From 4a6945983fa171fa843c6f8955ba601f733f3ca5 Mon Sep 17 00:00:00 2001 From: Michael Vrable Date: Sun, 24 Dec 2006 22:28:59 -0800 Subject: [PATCH] Add new interface for creating new segments. --- scandir.cc | 19 +++++++------------ store.cc | 43 ++++++++++++++++++++++++++++++++----------- store.h | 25 +++++++++++++++++++++++-- 3 files changed, 62 insertions(+), 25 deletions(-) diff --git a/scandir.cc b/scandir.cc index 98285ac..d0ed67d 100644 --- a/scandir.cc +++ b/scandir.cc @@ -201,19 +201,12 @@ void scandir(const string& path) int main(int argc, char *argv[]) { - struct uuid id = SegmentWriter::generate_uuid(); - string filename = SegmentWriter::format_uuid(id); - - printf("Backup UUID: %s\n", filename.c_str()); - FILE *dump = fopen(filename.c_str(), "w"); - if (dump == NULL) { - fprintf(stderr, "Cannot open file %s: %m\n", filename.c_str()); - return 1; - } + SegmentStore ss("."); + SegmentWriter *sw = ss.new_segment(); + info_dump = sw->new_object(); - FileOutputStream os(dump); - SegmentWriter sw(os, id); - info_dump = sw.new_object(); + string uuid = SegmentWriter::format_uuid(sw->get_uuid()); + printf("Backup UUID: %s\n", uuid.c_str()); try { scanfile("."); @@ -221,5 +214,7 @@ int main(int argc, char *argv[]) fprintf(stderr, "IOException: %s\n", e.getError().c_str()); } + delete sw; + return 0; } diff --git a/store.cc b/store.cc index 2dc6f84..1686798 100644 --- a/store.cc +++ b/store.cc @@ -166,15 +166,15 @@ string encode_u64(uint64_t val) return s.contents(); } -SegmentWriter::SegmentWriter(OutputStream &output, struct uuid u) +SegmentWriter::SegmentWriter(OutputStream *output, struct uuid u) : out(output), id(u), object_stream(NULL) { /* Write out the segment header first. */ static const char signature[] = "LBSSEG0\n"; - out.write(signature, strlen(signature)); - out.write(id.bytes, sizeof(struct uuid)); + out->write(signature, strlen(signature)); + out->write(id.bytes, sizeof(struct uuid)); } SegmentWriter::~SegmentWriter() @@ -185,18 +185,22 @@ SegmentWriter::~SegmentWriter() // Write out the object table which gives the sizes and locations of all // objects, and then add the trailing signature, which indicates the end of // the segment and gives the offset of the object table. - int64_t index_offset = out.get_pos(); + int64_t index_offset = out->get_pos(); for (object_table::const_iterator i = objects.begin(); i != objects.end(); ++i) { - out.write_s64(i->first); - out.write_s64(i->second); + out->write_s64(i->first); + out->write_s64(i->second); } static const char signature2[] = "LBSEND"; - out.write(signature2, strlen(signature2)); - out.write_s64(index_offset); - out.write_u32(objects.size()); + out->write(signature2, strlen(signature2)); + out->write_s64(index_offset); + out->write_u32(objects.size()); + + /* The SegmentWriter takes ownership of the OutputStream it is writing to, + * and destroys it automatically when done with the segment. */ + delete out; } OutputStream *SegmentWriter::new_object() @@ -204,8 +208,8 @@ OutputStream *SegmentWriter::new_object() if (object_stream) finish_object(); - object_start_offset = out.get_pos(); - object_stream = new WrapperOutputStream(out); + object_start_offset = out->get_pos(); + object_stream = new WrapperOutputStream(*out); return object_stream; } @@ -240,3 +244,20 @@ string SegmentWriter::format_uuid(const struct uuid u) return string(buf); } + +SegmentStore::SegmentStore(const string &path) + : directory(path) +{ +} + +SegmentWriter *SegmentStore::new_segment() +{ + struct uuid id = SegmentWriter::generate_uuid(); + string filename = directory + "/" + SegmentWriter::format_uuid(id); + + FILE *f = fopen(filename.c_str(), "wb"); + if (f == NULL) + throw IOException("Unable to open new segment"); + + return new SegmentWriter(new FileOutputStream(f), id); +} diff --git a/store.h b/store.h index 8344dda..0cd2c4b 100644 --- a/store.h +++ b/store.h @@ -122,9 +122,15 @@ struct uuid { uint8_t bytes[16]; }; +/* 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 { public: - SegmentWriter(OutputStream &output, struct uuid u); + SegmentWriter(OutputStream *output, struct uuid u); ~SegmentWriter(); struct uuid get_uuid() const { return id; } @@ -140,7 +146,7 @@ public: private: typedef std::vector > object_table; - OutputStream &out; + OutputStream *out; struct uuid id; int64_t object_start_offset; @@ -149,4 +155,19 @@ private: object_table objects; }; +/* 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 { +public: + // New segments will be stored in the given directory. + SegmentStore(const std::string &path); + + SegmentWriter *new_segment(); + +private: + std::string directory; +}; + #endif // _LBS_STORE_H -- 2.20.1