refac(elf): start on TryFrom impls for #85

elf/src/file.rs

@@ -9,7 +9,7 @@
 //! ELF file header
 use super::{ElfResult, ElfWord, Section, section};
 use super::ValidatesWord;
-use core::{fmt, mem};
+use core::{fmt, mem, convert};
 
 /// Trait representing an ELF File Header.
 ///
@@ -26,12 +26,10 @@ use core::{fmt, mem};
 /// [HeaderRepr]: struct.HeaderRepr.html
 /// [specification](http://www.sco.com/developers/gabi/latest/ch4.eheader.html)
 /// [OS Dev Wiki](http://wiki.osdev.org/ELF#Header)
-pub trait Header {
+pub trait Header: Sized {
     type Word: ElfWord;
 
     /// Attempt to extract an ELF file header from a slice of bytes.
-    /// TODO: rewrite this as a `TryFrom` implementation (see issue #85)
-    //          - eliza, 03/09/2017
     fn from_slice<'a>(input: &'a [u8]) -> ElfResult<&'a Self>;
 
     /// Attempt to extract a section header from a slice of bytes.
@@ -80,6 +78,8 @@ pub trait Header {
 
 }
 
+
+
 macro_rules! impl_getters {
     ($(#[$attr:meta])* pub fn $name:ident(&self) -> $ty:ident; $($rest:tt)*) => {
         $(#[$attr])* #[inline] pub fn $name(&self) -> $ty { self.$name as $ty }
@@ -170,7 +170,17 @@ macro_rules! Header {
                 fn ident(&self) -> Ident;
                 fn machine(&self) -> Machine;
             }
-        })+
+        }
+
+        impl<'a> convert::TryFrom<&'a [u8]> for $name<$size>
+        where $name<$size>: Header {
+            type Err = &'static str;
+            #[inline]
+            fn try_from(slice: &'a [u8]) -> ElfResult<Self> {
+                <Self as Header>::from_slice(slice).map(|x| *x)
+            }
+        }
+        )+
     }
 }
 
@@ -344,6 +354,8 @@ pub enum Version { None = 0, Current = 1 }
 struct TypeRepr(u16);
 
 impl TypeRepr {
+    /// TODO: rewrite this as a `convert::Into` implementation
+    ///         - eliza, 03/09/2017
     pub fn as_type(&self) -> Type {
         match self.0 {
             0 => Type::None

elf/src/lib.rs

@@ -17,6 +17,7 @@
 //!
 //! [elfspec]: http://www.skyfree.org/linux/references/ELF_Format.pdf
 #![feature(core_intrinsics)]
+#![feature(try_from)]
 #![no_std]
 
 #[macro_use] extern crate bitflags;
@@ -91,6 +92,12 @@ where Word: ElfWord + 'a
 //  thanks to Max for making  me figure this out.
 /// TODO: rewrite this as a `TryFrom` implementation (see issue #85)
 //          - eliza, 03/09/2017
+///       wait, possibly we should NOT do that. actually we should
+///       almost certainly not do that. since this function is unsafe,
+///       but `TryFrom` is not, and because this would be WAY generic.
+//          - eliza, 03/09/2017
+/// TODO: is this general enough to move into util?
+//          - eliza, 03/09/2017
 unsafe fn extract_from_slice<T: Sized>( data: &[u8]
                                       , offset: usize
                                       , n: usize)