fix rng bug

src/shred.cpp

@@ -196,9 +196,22 @@ void Shred::performExploration(Drive *drive)
     size_t savedChunkSize = currentChunkSize;
 
     // Generate random chunk size between MIN and MAX (aligned to STEP boundaries)
-    size_t numSteps = (CHUNK_SIZE_MAX - CHUNK_SIZE_MIN) / CHUNK_SIZE_STEP_UP;
+    // Calculate in MB to avoid overflow
-    size_t randomStep = rand() % (numSteps + 1);
+    size_t minMB = CHUNK_SIZE_MIN / (1024 * 1024);
-    explorationChunkSize = CHUNK_SIZE_MIN + (randomStep * CHUNK_SIZE_STEP_UP);
+    size_t maxMB = CHUNK_SIZE_MAX / (1024 * 1024);
+    size_t stepMB = CHUNK_SIZE_STEP_UP / (1024 * 1024);
+
+    // Number of possible steps: (max - min) / step
+    size_t numSteps = (maxMB - minMB) / stepMB;
+
+    // Generate random step: 0 to numSteps (inclusive)
+    // Using proper modulo to ensure range [0, numSteps]
+    int randVal = rand();
+    size_t randomStep = static_cast<size_t>(randVal) % (numSteps + 1);
+
+    // Calculate exploration chunk size in MB, then convert to bytes
+    size_t explorationMB = minMB + (randomStep * stepMB);
+    explorationChunkSize = explorationMB * 1024 * 1024;
 
     // Clamp to valid range (safety check)
     if (explorationChunkSize < CHUNK_SIZE_MIN)
@@ -213,7 +226,8 @@ void Shred::performExploration(Drive *drive)
     // Enhanced logging with debug info
     Logger::logThis()->info("EXPLORATION MODE: Testing " +
                             to_string(explorationChunkSize / (1024 * 1024)) + " MB chunks " +
-                            "(randomStep=" + to_string(randomStep) + "/" + to_string(numSteps) + ", " +
+                            "(randomStep=" + to_string(randomStep) + "/" + to_string(numSteps) +
+                            ", rand=" + to_string(randVal) + ", " +
                             "was " + to_string(savedChunkSize / (1024 * 1024)) + " MB, " +
                             "best: " + to_string(bestChunkSize / (1024 * 1024)) + " MB)" +
                             " - Drive: " + drive->getSerial());