Subzero: Add basic ELFObjectWriter (text section, symtab, strtab, headers)

src/IceELFStreamer.h

+//===- subzero/src/IceELFStreamer.h - Low level ELF writing -----*- C++ -*-===//
+//
+//                        The Subzero Code Generator
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Interface for serializing bits for common ELF types (words, extended words,
+// etc.), based on the ELF Class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SUBZERO_SRC_ICEELFSTREAMER_H
+#define SUBZERO_SRC_ICEELFSTREAMER_H
+
+#include "IceDefs.h"
+
+namespace Ice {
+
+// Low level writer that can that can handle ELFCLASS32/64.
+// Little endian only for now.
+class ELFStreamer {
+public:
+  explicit ELFStreamer(Fdstream &Out) : Out(Out) {}
+
+  void write8(uint8_t Value) { Out << char(Value); }
+
+  void writeLE16(uint16_t Value) {
+    write8(uint8_t(Value));
+    write8(uint8_t(Value >> 8));
+  }
+
+  void writeLE32(uint32_t Value) {
+    writeLE16(uint16_t(Value));
+    writeLE16(uint16_t(Value >> 16));
+  }
+
+  void writeLE64(uint64_t Value) {
+    writeLE32(uint32_t(Value));
+    writeLE32(uint32_t(Value >> 32));
+  }
+
+  template <bool IsELF64, typename T> void writeAddrOrOffset(T Value) {
+    if (IsELF64)
+      writeLE64(Value);
+    else
+      writeLE32(Value);
+  }
+
+  template <bool IsELF64, typename T> void writeELFWord(T Value) {
+    writeLE32(Value);
+  }
+
+  template <bool IsELF64, typename T> void writeELFXword(T Value) {
+    if (IsELF64)
+      writeLE64(Value);
+    else
+      writeLE32(Value);
+  }
+
+  void writeBytes(llvm::StringRef Bytes) { Out << Bytes; }
+
+  void writeZeroPadding(SizeT N) {
+    const char Zeros[16] = {0};

[Jim Stichnoth, 2014/11/21 21:32:22]

Can this be static, to avoid initializing on the stack every time?

[jvoung (off chromium), 2014/11/24 21:35:46]

Done.

+
+    for (SizeT i = 0, e = N / 16; i != e; ++i)
+      Out << llvm::StringRef(Zeros, 16);
+
+    Out << llvm::StringRef(Zeros, N % 16);
+  }
+
+  uint64_t tell() const { return Out.tell(); }
+
+  void seek(uint64_t Off) { Out.seek(Off); }
+
+private:
+  Fdstream &Out;
+};
+
+} // end of namespace Ice
+
+#endif // SUBZERO_SRC_ICEELFSTREAMER_H