Extract common rotl/rotr functions.

We have a ton of per-file rotation functions, often with generic names
that do not tell you whether they are uint32_t vs uint64_t, or rotl vs

Additionally, (x >> r) | (x << (32 - r)) is UB at r = 0.
(x >> r) | (x << ((-r) & 31)) works for 0 <= r < 32, which is what
cast.c does. GCC and Clang recognize this pattern as a rotate, but MSVC
doesn't. MSVC does, however, provide functions for this.

We usually rotate by a non-zero constant, which makes this moot, but
rotation comes up often enough that it's worth extracting out. Some
particular changes to call out:

- I've switched sha256.c from rotl to rotr. There was a comment
  explaining why it differed from the specification. Now that we have
  both functions, it's simpler to just match the specification.

- I've dropped all the inline assembly from sha512.c. Compilers should
  be able to recognize rotations in 2021.

Change-Id: Ia1030e8bfe94dad92514ed1c28777447c48b82f9
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/49765
Reviewed-by: Adam Langley <agl@google.com>
15 files changed
tree: 40da6f77e1c304b655462a1387948147a046a1d5
  1. .clang-format
  2. .github/
  3. .gitignore
  6. BUILDING.md
  7. CMakeLists.txt
  9. FUZZING.md
  12. PORTING.md
  13. README.md
  15. STYLE.md
  16. codereview.settings
  17. crypto/
  18. decrepit/
  19. fuzz/
  20. go.mod
  21. go.sum
  22. include/
  23. sources.cmake
  24. ssl/
  25. third_party/
  26. tool/
  27. util/


BoringSSL is a fork of OpenSSL that is designed to meet Google's needs.

Although BoringSSL is an open source project, it is not intended for general use, as OpenSSL is. We don't recommend that third parties depend upon it. Doing so is likely to be frustrating because there are no guarantees of API or ABI stability.

Programs ship their own copies of BoringSSL when they use it and we update everything as needed when deciding to make API changes. This allows us to mostly avoid compromises in the name of compatibility. It works for us, but it may not work for you.

BoringSSL arose because Google used OpenSSL for many years in various ways and, over time, built up a large number of patches that were maintained while tracking upstream OpenSSL. As Google's product portfolio became more complex, more copies of OpenSSL sprung up and the effort involved in maintaining all these patches in multiple places was growing steadily.

Currently BoringSSL is the SSL library in Chrome/Chromium, Android (but it's not part of the NDK) and a number of other apps/programs.

Project links:

There are other files in this directory which might be helpful: