126 lines
3.7 KiB
C++
126 lines
3.7 KiB
C++
//
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// tarball.cpp
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// BoE
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//
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// Created by Celtic Minstrel on 14-04-19.
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//
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//
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#include "tarball.hpp"
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#include <algorithm>
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#include <cstdio>
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#include <ctime>
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#include <cstring>
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#ifdef _MSC_VER
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// For some bizarre reason, Visual Studio doesn't declare snprintf in <cstdio>
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#define snprintf _snprintf_s
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#endif
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tarball::header_posix_ustar tarball::generateTarHeader(const std::string& fileName, unsigned long long fileSize, bool directory){
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static_assert(sizeof(header_posix_ustar) == 512, "Uh-oh! Padding in the tarball header!");
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if(fileSize > 077777777777LL)
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throw std::length_error("Specified file size >= 8 GB");
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if(fileName.length() >= 100)
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throw std::length_error("Specified file name longer than 99 characters.");
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header_posix_ustar header;
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char* init = (char*) &header;
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for(unsigned int i = 0; i < sizeof(header); i++) init[i] = 0;
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snprintf(header.name,100,"%s",fileName.c_str());
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snprintf(header.mode,8,"%07o",0600);
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// leave uid filled with NULs
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// leave gid filled with NULs
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snprintf(header.size,12,"%011llo",fileSize);
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snprintf(header.mtime,12,"%011lo",time(nullptr));
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memset(header.checksum,' ',8);
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header.typeflag[0] = directory ? '5' : '0';
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// leave linkname filled with NULs
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snprintf(header.magic,6,"ustar");
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snprintf(header.version,2," ");
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// leave uname filled with NULs
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// leave gname filled with NULs
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// leave devmajor filled with NULs
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// leave devminor filled with NULs
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// leave prefix filled with NULs
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// leave pad filled with NULs
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unsigned int sum = 0;
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unsigned char* ptr = reinterpret_cast<unsigned char*>(&header);
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for(unsigned int i = 0; i < sizeof(header); i++){
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sum += ptr[i];
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}
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if(sum > 0777777)
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throw std::runtime_error("Checksum overflow");
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snprintf(header.checksum,8,"%o",sum);
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return header;
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}
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void tarball::writeTo(std::ostream& out) {
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static const char padding[512] = {0};
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for(tarfile& entry : files) {
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entry.contents.seekg(0, std::ios_base::end);
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unsigned long long size = entry.contents.tellg();
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unsigned long long padLength = 512 - size % 512;
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entry.contents.seekg(0);
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entry.header = generateTarHeader(entry.filename, size);
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out.write((char*)&entry.header, sizeof(header_posix_ustar));
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if(size == 0) continue;
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out << entry.contents.rdbuf();
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if(padLength < 512)
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out.write(padding, padLength);
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}
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}
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void tarball::readFrom(std::istream& in) {
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static char buf[513];
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while(!in.eof()) {
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files.push_back(tarfile());
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header_posix_ustar& header = files.back().header;
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in.read((char*)&header, sizeof(header_posix_ustar));
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if(in.eof()) break; // Because it seems MSVC doesn't set the EOFbit until a read fails? Or something?
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files.back().filename = header.name;
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unsigned long long size;
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sscanf(header.size, "%llo", &size);
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unsigned long long padLength = 512 - size % 512;
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while(size > 0) {
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unsigned long long chunkSz = std::min(size, 512ull);
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in.read(buf, chunkSz);
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files.back().contents.write(buf, chunkSz);
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size -= chunkSz;
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}
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// Skip past the padding without using seekg.
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// This is because the gzstreams don't support seekg.
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// We're done with the data in this buffer, anyway, so just dump the padding here.
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if(padLength < 512)
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in.read(buf, padLength);
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}
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}
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std::ostream& tarball::newFile(std::string fname) {
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files.push_back(tarfile());
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files.back().filename = fname;
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return files.back().contents;
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}
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std::istream& tarball::getFile(std::string fname) {
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for(tarfile& entry : files) {
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if(entry.filename == fname)
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return entry.contents;
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}
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// If the file doesn't exist, return an empty stream
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static std::istringstream empty;
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empty.clear(std::ios_base::badbit);
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empty.seekg(0);
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return empty;
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}
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bool tarball::hasFile(std::string fname) {
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for(tarfile& entry : files) {
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if(entry.filename == fname) {
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return true;
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}
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}
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return false;
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}
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