[vlc-devel] [RFC Patch v2 1/2] libvlc: Add Rust API for writing modules in rust
Kartik Ohri
kartikohri13 at gmail.com
Tue Sep 15 16:34:09 CEST 2020
On Tue, Sep 15, 2020 at 1:54 PM Alexandre Janniaux <ajanni at videolabs.io>
wrote:
> Hi,
>
> I have a few additional points :)
>
> On Sat, Sep 12, 2020 at 01:03:45AM +0530, Kartik Ohri wrote:
> > The API is written in two layers. vlccore-sys
> > crate contains one to one bindings of libvlc
> > functions. vlccore-rs crate wraps vlccore-sys and
> > exposes a Rust idiomatic API for writing modules
> > in rust. As of now, the API exposes only a subset
> > of the vlc_stream API. More functionality can be
> > added to Rust API as required in the future.
> > ---
> > .gitignore | 2 +-
> > configure.ac | 13 ++++
> > src/vlccore-rs/Cargo.toml | 10 +++
> > src/vlccore-rs/src/lib.rs | 1 +
> > src/vlccore-rs/src/stream.rs | 120 ++++++++++++++++++++++++++++++++++
> > src/vlccore-sys/Cargo.toml | 10 +++
> > src/vlccore-sys/src/lib.rs | 2 +
> > src/vlccore-sys/src/stream.rs | 24 +++++++
> > 8 files changed, 181 insertions(+), 1 deletion(-)
> > create mode 100644 src/vlccore-rs/Cargo.toml
> > create mode 100644 src/vlccore-rs/src/lib.rs
> > create mode 100644 src/vlccore-rs/src/stream.rs
> > create mode 100644 src/vlccore-sys/Cargo.toml
> > create mode 100644 src/vlccore-sys/src/lib.rs
> > create mode 100644 src/vlccore-sys/src/stream.rs
> >
> > diff --git a/.gitignore b/.gitignore
> > index fc368212c8..6c049a80b1 100644
> > --- a/.gitignore
> > +++ b/.gitignore
> > @@ -46,7 +46,7 @@ wxvlc
> > vlc_install_dir/*
> > plugins.dat
> > patches/*
> > -
> > +**/Cargo.lock
> > include/vlc/libvlc_version.h
> >
> > # Ignore build dirs
> > diff --git a/configure.ac b/configure.ac
> > index 99e4669942..53d56a725c 100644
> > --- a/configure.ac
> > +++ b/configure.ac
> > @@ -1896,6 +1896,19 @@ AS_IF([test "${enable_sout}" != "no"], [
> > ])
> > AM_CONDITIONAL([ENABLE_SOUT], [test "${enable_sout}" != "no"])
> >
> > +dnl Rust Modules
> > +AC_ARG_ENABLE([rust],
> > + AS_HELP_STRING([--enable-rust], [enable building Rust modules
> (default disabled)]))
> > +AS_IF([test "${enable_rust}" = "yes"],
> > + [AC_DEFINE(ENABLE_RUST, 1, [Define to 1 for building rust
> modules.])])
> > +AM_CONDITIONAL([BUILD_RUST], [test "${enable_rust}" = "yes"])
> > +if test "${enable_rust}" = "yes"
> > +then
> > + AC_CHECK_PROG(CARGO, [cargo], [yes], [no])
> > + AS_IF([test "x$CARGO" = "xno"],
> > + AC_MSG_ERROR([cargo not found. cargo is required to build
> rust modules]))
> > +fi
> > +
> > dnl Lua modules
> > AC_ARG_ENABLE([lua],
> > AS_HELP_STRING([--disable-lua],
> > diff --git a/src/vlccore-rs/Cargo.toml b/src/vlccore-rs/Cargo.toml
> > new file mode 100644
> > index 0000000000..108c849f80
> > --- /dev/null
> > +++ b/src/vlccore-rs/Cargo.toml
> > @@ -0,0 +1,10 @@
> > +[package]
> > +name = "vlccore-rs"
> > +version = "0.1.0"
> > +authors = ["Kartik Ohri <kartikohri13 at gmail.com>"]
> > +edition = "2018"
> > +license = "LGPL-2.1-or-later"
> > +
> > +[dependencies]
> > +libc = "0.2"
> > +vlccore-sys = {path="../vlccore-sys"}
> > \ No newline at end of file
> > diff --git a/src/vlccore-rs/src/lib.rs b/src/vlccore-rs/src/lib.rs
> > new file mode 100644
> > index 0000000000..baf29e06ad
> > --- /dev/null
> > +++ b/src/vlccore-rs/src/lib.rs
