From 87805c080d397b1328e7227cd7741107d225f4c3 Mon Sep 17 00:00:00 2001
From: Amanieu d'Antras <amanieu@gmail.com>
Date: Wed, 8 Jan 2020 17:37:28 +0000
Subject: [PATCH] Use getrandom directly instead of rand

This works around https://github.com/rust-lang/cargo/issues/5730
for no_std crates that try to use rand.
---
 Cargo.toml       |  4 ++--
 macro/Cargo.toml |  4 ++--
 macro/src/lib.rs | 35 ++++++++++++++++++++++-------------
 3 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index bcfed29..0cc1cd9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "const-random"
-version = "0.1.6"
+version = "0.1.7"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/tkaitchuck/constrandom"
 documentation = "https://docs.rs/const-random"
@@ -11,5 +11,5 @@ readme = "README.md"
 edition = "2018"
 
 [dependencies]
-const-random-macro = { path = "macro", version = "0.1.6"}
+const-random-macro = { path = "macro", version = "0.1.7"}
 proc-macro-hack = { version = "0.5" }
diff --git a/macro/Cargo.toml b/macro/Cargo.toml
index 429c33f..4360709 100644
--- a/macro/Cargo.toml
+++ b/macro/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "const-random-macro"
-version = "0.1.6"
+version = "0.1.7"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/tkaitchuck/constrandom"
 documentation = "https://docs.rs/const-random"
@@ -14,4 +14,4 @@ proc-macro = true
 
 [dependencies]
 proc-macro-hack = { version = "0.5" }
-rand = { version = "0.7", default-features = false, features = ["getrandom"] }
+getrandom = "0.1"
diff --git a/macro/src/lib.rs b/macro/src/lib.rs
index c5fe64b..d996933 100644
--- a/macro/src/lib.rs
+++ b/macro/src/lib.rs
@@ -1,24 +1,33 @@
 extern crate proc_macro;
 
+use getrandom;
 use proc_macro::TokenStream;
 use proc_macro_hack::proc_macro_hack;
-use rand::rngs::OsRng;
-use rand::Rng;
+use std::mem;
+
+// Ideally we would use the proper interface for this through the rand crate,
+// but due to https://github.com/rust-lang/cargo/issues/5730 this leads to
+// issues for no_std crates that try to use rand themselves. So instead we skip
+// rand and generate random bytes straight from the OS.
+fn gen_random<T>() -> T {
+    let mut out = [0u8; 16];
+    getrandom::getrandom(&mut out).unwrap();
+    unsafe { mem::transmute_copy(&out) }
+}
 
 #[proc_macro_hack]
 pub fn const_random(input: TokenStream) -> TokenStream {
     match &input.to_string()[..] {
-        "u8" => format!("0x{:x}", OsRng.gen::<u8>()).parse().unwrap(),
-        "u16" => format!("0x{:x}", OsRng.gen::<u16>()).parse().unwrap(),
-        "u32" => format!("0x{:x}", OsRng.gen::<u32>()).parse().unwrap(),
-        "u64" => format!("0x{:x}", OsRng.gen::<u64>()).parse().unwrap(),
-        "u128" => format!("0x{:x}", OsRng.gen::<u128>()).parse().unwrap(),
-        "i8" => format!("0x{:x}", OsRng.gen::<i8>()).parse().unwrap(),
-        "i16" => format!("0x{:x}", OsRng.gen::<i16>()).parse().unwrap(),
-        "i32" => format!("0x{:x}", OsRng.gen::<i32>()).parse().unwrap(),
-        "i64" => format!("0x{:x}", OsRng.gen::<i64>()).parse().unwrap(),
-        "i128" => format!("0x{:x}", OsRng.gen::<i128>()).parse().unwrap(),
+        "u8" => format!("0x{:x}", gen_random::<u8>()).parse().unwrap(),
+        "u16" => format!("0x{:x}", gen_random::<u16>()).parse().unwrap(),
+        "u32" => format!("0x{:x}", gen_random::<u32>()).parse().unwrap(),
+        "u64" => format!("0x{:x}", gen_random::<u64>()).parse().unwrap(),
+        "u128" => format!("0x{:x}", gen_random::<u128>()).parse().unwrap(),
+        "i8" => format!("0x{:x}", gen_random::<i8>()).parse().unwrap(),
+        "i16" => format!("0x{:x}", gen_random::<i16>()).parse().unwrap(),
+        "i32" => format!("0x{:x}", gen_random::<i32>()).parse().unwrap(),
+        "i64" => format!("0x{:x}", gen_random::<i64>()).parse().unwrap(),
+        "i128" => format!("0x{:x}", gen_random::<i128>()).parse().unwrap(),
         _ => panic!("Invalid integer type"),
     }
-
 }