rpc: make wide_difficulty hexadecimal

This should be friendlier for clients which don't have bignum support

src/cryptonote_basic/difficulty.cpp

@@ -239,4 +239,19 @@ namespace cryptonote {
     return res.convert_to<difficulty_type>();
   }
 
+  std::string hex(difficulty_type v)
+  {
+    static const char chars[] = "0123456789abcdef";
+    std::string s;
+    while (v > 0)
+    {
+      s.push_back(chars[(v & 0xf).convert_to<unsigned>()]);
+      v >>= 4;
+    }
+    if (s.empty())
+      s += "0";
+    std::reverse(s.begin(), s.end());
+    return "0x" + s;
+  }
+
 }

src/cryptonote_basic/difficulty.h

@@ -32,6 +32,7 @@
 
 #include <cstdint>
 #include <vector>
+#include <string>
 #include <boost/multiprecision/cpp_int.hpp>
 
 #include "crypto/hash.h"
@@ -58,4 +59,6 @@ namespace cryptonote
     bool check_hash_128(const crypto::hash &hash, difficulty_type difficulty);
     bool check_hash(const crypto::hash &hash, difficulty_type difficulty);
     difficulty_type next_difficulty(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds);
+
+    std::string hex(difficulty_type v);
 }

src/rpc/core_rpc_server.cpp

@@ -74,7 +74,7 @@ namespace
   void store_difficulty(cryptonote::difficulty_type difficulty, uint64_t &sdiff, std::string &swdiff, uint64_t &stop64)
   {
     sdiff = (difficulty << 64 >> 64).convert_to<uint64_t>();
-    swdiff = difficulty.convert_to<std::string>();
+    swdiff = cryptonote::hex(difficulty);
     stop64 = (difficulty >> 64).convert_to<uint64_t>();
   }
 }

tests/functional_tests/blockchain.py

@@ -60,8 +60,8 @@ class BlockchainTest():
         prev_block = res_info.top_block_hash
         res_height = daemon.get_height()
         assert res_height.height == height
-        assert int(res_info.wide_cumulative_difficulty) == (res_info.cumulative_difficulty_top64 << 64) + res_info.cumulative_difficulty
-        cumulative_difficulty = int(res_info.wide_cumulative_difficulty)
+        assert int(res_info.wide_cumulative_difficulty, 16) == (res_info.cumulative_difficulty_top64 << 64) + res_info.cumulative_difficulty
+        cumulative_difficulty = int(res_info.wide_cumulative_difficulty, 16)
 
         # we should not see a block at height
         ok = False
@@ -90,11 +90,11 @@ class BlockchainTest():
             assert block_header.orphan_status == False
             assert block_header.depth == blocks - n - 1
             assert block_header.prev_hash == prev_block, prev_block
-            assert int(block_header.wide_difficulty) == (block_header.difficulty_top64 << 64) + block_header.difficulty
-            assert int(block_header.wide_cumulative_difficulty) == (block_header.cumulative_difficulty_top64 << 64) + block_header.cumulative_difficulty
+            assert int(block_header.wide_difficulty, 16) == (block_header.difficulty_top64 << 64) + block_header.difficulty
+            assert int(block_header.wide_cumulative_difficulty, 16) == (block_header.cumulative_difficulty_top64 << 64) + block_header.cumulative_difficulty
             assert block_header.reward >= 600000000000 # tail emission
-            cumulative_difficulty += int(block_header.wide_difficulty)
-            assert cumulative_difficulty == int(block_header.wide_cumulative_difficulty)
+            cumulative_difficulty += int(block_header.wide_difficulty, 16)
+            assert cumulative_difficulty == int(block_header.wide_cumulative_difficulty, 16)
             assert block_header.block_size > 0
             assert block_header.block_weight >= block_header.block_size
             assert block_header.long_term_weight > 0
@@ -122,7 +122,7 @@ class BlockchainTest():
         assert res_getblocktemplate.expected_reward >= 600000000000
         assert len(res_getblocktemplate.blocktemplate_blob) > 0
         assert len(res_getblocktemplate.blockhashing_blob) > 0
-        assert int(res_getblocktemplate.wide_difficulty) == (res_getblocktemplate.difficulty_top64 << 64) + res_getblocktemplate.difficulty
+        assert int(res_getblocktemplate.wide_difficulty, 16) == (res_getblocktemplate.difficulty_top64 << 64) + res_getblocktemplate.difficulty
 
         # diff etc should be the same
         assert res_getblocktemplate.prev_hash == res_info.top_block_hash