[libvirt] [PATCH 1/2] libvirt-rust: Fix bugs in Stream::recv

[Martin Kletzander]

On Thu, Sep 19, 2019 at 05:48:37AM +0000, Linus Färnstrand wrote:
>* pass same size to virStreamRecv as the buffer has allocated
>* Handle -2 error case
>* Fix FFI declaration to take size_t instead of c_uint
>* Allow user to pass in buffer. To allow user to decide where to
>  allocate it. And to be able to re-use the same buffer
>* Don't try to treat binary data as a string
>
>Signed-off-by: Linus Färnstrand <faern at faern.net>
>---
> src/stream.rs | 21 +++++++++++----------
> 1 file changed, 11 insertions(+), 10 deletions(-)
>
>diff --git a/src/stream.rs b/src/stream.rs
>index 8333ee5..af6c8ec 100644
>--- a/src/stream.rs
>+++ b/src/stream.rs
>@@ -18,6 +18,7 @@
>
> extern crate libc;
>
>+use std::convert::TryFrom;
> use std::str;
>
> use error::Error;
>@@ -37,7 +38,7 @@ extern "C" {
>                      -> libc::c_int;
>     fn virStreamRecv(c: sys::virStreamPtr,
>                      data: *mut libc::c_char,
>-                     nbytes: libc::c_uint)
>+                     nbytes: libc::size_t)
>                      -> libc::c_int;
>     fn virStreamFree(c: sys::virStreamPtr) -> libc::c_int;
>     fn virStreamAbort(c: sys::virStreamPtr) -> libc::c_int;
>@@ -116,14 +117,14 @@ impl Stream {
>         }
>     }
>
>-    pub fn recv(&self, size: u32) -> Result<String, Error> {
>-        unsafe {
>-            let mut data: [libc::c_char; 2048] = ['\0' as i8; 2048];
>-            let ret = virStreamRecv(self.as_ptr(), data.as_mut_ptr(), size as libc::c_uint);
>-            if ret == -1 {
>-                return Err(Error::new());
>-            }
>-            return Ok(c_chars_to_string!(data.as_ptr()));
>-        }
>+    pub fn recv(&self, buf: &mut [u8]) -> Result<usize, Error> {
>+        let ret = unsafe {
>+            virStreamRecv(
>+                self.as_ptr(),
>+                buf.as_mut_ptr() as *mut libc::c_char,
>+                buf.len(),
>+            )
>+        };
>+        usize::try_from(ret).map_err(|_| Error::new())

This way it is impossible to distinguish -1 and -2.  We could get a bit closer
to std::io::Read if -2 gets transformed to 0, as we haven't read anything.

Other than that it's good.

>}
> }
>--
>2.21.0
>
>
>--
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