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