diff --git a/bitman.hh b/bitman.hh
index 074841b..ad5335d 100644
--- a/bitman.hh
+++ b/bitman.hh
@@ -29,12 +29,12 @@ void set_le_bit(uint8_t *buf, int pos, bool val)
 	buf[pos/8] = (~(1<<(pos%8))&buf[pos/8])|(val<<(pos%8));
 }
 
-bool get_be_bit(uint8_t *buf, int pos)
+bool get_be_bit(const uint8_t *buf, int pos)
 {
 	return (buf[pos/8]>>(7-pos%8))&1;
 }
 
-bool get_le_bit(uint8_t *buf, int pos)
+bool get_le_bit(const uint8_t *buf, int pos)
 {
 	return (buf[pos/8]>>(pos%8))&1;
 }
diff --git a/bose_chaudhuri_hocquenghem_decoder.hh b/bose_chaudhuri_hocquenghem_decoder.hh
index ece25b6..3e11185 100644
--- a/bose_chaudhuri_hocquenghem_decoder.hh
+++ b/bose_chaudhuri_hocquenghem_decoder.hh
@@ -23,7 +23,7 @@ public:
 	static const int N = GF::N, K = MSG, NP = N - K;
 private:
 	ReedSolomonErrorCorrection<NR, FCR, GF> algorithm;
-	void update_syndromes(uint8_t *poly, ValueType *syndromes, int begin, int end)
+	void update_syndromes(const uint8_t *poly, ValueType *syndromes, int begin, int end)
 	{
 		for (int j = begin; j < end; ++j) {
 			ValueType coeff(get_be_bit(poly, j));
@@ -35,7 +35,7 @@ private:
 		}
 	}
 public:
-	int compute_syndromes(uint8_t *data, uint8_t *parity, ValueType *syndromes, int data_len = K)
+	int compute_syndromes(const uint8_t *data, const uint8_t *parity, ValueType *syndromes, int data_len = K)
 	{
 		assert(0 < data_len && data_len <= K);
 		// $syndromes_i = code(pe^{FCR+i})$
@@ -49,7 +49,7 @@ public:
 			nonzero += !!syndromes[i];
 		return nonzero;
 	}
-	int compute_syndromes(uint8_t *data, uint8_t *parity, value_type *syndromes, int data_len = K)
+	int compute_syndromes(const uint8_t *data, const uint8_t *parity, value_type *syndromes, int data_len = K)
 	{
 		return compute_syndromes(data, parity, reinterpret_cast<ValueType *>(syndromes), data_len);
 	}
@@ -110,7 +110,7 @@ public:
 	static const int N = GF::N, K = MSG, NP = N - K;
 private:
 	ReedSolomonErrorCorrection<NR, FCR, GF> algorithm;
-	void update_syndromes(ValueType *poly, ValueType *syndromes, int begin, int end)
+	void update_syndromes(const ValueType *poly, ValueType *syndromes, int begin, int end)
 	{
 		for (int j = begin; j < end; ++j) {
 			ValueType coeff(poly[j]);
@@ -122,7 +122,7 @@ private:
 		}
 	}
 public:
-	int compute_syndromes(ValueType *data, ValueType *parity, ValueType *syndromes, int data_len = K)
+	int compute_syndromes(const ValueType *data, const ValueType *parity, ValueType *syndromes, int data_len = K)
 	{
 		assert(0 < data_len && data_len <= K);
 		// $syndromes_i = code(pe^{FCR+i})$
diff --git a/bose_chaudhuri_hocquenghem_encoder.hh b/bose_chaudhuri_hocquenghem_encoder.hh
index 2424066..d561e7b 100644
--- a/bose_chaudhuri_hocquenghem_encoder.hh
+++ b/bose_chaudhuri_hocquenghem_encoder.hh
@@ -59,7 +59,7 @@ public:
 			set_be_bit(generator, i, get_be_bit(generator, i+1));
 		set_be_bit(generator, NP, 0);
 	}
-	void operator()(uint8_t *data, uint8_t *parity, int data_len = K)
+	void operator()(const uint8_t *data, uint8_t *parity, int data_len = K)
 	{
 		assert(0 < data_len && data_len <= K);
 		// $code = data * x^{NP} + (data * x^{NP}) \mod{generator}$
@@ -129,7 +129,7 @@ public:
 			std::cerr << std::endl;
 		}
 	}
-	void operator()(ValueType *data, ValueType *parity, int data_len = K)
