Support STAmount conversions to XRPAmount and IOUAmount

src/ripple/protocol/STAmount.h

@@ -24,6 +24,8 @@
 #include <ripple/protocol/Serializer.h>
 #include <ripple/protocol/STBase.h>
 #include <ripple/protocol/Issue.h>
+#include <ripple/protocol/IOUAmount.h>
+#include <ripple/protocol/XRPAmount.h>
 #include <beast/cxx14/memory.h> // <memory>
 
 namespace ripple {
@@ -114,6 +116,10 @@ public:
 
     STAmount (Issue const& issue, int mantissa, int exponent = 0);
 
+    // Legacy support for new-style amounts
+    STAmount (IOUAmount const& amount, Issue const& issue);
+    STAmount (XRPAmount const& amount);
+
     STBase*
     copy (std::size_t n, void* buf) const override
     {
@@ -271,6 +277,9 @@ public:
     {
         return (mValue == 0) && mIsNative;
     }
+
+    XRPAmount xrp () const;
+    IOUAmount iou () const;
 };
 
 //------------------------------------------------------------------------------

src/ripple/protocol/XRPAmount.h

@@ -25,6 +25,7 @@
 #include <beast/utility/Zero.h>
 #include <boost/operators.hpp>
 #include <cstdint>
+#include <beast/cxx14/type_traits.h>
 
 using beast::zero;
 
@@ -35,82 +36,94 @@ class XRPAmount
     , private boost::additive <XRPAmount>
 {
 private:
-    std::int64_t value_;
+    std::int64_t drops_;
 
 public:
-    /** @{ */
     XRPAmount () = default;
     XRPAmount (XRPAmount const& other) = default;
     XRPAmount& operator= (XRPAmount const& other) = default;
 
     XRPAmount (beast::Zero)
-        : value_ (0)
+        : drops_ (0)
     {
     }
 
     XRPAmount&
     operator= (beast::Zero)
     {
-        value_ = 0;
+        drops_ = 0;
         return *this;
     }
 
-    XRPAmount (std::int64_t value)
-        : value_ (value)
+    template <class Integer,
+        class = typename std::enable_if_t <
+            std::is_integral<Integer>::value>>
+    XRPAmount (Integer drops)
+        : drops_ (static_cast<std::int64_t> (drops))
     {
     }
 
+    template <class Integer,
+        class = typename std::enable_if_t <
+            std::is_integral<Integer>::value>>
     XRPAmount&
-    operator= (std::int64_t v)
+    operator= (Integer drops)
     {
-        value_ = v;
+        drops_ = static_cast<std::int64_t> (drops);
         return *this;
     }
 
     XRPAmount&
     operator+= (XRPAmount const& other)
     {
-        value_ += other.value_;
+        drops_ += other.drops_;
         return *this;
     }
 
     XRPAmount&
     operator-= (XRPAmount const& other)
     {
-        value_ -= other.value_;
+        drops_ -= other.drops_;
         return *this;
     }
 
     XRPAmount
     operator- () const
     {
-        return { -value_ };
+        return { -drops_ };
     }
 
     bool
     operator==(XRPAmount const& other) const
     {
-        return value_ == other.value_;
+        return drops_ == other.drops_;
     }
 
     bool
     operator<(XRPAmount const& other) const
     {
-        return value_ < other.value_;
+        return drops_ < other.drops_;
     }
 
     /** Returns true if the amount is not zero */
     explicit
     operator bool() const noexcept
     {
-        return value_ != 0;
+        return drops_ != 0;
     }
 
     /** Return the sign of the amount */
     int
     signum() const noexcept
     {
-        return (value_ < 0) ? -1 : (value_ ? 1 : 0);
+        return (drops_ < 0) ? -1 : (drops_ ? 1 : 0);
+    }
+
+    /** Returns the number of drops */
+    std::int64_t
+    drops () const
+    {
+        return drops_;
     }
 };
 
@@ -118,7 +131,7 @@ public:
 inline
 bool isLegalAmount (XRPAmount const& amount)
 {
-    return amount <= SYSTEM_CURRENCY_START;
+    return amount.drops () <= SYSTEM_CURRENCY_START;
 }
 
