[fold] Bring back safe case & misc reviews changes

src/ripple/protocol/impl/b58_utils.h

@@ -122,6 +122,14 @@ inplace_bigint_mul(std::span<std::uint64_t> a, std::uint64_t b)
 [[nodiscard]] inline std::uint64_t
 inplace_bigint_div_rem(std::span<uint64_t> numerator, std::uint64_t divisor)
 {
+    if (numerator.size() == 0)
+    {
+        // should never happen, but if it does then it seems natural to define
+        // the a null set of numbers to be zero, so the remainder is also zero.
+        assert(0);
+        return 0;
+    }
+
     auto to_u128 = [](std::uint64_t high,
                       std::uint64_t low) -> unsigned __int128 {
         unsigned __int128 const high128 = high;
@@ -134,11 +142,13 @@ inplace_bigint_div_rem(std::span<uint64_t> numerator, std::uint64_t divisor)
         unsigned __int128 const denom128 = denom;
         unsigned __int128 const d = num / denom128;
         unsigned __int128 const r = num - (denom128 * d);
+        assert(d >> 64 == 0);
+        assert(r >> 64 == 0);
         return {static_cast<std::uint64_t>(d), static_cast<std::uint64_t>(r)};
     };
 
     std::uint64_t prev_rem = 0;
-    std::size_t const last_index = numerator.size() - 1;
+    int const last_index = numerator.size() - 1;
     std::tie(numerator[last_index], prev_rem) =
         div_rem(numerator[last_index], divisor);
     for (int i = last_index - 1; i >= 0; --i)

src/ripple/protocol/impl/tokens.cpp

@@ -27,6 +27,7 @@
 
 #include <ripple/protocol/tokens.h>
 
+#include <ripple/basics/safe_cast.h>
 #include <ripple/protocol/digest.h>
 #include <ripple/protocol/impl/b58_utils.h>
 
@@ -329,7 +330,7 @@ encodeBase58Token(TokenType type, void const* token, std::size_t size)
 
     // Lay the data out as
     //      <type><token><checksum>
-    buf[0] = static_cast<std::underlying_type_t<TokenType>>(type);
+    buf[0] = safe_cast<std::underlying_type_t<TokenType>>(type);
     if (size)
         std::memcpy(buf.data() + 1, token, size);
     checksum(buf.data() + 1 + size, buf.data(), 1 + size);
@@ -348,7 +349,7 @@ decodeBase58Token(std::string const& s, TokenType type)
         return {};
 
     // The type must match.
-    if (type != static_cast<TokenType>(static_cast<std::uint8_t>(ret[0])))
+    if (type != safe_cast<TokenType>(static_cast<std::uint8_t>(ret[0])))
         return {};
 
     // And the checksum must as well.