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//===- WasmWriter.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 "WasmWriter.h"
#include "llvm/BinaryFormat/Wasm.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/Errc.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();
// If we read this section from an object file, use its original size for the
// padding of the LEB value to avoid changing the file size. Otherwise, pad
// out to 5 bytes to make it predictable, and match the behavior of clang.
unsigned HeaderSecSizeEncodingLen =
S.HeaderSecSizeEncodingLen ? *S.HeaderSecSizeEncodingLen : 5;
encodeULEB128(SectionSize, OS, HeaderSecSizeEncodingLen);
if (HasName) {
encodeULEB128(S.Name.size(), OS);
OS << S.Name;
}
// Total section size is the content size plus 1 for the section type and
// the LEB-encoded size.
SectionSize = SectionSize + 1 + HeaderSecSizeEncodingLen;
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 TotalSize = finalize();
Out.reserveExtraSpace(TotalSize);
// Write the header.
Out.write(Obj.Header.Magic.data(), Obj.Header.Magic.size());
uint32_t Version;
support::endian::write32le(&Version, Obj.Header.Version);
Out.write(reinterpret_cast<const char *>(&Version), sizeof(Version));
// Write each section.
for (size_t I = 0, S = SectionHeaders.size(); I < S; ++I) {
Out.write(SectionHeaders[I].data(), SectionHeaders[I].size());
Out.write(reinterpret_cast<const char *>(Obj.Sections[I].Contents.data()),
Obj.Sections[I].Contents.size());
}
return Error::success();
}
} // end namespace wasm
} // end namespace objcopy
} // end namespace llvm
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