From 71b1b4634fd5496a6ebdf2ec4ef38c420c56e202 Mon Sep 17 00:00:00 2001
From: Arkadiusz Bokowy <arkadiusz.bokowy@gmail.com>
Date: Sun, 6 Nov 2022 23:19:07 +0100
Subject: [PATCH] Provide fallback implementation for getentropy()

Commit ba3396f changed getRandomBytes() implementation from c++ std
uniform distribution to getentropy(). The getentropy() function first
appeared in glibc 2.25. In order to provide backward compatibility for
older glibc (e.g. Android SDK <= 19) restore previous getRandomBytes()
implementation as a fallback.
---
 src/SimpleRandomizer.cc | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/SimpleRandomizer.cc b/src/SimpleRandomizer.cc
index 8dbef82f..7748ba0d 100644
--- a/src/SimpleRandomizer.cc
+++ b/src/SimpleRandomizer.cc
@@ -106,6 +106,20 @@ void SimpleRandomizer::getRandomBytes(unsigned char* buf, size_t len)
   auto iter = len / blocklen;
   auto p = buf;
 
+#if !HAVE_GETENTROPY
+  auto getentropy = [this](void *buffer, size_t length) {
+    auto buf = reinterpret_cast<unsigned int*>(buffer);
+    auto dis = std::uniform_int_distribution<unsigned int>();
+    for (size_t q = length / sizeof(unsigned int); q > 0; --q, ++buf) {
+      *buf = dis(gen_);
+    }
+    const size_t r = length % sizeof(unsigned int);
+    auto last = dis(gen_);
+    memcpy(buf, &last, r);
+    return 0;
+  };
+#endif // !HAVE_GETENTROPY
+
   for (size_t i = 0; i < iter; ++i) {
     auto rv = getentropy(p, blocklen);
     if (rv != 0) {
@@ -128,7 +142,7 @@ void SimpleRandomizer::getRandomBytes(unsigned char* buf, size_t len)
     assert(0);
     abort();
   }
-#endif // ! __MINGW32__
+#endif // !__MINGW32__ && !__APPLE__
 }
 
 } // namespace aria2