X-Git-Url: http://git.vrable.net/?a=blobdiff_plain;f=store.h;h=6906d6360b79fd8d384bc3fd7ae44937623212e5;hb=b1a0bfe834d45694851787317da2cd55add2d7bb;hp=5d877c66c4a11619a4c8f403022d74856b1750e9;hpb=15f7cef45e82e54a039e5486f08134c4f9a05471;p=cumulus.git

diff --git a/store.h b/store.h
index 5d877c6..6906d63 100644
--- a/store.h
+++ b/store.h
@@ -2,32 +2,31 @@
  * Copyright (C) 2006  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. */
 
-#ifndef _LBS_STORE_H
-#define _LBS_STORE_H
+#ifndef _LBS_TARSTORE_H
+#define _LBS_TARSTORE_H
 
 #include <stdint.h>
+#include <libtar.h>
 
-#include <exception>
+#include <list>
 #include <map>
+#include <set>
 #include <string>
+#include <iostream>
 #include <sstream>
-#include <vector>
 
 #include "sha1.h"
 
+class LbsObject;
+
 /* In memory datatype to represent key/value pairs of information, such as file
  * metadata.  Currently implemented as map<string, string>. */
 typedef std::map<std::string, std::string> dictionary;
 
-/* In-memory representation of a UUID (Universally-Unique Identifier), which is
- * used to name a segment. */
-struct uuid {
-    uint8_t bytes[16];
-};
-
 /* IOException will be thrown if an error occurs while reading or writing in
  * one of the I/O wrappers.  Depending upon the context; this may be fatal or
  * not--typically, errors reading/writing the store will be serious, but errors
@@ -41,187 +40,113 @@ public:
     std::string getError() const { return error; }
 };
 
-/* OutputStream is an abstract interface for writing data without seeking.
- * Output could be to a file, to an object within a segment, or even to a
- * memory buffer to help serialize data. */
-class OutputStream {
-public:
-    OutputStream();
-    virtual ~OutputStream() { }
-
-    // Write the given data buffer
-    void write(const void *data, size_t len);
-
-    // Return the total number of bytes written so far
-    int64_t get_pos() const { return bytes_written; }
-
-    // Convenience functions for writing other data types.  Values are always
-    // written out in little-endian order.
-    void write_u8(uint8_t val);
-    void write_u16(uint16_t val);
-    void write_u32(uint32_t val);
-    void write_u64(uint64_t val);
-
-    void write_s32(int32_t val) { write_u32((uint32_t)val); }
-    void write_s64(int64_t val) { write_u64((uint64_t)val); }
-
-    void write_varint(uint64_t val);
-
-    void write_uuid(const struct uuid &u);
-    void write_string(const std::string &s);
-    void write_dictionary(const dictionary &d);
-
-protected:
-    // Function which actually causes a write: must be overridden by
-    // implementation.
-    virtual void write_internal(const void *data, size_t len) = 0;
-
-private:
-    int64_t bytes_written;
-};
-
-/* An OutputStream implementation which writes data to memory and returns the
- * result as a string. */
-class StringOutputStream : public OutputStream {
-public:
-    StringOutputStream();
-    std::string contents() const { return buf.str(); }
-
-protected:
-    virtual void write_internal(const void *data, size_t len);
-
-private:
-    std::stringstream buf;
-};
-
-/* An OutputStream implementation which writes data via the C stdio layer. */
-class FileOutputStream : public OutputStream {
+/* A simple wrapper around a single TAR file to represent a segment.  Objects
+ * may only be written out all at once, since the tar header must be written
+ * first; incremental writing is not supported. */
+class Tarfile {
 public:
-    explicit FileOutputStream(FILE *file);
-    virtual ~FileOutputStream();
+    Tarfile(const std::string &path, const std::string &segment);
+    ~Tarfile();
 
-protected:
-    virtual void write_internal(const void *data, size_t len);
+    void write_object(int id, const char *data, size_t len);
 
-private:
-    FILE *f;
-};
-
-/* An OutputStream which is simply sends writes to another OutputStream, but
- * does provide separate tracking of bytes written. */
-class WrapperOutputStream : public OutputStream {
-public:
-    explicit WrapperOutputStream(OutputStream &o);
-    virtual ~WrapperOutputStream() { }
-
-protected:
-    virtual void write_internal(const void *data, size_t len);
-
-private:
-    OutputStream &real;
-};
-
-/* Like WrapperOutputStream, but additionally computes a checksum of data as it
- * is written. */
-class ChecksumOutputStream : public OutputStream {
-public:
-    explicit ChecksumOutputStream(OutputStream &o);
-    virtual ~ChecksumOutputStream() { }
-
-    /* Once a checksum is computed, no further data should be written to the
-     * stream. */
-    const uint8_t *finish_and_checksum();
-    size_t checksum_size() const { return csum.checksum_size(); }
+    // Return an estimate of the size of the file.
+    size_t size_estimate() { return size; }
 
-protected:
-    virtual void write_internal(const void *data, size_t len);
+    void internal_write_object(const std::string &path,
+                               const char *data, size_t len);
 
 private:
-    OutputStream &real;
-    SHA1Checksum csum;
+    size_t size;
+    std::string segment_name;
+    std::ostringstream checksums;
+    TAR *t;
 };
 
