Merge pull request #4392

8ae973c Allocate more space if necessary in RandSeedAddPerfMon (Wladimir J. van der Laan)
be873f6 Issue warning if collecting RandSeed data failed (Wladimir J. van der Laan)
fcb0a1b change "char pch[200000]" to "new char[200000]" (daniel)

Author: laanwj

src/util.cpp

@@ -167,16 +167,31 @@ void RandAddSeedPerfmon()
 #ifdef WIN32
     // Don't need this on Linux, OpenSSL automatically uses /dev/urandom
     // Seed with the entire set of perfmon data
-    unsigned char pdata[250000];
-    memset(pdata, 0, sizeof(pdata));
-    unsigned long nSize = sizeof(pdata);
-    long ret = RegQueryValueExA(HKEY_PERFORMANCE_DATA, "Global", NULL, NULL, pdata, &nSize);
+    std::vector <unsigned char> vData(250000,0);
+    long ret = 0;
+    unsigned long nSize = 0;
+    const size_t nMaxSize = 10000000; // Bail out at more than 10MB of performance data
+    while (true)
+    {
+        nSize = vData.size();
+        ret = RegQueryValueExA(HKEY_PERFORMANCE_DATA, "Global", NULL, NULL, begin_ptr(vData), &nSize);
+        if (ret != ERROR_MORE_DATA || vData.size() >= nMaxSize)
+            break;
+        vData.resize(std::max((vData.size()*3)/2, nMaxSize)); // Grow size of buffer exponentially
+    }
     RegCloseKey(HKEY_PERFORMANCE_DATA);
     if (ret == ERROR_SUCCESS)
     {
-        RAND_add(pdata, nSize, nSize/100.0);
-        OPENSSL_cleanse(pdata, nSize);
-        LogPrint("rand", "RandAddSeed() %lu bytes\n", nSize);
+        RAND_add(begin_ptr(vData), nSize, nSize/100.0);
+        OPENSSL_cleanse(begin_ptr(vData), nSize);
+        LogPrint("rand", "%s: %lu bytes\n", __func__, nSize);
+    } else {
+        static bool warned = false; // Warn only once
+        if (!warned)
+        {
+            LogPrintf("%s: Warning: RegQueryValueExA(HKEY_PERFORMANCE_DATA) failed with code %i\n", __func__, ret);
+            warned = true;
+        }
     }
 #endif
 }
@@ -1140,15 +1155,15 @@ void ShrinkDebugFile()
     if (file && boost::filesystem::file_size(pathLog) > 10 * 1000000)
     {
         // Restart the file with some of the end
-        char pch[200000];
-        fseek(file, -sizeof(pch), SEEK_END);
-        int nBytes = fread(pch, 1, sizeof(pch), file);
+        std::vector <char> vch(200000,0);
+        fseek(file, -vch.size(), SEEK_END);
+        int nBytes = fread(begin_ptr(vch), 1, vch.size(), file);
         fclose(file);
 
         file = fopen(pathLog.string().c_str(), "w");
         if (file)
         {
-            fwrite(pch, 1, nBytes, file);
+            fwrite(begin_ptr(vch), 1, nBytes, file);
             fclose(file);
         }
     }