/* LBS: An LFS-inspired filesystem backup system
- * Copyright (C) 2006 Michael Vrable
+ * Copyright (C) 2007 Michael Vrable
*
* Backup data is stored in a collection of objects, which are grouped together
- * into segments for storage purposes. This file provides interfaces for
- * reading and writing objects and segments. */
+ * into segments for storage purposes. This implementation of the object store
+ * is built on top of libtar, and represents segments as TAR files and objects
+ * as files within them. */
#include <assert.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <time.h>
+#include <uuid/uuid.h>
+
+#include <list>
+#include <set>
+#include <string>
+#include <iostream>
#include "store.h"
+using std::list;
+using std::set;
using std::string;
-void OutputStream::write_u8(uint8_t val)
-{
- write(&val, 1);
-}
+list<string> TarSegmentStore::norefs;
-void OutputStream::write_u16(uint16_t val)
+Tarfile::Tarfile(const string &path, const string &segment)
+ : size(0),
+ segment_name(segment)
{
- unsigned char buf[2];
-
- buf[0] = val & 0xff;
- buf[1] = (val >> 8) & 0xff;
- write(buf, 2);
+ if (tar_open(&t, (char *)path.c_str(), NULL, O_WRONLY | O_CREAT, 0600,
+ TAR_VERBOSE | TAR_GNU) == -1)
+ throw IOException("Error opening Tarfile");
}
-void OutputStream::write_u32(uint32_t val)
+Tarfile::~Tarfile()
{
- unsigned char buf[4];
+ string checksum_list = checksums.str();
+ internal_write_object(segment_name + "/checksums",
+ checksum_list.data(), checksum_list.size());
+ tar_append_eof(t);
- buf[0] = val & 0xff;
- buf[1] = (val >> 8) & 0xff;
- buf[2] = (val >> 16) & 0xff;
- buf[3] = (val >> 24) & 0xff;
- write(buf, 4);
+ if (tar_close(t) != 0)
+ throw IOException("Error closing Tarfile");
}
-void OutputStream::write_u64(uint64_t val)
+void Tarfile::write_object(int id, const char *data, size_t len)
{
- unsigned char buf[8];
-
- buf[0] = val & 0xff;
- buf[1] = (val >> 8) & 0xff;
- buf[2] = (val >> 16) & 0xff;
- buf[3] = (val >> 24) & 0xff;
- buf[4] = (val >> 32) & 0xff;
- buf[5] = (val >> 40) & 0xff;
- buf[6] = (val >> 48) & 0xff;
- buf[7] = (val >> 56) & 0xff;
- write(buf, 8);
+ char buf[64];
+ sprintf(buf, "%08x", id);
+ string path = segment_name + "/" + buf;
+
+ internal_write_object(path, data, len);
+
+ // Compute a checksum for the data block, which will be stored at the end
+ // of the TAR file.
+ SHA1Checksum hash;
+ hash.process(data, len);
+ sprintf(buf, "%08x", id);
+ checksums << buf << " " << hash.checksum_str() << "\n";
}
-/* Writes an integer to an output stream using a variable-sized representation:
- * seven bits are written at a time (little-endian), and the eigth bit of each
- * byte is set if more data follows. */
-void OutputStream::write_varint(uint64_t val)
+void Tarfile::internal_write_object(const string &path,
+ const char *data, size_t len)
{
- do {
- uint8_t remainder = (val & 0x7f);
- val >>= 7;
- if (val)
- remainder |= 0x80;
- write_u8(remainder);
- } while (val);
-}
+ memset(&t->th_buf, 0, sizeof(struct tar_header));
-/* Write an arbitrary string by first writing out the length, followed by the
- * data itself. */
-void OutputStream::write_string(const string &s)
-{
- size_t len = s.length();
- write_varint(len);
- write(s.data(), len);
-}
+ th_set_type(t, S_IFREG | 0600);
+ th_set_user(t, 0);
+ th_set_group(t, 0);
+ th_set_mode(t, 0600);
+ th_set_size(t, len);
+ th_set_mtime(t, time(NULL));
+ th_set_path(t, const_cast<char *>(path.c_str()));
+ th_finish(t);
-void OutputStream::write_dictionary(const dictionary &d)
-{
- size_t size = d.size();
- size_t written = 0;
+ if (th_write(t) != 0)
+ throw IOException("Error writing tar header");
+
+ size += T_BLOCKSIZE;
- write_varint(size);
+ if (len == 0)
+ return;
- for (dictionary::const_iterator i = d.begin(); i != d.end(); ++i) {
- write_string(i->first);
- write_string(i->second);
- written++;
+ size_t blocks = (len + T_BLOCKSIZE - 1) / T_BLOCKSIZE;
+ size_t padding = blocks * T_BLOCKSIZE - len;
+
+ for (size_t i = 0; i < blocks - 1; i++) {
+ if (tar_block_write(t, &data[i * T_BLOCKSIZE]) == -1)
+ throw IOException("Error writing tar block");
}
- assert(written == size);
+ char block[T_BLOCKSIZE];
+ memset(block, 0, sizeof(block));
+ memcpy(block, &data[T_BLOCKSIZE * (blocks - 1)], T_BLOCKSIZE - padding);
+ if (tar_block_write(t, block) == -1)
+ throw IOException("Error writing final tar block");
+
+ size += blocks * T_BLOCKSIZE;
}
-StringOutputStream::StringOutputStream()
- : buf(std::ios_base::out)
+static const size_t SEGMENT_SIZE = 4 * 1024 * 1024;
+
+string TarSegmentStore::write_object(const char *data, size_t len, const
+ std::string &group,
+ const std::list<std::string> &refs)
{
+ struct segment_info *segment;
+
+ // Find the segment into which the object should be written, looking up by
+ // group. If no segment exists yet, create one.
