wip

Makefile

@@ -1,8 +1,8 @@
 
-#LIBS=lmdb-0.9.21/libraries/liblmdb/liblmdb.a
-#INCLUDES=-Ilmdb-0.9.21/libraries/liblmdb/liblmdb
+LIBS=lmdb-LMDB_0.9.22/libraries/liblmdb/liblmdb.a
+INCLUDES=-Ilmdb-LMDB_0.9.22/libraries/liblmdb
 
-LIBS=-llmdb
+#LIBS=-llmdb
 CXXFLAGS:=-std=gnu++11 -Wall -O2 -MMD -MP -ggdb -pthread $(INCLUDES)
 CFLAGS:= -Wall -O2 -MMD -MP -ggdb 
 

lmdb-safe.cc

@@ -1,4 +1,66 @@
 #include "lmdb-safe.hh"
+#include <fcntl.h>
+#include <mutex>
+#include <memory>
+#include <sys/stat.h>
+#include <string.h>
+#include <map>
+
+std::shared_ptr<MDBEnv> getMDBEnv(const char* fname, int mode, int flags)
+{
+  struct Value
+  {
+    weak_ptr<MDBEnv> wp;
+    int flags;
+  };
+  
+  static std::map<tuple<dev_t, ino_t>, Value> s_envs;
+  static std::mutex mut;
+  
+  struct stat statbuf;
+  if(stat(fname, &statbuf)) {
+    if(errno != ENOENT)
+      throw std::runtime_error("Unable to stat prospective mdb database: "+string(strerror(errno)));
+    else {
+      std::lock_guard<std::mutex> l(mut);
+      cout<<"Making a fresh one, file did not exist yet"<<endl;
+      auto fresh = std::make_shared<MDBEnv>(fname, mode, flags);
+      if(stat(fname, &statbuf))
+        throw std::runtime_error("Unable to stat prospective mdb database: "+string(strerror(errno)));
+      auto key = std::tie(statbuf.st_dev, statbuf.st_ino);
+      s_envs[key] = {fresh, flags};
+      return fresh;
+    }
+  }
+
+  std::lock_guard<std::mutex> l(mut);
+  auto key = std::tie(statbuf.st_dev, statbuf.st_ino);
+  auto iter = s_envs.find(key);
+  if(iter != s_envs.end()) {
+    cout<<"Found something!"<<endl;
+    
+    auto sp = iter->second.wp.lock();
+    if(sp) {
+      if(iter->second.flags != flags)
+        throw std::runtime_error("Can't open mdb with differing flags");
+
+      cout<<"It was live!"<<endl;
+      return sp;
+    }
+    else {
+      cout<<"It was dead already"<<endl;
+      s_envs.erase(iter); // useful if make_shared fails
+    }
+  }
+  else
+    cout<<"Found nothing"<<endl;
+  cout<<"Making a fresh one"<<endl;
+  auto fresh = std::make_shared<MDBEnv>(fname, mode, flags);
+  s_envs[key] = {fresh, flags};
+  
+  return fresh;
+}
+
 
 MDBDbi MDBEnv::openDB(const char* dbname, int flags)
 {

lmdb-safe.hh

@@ -2,6 +2,9 @@
 #include <iostream>
 #include <fstream>
 #include <set>
+#include <map>
+#include <thread>
+#include <memory>
 
 using namespace std;
 
@@ -69,6 +72,9 @@ public:
 class MDBRWTransaction;
 class MDBROTransaction;
 
+
+
+
 class MDBEnv
 {
 public:
@@ -111,10 +117,13 @@ Various other options may also need to be set before opening the handle, e.g. md
     return d_env;
   }
   MDB_env* d_env;
-  bool d_transactionOut{false};
+  std::map<std::thread::id, int> d_RWtransactionsOut;
+  std::map<std::thread::id, int> d_ROtransactionsOut;
 
 };
 
+std::shared_ptr<MDBEnv> getMDBEnv(const char* fname, int mode, int flags);
+
 class MDBROCursor;
 
 class MDBROTransaction
@@ -122,7 +131,7 @@ class MDBROTransaction
 public:
   explicit MDBROTransaction(MDBEnv* parent, int flags=0) : d_parent(parent)
   {
-    if(d_parent->d_transactionOut)
+    if(d_parent->d_RWtransactionsOut[std::this_thread::get_id()])
       throw std::runtime_error("Duplicate transaction");
 
     /*
@@ -130,7 +139,9 @@ public:
     
     if(mdb_txn_begin(d_parent->d_env, 0, MDB_RDONLY | flags, &d_txn))
       throw std::runtime_error("Unable to start RO transaction");
+    ++d_parent->d_ROtransactionsOut[std::this_thread::get_id()];
   }
+  
 
