Auto merge of #5214 - str4d:streams-data, r=str4d

Add `data()` method to `CDataStream`

Analogous to C++11 `std::vector::data()`.

Cherry-picked from bitcoin/bitcoin#9353 (excluding bench change).

src/dbwrapper.h

@@ -57,12 +57,12 @@ public:
         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
         ssKey << key;
-        leveldb::Slice slKey(&ssKey[0], ssKey.size());
+        leveldb::Slice slKey(ssKey.data(), ssKey.size());
 
         CDataStream ssValue(SER_DISK, CLIENT_VERSION);
         ssValue.reserve(DBWRAPPER_PREALLOC_VALUE_SIZE);
         ssValue << value;
-        leveldb::Slice slValue(&ssValue[0], ssValue.size());
+        leveldb::Slice slValue(ssValue.data(), ssValue.size());
 
         batch.Put(slKey, slValue);
     }
@@ -73,7 +73,7 @@ public:
         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
         ssKey << key;
-        leveldb::Slice slKey(&ssKey[0], ssKey.size());
+        leveldb::Slice slKey(ssKey.data(), ssKey.size());
 
         batch.Delete(slKey);
     }
@@ -103,7 +103,7 @@ public:
         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
         ssKey.reserve(GetSerializeSize(ssKey, key));
         ssKey << key;
-        leveldb::Slice slKey(&ssKey[0], ssKey.size());
+        leveldb::Slice slKey(ssKey.data(), ssKey.size());
         piter->Seek(slKey);
     }
 
@@ -181,7 +181,7 @@ public:
         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
         ssKey << key;
-        leveldb::Slice slKey(&ssKey[0], ssKey.size());
+        leveldb::Slice slKey(ssKey.data(), ssKey.size());
 
         std::string strValue;
         leveldb::Status status = pdb->Get(readoptions, slKey, &strValue);
@@ -214,7 +214,7 @@ public:
         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
         ssKey << key;
-        leveldb::Slice slKey(&ssKey[0], ssKey.size());
+        leveldb::Slice slKey(ssKey.data(), ssKey.size());
 
         std::string strValue;
         leveldb::Status status = pdb->Get(readoptions, slKey, &strValue);

src/streams.h

@@ -106,12 +106,10 @@ public:
         Init(nTypeIn, nVersionIn);
     }
 
-#if !defined(_MSC_VER) || _MSC_VER >= 1300
     CBaseDataStream(const char* pbegin, const char* pend, int nTypeIn, int nVersionIn) : vch(pbegin, pend)
     {
         Init(nTypeIn, nVersionIn);
     }
-#endif
 
     CBaseDataStream(const vector_type& vchIn, int nTypeIn, int nVersionIn) : vch(vchIn.begin(), vchIn.end())
     {
@@ -177,6 +175,8 @@ public:
     void clear()                                     { vch.clear(); nReadPos = 0; }
     iterator insert(iterator it, const char& x=char()) { return vch.insert(it, x); }
     void insert(iterator it, size_type n, const char& x) { vch.insert(it, n, x); }
+    value_type* data()                               { return vch.data() + nReadPos; }
+    const value_type* data() const                   { return vch.data() + nReadPos; }
 
     void insert(iterator it, std::vector<char>::const_iterator first, std::vector<char>::const_iterator last)
     {
@@ -192,7 +192,6 @@ public:
             vch.insert(it, first, last);
     }
 
-#if !defined(_MSC_VER) || _MSC_VER >= 1300
     void insert(iterator it, const char* first, const char* last)
     {
         if (last == first) return;
@@ -206,7 +205,6 @@ public:
         else
             vch.insert(it, first, last);
     }
-#endif
 
     iterator erase(iterator it)
     {

src/wallet/db.cpp

@@ -378,15 +378,15 @@ bool CDB::Rewrite(const string& strFile, const char* pszSkip)
                                 break;
                             }
                             if (pszSkip &&
-                                strncmp(&ssKey[0], pszSkip, std::min(ssKey.size(), strlen(pszSkip))) == 0)
+                                strncmp(ssKey.data(), pszSkip, std::min(ssKey.size(), strlen(pszSkip))) == 0)
                                 continue;
-                            if (strncmp(&ssKey[0], "\x07version", 8) == 0) {
+                            if (strncmp(ssKey.data(), "\x07version", 8) == 0) {
                                 // Update version:
                                 ssValue.clear();
                                 ssValue << CLIENT_VERSION;
                             }
-                            Dbt datKey(&ssKey[0], ssKey.size());
+                            Dbt datKey(ssKey.data(), ssKey.size());
-                            Dbt datValue(&ssValue[0], ssValue.size());
+                            Dbt datValue(ssValue.data(), ssValue.size());
                             int ret2 = pdbCopy->put(NULL, &datKey, &datValue, DB_NOOVERWRITE);
                             if (ret2 > 0)
                                 fSuccess = false;

src/wallet/db.h

@@ -121,7 +121,7 @@ protected:
         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
         ssKey.reserve(1000);
         ssKey << key;
-        Dbt datKey(&ssKey[0], ssKey.size());
+        Dbt datKey(ssKey.data(), ssKey.size());
 
         // Read
         Dbt datValue;
@@ -158,13 +158,13 @@ protected:
         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
         ssKey.reserve(1000);
         ssKey << key;
-        Dbt datKey(&ssKey[0], ssKey.size());
+        Dbt datKey(ssKey.data(), ssKey.size());
 
         // Value
         CDataStream ssValue(SER_DISK, CLIENT_VERSION);
         ssValue.reserve(10000);
         ssValue << value;
-        Dbt datValue(&ssValue[0], ssValue.size());
+        Dbt datValue(ssValue.data(), ssValue.size());
 
         // Write
         int ret = pdb->put(activeTxn, &datKey, &datValue, (fOverwrite ? 0 : DB_NOOVERWRITE));
@@ -187,7 +187,7 @@ protected:
         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
         ssKey.reserve(1000);
         ssKey << key;
-        Dbt datKey(&ssKey[0], ssKey.size());
+        Dbt datKey(ssKey.data(), ssKey.size());
 
         // Erase
         int ret = pdb->del(activeTxn, &datKey, 0);
@@ -207,7 +207,7 @@ protected:
         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
         ssKey.reserve(1000);
         ssKey << key;
-        Dbt datKey(&ssKey[0], ssKey.size());
+        Dbt datKey(ssKey.data(), ssKey.size());
 
         // Exists
         int ret = pdb->exists(activeTxn, &datKey, 0);
@@ -233,7 +233,7 @@ protected:
         // Read at cursor
         Dbt datKey;
         if (fFlags == DB_SET || fFlags == DB_SET_RANGE || fFlags == DB_GET_BOTH || fFlags == DB_GET_BOTH_RANGE) {
-            datKey.set_data(&ssKey[0]);
+            datKey.set_data(ssKey.data());
             datKey.set_size(ssKey.size());
         }
         Dbt datValue;