Add API to create a Buffer from a Vec<u8> with memory reuse and use it for the Speex headers

gst-plugin-flv/src/flvdemux.rs

@@ -194,10 +194,8 @@ impl AudioFormat {
                 })
             }
             flavors::SoundFormat::SPEEX => {
-                let mut header = Buffer::new_with_size(80).unwrap();
-                {
-                    let mut map = header.map_readwrite().unwrap();
-                    let mut data = Cursor::new(map.as_mut_slice());
+                let header = {
+                    let mut data = Cursor::new(Vec::with_capacity(80));
                     data.write(b"Speex   1.1.12").unwrap();
                     data.write(&[0; 14]).unwrap();
                     data.write_u32le(1).unwrap(); // version
@@ -213,19 +211,28 @@ impl AudioFormat {
                     data.write_u32le(0).unwrap(); // extra headers
                     data.write_u32le(0).unwrap(); // reserved 1
                     data.write_u32le(0).unwrap(); // reserved 2
-                }
+
+                    assert_eq!(data.position(), 80);
+
+                    data.into_inner()
+                };
+                let header = Buffer::new_from_vec(header).unwrap();
 
                 let comment_size = 4 + 7 /* nothing */ + 4 + 1;
 
-                let mut comment = Buffer::new_with_size(comment_size).unwrap();
-                {
-                    let mut map = comment.map_readwrite().unwrap();
-                    let mut data = Cursor::new(map.as_mut_slice());
+                let comment = {
+                    let mut data = Cursor::new(Vec::with_capacity(comment_size));
                     data.write_u32le(7).unwrap(); // length of "nothing"
                     data.write(b"nothing").unwrap(); // "vendor" string
                     data.write_u32le(0).unwrap(); // number of elements
-                    data.write_u8(1);
-                }
+                    data.write_u8(1).unwrap();
+
+                    assert_eq!(data.position() as usize, comment_size);
+
+                    data.into_inner()
+                };
+                let comment = Buffer::new_from_vec(comment).unwrap();
+
                 Some(Caps::new_simple("audio/x-speex",
                                       &[("streamheader",
                                          &vec![header.into(), comment.into()].into())]))

gst-plugin/src/buffer.rs

@@ -151,6 +151,48 @@ impl Buffer {
         }
     }
 
+    extern "C" fn vec_drop(vec: *mut c_void) {
+        let vec: Box<Vec<u8>> = unsafe { Box::from_raw(vec as *mut Vec<u8>) };
+        drop(vec);
+    }
+
+    pub fn new_from_vec(vec: Vec<u8>) -> Option<Buffer> {
+        extern "C" {
+            fn gst_buffer_new_wrapped_full(flags: u32,
+                                           data: *mut u8,
+                                           maxsize: usize,
+                                           offset: usize,
+                                           size: usize,
+                                           user_data: *mut c_void,
+                                           destroy_notify: extern "C" fn(*mut c_void))
+                                           -> *mut c_void;
+        }
+
+        let raw = unsafe {
+            let mut vec = Box::new(vec);
+            let maxsize = vec.capacity();
+            let size = vec.len();
+            let data = vec.as_mut_ptr();
+            let user_data = Box::into_raw(vec);
+            gst_buffer_new_wrapped_full(0,
+                                        data,
+                                        maxsize,
+                                        0,
+                                        size,
+                                        user_data as *mut c_void,
+                                        Buffer::vec_drop)
+        };
+
+        if raw.is_null() {
+            None
+        } else {
+            Some(Buffer {
+                raw: raw,
+                owned: true,
+            })
+        }
+    }
+
     pub fn map_read(&self) -> Option<ReadBufferMap> {
         extern "C" {
             fn gst_buffer_map(buffer: *mut c_void,