> > @@ -0,0 +1 @@
> > +pub mod stream;
> > diff --git a/src/vlccore-rs/src/stream.rs b/src/vlccore-rs/src/stream.rs
> > new file mode 100644
> > index 0000000000..0725a8fe6e
> > --- /dev/null
> > +++ b/src/vlccore-rs/src/stream.rs
> > @@ -0,0 +1,120 @@
> > +use libc::{c_char, c_void};
> > +use std::ffi::{CStr, CString};
> > +use std::io::{Error, ErrorKind, Read, Result, Seek, SeekFrom};
> > +use std::ptr::null_mut;
> > +use vlccore_sys::stream as ffi;
> > +
> > +pub struct Stream {
> > + stream: *mut ffi::stream_t,
> > +}
> > +
> > +impl Read for Stream {
> > + fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
> > + let bytes_read: isize = unsafe {
> > + ffi::vlc_stream_Read(self.stream, buf.as_mut_ptr() as *mut
> c_void, buf.len())
> > + };
> > + if bytes_read < 0 {
> > + Err(Error::new(
> > + ErrorKind::Other,
> > + "Error while reading from stream",
> > + ))
> > + } else {
> > + Ok(bytes_read as usize)
> > + }
> > + }
> > +}
> > +
> > +impl Seek for Stream {
> > + fn seek(&mut self, pos: SeekFrom) -> Result<u64> {
> > + let offset = match pos {
> > + SeekFrom::Start(n) => n,
> > + SeekFrom::Current(n) => {
> > + let len = self.position();
> > + if n >= 0 {
> > + len.checked_add(n as u64)
> > + } else {
> > + len.checked_sub(n.wrapping_neg() as u64)
> > + }
> > + .ok_or(Error::new(ErrorKind::Other, "Position
> Overflow"))?
> > + }
> > + SeekFrom::End(n) => self.len().and_then(|position| {
> > + if n >= 0 {
> > + position.checked_add(n as u64)
> > + } else {
> > + position.checked_sub(n.wrapping_neg() as u64)
> > + }
> > + .ok_or(Error::new(ErrorKind::Other, "Position
> Overflow"))
> > + })?,
> > + };
> > +
> > + let result = unsafe { ffi::vlc_stream_Seek(self.stream, offset)
> };
> > + if result != 0 {
> > + return Err(Error::new(ErrorKind::Other, "Could not seek
> stream"));
> > + }
> > + Ok(offset)
> > + }
> > +}
> > +
> > +impl Drop for Stream {
> > + fn drop(&mut self) {
> > + unsafe { ffi::vlc_stream_Delete(self.stream) }
> > + }
> > +}
> > +
> > +impl From<*mut ffi::stream_t> for Stream {
> > + fn from(stream: *mut ffi::stream_t) -> Self {
> > + Stream { stream }
> > + }
> > +}
> > +
> > +impl Stream {
> > + pub fn len(&self) -> std::result::Result<u64, Error> {
> > + let size: u64 = 0;
> > + const STREAM_GET_SIZE: i32 = 6;
> > + let result = unsafe { ffi::vlc_stream_vaControl(self.stream,
> STREAM_GET_SIZE, &size) };
> > + if result != 0 {
> > + return Err(Error::new(
> > + ErrorKind::Other,
> > + "Could not determine stream size",
> > + ));
> > + }
> > + Ok(size)
> > + }
> > +
> > + pub fn position(&self) -> u64 {
> > + unsafe { ffi::vlc_stream_Tell(self.stream) }
> > + }
> > +
> > + pub fn eof(&self) -> Result<bool> {
> > + Ok(unsafe { ffi::vlc_stream_Eof(self.stream) })
> > + }
> > +
> > + pub fn mimetype(&self) -> Option<String> {
> > + self.contenttype().map(|content_type| {
> > + let index = content_type.chars().position(|c| c ==
> ';').unwrap();
> > + let mime_type: String = content_type[..index].to_owned();
> > + mime_type
> > + })
>
> Since you don't chain map, you can probably just use early return here.
>
> pub fn mimetype(&self) -> Option<String> {
> let contenttype = self.contenttype()?;
> let index = content_type.chars().position(|c| c == ';')?;
> Some(content_type[..index].to_owned())
> }
>
> Will fix!