+ if (segments.find(group) == segments.end()) {
+ segment = new segment_info;
+
+ uint8_t uuid[16];
+ char uuid_buf[40];
+ uuid_generate(uuid);
+ uuid_unparse_lower(uuid, uuid_buf);
+ segment->name = uuid_buf;
+
+ string filename = path + "/" + segment->name + ".tar";
+ segment->file = new Tarfile(filename, segment->name);
+
+ segment->count = 0;
+
+ segments[group] = segment;
+ } else {
+ segment = segments[group];
+ }
+
+ int id = segment->count;
+ char id_buf[64];
+ sprintf(id_buf, "%08x", id);
+
+ segment->file->write_object(id, data, len);
+ segment->count++;
+
+ string full_name = segment->name + "/" + id_buf;
+
+ // Store any dependencies this object has on other segments, so they can be
+ // written when the segment is closed.
+ for (list<string>::const_iterator i = refs.begin(); i != refs.end(); ++i) {
+ segment->refs.insert(*i);
+ }
+
+ // If this segment meets or exceeds the size target, close it so that
+ // future objects will go into a new segment.
+ if (segment->file->size_estimate() >= SEGMENT_SIZE)
+ close_segment(group);
+
+ return full_name;
}
-void StringOutputStream::write(const void *data, size_t len)
+void TarSegmentStore::sync()
{
- buf.write((const char *)data, len);
- if (!buf.good())
- throw IOException("error writing to StringOutputStream");
+ while (!segments.empty())
+ close_segment(segments.begin()->first);
}
-FileOutputStream::FileOutputStream(FILE *file)
+void TarSegmentStore::close_segment(const string &group)
{
- f = file;
+ struct segment_info *segment = segments[group];
+ fprintf(stderr, "Closing segment group %s (%s)\n",
+ group.c_str(), segment->name.c_str());
+
+ string reflist;
+ for (set<string>::iterator i = segment->refs.begin();
+ i != segment->refs.end(); ++i) {
+ reflist += *i + "\n";
+ }
+ segment->file->internal_write_object(segment->name + "/references",
+ reflist.data(), reflist.size());
+
+ delete segment->file;
+ segments.erase(segments.find(group));
+ delete segment;
}
-FileOutputStream::~FileOutputStream()
+string TarSegmentStore::object_reference_to_segment(const string &object)
{
- fclose(f);
+ return object;
}
-void FileOutputStream::write(const void *data, size_t len)
+LbsObject::LbsObject()
+ : group(""), data(NULL), data_len(0), written(false)
{
- size_t res;
-
- res = fwrite(data, 1, len, f);
- if (res != len) {
- throw IOException("write error");
- }
}
-/* Utility functions, for encoding data types to strings. */
-string encode_u16(uint16_t val)
+LbsObject::~LbsObject()
{
- StringOutputStream s;
- s.write_u16(val);
- return s.contents();
}
-string encode_u32(uint32_t val)
+void LbsObject::add_reference(const LbsObject *o)
{
- StringOutputStream s;
- s.write_u32(val);
- return s.contents();
+ refs.insert(o->get_name());
}
-string encode_u64(uint64_t val)
+void LbsObject::write(TarSegmentStore *store)
{
- StringOutputStream s;
- s.write_u64(val);
- return s.contents();
+ assert(data != NULL);
+ assert(!written);
+
+ list<string> reflist;
+ for (set<string>::iterator i = refs.begin(); i != refs.end(); ++i) {
+ reflist.push_back(*i);
+ }
+
+ name = store->write_object(data, data_len, group, reflist);
+
+ written = true;
+ data = NULL;
}
projects / cumulus.git / blobdiff