From 59b843517df8d35b339eaee95ba4e533b190f9d6 Mon Sep 17 00:00:00 2001
From: Valerii Hiora <valerii.hiora@gmail.com>
Date: Thu, 9 Oct 2014 12:33:29 +0300
Subject: BN_is_zero as a Rust function
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Although wrapping was relatively easy it basically meant
that we depend on C compilation which becomes nightmare
as soon as multiple platforms are used. I’ve got a huge pain
once iOS was involved with 3 device archs and 2 simulator
arches to support, not mentioning different set of include
and lib flags.

So there are 2 different approaches:

- continue this way, maintaining all compilation issues like
  like managing correct flags, providing correct paths and so
  on. This way our Makefile will grow extremely fast and will
  actually take more efforts to maintain.

- doing it pure Rust way. In this case we provide all the
  macros expansions inside our wrappers and there should be
  no other way to access raw data other than through those
  wrappers. It might be fragile if OpenSSL internal data
  structures will ever change, but I think (or hope) it is
  pretty stable and wouldn’t change anytime soon.

This PR eliminates `BN_is_zero` at all from public API. It’s
functionality is implemented in `BigNum.is_zero` and should
be enough.

Additional notes:

1. I’ve moved BIGNUM into `bn` so it could access fields
   directly and keep it as an opaque structure for everyone
   else

2. I’ve kept empty Makefile as I hope to land `feature-matrix`
   branch soon and I don’t like merging deleted/added file
   conflicts.
---
 src/bn/mod.rs | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

(limited to 'src/bn')

diff --git a/src/bn/mod.rs b/src/bn/mod.rs
index fb836a39..129f6b90 100644
--- a/src/bn/mod.rs
+++ b/src/bn/mod.rs
@@ -1,4 +1,4 @@
-use libc::{c_int, c_ulong};
+use libc::{c_int, c_ulong, c_void};
 use std::{fmt, ptr};
 use std::c_str::CString;
 use std::num::{One, Zero};
@@ -6,6 +6,16 @@ use std::num::{One, Zero};
 use ffi;
 use ssl::error::SslError;
 
+#[allow(dead_code)]
+#[repr(C)]
+pub struct BIGNUM {
+    d: *mut c_void,
+    top: c_int,
+    dmax: c_int,
+    neg: c_int,
+    flags: c_int,
+}
+
 pub struct BigNum(*mut ffi::BIGNUM);
 
 #[repr(C)]
@@ -381,9 +391,11 @@ impl Zero for BigNum {
     fn zero() -> BigNum {
         BigNum::new_from(0).unwrap()
     }
+
     fn is_zero(&self) -> bool {
         unsafe {
-            ffi::BN_is_zero(self.raw()) == 1
+            // It is raw contents of BN_is_zero macro
+            (*self.raw()).top == 0
         }
     }
 }
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