Add RAII memory management, estimator tracking, and detailed test results in entropy calculations

- Introduce `DataGuard` class for automated cleanup using RAII.
- Add per-estimator tracking and result population in `EntropyResult`.
- Replace VLAs with `std::array` for C++ standard compliance.
- Update gRPC layer to expose detailed test results and individual estimator details for IID and Non-IID assessments.
- Enhance unit tests to validate individual estimator outputs and counts.

Author: Christian

internal/entropy/cgo_bridge.go

@@ -49,11 +49,32 @@ func calculateIIDEntropy(data []byte, bitsPerSymbol int, verbose int) (*Result,
 		HAssessed:    float64(cResult.h_assessed),
 		DataWordSize: int(cResult.data_word_size),
 		TestType:     IID,
+		Estimators:   convertEstimators(cResult),
 	}
 
 	return result, nil
 }
 
+// convertEstimators converts C estimator array to Go slice
+func convertEstimators(cResult *C.EntropyResult) []EstimatorResult {
+	count := int(cResult.estimator_count)
+	if count <= 0 {
+		return nil
+	}
+
+	estimators := make([]EstimatorResult, count)
+	for i := 0; i < count; i++ {
+		cEst := cResult.estimators[i]
+		estimators[i] = EstimatorResult{
+			Name:            C.GoString(&cEst.name[0]),
+			EntropyEstimate: float64(cEst.entropy_estimate),
+			Passed:          bool(cEst.passed),
+			IsEntropyValid:  bool(cEst.is_entropy_valid),
+		}
+	}
+	return estimators
+}
+
 // calculateNonIIDEntropy calls the C wrapper to perform Non-IID entropy calculation
 func calculateNonIIDEntropy(data []byte, bitsPerSymbol int, verbose int) (*Result, error) {
 	if len(data) == 0 {
@@ -90,6 +111,7 @@ func calculateNonIIDEntropy(data []byte, bitsPerSymbol int, verbose int) (*Resul
 		HAssessed:    float64(cResult.h_assessed),
 		DataWordSize: int(cResult.data_word_size),
 		TestType:     NonIID,
+		Estimators:   convertEstimators(cResult),
 	}
 
 	return result, nil

internal/entropy/cgo_stub.go

@@ -6,6 +6,32 @@ import "math"
 
 // Test stub for CGO-backed functions to allow fast unit testing without the C++ library.
 
+// stubIIDEstimators returns mock IID estimator results
+func stubIIDEstimators() []EstimatorResult {
+	return []EstimatorResult{
+		{Name: "Most Common Value", EntropyEstimate: 7.6, Passed: true, IsEntropyValid: true},
+		{Name: "Chi-Square Tests", EntropyEstimate: -1.0, Passed: true, IsEntropyValid: false},
+		{Name: "Length of Longest Repeated Substring Test", EntropyEstimate: -1.0, Passed: true, IsEntropyValid: false},
+		{Name: "Permutation Tests", EntropyEstimate: -1.0, Passed: true, IsEntropyValid: false},
+	}
+}
+
+// stubNonIIDEstimators returns mock Non-IID estimator results
+func stubNonIIDEstimators() []EstimatorResult {
+	return []EstimatorResult{
+		{Name: "Most Common Value", EntropyEstimate: 6.8, Passed: true, IsEntropyValid: true},
+		{Name: "Collision Test", EntropyEstimate: 6.9, Passed: true, IsEntropyValid: true},
+		{Name: "Markov Test", EntropyEstimate: 6.7, Passed: true, IsEntropyValid: true},
+		{Name: "Compression Test", EntropyEstimate: 6.5, Passed: true, IsEntropyValid: true},
+		{Name: "t-Tuple Test", EntropyEstimate: 6.6, Passed: true, IsEntropyValid: true},
+		{Name: "LRS Test", EntropyEstimate: 6.8, Passed: true, IsEntropyValid: true},
+		{Name: "Multi Most Common in Window Test", EntropyEstimate: 6.7, Passed: true, IsEntropyValid: true},
+		{Name: "Lag Prediction Test", EntropyEstimate: 6.9, Passed: true, IsEntropyValid: true},
+		{Name: "Multi Markov Model with Counting Test", EntropyEstimate: 6.6, Passed: true, IsEntropyValid: true},
+		{Name: "LZ78Y Test", EntropyEstimate: 6.5, Passed: true, IsEntropyValid: true},
+	}
+}
+
 func calculateIIDEntropy(data []byte, bitsPerSymbol int, verbose int) (*Result, error) {
 	if len(data) > 0 && data[0] == 0xFF {
 		return nil, newError("calculateIIDEntropy", ErrInvalidData, "stub failure")
@@ -18,6 +44,7 @@ func calculateIIDEntropy(data []byte, bitsPerSymbol int, verbose int) (*Result,
 			HAssessed:    math.Inf(1),
 			DataWordSize: bitsPerSymbol,
 			TestType:     IID,
+			Estimators:   nil,
 		}, nil
 	}
 	return &Result{
@@ -27,6 +54,7 @@ func calculateIIDEntropy(data []byte, bitsPerSymbol int, verbose int) (*Result,
 		HAssessed:    7.5,
 		DataWordSize: bitsPerSymbol,
 		TestType:     IID,
+		Estimators:   stubIIDEstimators(),
 	}, nil
 }
 
@@ -42,6 +70,7 @@ func calculateNonIIDEntropy(data []byte, bitsPerSymbol int, verbose int) (*Resul
 			HAssessed:    math.Inf(1),
 			DataWordSize: bitsPerSymbol,
 			TestType:     NonIID,
+			Estimators:   nil,
 		}, nil
 	}
 	return &Result{
@@ -51,5 +80,6 @@ func calculateNonIIDEntropy(data []byte, bitsPerSymbol int, verbose int) (*Resul
 		HAssessed:    6.5,
 		DataWordSize: bitsPerSymbol,
 		TestType:     NonIID,
+		Estimators:   stubNonIIDEstimators(),
 	}, nil
 }

internal/entropy/types.go

@@ -22,6 +22,14 @@ func (t TestType) String() string {
 	}
 }
 
+// EstimatorResult contains the result of a single NIST SP 800-90B estimator
+type EstimatorResult struct {
+	Name            string  // Estimator name (e.g., "Most Common Value")
+	EntropyEstimate float64 // Entropy estimate (-1.0 if not applicable)
+	Passed          bool    // Whether the test passed
+	IsEntropyValid  bool    // true if EntropyEstimate is valid
+}
+
 // Result contains the entropy assessment results
 type Result struct {
 	MinEntropy   float64  // Minimum entropy estimate
@@ -30,6 +38,9 @@ type Result struct {
 	HAssessed    float64  // Assessed entropy value
 	DataWordSize int      // Bits per symbol
 	TestType     TestType // Type of test performed
+
+	// Individual estimator results
+	Estimators []EstimatorResult
 }
 
 // Assessment configuration