+	void operator()(const ValueType *data, ValueType *parity, int data_len = K)
 	{
 		assert(0 < data_len && data_len <= K);
 		// $code = data * x^{NP} + (data * x^{NP}) \mod{generator}$
diff --git a/ldpc_encoder.hh b/ldpc_encoder.hh
index 1de86e9..73e549d 100644
--- a/ldpc_encoder.hh
+++ b/ldpc_encoder.hh
@@ -55,7 +55,7 @@ public:
 			}
 		}
 	}
-	void operator()(int8_t *data, int8_t *parity)
+	void operator()(const int8_t *data, int8_t *parity)
 	{
 		int8_t tmp = 1;
 		for (int j = 0; j < M; ++j) {
diff --git a/reed_solomon_decoder.hh b/reed_solomon_decoder.hh
index d469a28..aa99e43 100644
--- a/reed_solomon_decoder.hh
+++ b/reed_solomon_decoder.hh
@@ -22,7 +22,7 @@ public:
 	static const int N = GF::N, K = N - NR, NP = NR;
 private:
 	ReedSolomonErrorCorrection<NR, FCR, GF> algorithm;
-	void update_syndromes(ValueType *poly, ValueType *syndromes, int begin, int end)
+	void update_syndromes(const ValueType *poly, ValueType *syndromes, int begin, int end)
 	{
 		for (int j = begin; j < end; ++j) {
 			ValueType coeff(poly[j]);
@@ -34,7 +34,7 @@ private:
 		}
 	}
 public:
-	int compute_syndromes(ValueType *data, ValueType *parity, ValueType *syndromes, int data_len = K)
+	int compute_syndromes(const ValueType *data, const ValueType *parity, ValueType *syndromes, int data_len = K)
 	{
 		assert(0 < data_len && data_len <= K);
 		// $syndromes_i = code(pe^{FCR+i})$
@@ -92,9 +92,9 @@ public:
 	{
 		return (*this)(reinterpret_cast<ValueType *>(data), reinterpret_cast<ValueType *>(parity), reinterpret_cast<IndexType *>(erasures), erasures_count, data_len);
 	}
-	int compute_syndromes(value_type *data, value_type *parity, value_type *syndromes, int data_len = K)
+	int compute_syndromes(const value_type *data, const value_type *parity, value_type *syndromes, int data_len = K)
 	{
-		return compute_syndromes(reinterpret_cast<ValueType *>(data), reinterpret_cast<ValueType *>(parity), reinterpret_cast<ValueType *>(syndromes), data_len);
+		return compute_syndromes(reinterpret_cast<const ValueType *>(data), reinterpret_cast<const ValueType *>(parity), reinterpret_cast<ValueType *>(syndromes), data_len);
 	}
 };
 
diff --git a/reed_solomon_encoder.hh b/reed_solomon_encoder.hh
index 6de493d..3c813fa 100644
--- a/reed_solomon_encoder.hh
+++ b/reed_solomon_encoder.hh
@@ -51,7 +51,7 @@ public:
 		for (int i = 0; i <= NR; ++i)
 			generator[i] = index(tmp[i]);
 	}
-	void operator()(ValueType *data, ValueType *parity, int data_len = K)
+	void operator()(const ValueType *data, ValueType *parity, int data_len = K)
 	{
 		assert(0 < data_len && data_len <= K);
 		// $code = data * x^{NR} + (data * x^{NR}) \mod{generator}$
@@ -71,9 +71,9 @@ public:
 			}
 		}
 	}
-	void operator()(value_type *data, value_type *parity, int data_len = K)
+	void operator()(const value_type *data, value_type *parity, int data_len = K)
 	{
-		(*this)(reinterpret_cast<ValueType *>(data), reinterpret_cast<ValueType *>(parity), data_len);
+		(*this)(reinterpret_cast<const ValueType *>(data), reinterpret_cast<ValueType *>(parity), data_len);
 	}
 };
 
diff --git a/reed_solomon_error_correction.hh b/reed_solomon_error_correction.hh
index 9283b28..cee462d 100644
--- a/reed_solomon_error_correction.hh
