Initial commit

.gitignore

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+target
+Cargo.lock

Cargo.toml

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+[package]
+name = "cfg-if"
+version = "0.1.0"
+authors = ["Alex Crichton <alex@alexcrichton.com>"]
+license = "MIT/Apache-2.0"
+readme = "README.md"
+repository = "https://github.com/alexcrichton/cfg-if"
+homepage = "https://github.com/alexcrichton/cfg-if"
+documentation = "http://alexcrichton.com/cfg-if"
+description = """
+A macro to ergonomically define an item depending on a large number of #[cfg]
+parameters. Structured like an if-else chain, the first matching branch is the
+item that gets emitted.
+"""

README.md

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+# cfg-if
+
+[![Build Status](https://travis-ci.org/alexcrichton/cfg-if.svg?branch=master)](https://travis-ci.org/alexcrichton/cfg-if)
+
+[Documentation](http://alexcrichton.com/cfg-if)
+
+A macro to ergonomically define an item depending on a large number of #[cfg]
+parameters. Structured like an if-else chain, the first matching branch is the
+item that gets emitted.
+
+```toml
+[dependencies]
+cfg-if = "0.1"
+```
+
+## Example
+
+```rust
+#[macro_use]
+extern crate cfg_if;
+
+cfg_if! {
+    if #[cfg(unix)] {
+        fn foo() { /* unix specific functionality */ }
+    } else if #[cfg(target_pointer_width = "32")] {
+        fn foo() { /* non-unix, 32-bit functionality */ }
+    } else {
+        fn foo() { /* fallback implementation */ }
+    }
+}
+```
+
+# License
+
+`cfg-if` is primarily distributed under the terms of both the MIT license and
+the Apache License (Version 2.0), with portions covered by various BSD-like
+licenses.
+
+See LICENSE-APACHE, and LICENSE-MIT for details.
+

src/lib.rs

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+//! A macro for defining #[cfg] if-else statements.
+//!
+//! The macro provided by this crate, `cfg_if`, is similar to the `if/elif` C
+//! preprocessor macro by allowing definition of a cascade of `#[cfg]` cases,
+//! emitting the implementation which matches first.
+//!
+//! This allows you to conveniently provide a long list #[cfg]'d blocks of code
+//! without having to rewrite each clause multiple times.
+//!
+//! # Example
+//!
+//! ```
+//! #[macro_use]
+//! extern crate cfg_if;
+//!
+//! cfg_if! {
+//!     if #[cfg(unix)] {
+//!         fn foo() { /* unix specific functionality */ }
+//!     } else if #[cfg(target_pointer_width = "32")] {
+//!         fn foo() { /* non-unix, 32-bit functionality */ }
+//!     } else {
+//!         fn foo() { /* fallback implementation */ }
+//!     }
+//! }
+//!
+//! # fn main() {}
+//! ```
+
+#![doc(html_root_url = "http://alexcrichton.com/cfg-if")]
+#![deny(missing_docs)]
+#![cfg_attr(test, deny(warnings))]
+
+#[macro_export]
+macro_rules! cfg_if {
+    ($(
+        if #[cfg($($meta:meta),*)] { $($it:item)* }
+    ) else * else {
+        $($it2:item)*
+    }) => {
+        __cfg_if_items! {
+            () ;
+            $( ( ($($meta),*) ($($it)*) ), )*
+            ( () ($($it2)*) ),
+        }
+    }
+}
+
+#[macro_export]
+#[doc(hidden)]
+macro_rules! __cfg_if_items {
+    (($($not:meta,)*) ; ) => {};
+    (($($not:meta,)*) ; ( ($($m:meta),*) ($($it:item)*) ), $($rest:tt)*) => {
+        __cfg_if_apply! { cfg(all($($m,)* not(any($($not),*)))), $($it)* }
+        __cfg_if_items! { ($($not,)* $($m,)*) ; $($rest)* }
+    }
+}
+
+#[macro_export]
+#[doc(hidden)]
+macro_rules! __cfg_if_apply {
+    ($m:meta, $($it:item)*) => {
+        $(#[$m] $it)*
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    cfg_if! {
+        if #[cfg(test)] {
+            use std::option::Option as Option2;
+            fn works1() -> Option2<u32> { Some(1) }
+        } else {
+            fn works1() -> Option<u32> { None }
+        }
+    }
+
+    cfg_if! {
+        if #[cfg(foo)] {
+            fn works2() -> bool { false }
+        } else if #[cfg(test)] {
+            fn works2() -> bool { true }
+        } else {
+            fn works2() -> bool { false }
+        }
+    }
+
+    cfg_if! {
+        if #[cfg(foo)] {
+            fn works3() -> bool { false }
+        } else {
+            fn works3() -> bool { true }
+        }
+    }
+
+    #[test]
+    fn it_works() {
+        assert!(works1().is_some());
+        assert!(works2());
+        assert!(works3());
+    }
+}

tests/xcrate.rs

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+#[macro_use]
+extern crate cfg_if;
+
+cfg_if! {
+    if #[cfg(foo)] {
+        fn works() -> bool { false }
+    } else if #[cfg(test)] {
+        fn works() -> bool { true }
+    } else {
+        fn works() -> bool { false }
+    }
+}
+
+#[test]
+fn smoke() {
+    assert!(works());
+}