From 08147fb0bc1d09610b05f3f7d54eda88ef5776ec Mon Sep 17 00:00:00 2001
From: Michael Vrable <mvrable@cs.ucsd.edu>
Date: Fri, 11 May 2007 10:37:29 -0700
Subject: [PATCH] Remove checksums and reference tracking; I think they are not
 needed.

---
 store.cc | 41 ++---------------------------------------
 store.h  | 14 +-------------
 2 files changed, 3 insertions(+), 52 deletions(-)

diff --git a/store.cc b/store.cc
index 0533630..ce91e55 100644
--- a/store.cc
+++ b/store.cc
@@ -26,8 +26,6 @@ using std::list;
 using std::set;
 using std::string;
 
-list<string> TarSegmentStore::norefs;
-
 Tarfile::Tarfile(const string &path, const string &segment)
     : size(0),
       segment_name(segment)
@@ -39,9 +37,6 @@ Tarfile::Tarfile(const string &path, const string &segment)
 
 Tarfile::~Tarfile()
 {
-    string checksum_list = checksums.str();
-    internal_write_object(segment_name + "/checksums",
-                          checksum_list.data(), checksum_list.size());
     tar_append_eof(t);
 
     if (tar_close(t) != 0)
@@ -55,13 +50,6 @@ void Tarfile::write_object(int id, const char *data, size_t len)
     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";
 }
 
 void Tarfile::internal_write_object(const string &path,
@@ -106,8 +94,7 @@ void Tarfile::internal_write_object(const string &path,
 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)
+                                     std::string &group)
 {
     struct segment_info *segment;
 
@@ -137,12 +124,6 @@ string TarSegmentStore::write_object(const char *data, size_t len, const
 
     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)
@@ -163,14 +144,6 @@ void TarSegmentStore::close_segment(const string &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;
@@ -190,22 +163,12 @@ LbsObject::~LbsObject()
 {
 }
 
-void LbsObject::add_reference(const LbsObject *o)
-{
-    refs.insert(o->get_name());
-}
-
 void LbsObject::write(TarSegmentStore *store)
 {
     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);
+    name = store->write_object(data, data_len, group);
 
     written = true;
     data = NULL;
diff --git a/store.h b/store.h
index 6fec763..a9d6365 100644
--- a/store.h
+++ b/store.h
@@ -59,7 +59,6 @@ public:
 private:
     size_t size;
     std::string segment_name;
-    std::ostringstream checksums;
     TAR *t;
 };
 
@@ -74,8 +73,7 @@ public:
     // 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);
+                             const std::string &group = "");
 
     // Ensure all segments have been fully written.
     void sync();
@@ -91,10 +89,6 @@ private:
     std::string path;
     std::map<std::string, struct segment_info *> segments;
 
-    // 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;
-
     // Ensure that all segments in the given group have been fully written.
     void close_segment(const std::string &group);
 
@@ -132,12 +126,6 @@ public:
     // 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 group;
     const char *data;
-- 
2.20.1