 }

src/ripple/protocol/impl/STAmount.cpp

@@ -248,12 +248,72 @@ STAmount::STAmount (Issue const& issue,
 {
 }
 
+// Legacy support for new-style amounts
+STAmount::STAmount (IOUAmount const& amount, Issue const& issue)
+    : mIssue (issue)
+    , mOffset (amount.exponent ())
+    , mIsNative (false)
+    , mIsNegative (amount < zero)
+{
+    if (mIsNegative)
+        mValue = static_cast<std::uint64_t> (-amount.mantissa ());
+    else
+        mValue = static_cast<std::uint64_t> (amount.mantissa ());
+
+    canonicalize ();
+}
+
+STAmount::STAmount (XRPAmount const& amount)
+    : mOffset (0)
+    , mIsNative (true)
+    , mIsNegative (amount < zero)
+{
+    if (mIsNegative)
+        mValue = static_cast<std::uint64_t> (-amount.drops ());
+    else
+        mValue = static_cast<std::uint64_t> (amount.drops ());
+
+    canonicalize ();
+}
+
 std::unique_ptr<STAmount>
 STAmount::construct (SerialIter& sit, SField const& name)
 {
     return std::make_unique<STAmount>(sit, name);
 }
 
+//------------------------------------------------------------------------------
+//
+// Conversion
+//
+//------------------------------------------------------------------------------
+XRPAmount STAmount::xrp () const
+{
+    if (!mIsNative)
+        throw std::logic_error ("Cannot return non-native STAmount as XRPAmount");
+
+    auto drops = static_cast<std::int64_t> (mValue);
+
+    if (mIsNegative)
+        drops = -drops;
+
+    return { drops };
+}
+
+IOUAmount STAmount::iou () const
+{
+    if (mIsNative)
+        throw std::logic_error ("Cannot return native STAmount as IOUAmount");
+
+    auto mantissa = static_cast<std::int64_t> (mValue);
+    auto exponent = mOffset;
+
+    if (mIsNegative)
+        mantissa = -mantissa;
+
+    return { mantissa, exponent };
+}
+
 //------------------------------------------------------------------------------
 //
 // Operators

src/ripple/protocol/tests/STAmount.test.cpp

@@ -567,6 +567,70 @@ public:
 #endif
     }
 
+    void
+    testConvertXRP ()
+    {
+        testcase ("STAmount to XRPAmount conversions");
+
+        Issue const usd { Currency (0x5553440000000000), AccountID (0x4985601) };
+        Issue const xrp { xrpIssue () };
+
+        for (std::uint64_t drops = 100000000000000000; drops != 1; drops = drops / 10)
+        {
+            auto const t = amountFromString (xrp, std::to_string (drops));
+            auto const s = t.xrp ();
+            expect (s.drops() == drops);
+            expect (t == STAmount (XRPAmount (drops)));
+            expect (s == XRPAmount (drops));
+        }
+
+        try
+        {
+            auto const t = amountFromString (usd, "136500");
+            fail (to_string (t.xrp ()));
+        }
+        catch (std::logic_error const&)
+        {
+            pass ();
+        }
+        catch (...)
+        {
+            fail ("wrong exception");
+        }
+    }
+
+    void
+    testConvertIOU ()
+    {
+        testcase ("STAmount to IOUAmount conversions");
+
+        Issue const usd { Currency (0x5553440000000000), AccountID (0x4985601) };
+        Issue const xrp { xrpIssue () };
+
+        for (std::uint64_t dollars = 10000000000; dollars != 1; dollars = dollars / 10)
+        {
+            auto const t = amountFromString (usd, std::to_string (dollars));
+            auto const s = t.iou ();
+            expect (t == STAmount (s, usd));
+            expect (s.mantissa () == t.mantissa ());
+            expect (s.exponent () == t.exponent ());
+        }
+
+        try
+        {
+            auto const t = amountFromString (xrp, "136500");
+            fail (to_string (t.iou ()));
+        }
+        catch (std::logic_error const&)
+        {
+            pass ();
+        }
+        catch (...)
+        {
+            fail ("wrong exception");
+        }
+    }
+
     //--------------------------------------------------------------------------
 
     void run ()
@@ -577,6 +641,8 @@ public:
         testArithmetic ();
         testUnderflow ();
         testRounding ();
+        testConvertXRP ();
+        testConvertIOU ();
     }
 };