+++ b/reed_solomon_error_correction.hh
@@ -15,7 +15,7 @@ struct Chien
 {
 	typedef typename GF::ValueType ValueType;
 	typedef typename GF::IndexType IndexType;
-	static int search(ValueType *locator, int locator_degree, IndexType *locations)
+	static int search(const ValueType *locator, int locator_degree, IndexType *locations)
 	{
 		ValueType tmp[locator_degree+1];
 		for (int i = 0; i <= locator_degree; ++i)
@@ -65,7 +65,7 @@ struct LocationFinder
 	typedef typename GF::ValueType ValueType;
 	typedef typename GF::IndexType IndexType;
 	ArtinSchreier<GF> imap;
-	int operator()(ValueType *locator, int locator_degree, IndexType *locations)
+	int operator()(const ValueType *locator, int locator_degree, IndexType *locations)
 	{
 		if (locator_degree == 1) {
 			locations[0] = (index(locator[0]) / index(locator[1])) / IndexType(1);
@@ -91,7 +91,7 @@ struct Forney
 {
 	typedef typename GF::ValueType ValueType;
 	typedef typename GF::IndexType IndexType;
-	static int compute_evaluator(ValueType *syndromes, ValueType *locator, int locator_degree, ValueType *evaluator)
+	static int compute_evaluator(const ValueType *syndromes, const ValueType *locator, int locator_degree, ValueType *evaluator)
 	{
 		// $evaluator = (syndromes * locator) \bmod{x^{NR}}$
 		int tmp = std::min(locator_degree, NR-1);
@@ -105,7 +105,7 @@ struct Forney
 		}
 		return degree;
 	}
-	static void compute_magnitudes(ValueType *locator, IndexType *locations, int count, ValueType *evaluator, int evaluator_degree, ValueType *magnitudes)
+	static void compute_magnitudes(const ValueType *locator, const IndexType *locations, int count, const ValueType *evaluator, int evaluator_degree, ValueType *magnitudes)
 	{
 		// $magnitude = root^{FCR-1} * \frac{evaluator(root)}{locator'(root)}$
 		for (int i = 0; i < count; ++i) {
@@ -134,7 +134,7 @@ struct Forney
 			magnitudes[i] = value(magnitude);
 		}
 	}
-	static int algorithm(ValueType *syndromes, ValueType *locator, IndexType *locations, int count, ValueType *evaluator, ValueType *magnitudes)
+	static int algorithm(const ValueType *syndromes, const ValueType *locator, const IndexType *locations, int count, ValueType *evaluator, ValueType *magnitudes)
 	{
 		int evaluator_degree = compute_evaluator(syndromes, locator, count, evaluator);
 		compute_magnitudes(locator, locations, count, evaluator, evaluator_degree, magnitudes);
@@ -147,7 +147,7 @@ struct BerlekampMassey
 {
 	typedef typename GF::ValueType ValueType;
 	typedef typename GF::IndexType IndexType;
-	static int algorithm(ValueType *s, ValueType *C, int count = 0)
+	static int algorithm(const ValueType *s, ValueType *C, int count = 0)
 	{
 		ValueType B[NR+1];
 		for (int i = 0; i <= NR; ++i)
@@ -189,7 +189,7 @@ struct ReedSolomonErrorCorrection
 	typedef typename GF::ValueType ValueType;
 	typedef typename GF::IndexType IndexType;
 	RS::LocationFinder<NR, GF> search;
-	int operator()(ValueType *syndromes, IndexType *locations, ValueType *magnitudes, IndexType *erasures = 0, int erasures_count = 0)
+	int operator()(const ValueType *syndromes, IndexType *locations, ValueType *magnitudes, const IndexType *erasures = 0, int erasures_count = 0)
 	{
 		assert(0 <= erasures_count && erasures_count <= NR);
 		ValueType locator[NR+1];