Bitcode streaming

lib/Support/BitcodeStream.cpp

+//===---- llvm/Bitcode/Reader/BitcodeStream.cpp - Lazy bitcode -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements BitcodeStreamer, which fetches bytes of bitcode from
+// a stream source. It provides support for streaming (lazy reading) of
+// bitcode. An example implementation of streaming from a file or stdin 
+// is included.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "bitcode-stream"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/BitcodeStream.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/system_error.h"
+#include <string>
+#include <cerrno>
+#include <cstdio>
+#if !defined(_MSC_VER) && !defined(__MINGW32__)
+#include <unistd.h>
+#else
+#include <io.h>
+#endif
+#include <fcntl.h>
+using namespace llvm;
+
+// Interface goals:
+// * BitstreamBytes doesn't care about complexities like using
+//   threads/async callbacks to actually overlap download+compile
+// * Don't want to duplicate bitcode in memory
+// * Don't need to know total bitcode len in advance
+// Non-goals:
+// BitstreamBytes already has random access so this interface only does in-order
+// streaming (no arbitrary seeking, else we'd have to buffer all the bitcode
+// here in addition to BitstreamBytes). This also means that if we want to
+// be able to to free bitcode, BitstreamBytes/BitcodeReader will implement it.
+
+STATISTIC(NumStreamFetches, "Number of calls to bitcode stream fetch");
+
+namespace llvm {
+BitcodeStreamer::~BitcodeStreamer() {}
+}
+
+namespace {
+
+const static error_code success;
+
+// Very simple stream backed by a file. Mostly useful for stdin and debugging;
+// actual file access is probably still best done with mmap
+class BitcodeFileStreamer : public BitcodeStreamer {
+ int Fd;
+public:
+  BitcodeFileStreamer() : Fd(0) {}
+  virtual ~BitcodeFileStreamer() {
+    close(Fd);
+  }
+  virtual size_t GetBytes(unsigned char *buf, size_t len) {
+    NumStreamFetches++;
+    return read(Fd, buf, len);
+  }
+
+  error_code OpenFile(const std::string &Filename) {
+    int OpenFlags = O_RDONLY;
+#ifdef O_BINARY
+    OpenFlags |= O_BINARY;  // Open input file in binary mode on win32.
+#endif
+    if (Filename == "-")
+      Fd = 0;
+    else
+      Fd = ::open(Filename.c_str(), OpenFlags);
+    if (Fd == -1) return error_code(errno, posix_category());
+      return success;
+  }
+};
+
+}
+
+namespace llvm {
+BitcodeStreamer *getBitcodeFileStreamer(const std::string &Filename,
+                                        std::string *StrError) {
+  BitcodeFileStreamer *s = new BitcodeFileStreamer();
+  error_code e = s->OpenFile(Filename);
+  if (e != success) {
+    *StrError = std::string() + "Could not open " + Filename + ": "
+        + e.message() + "\n";
+    return NULL;
+  }
+  return s;
+}
+
+}