Add support for in-memory download

src/media.rs

@@ -1,9 +1,9 @@
-use std::ffi::{CString};
+use std::ffi::CString;
 use std::mem;
 use std::path::Path;
-
+use libc::c_ulong;
 use std::os::unix::prelude::*;
-
+use std::slice;
 
 /// A trait for types that can store media.
 pub trait Media {
@@ -63,6 +63,28 @@ impl FileMedia {
             }
         }
     }
+
+    pub fn create_mem() -> ::Result<Self> {
+        let mut ptr = unsafe { mem::uninitialized() };
+
+        match unsafe { ::gphoto2::gp_file_new(&mut ptr) } {
+            ::gphoto2::GP_OK => Ok(FileMedia { file: ptr }),
+            err => Err(::error::from_libgphoto2(err)),
+        }
+    }
+
+    pub fn get_data(&mut self) -> Vec<u8> {
+        let mut ptr = unsafe { mem::uninitialized() };
+        let mut len: c_ulong = 0;
+
+        unsafe {
+            ::gphoto2::gp_file_get_data_and_size(self.file, &mut ptr, &mut len)
+        };
+
+        unsafe { 
+            slice::from_raw_parts(ptr as *const u8, len as usize).to_vec() 
+        }
+    }
 }
 
 impl Media for FileMedia {