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 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. */
9 #ifndef _LBS_TARSTORE_H
10 #define _LBS_TARSTORE_H
24 /* In memory datatype to represent key/value pairs of information, such as file
25 * metadata. Currently implemented as map<string, string>. */
26 typedef std::map<std::string, std::string> dictionary;
28 /* IOException will be thrown if an error occurs while reading or writing in
29 * one of the I/O wrappers. Depending upon the context; this may be fatal or
30 * not--typically, errors reading/writing the store will be serious, but errors
31 * reading an individual file are less so. */
32 class IOException : public std::exception {
36 explicit IOException(const std::string &err) { error = err; }
37 virtual ~IOException() throw () { }
38 std::string getError() const { return error; }
41 /* A simple wrapper around a single TAR file to represent a segment. Objects
42 * may only be written out all at once, since the tar header must be written
43 * first; incremental writing is not supported. */
46 Tarfile(const std::string &path, const std::string &segment);
49 void write_object(int id, const char *data, size_t len);
51 // Return an estimate of the size of the file.
52 size_t size_estimate() { return size; }
54 void internal_write_object(const std::string &path,
55 const char *data, size_t len);
59 std::string segment_name;
60 std::ostringstream checksums;
64 class TarSegmentStore {
66 // New segments will be stored in the given directory.
67 TarSegmentStore(const std::string &path) { this->path = path; }
68 ~TarSegmentStore() { sync(); }
70 // Writes an object to segment in the store, and returns the name
71 // (segment/object) to refer to it. The optional parameter group can be
72 // used to control object placement; objects with different group
73 // parameters are kept in separate segments.
74 std::string write_object(const char *data, size_t len,
75 const std::string &group = "",
76 const std::list<std::string> &refs = norefs);
78 // Ensure all segments have been fully written.
84 std::string name; // UUID
85 std::set<std::string> refs; // Other segments this one refers to
86 int count; // Objects written to this segment
90 std::map<std::string, struct segment_info *> segments;
92 // An empty list which can be used as an argument to write_object to
93 // indicate that this object depends on no others.
94 static std::list<std::string> norefs;
96 // Ensure that all segments in the given group have been fully written.
97 void close_segment(const std::string &group);
99 // Parse an object reference string and return just the segment name
101 std::string object_reference_to_segment(const std::string &object);
104 #endif // _LBS_TARSTORE_H