Use span<> and Bytes pervasively in the schemes APIs

This results in a smaller interface, since the conversion vector -> Bytes is
done in the span constructor. Additionally it make the interface more flexible
in that it no longer requires the caller to allocate the array in a std::vector

src/elements.cpp

@@ -18,7 +18,7 @@
 
 namespace bls {
 
-G1Element G1Element::FromBytes(const Bytes& bytes)
+G1Element G1Element::FromBytes(const Bytes bytes)
 {
     if (bytes.size() != SIZE) {
         throw std::invalid_argument("G1Element::FromBytes: Invalid size");
@@ -64,7 +64,7 @@ G1Element G1Element::FromBytes(const Bytes& bytes)
 
 G1Element G1Element::FromByteVector(const std::vector<uint8_t>& bytevec)
 {
-    return G1Element::FromBytes(Bytes(bytevec));
+    return G1Element::FromBytes(bytevec);
 }
 
 G1Element G1Element::FromNative(const g1_t element)
@@ -75,19 +75,12 @@ G1Element G1Element::FromNative(const g1_t element)
     return ele;
 }
 
-G1Element G1Element::FromMessage(const std::vector<uint8_t>& message,
-                                 const uint8_t* dst,
-                                 int dst_len)
-{
-    return FromMessage(Bytes(message), dst, dst_len);
-}
-
-G1Element G1Element::FromMessage(const Bytes& message,
+G1Element G1Element::FromMessage(const Bytes message,
                                  const uint8_t* dst,
                                  int dst_len)
 {
     G1Element ans;
-    ep_map_dst(ans.p, message.begin(), (int)message.size(), dst, dst_len);
+    ep_map_dst(ans.p, message.data(), (int)message.size(), dst, dst_len);
     ans.CheckValid();
     return ans;
 }
@@ -203,7 +196,7 @@ G1Element operator*(const bn_t& k, const G1Element& a) { return a * k; }
 
 
 
-G2Element G2Element::FromBytes(const Bytes& bytes)
+G2Element G2Element::FromBytes(const Bytes bytes)
 {
     if (bytes.size() != SIZE) {
         throw std::invalid_argument("G2Element::FromBytes: Invalid size");
@@ -252,7 +245,7 @@ G2Element G2Element::FromBytes(const Bytes& bytes)
 
 G2Element G2Element::FromByteVector(const std::vector<uint8_t>& bytevec)
 {
-    return G2Element::FromBytes(Bytes(bytevec));
+    return G2Element::FromBytes(bytevec);
 }
 
 G2Element G2Element::FromNative(const g2_t element)
@@ -263,19 +256,12 @@ G2Element G2Element::FromNative(const g2_t element)
     return ele;
 }
 
-G2Element G2Element::FromMessage(const std::vector<uint8_t>& message,
-                                 const uint8_t* dst,
-                                 int dst_len)
-{
-    return FromMessage(Bytes(message), dst, dst_len);
-}
-
-G2Element G2Element::FromMessage(const Bytes& message,
+G2Element G2Element::FromMessage(const Bytes message,
                                  const uint8_t* dst,
                                  int dst_len)
 {
     G2Element ans;
-    ep2_map_dst(ans.q, message.begin(), (int)message.size(), dst, dst_len);
+    ep2_map_dst(ans.q, message.data(), (int)message.size(), dst, dst_len);
     ans.CheckValid();
     return ans;
 }

src/elements.hpp

@@ -39,13 +39,16 @@ class G1Element {
         g1_set_infty(p);
     }
 
-    static G1Element FromBytes(const Bytes& bytes);
+    static G1Element FromBytes(Bytes bytes);
     static G1Element FromByteVector(const std::vector<uint8_t> &bytevec);
     static G1Element FromNative(const g1_t element);
     static G1Element FromMessage(const std::vector<uint8_t> &message,
                                  const uint8_t *dst,
-                                 int dst_len);
-    static G1Element FromMessage(const Bytes& message,
+                                 int dst_len)
+    {
+        return G1Element::FromMessage(Bytes(message), dst, dst_len);
+    }
+    static G1Element FromMessage(Bytes message,
                                  const uint8_t* dst,
                                  int dst_len);
     static G1Element Generator();
@@ -76,13 +79,16 @@ class G2Element {
         g2_set_infty(q);
     }
 
-    static G2Element FromBytes(const Bytes& bytes);
+    static G2Element FromBytes(Bytes bytes);
     static G2Element FromByteVector(const std::vector<uint8_t> &bytevec);
     static G2Element FromNative(const g2_t element);
     static G2Element FromMessage(const std::vector<uint8_t>& message,
                                  const uint8_t* dst,
-                                 int dst_len);
-    static G2Element FromMessage(const Bytes& message,
+                                 int dst_len)
+    {
+        return G2Element::FromMessage(Bytes(message), dst, dst_len);
+    }
+    static G2Element FromMessage(Bytes message,
                                  const uint8_t* dst,
                                  int dst_len);
     static G2Element Generator();

src/hdkeys.hpp

@@ -34,13 +34,7 @@ class HDKeys {
      **/
  public:
     static const uint8_t HASH_LEN = 32;
-
-    static PrivateKey KeyGen(const std::vector<uint8_t>& seed)
-    {
-        return KeyGen(Bytes(seed));
-    }
-
-    static PrivateKey KeyGen(const Bytes& seed)
+    static PrivateKey KeyGen(const Bytes seed)
     {
         // KeyGen
         // 1. PRK = HKDF-Extract("BLS-SIG-KEYGEN-SALT-", IKM || I2OSP(0, 1))