mirror of
https://github.com/rui314/mold.git
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110 lines
3.0 KiB
C++
110 lines
3.0 KiB
C++
#include "mold.h"
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namespace mold {
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// A tar file consists of one or more Ustar header followed by data.
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// Each Ustar header represents a single file in an archive.
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//
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// tar is an old file format, and its `name` field is only 100 bytes long.
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// If `name` is longer than 100 bytes, we can emit a PAX header before a
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// Ustar header to store a long filename.
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//
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// For simplicity, we always emit a PAX header even for a short filename.
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struct UstarHeader {
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UstarHeader() {
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memset(this, 0, sizeof(*this));
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}
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void finalize() {
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memset(checksum, ' ', sizeof(checksum));
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memcpy(magic, "ustar", 5);
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memcpy(version, "00", 2);
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// Compute checksum
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int sum = 0;
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for (i64 i = 0; i < sizeof(*this); i++)
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sum += ((u8 *)this)[i];
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assert(sum < 01000000);
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snprintf(checksum, sizeof(checksum), "%06o", sum);
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}
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char name[100];
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char mode[8];
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char uid[8];
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char gid[8];
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char size[12];
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char mtime[12];
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char checksum[8];
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char typeflag[1];
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char linkname[100];
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char magic[6];
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char version[2];
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char uname[32];
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char gname[32];
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char devmajor[8];
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char devminor[8];
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char prefix[155];
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char pad[12];
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};
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static std::string encode_path(std::string basedir, std::string path) {
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path = path_clean(basedir + "/" + path);
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// Construct a string which contains something like
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// "16 path=foo/bar\n" where 16 is the size of the string
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// including the size string itself.
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i64 len = std::string(" path=\n").size() + path.size();
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i64 total = std::to_string(len).size() + len;
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total = std::to_string(total).size() + len;
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return std::to_string(total) + " path=" + path + "\n";
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}
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std::unique_ptr<TarWriter>
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TarWriter::open(std::string output_path, std::string basedir) {
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FILE *out = fopen(output_path.c_str(), "w");
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if (!out)
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return nullptr;
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return std::unique_ptr<TarWriter>(new TarWriter(out, basedir));
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}
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TarWriter::~TarWriter() {
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fclose(out);
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}
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void TarWriter::append(std::string path, std::string_view data) {
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// Write PAX header
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static_assert(sizeof(UstarHeader) == BLOCK_SIZE);
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UstarHeader pax;
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std::string attr = encode_path(basedir, path);
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snprintf(pax.size, sizeof(pax.size), "%011zo", attr.size());
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pax.typeflag[0] = 'x';
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pax.finalize();
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fwrite(&pax, sizeof(pax), 1, out);
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// Write pathname
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fwrite(attr.data(), attr.size(), 1, out);
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fseek(out, align_to(ftell(out), BLOCK_SIZE), SEEK_SET);
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// Write Ustar header
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UstarHeader ustar;
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memcpy(ustar.mode, "0000664", 8);
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snprintf(ustar.size, sizeof(ustar.size), "%011zo", data.size());
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ustar.finalize();
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fwrite(&ustar, sizeof(ustar), 1, out);
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// Write file contents
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fwrite(data.data(), data.size(), 1, out);
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fseek(out, align_to(ftell(out), BLOCK_SIZE), SEEK_SET);
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// A tar file must ends with two empty blocks, so write such
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// terminator and seek back.
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u8 terminator[BLOCK_SIZE * 2] = {};
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fwrite(&terminator, BLOCK_SIZE * 2, 1, out);
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fseek(out, -BLOCK_SIZE * 2, SEEK_END);
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assert(ftell(out) % BLOCK_SIZE == 0);
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}
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} // namespace mold
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