr as *mut u8, v4l2_buf.length as usize);
+                self.bufs.push(Mmap(slice));
+            }
+        }
+
+        Ok(count)
+    }
+}
+
+impl Arena<UserPtr> {
+    /// Returns a new buffer manager instance
+    ///
+    /// You usually do not need to use this directly.
+    /// A MappedBufferStream creates its own manager instance by default.
+    ///
+    /// # Arguments
+    ///
+    /// * `handle` - Device handle to get its file descriptor
+    /// * `buf_type` - Type of the buffers
+    pub fn new(handle: Arc<Handle>, buf_type: buffer::Type) -> Self {
+        Arena {
+            handle,
+            bufs: Vec::new(),
+            buf_mem: Memory::UserPtr,
+            buf_type,
+        }
+    }
+
+    pub fn allocate(&mut self, count: u32) -> io::Result<u32> {
+        // we need to get the maximum buffer size from the format first
+        let mut v4l2_fmt = v4l2_format {
+            type_: self.buf_type as u32,
+            ..unsafe { mem::zeroed() }
+        };
+        unsafe {
+            v4l2::ioctl(
+                self.handle.fd(),
+                v4l2::vidioc::VIDIOC_G_FMT,
+                &mut v4l2_fmt as *mut _ as *mut std::os::raw::c_void,
+            )?;
+        }
+
+        #[cfg(feature = "v4l-sys")]
+        eprintln!(
+            "\n### WARNING ###\n\
+As of early 2020, libv4l2 still does not support USERPTR buffers!\n\
+You may want to use this crate with the raw v4l2 FFI bindings instead!\n"
+        );
+
+        // allocate the new user buffers
+        let count = self.request(count)?;
+        for _ in 0..count {
+            let size = unsafe { v4l2_fmt.fmt.pix.sizeimage };
+            let buf = vec![0u8; size as usize];
+            self.bufs.push(UserPtr(buf));
+        }
+
+        Ok(count)
+    }
+}