Adding Ocaml bindings for the bitreader as requested by Sarah

Thompson. Usage should be something like this:

open Llvm
open Llvm_bitreader

match read_bitcode_file fn with
  | Bitreader_failure msg ->
      prerr_endline msg
  | Bitreader_success m -> 
      ...;
      dispose_module m

Compile with: ocamlc llvm.cma llvm_bitreader.cma
              ocamlopt llvm.cmxa llvm_bitreader.cmxa


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44824 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Bitcode/Reader/BitReader.cpp

@@ -0,0 +1,42 @@
+//===-- BitReader.cpp -----------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Gordon Henriksen and is distributed under the
+// University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm-c/BitReader.h"
+#include "llvm/Bitcode/ReaderWriter.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include <string>
+
+using namespace llvm;
+
+
+int LLVMReadBitcodeFromFile(const char *Path, LLVMModuleRef *OutModule,
+                            char **OutMessage) {
+  std::string Message;
+  
+  MemoryBuffer *buf = MemoryBuffer::getFile(Path, strlen(Path), &Message);
+  if (!buf) {
+    if (!OutMessage)
+      *OutMessage = strdup(Message.c_str());
+    return 1;
+  }
+  
+  *OutModule = wrap(ParseBitcodeFile(buf, &Message));
+  if (!*OutModule) {
+    if (OutMessage)
+      *OutMessage = strdup(Message.c_str());
+    return 1;
+  }
+  
+  return 0;
+}
+
+void LLVMDisposeBitcodeReaderMessage(char *Message) {
+  if (Message)
+    free(Message);
+}