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TarWriter: Use Ustar header's "prefix" field to store long filenames.

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Tar's Ustar header has the "prefix" field to store a directory
part of a filename. It is not as flexible as the PAX-extended
filename because there's still a limitation on the maximum filename
size, but it mitigates the situation.

This patch should unbreak some Windows buildbots that uses very
old tar command.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291340 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rui Ueyama 2017-01-07 08:28:56 +00:00
parent 7be24b7e92
commit 8d4b4e6f8a
1 changed files with 27 additions and 1 deletions
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28
lib/Support/TarWriter.cpp
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@ -109,14 +109,40 @@ static void writePaxHeader(raw_fd_ostream &OS, StringRef Path) {
pad(OS);
}
// In the Ustar header, a path can be split at any '/' to store
// a path into UstarHeader::Name and UstarHeader::Prefix. This
// function splits a given path for that purpose.
static std::pair<StringRef, StringRef> splitPath(StringRef Path) {
if (Path.size() <= sizeof(UstarHeader::Name))
return {"", Path};
size_t Sep = Path.rfind('/', sizeof(UstarHeader::Name) + 1);
if (Sep == StringRef::npos)
return {"", Path};
return {Path.substr(0, Sep), Path.substr(Sep + 1)};
}
// Returns true if a given path can be stored to a Ustar header
// without the PAX extension.
static bool fitInUstar(StringRef Path) {
StringRef Prefix;
StringRef Name;
std::tie(Prefix, Name) = splitPath(Path);
return Name.size() <= sizeof(UstarHeader::Name);
}
// The PAX header is an extended format, so a PAX header needs
// to be followed by a "real" header.
static void writeUstarHeader(raw_fd_ostream &OS, StringRef Path, size_t Size) {
StringRef Prefix;
StringRef Name;
std::tie(Prefix, Name) = splitPath(Path);
UstarHeader Hdr = {};
memcpy(Hdr.Name, Path.data(), Path.size());
memcpy(Hdr.Name, Name.data(), Name.size());
memcpy(Hdr.Mode, "0000664", 8);
snprintf(Hdr.Size, sizeof(Hdr.Size), "%011zo", Size);
memcpy(Hdr.Magic, "ustar", 6);
memcpy(Hdr.Prefix, Prefix.data(), Prefix.size());
computeChecksum(Hdr);
OS << StringRef(reinterpret_cast<char *>(&Hdr), sizeof(Hdr));
}