1 /* LBS: An LFS-inspired filesystem backup system
2 * Copyright (C) 2006 Michael Vrable
4 * Backup data is stored in a collection of objects, which are grouped together
5 * into segments for storage purposes. This file provides interfaces for
6 * reading and writing objects and segments. */
15 OutputStream::OutputStream()
20 void OutputStream::write(const void *data, size_t len)
22 write_internal(data, len);
26 void OutputStream::write_u8(uint8_t val)
31 void OutputStream::write_u16(uint16_t val)
36 buf[1] = (val >> 8) & 0xff;
40 void OutputStream::write_u32(uint32_t val)
45 buf[1] = (val >> 8) & 0xff;
46 buf[2] = (val >> 16) & 0xff;
47 buf[3] = (val >> 24) & 0xff;
51 void OutputStream::write_u64(uint64_t val)
56 buf[1] = (val >> 8) & 0xff;
57 buf[2] = (val >> 16) & 0xff;
58 buf[3] = (val >> 24) & 0xff;
59 buf[4] = (val >> 32) & 0xff;
60 buf[5] = (val >> 40) & 0xff;
61 buf[6] = (val >> 48) & 0xff;
62 buf[7] = (val >> 56) & 0xff;
66 /* Writes an integer to an output stream using a variable-sized representation:
67 * seven bits are written at a time (little-endian), and the eigth bit of each
68 * byte is set if more data follows. */
69 void OutputStream::write_varint(uint64_t val)
72 uint8_t remainder = (val & 0x7f);
80 void OutputStream::write_uuid(const struct uuid &u)
85 /* Write an arbitrary string by first writing out the length, followed by the
87 void OutputStream::write_string(const string &s)
89 size_t len = s.length();
94 void OutputStream::write_dictionary(const dictionary &d)
96 size_t size = d.size();
101 for (dictionary::const_iterator i = d.begin(); i != d.end(); ++i) {
102 write_string(i->first);
103 write_string(i->second);
107 assert(written == size);
110 StringOutputStream::StringOutputStream()
111 : buf(std::ios_base::out)
115 void StringOutputStream::write_internal(const void *data, size_t len)
117 buf.write((const char *)data, len);
119 throw IOException("error writing to StringOutputStream");
122 FileOutputStream::FileOutputStream(FILE *file)
127 FileOutputStream::~FileOutputStream()
132 void FileOutputStream::write_internal(const void *data, size_t len)
136 res = fwrite(data, 1, len, f);
138 throw IOException("write error");
142 WrapperOutputStream::WrapperOutputStream(OutputStream &o)
147 void WrapperOutputStream::write_internal(const void *data, size_t len)
149 real.write(data, len);
152 /* Provide checksumming of a data stream. */
153 ChecksumOutputStream::ChecksumOutputStream(OutputStream &o)
158 void ChecksumOutputStream::write_internal(const void *data, size_t len)
160 real.write(data, len);
161 csum.process(data, len);
164 const uint8_t *ChecksumOutputStream::finish_and_checksum()
166 return csum.checksum();
169 /* Utility functions, for encoding data types to strings. */
170 string encode_u16(uint16_t val)
172 StringOutputStream s;
177 string encode_u32(uint32_t val)
179 StringOutputStream s;
184 string encode_u64(uint64_t val)
186 StringOutputStream s;
191 string encode_objref(const struct uuid &segment, uint32_t object)
193 StringOutputStream s;
194 s.write_uuid(segment);
199 SegmentWriter::SegmentWriter(OutputStream *output, struct uuid u)
204 /* All output data will be checksummed except the very last few bytes,
205 * which are the checksum itself. */
206 out = new ChecksumOutputStream(*raw_out);
208 /* Write out the segment header first. */
209 static const char signature[] = "LBSSEG0\n";
210 out->write(signature, strlen(signature));
214 SegmentWriter::~SegmentWriter()
219 // Write out the object table which gives the sizes and locations of all
220 // objects, and then add the trailing signature, which indicates the end of
221 // the segment and gives the offset of the object table.
222 int64_t index_offset = out->get_pos();
224 for (object_table::const_iterator i = objects.begin();
225 i != objects.end(); ++i) {
226 out->write_s64(i->first);
227 out->write_s64(i->second);
230 static const char signature2[] = "LBSEND";
231 out->write(signature2, strlen(signature2));
232 out->write_s64(index_offset);
233 out->write_u32(objects.size());
235 /* Finally, append a checksum to the end of the file, so that its integrity
236 * (against accidental, not malicious, corruption) can be verified. */
237 const uint8_t *csum = out->finish_and_checksum();
238 raw_out->write(csum, out->checksum_size());
240 /* The SegmentWriter takes ownership of the OutputStream it is writing to,
241 * and destroys it automatically when done with the segment. */
246 OutputStream *SegmentWriter::new_object(int *id)
251 object_start_offset = out->get_pos();
252 object_stream = new WrapperOutputStream(*out);
255 *id = objects.size();
258 return object_stream;
261 void SegmentWriter::finish_object()
263 assert(object_stream != NULL);
265 // store (start, length) information for locating this object
266 objects.push_back(std::make_pair(object_start_offset,
267 object_stream->get_pos()));
269 delete object_stream;
270 object_stream = NULL;
273 struct uuid SegmentWriter::generate_uuid()
277 uuid_generate(u.bytes);
282 string SegmentWriter::format_uuid(const struct uuid u)
284 // A UUID only takes 36 bytes, plus the trailing '\0', so this is safe.
287 uuid_unparse_lower(u.bytes, buf);
292 SegmentStore::SegmentStore(const string &path)
297 SegmentWriter *SegmentStore::new_segment()
299 struct uuid id = SegmentWriter::generate_uuid();
300 string filename = directory + "/" + SegmentWriter::format_uuid(id);
302 FILE *f = fopen(filename.c_str(), "wb");
304 throw IOException("Unable to open new segment");
306 return new SegmentWriter(new FileOutputStream(f), id);
309 SegmentPartitioner::SegmentPartitioner(SegmentStore *s)
314 // Default target size is around 1 MB
315 target_size = 1024 * 1024;
318 SegmentPartitioner::~SegmentPartitioner()
324 OutputStream *SegmentPartitioner::new_object(struct uuid *uuid, int *id)
326 if (segment != NULL && segment->get_size() > target_size) {
332 segment = store->new_segment();
335 *uuid = segment->get_uuid();
337 return segment->new_object(id);