Add support for computing SHA1 in LLVM

Provide a class to generate a SHA1 from a sequence of bytes, and
a convenience raw_ostream adaptor.
This will be used to provide a "build-id" by hashing the Module
block when writing bitcode. ThinLTO will use this information for
incremental build.

Reapply r265094 which was reverted in r265102 because it broke
MSVC bots (constexpr is not supported).

http://reviews.llvm.org/D16325

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 265107

2 files changed, 121 insertions, 0 deletions

diff --git a/llvm/include/llvm/Support/SHA1.h b/llvm/include/llvm/Support/SHA1.h
new file mode 100644
index 00000000000..57af39ab844
--- /dev/null
+++ b/llvm/include/llvm/Support/SHA1.h
@@ -0,0 +1,75 @@
+//==- SHA1.h - SHA1 implementation for LLVM                     --*- C++ -*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// This code is taken from public domain
+// (http://oauth.googlecode.com/svn/code/c/liboauth/src/sha1.c)
+// and modified by wrapping it in a C++ interface for LLVM,
+// and removing unnecessary code.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_SHA1_H
+#define LLVM_SUPPORT_SHA1_H
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/StringRef.h"
+
+#include <cstdint>
+
+namespace llvm {
+
+/// A class that wrap the SHA1 algorithm.
+class SHA1 {
+public:
+  SHA1() { init(); }
+
+  /// Reinitialize the internal state
+  void init();
+
+  /// Digest more data.
+  void update(ArrayRef<uint8_t> Data);
+
+  /// Return a reference to the current raw 160-bits SHA1 for the digested data
+  /// since the last call to init(). This call will add data to the internal
+  /// state and as such is not suited for getting an intermediate result
+  /// (see result()).
+  StringRef final();
+
+  /// Return a reference to the current raw 160-bits SHA1 for the digested data
+  /// since the last call to init(). This is suitable for getting the SHA1 at
+  /// any time without invalidating the internal state so that more calls can be
+  /// made into update.
+  StringRef result();
+
+private:
+  /// Define some constants.
+  /// "static constexpr" would be cleaner but MSVC does not support it yet.
+  enum { BLOCK_LENGTH = 64 };
+  enum { HASH_LENGTH = 20 };
+
+  // Internal State
+  struct {
+    uint32_t Buffer[BLOCK_LENGTH / 4];
+    uint32_t State[HASH_LENGTH / 4];
+    uint32_t ByteCount;
+    uint8_t BufferOffset;
+  } InternalState;
+
+  // Internal copy of the hash, populated and accessed on calls to result()
+  uint32_t HashResult[HASH_LENGTH / 4];
+
+  // Helper
+  void writebyte(uint8_t data);
+  void hashBlock();
+  void addUncounted(uint8_t data);
+  void pad();
+};
+
+} // end llvm namespace
+
+#endif
diff --git a/llvm/include/llvm/Support/raw_sha1_ostream.h b/llvm/include/llvm/Support/raw_sha1_ostream.h
new file mode 100644
index 00000000000..9f136dfa7e1
--- /dev/null
+++ b/llvm/include/llvm/Support/raw_sha1_ostream.h
@@ -0,0 +1,46 @@
+//==- raw_sha1_ostream.h - raw_ostream that compute SHA1        --*- C++ -*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the raw_sha1_ostream class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_RAW_SHA1_OSTREAM_H
+#define LLVM_SUPPORT_RAW_SHA1_OSTREAM_H
+
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/SHA1.h"
+
+namespace llvm {
+
+/// A raw_ostream that hash the content using the sha1 algorithm.
+class raw_sha1_ostream : public raw_ostream {
+  SHA1 State;
+
+  /// See raw_ostream::write_impl.
+  void write_impl(const char *Ptr, size_t Size) override {
+    State.update(ArrayRef<uint8_t>((uint8_t *)Ptr, Size));
+  }
+
+public:
+  /// Return the current SHA1 hash for the content of the stream
+  StringRef sha1() {
+    flush();
+    return State.result();
+  }
+
+  /// Reset the internal state to start over from scratch.
+  void resetHash() { State.init(); }
+
+  uint64_t current_pos() const override { return 0; }
+};
+
+} // end llvm namespace
+
+#endif