Simplify strHex:

Problem:
- There are several specific overloads with some custom code that can be
  easily replaced using Boost.Hex.

Solution:
- Introduce `strHex(itr, itr)` to return a string given a begin and end
  iterator.
- Remove `strHex(itr, size)` in favor of the `strHex(T)` where T is
  something that has a `begin()` member function. This allows us to
  remove the strHex overloads for `std::string`, Blob, and Slice.

src/ripple/protocol/PublicKey.h

@@ -63,6 +63,8 @@ protected:
     std::uint8_t buf_[33]; // should be large enough
 
 public:
+    using const_iterator = std::uint8_t const*;
+
     PublicKey() = default;
     PublicKey (PublicKey const& other);
     PublicKey& operator= (PublicKey const& other);
@@ -87,6 +89,30 @@ public:
         return size_;
     }
 
+    const_iterator
+    begin() const noexcept
+    {
+        return buf_;
+    }
+
+    const_iterator
+    cbegin() const noexcept
+    {
+        return buf_;
+    }
+
+    const_iterator
+    end() const noexcept
+    {
+        return buf_ + size_;
+    }
+
+    const_iterator
+    cend() const noexcept
+    {
+        return buf_ + size_;
+    }
+
     bool
     empty() const noexcept
     {

src/ripple/protocol/STPathSet.h

@@ -120,7 +120,7 @@ public:
     STPathElement(STPathElement const&) = default;
     STPathElement& operator=(STPathElement const&) = default;
 
-    int
+    auto
     getNodeType () const
     {
         return mType;

src/ripple/protocol/SecretKey.h

@@ -38,6 +38,8 @@ private:
     std::uint8_t buf_[32];
 
 public:
+    using const_iterator = std::uint8_t const*;
+
     SecretKey() = default;
     SecretKey (SecretKey const&) = default;
     SecretKey& operator= (SecretKey const&) = default;
@@ -66,6 +68,30 @@ public:
     */
     std::string
     to_string() const;
+
+    const_iterator
+    begin() const noexcept
+    {
+        return buf_;
+    }
+
+    const_iterator
+    cbegin() const noexcept
+    {
+        return buf_;
+    }
+
+    const_iterator
+    end() const noexcept
+    {
+        return buf_ + sizeof(buf_);
+    }
+
+    const_iterator
+    cend() const noexcept
+    {
+        return buf_ + sizeof(buf_);
+    }
 };
 
 inline

src/ripple/protocol/Seed.h

@@ -35,6 +35,8 @@ private:
     std::array<uint8_t, 16> buf_;
 
 public:
+    using const_iterator = std::array<uint8_t, 16>::const_iterator;
+
     Seed() = delete;
 
     Seed (Seed const&) = default;
@@ -62,6 +64,30 @@ public:
     {
         return buf_.size();
     }
+
+    const_iterator
+    begin() const noexcept
+    {
+        return buf_.begin();
+    }
+
+    const_iterator
+    cbegin() const noexcept
+    {
+        return buf_.cbegin();
+    }
+
+    const_iterator
+    end() const noexcept
+    {
+        return buf_.end();
+    }
+
+    const_iterator
+    cend() const noexcept
+    {
+        return buf_.cend();
+    }
 };
 
 //------------------------------------------------------------------------------

src/ripple/protocol/impl/PublicKey.cpp

@@ -31,7 +31,7 @@ namespace ripple {
 std::ostream&
 operator<<(std::ostream& os, PublicKey const& pk)
 {
-    os << strHex(pk.data(), pk.size());
+    os << strHex(pk);
     return os;
 }
 

src/ripple/protocol/impl/STBlob.cpp

@@ -31,7 +31,7 @@ STBlob::STBlob (SerialIter& st, SField const& name)
 std::string
 STBlob::getText () const
 {
-    return strHex (value_.data (), value_.size ());
+    return strHex (value_);
 }
 
 bool

src/ripple/protocol/impl/STPathSet.cpp

@@ -156,7 +156,7 @@ STPath::getJson (int) const
     for (auto it: mPath)
     {
         Json::Value elem (Json::objectValue);
-        int         iType   = it.getNodeType ();
+        auto const iType   = it.getNodeType ();
 
         elem[jss::type]      = iType;
         elem[jss::type_hex]  = strHex (iType);

src/ripple/protocol/impl/SecretKey.cpp

@@ -51,7 +51,7 @@ SecretKey::SecretKey (Slice const& slice)
 std::string
 SecretKey::to_string() const
 {
-    return strHex(data(), size());
+    return strHex(*this);
 }
 
 //------------------------------------------------------------------------------

src/ripple/protocol/impl/UintTypes.cpp

@@ -61,7 +61,7 @@ std::string to_string(Currency const& currency)
         }
     }
 
-    return strHex (currency.begin (), currency.size ());
+    return strHex (currency);
 }
 
 bool to_currency(Currency& currency, std::string const& code)