1 files changed, 78 insertions, 0 deletions
diff --git a/llvm/tools/llvm-objcopy/wasm/Writer.cpp b/llvm/tools/llvm-objcopy/wasm/Writer.cpp
new file mode 100644
index 000000000000..50d26507b498
--- /dev/null
+++ b/llvm/tools/llvm-objcopy/wasm/Writer.cpp
@@ -0,0 +1,78 @@
+//===- Writer.cpp ---------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "Writer.h"
+#include "llvm/BinaryFormat/Wasm.h"
+#include "llvm/Support/Endian.h"
+#include "llvm/Support/LEB128.h"
+#include "llvm/Support/raw_ostream.h"
+
+namespace llvm {
+namespace objcopy {
+namespace wasm {
+
+using namespace object;
+using namespace llvm::wasm;
+
+Writer::SectionHeader Writer::createSectionHeader(const Section &S,
+                                                  size_t &SectionSize) {
+  SectionHeader Header;
+  raw_svector_ostream OS(Header);
+  OS << S.SectionType;
+  bool HasName = S.SectionType == WASM_SEC_CUSTOM;
+  SectionSize = S.Contents.size();
+  if (HasName)
+    SectionSize += getULEB128Size(S.Name.size()) + S.Name.size();
+  // Pad the LEB value out to 5 bytes to make it a predictable size, and
+  // match the behavior of clang.
+  encodeULEB128(SectionSize, OS, 5);
+  if (HasName) {
+    encodeULEB128(S.Name.size(), OS);
+    OS << S.Name;
+  }
+  // Total section size is the content size plus 1 for the section type and
+  // 5 for the LEB-encoded size.
+  SectionSize = SectionSize + 1 + 5;
+  return Header;
+}
+
+size_t Writer::finalize() {
+  size_t ObjectSize = sizeof(WasmMagic) + sizeof(WasmVersion);
+  SectionHeaders.reserve(Obj.Sections.size());
+  // Finalize the headers of each section so we know the total size.
+  for (const Section &S : Obj.Sections) {
+    size_t SectionSize;
+    SectionHeaders.push_back(createSectionHeader(S, SectionSize));
+    ObjectSize += SectionSize;
+  }
+  return ObjectSize;
+}
+
+Error Writer::write() {
+  size_t FileSize = finalize();
+  if (Error E = Buf.allocate(FileSize))
+    return E;
+
+  // Write the header.
+  uint8_t *Ptr = Buf.getBufferStart();
+  Ptr = std::copy(Obj.Header.Magic.begin(), Obj.Header.Magic.end(), Ptr);
+  support::endian::write32le(Ptr, Obj.Header.Version);
+  Ptr += sizeof(Obj.Header.Version);
+
+  // Write each section.
+  for (size_t I = 0, S = SectionHeaders.size(); I < S; ++I) {
+    Ptr = std::copy(SectionHeaders[I].begin(), SectionHeaders[I].end(), Ptr);
+    ArrayRef<uint8_t> Contents = Obj.Sections[I].Contents;
+    Ptr = std::copy(Contents.begin(), Contents.end(), Ptr);
+  }
+  return Buf.commit();
+}
+
+} // end namespace wasm
+} // end namespace objcopy
+} // end namespace llvm