> > + }
> > +
> > + pub fn contenttype(&self) -> Option<String> {
> > + // FIXME: STREAM_GET_CONTENT_TYPE does not have a fixed value
> > + const STREAM_GET_CONTENT_TYPE: i32 = 0;
> > + let result: *mut c_char = null_mut();
> > + unsafe {
> > + if ffi::vlc_stream_vaControl(self.stream,
> STREAM_GET_CONTENT_TYPE, result) != 0 {
> > + return None;
> > + } else if result.is_null() {
> > + return None;
> > + }
> > + // FIXME: Free the C pointer received but retain copy of
> data in Rust
> > + CStr::from_ptr(result).to_str().map(|s| s.to_string()).ok()
> > + }
> > + }
> > +
> > + pub fn new_with_url(&mut self, url: &str) -> Self {
> > + let c_url = CString::new(url).unwrap().as_ptr();
> > + let stream = unsafe { ffi::vlc_stream_NewURL(self.stream,
> c_url) };
> > + Stream { stream }
> > + }
> > +}
> > diff --git a/src/vlccore-sys/Cargo.toml b/src/vlccore-sys/Cargo.toml
> > new file mode 100644
> > index 0000000000..0dde7b2e7d
> > --- /dev/null
> > +++ b/src/vlccore-sys/Cargo.toml
> > @@ -0,0 +1,10 @@
> > +[package]
> > +name = "vlccore-sys"
> > +version = "0.1.0"
> > +authors = ["Kartik Ohri <kartikohri13 at gmail.com>"]
> > +edition = "2018"
> > +license = "LGPL-2.1-or-later"
> > +
> > +[dependencies]
> > +libc = "0.2"
> > +
> > diff --git a/src/vlccore-sys/src/lib.rs b/src/vlccore-sys/src/lib.rs
> > new file mode 100644
> > index 0000000000..42a75452cd
> > --- /dev/null
> > +++ b/src/vlccore-sys/src/lib.rs
> > @@ -0,0 +1,2 @@
> > +#![allow(non_camel_case_types)]
> > +pub mod stream;
> > diff --git a/src/vlccore-sys/src/stream.rs b/src/vlccore-sys/src/
> stream.rs
> > new file mode 100644
> > index 0000000000..c9e8d5f0b3
> > --- /dev/null
> > +++ b/src/vlccore-sys/src/stream.rs
> > @@ -0,0 +1,24 @@
> > +use libc::{c_char, c_int, c_void, size_t, ssize_t};
> > +
> > +#[repr(C)]
> > +pub struct stream_t {
> > + _private: [u8; 0],
> > +}
> > +
> > +pub type vlc_object_t = stream_t;
> > +
> > +extern "C" {
> > + pub fn vlc_stream_Read(s: *mut stream_t, buf: *mut c_void, len:
> size_t) -> ssize_t;
> > +
> > + pub fn vlc_stream_Tell(s: *const stream_t) -> u64;
> > +
> > + pub fn vlc_stream_Eof(s: *const stream_t) -> bool;
> > +
> > + pub fn vlc_stream_Seek(s: *mut stream_t, offset: u64) -> c_int;
> > +
> > + pub fn vlc_stream_vaControl(s: *mut stream_t, query: c_int, ...) ->
> c_int;
>
> After checking [1], you probably need the following code instead:
>
> extern "C" {
> pub unsafe fn vlc_stream_vaControl(s: *mut stream_t, query: c_int,
> ap: VaList) -> c_int;
> }
> pub unsafe fn vlc_stream_Control(s: *mut stream_t, query: c_int, mut
> args: ...) -> c_int {
> vlc_stream_vaControl(s, query, args)
> }
>
> Otherwise, as far as I understand this document, va_start/va_end might not
> be called correctly.
> I haven't checked in details though, and it needs the
> #![feature(c_variadic)] attribute.
>
> [1]
> https://github.com/rust-lang/rfcs/blob/26197104b7bb9a5a35db243d639aee6e46d35d75/text/2137-variadic.md
>
>
You are probably right. In that case, the RFC is not yet stabilized so
should we drop this part till then from the patch ?
> +
> > + pub fn vlc_stream_Delete(s: *mut stream_t);
> > +
> > + pub fn vlc_stream_NewURL(obj: *mut vlc_object_t, url: *const
> c_char) -> *mut stream_t;
> > +}
> > --
> > 2.25.1
> >
> > _______________________________________________
> > vlc-devel mailing list
> > To unsubscribe or modify your subscription options:
> > https://mailman.videolan.org/listinfo/vlc-devel
>
>
> Regards,
> --
> Alexandre Janniaux
> Videolabs
> _______________________________________________
> vlc-devel mailing list
> To unsubscribe or modify your subscription options:
> https://mailman.videolan.org/listinfo/vlc-devel
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