-/* Simple wrappers that encode integers using a StringOutputStream and return
- * the encoded result. */
-std::string encode_u16(uint16_t val);
-std::string encode_u32(uint32_t val);
-std::string encode_u64(uint64_t val);
-std::string encode_objref(const struct uuid &segment, uint32_t object);
-
-/* A class which is used to pack multiple objects into a single segment, with a
- * lookup table to quickly locate each object.  Call new_object() to get an
- * OutputStream to which a new object may be written, and optionally
- * finish_object() when finished writing the current object.  Only one object
- * may be written to a segment at a time; if multiple objects must be written
- * concurrently, they must be to different segments. */
-class SegmentWriter {
+class TarSegmentStore {
 public:
-    SegmentWriter(OutputStream *output, struct uuid u);
-    ~SegmentWriter();
-
-    struct uuid get_uuid() const { return id; }
-
-    // Start writing out a new object to this segment.
-    OutputStream *new_object(int *id, const char *type);
-    void finish_object();
+    // New segments will be stored in the given directory.
+    TarSegmentStore(const std::string &path) { this->path = path; }
+    ~TarSegmentStore() { sync(); }
 
-    // Determine size of segment data written out so far.
-    size_t get_size() const { return raw_out->get_pos(); }
+    // Writes an object to segment in the store, and returns the name
+    // (segment/object) to refer to it.  The optional parameter group can be
+    // used to control object placement; objects with different group
+    // parameters are kept in separate segments.
+    std::string write_object(const char *data, size_t len,
+                             const std::string &group = "",
+                             const std::list<std::string> &refs = norefs);
 
-    // Utility functions for generating and formatting UUIDs for display.
-    static struct uuid generate_uuid();
-    static std::string format_uuid(const struct uuid u);
+    // Ensure all segments have been fully written.
+    void sync();
 
 private:
-    struct index_info {
-        int64_t offset;         // File offset at which object starts
-        int64_t size;           // Size of object in bytes
-        char type[4];           // Object type code
+    struct segment_info {
+        Tarfile *file;
+        std::string name;           // UUID
+        std::set<std::string> refs; // Other segments this one refers to
+        int count;                  // Objects written to this segment
     };
 
-    typedef std::vector<struct index_info> object_table;
+    std::string path;
+    std::map<std::string, struct segment_info *> segments;
 
-    ChecksumOutputStream *out;  // Output stream with checksumming enabled
-    OutputStream *raw_out;      // Raw output stream, without checksumming
-    struct uuid id;
+    // An empty list which can be used as an argument to write_object to
+    // indicate that this object depends on no others.
+    static std::list<std::string> norefs;
 
-    OutputStream *object_stream;
+    // Ensure that all segments in the given group have been fully written.
+    void close_segment(const std::string &group);
 
-    object_table objects;
+    // Parse an object reference string and return just the segment name
+    // portion.
+    std::string object_reference_to_segment(const std::string &object);
 };
 
-/* A SegmentStore, as the name suggests, is used to store the contents of many
- * segments.  The SegmentStore internally tracks where data should be placed
- * (such as a local directory or remote storage), and allows new segments to be
- * easily created as needed. */
-class SegmentStore {
+/* An in-memory representation of an object, which can be incrementally built
+ * before it is written out to a segment. */
+class LbsObject {
 public:
-    // New segments will be stored in the given directory.
-    SegmentStore(const std::string &path);
-
-    SegmentWriter *new_segment();
+    LbsObject();
+    ~LbsObject();
+
+    // If an object is placed in a group, it will be written out to segments
+    // only containing other objects in the same group.  A group name is simply
+    // a string.
+    //std::string get_group() const { return group; }
+    void set_group(const std::string &g) { group = g; }
+
+    // Data in an object must be written all at once, and cannot be generated
+    // incrementally.  Data can be an arbitrary block of binary data of any
+    // size.  The pointer to the data need only remain valid until write() is
+    // called.
+    //const char *get_data() const { return data; }
+    //size_t get_data_len() const { return data_len; }
+    void set_data(const char *d, size_t len) { data = d; data_len = len; }
+
+    // Write an object to a segment, thus making it permanent.  This function
+    // can be called at most once.
+    void write(TarSegmentStore *store);
+
+    // An object is assigned a permanent name once it has been written to a
+    // segment.  Until that time, its name cannot be determined.
+    std::string get_name() const { return name; }
+
+    // Logically, one object may reference other objects (such as a metadata
+    // listing referncing actual file data blocks).  Such references should be
+    // noted explicitly.  It may eventually be used to build up a tree of
+    // checksums for later verifying integrity.
+    void add_reference(const LbsObject *o);
 
 private:
-    std::string directory;
-};
-
-/* A SegmentPartitioner helps to divide objects up among a collection of
- * segments to meet a rough size limit per segment.  Like a SegmentWriter, only
- * one object should be written at a time; however, multiple
- * SegmentPartitioners can be created using the same base SegmentStore. */
-class SegmentPartitioner {
-public:
-    explicit SegmentPartitioner(SegmentStore *s);
-    ~SegmentPartitioner();
+    std::string group;
+    const char *data;
+    size_t data_len;
 
-    OutputStream *new_object(struct uuid *uuid, int *id, const char *type);
-
-private:
-    size_t target_size;
+    bool written;
+    std::string name;
 
-    SegmentStore *store;
-    SegmentWriter *segment;
-    OutputStream *object;
+    std::set<std::string> refs;
 };
 
-#endif // _LBS_STORE_H
+#endif // _LBS_TARSTORE_H