   MDBROTransaction(MDBROTransaction&& rhs)
   {
@@ -144,14 +155,14 @@ public:
   {
     // this does not free cursors
     mdb_txn_reset(d_txn);
-    d_parent->d_transactionOut=false;
+    --d_parent->d_ROtransactionsOut[std::this_thread::get_id()];
   }
 
   void renew()
   {
-    if(d_parent->d_transactionOut)
+    if(d_parent->d_RWtransactionsOut[std::this_thread::get_id()])
       throw std::runtime_error("Duplicate transaction");
-    d_parent->d_transactionOut=1;
+    d_parent->d_ROtransactionsOut[std::this_thread::get_id()]++;
     if(mdb_txn_renew(d_txn))
       throw std::runtime_error("Renewing transaction");
   }
@@ -173,7 +184,7 @@ public:
   ~MDBROTransaction()
   {
     if(d_txn) {
-      d_parent->d_transactionOut=false;
+      --d_parent->d_ROtransactionsOut[std::this_thread::get_id()];
       mdb_txn_commit(d_txn); // this appears to work better than abort for r/o database opening
     }
   }
@@ -239,9 +250,9 @@ class MDBRWTransaction
 public:
   explicit MDBRWTransaction(MDBEnv* parent, int flags=0) : d_parent(parent)
   {
-    if(d_parent->d_transactionOut)
+    if(d_parent->d_ROtransactionsOut[std::this_thread::get_id()] || d_parent->d_RWtransactionsOut[std::this_thread::get_id()])
       throw std::runtime_error("Duplicate transaction");
-    d_parent->d_transactionOut = true;
+    ++d_parent->d_RWtransactionsOut[std::this_thread::get_id()];
     if(int rc=mdb_txn_begin(d_parent->d_env, 0, flags, &d_txn))
       throw std::runtime_error("Unable to start RW transaction: "+std::string(mdb_strerror(rc)));
   }
@@ -270,7 +281,7 @@ public:
   ~MDBRWTransaction()
   {
     if(d_txn) {
-      d_parent->d_transactionOut=false;
+      --d_parent->d_RWtransactionsOut[std::this_thread::get_id()];
       closeCursors();
       mdb_txn_abort(d_txn);
     }
@@ -283,7 +294,7 @@ public:
     if(mdb_txn_commit(d_txn)) {
       throw std::runtime_error("committing");
     }
-    d_parent->d_transactionOut=false;
+    --d_parent->d_RWtransactionsOut[std::this_thread::get_id()];
 
     d_txn=0;
   }
@@ -293,7 +304,7 @@ public:
     closeCursors();
     mdb_txn_abort(d_txn);
     d_txn = 0;
-    d_parent->d_transactionOut=false;
+    --d_parent->d_RWtransactionsOut[std::this_thread::get_id()];
   }
 
   void put(MDB_dbi dbi, const MDB_val& key, const MDB_val& val, int flags)

lmdb-test.cc

@@ -3,17 +3,29 @@
 #include <string.h>
 #include "lmdb-safe.hh"
 #include <unistd.h>
+#include <thread>
 
 static void closeTest()
 {
-  MDBEnv env("./database", MDB_RDONLY, 0600);
-  int c=  MDB_CREATE;
-  MDBDbi dbi = env.openDB("ahu", c);
-  MDBDbi main = env.openDB(0, c);
-  MDBDbi hyc = env.openDB("hyc2", c);
+  auto env = getMDBEnv("./database", 0, 0600);
+  
+  int c =  MDB_CREATE;
+  MDBDbi dbi = env->openDB("ahu", c);
+  MDBDbi main = env->openDB(0, c);
+  MDBDbi hyc = env->openDB("hyc", c);
 
-  auto txn = env.getROTransaction();
-  auto cursor = txn.getCursor(dbi);
+  auto txn = env->getROTransaction();
+  for(auto& d : {&main, &dbi, &hyc}) {
+    auto rocursor = txn.getCursor(*d);
+    MDB_val key{0,0}, data{0,0};
+    if(rocursor.get(key, data, MDB_FIRST))
+      continue;
+    int count=0;
+    do {
+      count++;
+    }while(!rocursor.get(key, data, MDB_NEXT));
+    cout<<"Have "<<count<<" entries"<<endl;
+  }
   
   return;
 }
@@ -21,18 +33,18 @@ static void closeTest()
 
 int main(int argc, char** argv)
 {
+  cout<<std::this_thread::get_id()<<endl;
   closeTest();
-  return 0;
-  MDBEnv env("./database", 0, 0600);
+  auto env = getMDBEnv("./database", 0, 0600);
   
   MDB_stat stat;
-  mdb_env_stat(env, &stat);
+  mdb_env_stat(*env.get(), &stat);
   cout << stat.ms_entries<< " entries in database"<<endl;
   
-  MDBDbi dbi = env.openDB("ahu", MDB_CREATE);
+  MDBDbi dbi = env->openDB("ahu", MDB_CREATE);
 
   {
-    MDBROTransaction rotxn = env.getROTransaction();
+    MDBROTransaction rotxn = env->getROTransaction();
 
     {
       auto rocursor = rotxn.getCursor(dbi);
@@ -68,7 +80,7 @@ int main(int argc, char** argv)
 
   }
 
-  auto txn = env.getRWTransaction();
+  auto txn = env->getRWTransaction();
 
   auto cursor = txn.getCursor(dbi);
   
@@ -87,7 +99,7 @@ int main(int argc, char** argv)
   cout<<"Done deleting, committing"<<endl;
   txn.commit();
   cout<<"Done with commit"<<endl;
-  txn = env.getRWTransaction();
+  txn = env->getRWTransaction();
   
   start=time(0);
   ofstream plot("plot");