1 | //===- WasmWriter.cpp -----------------------------------------------------===// |
2 | // |
3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
4 | // See https://llvm.org/LICENSE.txt for license information. |
5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
6 | // |
7 | //===----------------------------------------------------------------------===// |
8 | |
9 | #include "WasmWriter.h" |
10 | #include "llvm/BinaryFormat/Wasm.h" |
11 | #include "llvm/Support/Endian.h" |
12 | #include "llvm/Support/LEB128.h" |
13 | #include "llvm/Support/raw_ostream.h" |
14 | |
15 | namespace llvm { |
16 | namespace objcopy { |
17 | namespace wasm { |
18 | |
19 | using namespace object; |
20 | using namespace llvm::wasm; |
21 | |
22 | Writer::SectionHeader Writer::(const Section &S, |
23 | size_t &SectionSize) { |
24 | SectionHeader ; |
25 | raw_svector_ostream OS(Header); |
26 | OS << S.SectionType; |
27 | bool HasName = S.SectionType == WASM_SEC_CUSTOM; |
28 | SectionSize = S.Contents.size(); |
29 | if (HasName) |
30 | SectionSize += getULEB128Size(Value: S.Name.size()) + S.Name.size(); |
31 | // If we read this section from an object file, use its original size for the |
32 | // padding of the LEB value to avoid changing the file size. Otherwise, pad |
33 | // out to 5 bytes to make it predictable, and match the behavior of clang. |
34 | unsigned = S.HeaderSecSizeEncodingLen.value_or(u: 5); |
35 | encodeULEB128(Value: SectionSize, OS, PadTo: HeaderSecSizeEncodingLen); |
36 | if (HasName) { |
37 | encodeULEB128(Value: S.Name.size(), OS); |
38 | OS << S.Name; |
39 | } |
40 | // Total section size is the content size plus 1 for the section type and |
41 | // the LEB-encoded size. |
42 | SectionSize = SectionSize + 1 + HeaderSecSizeEncodingLen; |
43 | return Header; |
44 | } |
45 | |
46 | size_t Writer::finalize() { |
47 | size_t ObjectSize = sizeof(WasmMagic) + sizeof(WasmVersion); |
48 | SectionHeaders.reserve(n: Obj.Sections.size()); |
49 | // Finalize the headers of each section so we know the total size. |
50 | for (const Section &S : Obj.Sections) { |
51 | size_t SectionSize; |
52 | SectionHeaders.push_back(x: createSectionHeader(S, SectionSize)); |
53 | ObjectSize += SectionSize; |
54 | } |
55 | return ObjectSize; |
56 | } |
57 | |
58 | Error Writer::write() { |
59 | size_t TotalSize = finalize(); |
60 | Out.reserveExtraSpace(ExtraSize: TotalSize); |
61 | |
62 | // Write the header. |
63 | Out.write(Ptr: Obj.Header.Magic.data(), Size: Obj.Header.Magic.size()); |
64 | uint32_t Version; |
65 | support::endian::write32le(P: &Version, V: Obj.Header.Version); |
66 | Out.write(Ptr: reinterpret_cast<const char *>(&Version), Size: sizeof(Version)); |
67 | |
68 | // Write each section. |
69 | for (size_t I = 0, S = SectionHeaders.size(); I < S; ++I) { |
70 | Out.write(Ptr: SectionHeaders[I].data(), Size: SectionHeaders[I].size()); |
71 | Out.write(Ptr: reinterpret_cast<const char *>(Obj.Sections[I].Contents.data()), |
72 | Size: Obj.Sections[I].Contents.size()); |
73 | } |
74 | |
75 | return Error::success(); |
76 | } |
77 | |
78 | } // end namespace wasm |
79 | } // end namespace objcopy |
80 | } // end namespace llvm |
81 | |