X-Git-Url: http://git.vrable.net/?a=blobdiff_plain;f=store.h;h=1fd366b6ed24aed9ddfb6cb7ed898b07a4038f26;hb=117fafdd16cf070cda130d6d8ac321947692055a;hp=d4847806c26a851cf0eb66d1afa9ef884a703957;hpb=38c66f088ed65d2f42264c92add6e0b33eac2bfc;p=cumulus.git diff --git a/store.h b/store.h index d484780..1fd366b 100644 --- a/store.h +++ b/store.h @@ -2,18 +2,36 @@ * 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 #include +#include -#include +#include #include +#include #include +#include #include +#include "sha1.h" +#include "ref.h" + +class LbsObject; + +/* In memory datatype to represent key/value pairs of information, such as file + * metadata. Currently implemented as map. */ typedef std::map dictionary; +/* 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 + * reading an individual file are less so. */ class IOException : public std::exception { private: std::string error; @@ -23,47 +41,117 @@ public: std::string getError() const { return error; } }; -class 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: - virtual ~OutputStream() { } - virtual void write(const void *data, size_t len) = 0; + Tarfile(const std::string &path, const std::string &segment); + ~Tarfile(); - /* 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); + int spawn_filter(int fd_out); + void write_object(int id, const char *data, size_t len); - void write_s32(int32_t val) { write_u32((uint32_t)val); } - void write_s64(int64_t val) { write_u64((uint64_t)val); } + // Return an estimate of the size of the file. + size_t size_estimate(); - void write_varint(uint64_t val); + void internal_write_object(const std::string &path, + const char *data, size_t len); - void write_string(const std::string &s); - void write_dictionary(const dictionary &d); +private: + size_t size; + std::string segment_name; + TAR *t; + + /* Filter support. */ + int real_fd, filter_fd; + pid_t filter_pid; }; -class StringOutputStream : public OutputStream { -private: - std::stringstream buf; +class TarSegmentStore { public: - StringOutputStream(); + // New segments will be stored in the given directory. + TarSegmentStore(const std::string &path) { this->path = path; } + ~TarSegmentStore() { sync(); } - virtual void write(const void *data, size_t len); - std::string contents() const { return buf.str(); } -}; + // 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. + ObjectReference write_object(const char *data, size_t len, + const std::string &group = ""); + + // Ensure all segments have been fully written. + void sync(); + + // Dump statistics to stdout about how much data has been written + void dump_stats(); -class FileOutputStream : public OutputStream { private: - FILE *f; + struct segment_info { + Tarfile *file; + std::string name; // UUID + int count; // Objects written to this segment + }; + + std::string path; + std::map segments; + + // Ensure that all segments in the given group have been fully written. + void close_segment(const std::string &group); + + // Parse an object reference string and return just the segment name + // portion. + std::string object_reference_to_segment(const std::string &object); +}; + +/* An in-memory representation of an object, which can be incrementally built + * before it is written out to a segment. */ +class LbsObject { public: - explicit FileOutputStream(FILE *file); - virtual ~FileOutputStream(); + 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. + 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); + + // Compute the checksum of an object, and include it in the object + // reference. This should be called after write(), and the data specified + // by set_data() must remain valid through the call to checksum(). + void checksum(); - virtual void write(const void *data, size_t len); + // 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 ref.to_string(); } + ObjectReference get_ref() { return ref; } + +private: + std::string group; + const char *data; + size_t data_len; + + bool written; + ObjectReference ref; }; -std::string encode_u16(uint16_t val); -std::string encode_u32(uint32_t val); -std::string encode_u64(uint64_t val); +/* Program through which segment data is piped before being written to file. */ +extern const char *filter_program; + +/* Extension which should be appended to segments written out (.tar is already + * included; this adds to it) */ +extern const char *filter_extension; + +#endif // _LBS_STORE_H