1 /* LBS: An LFS-inspired filesystem backup system
2 * Copyright (C) 2007 Michael Vrable
4 * Backup data is stored in a collection of objects, which are grouped together
5 * into segments for storage purposes. This implementation of the object store
6 * is built on top of libtar, and represents segments as TAR files and objects
7 * as files within them. */
10 #include <sys/types.h>
15 #include <uuid/uuid.h>
24 Tarfile::Tarfile(const string &path, const string &segment)
28 if (tar_open(&t, (char *)path.c_str(), NULL, O_WRONLY | O_CREAT, 0600,
29 TAR_VERBOSE | TAR_GNU) == -1)
30 throw IOException("Error opening Tarfile");
35 string checksum_list = checksums.str();
36 internal_write_object(segment_name + "/checksums",
37 checksum_list.data(), checksum_list.size());
40 if (tar_close(t) != 0)
41 throw IOException("Error closing Tarfile");
44 void Tarfile::write_object(int id, const char *data, size_t len)
47 sprintf(buf, "%08x", id);
48 string path = segment_name + "/" + buf;
50 internal_write_object(path, data, len);
52 // Compute a checksum for the data block, which will be stored at the end
55 hash.process(data, len);
56 sprintf(buf, "%08x", id);
57 checksums << buf << " " << hash.checksum_str() << "\n";
60 void Tarfile::internal_write_object(const string &path,
61 const char *data, size_t len)
63 memset(&t->th_buf, 0, sizeof(struct tar_header));
65 th_set_type(t, S_IFREG | 0600);
70 th_set_mtime(t, time(NULL));
71 th_set_path(t, const_cast<char *>(path.c_str()));
75 throw IOException("Error writing tar header");
82 size_t blocks = (len + T_BLOCKSIZE - 1) / T_BLOCKSIZE;
83 size_t padding = blocks * T_BLOCKSIZE - len;
85 for (size_t i = 0; i < blocks - 1; i++) {
86 if (tar_block_write(t, &data[i * T_BLOCKSIZE]) == -1)
87 throw IOException("Error writing tar block");
90 char block[T_BLOCKSIZE];
91 memset(block, 0, sizeof(block));
92 memcpy(block, &data[T_BLOCKSIZE * (blocks - 1)], T_BLOCKSIZE - padding);
93 if (tar_block_write(t, block) == -1)
94 throw IOException("Error writing final tar block");
96 size += blocks * T_BLOCKSIZE;
99 static const size_t SEGMENT_SIZE = 4 * 1024 * 1024;
101 string TarSegmentStore::write_object(const char *data, size_t len, const
104 struct segment_info *segment;
106 // Find the segment into which the object should be written, looking up by
107 // group. If no segment exists yet, create one.
108 if (segments.find(group) == segments.end()) {
109 segment = new segment_info;
114 uuid_unparse_lower(uuid, uuid_buf);
115 segment->name = uuid_buf;
117 string filename = path + "/" + segment->name + ".tar";
118 segment->file = new Tarfile(filename, segment->name);
122 segments[group] = segment;
124 segment = segments[group];
127 int id = segment->count;
129 sprintf(id_buf, "%08x", id);
131 segment->file->write_object(id, data, len);
134 string full_name = segment->name + "/" + id_buf;
136 // If this segment meets or exceeds the size target, close it so that
137 // future objects will go into a new segment.
138 if (segment->file->size_estimate() >= SEGMENT_SIZE)
139 close_segment(group);
144 void TarSegmentStore::sync()
146 while (!segments.empty())
147 close_segment(segments.begin()->first);
150 void TarSegmentStore::close_segment(const string &group)
152 struct segment_info *segment = segments[group];
153 fprintf(stderr, "Closing segment group %s (%s)\n",
154 group.c_str(), segment->name.c_str());
156 delete segment->file;
157 segments.erase(segments.find(group));