wallet: feature: transfer amount with fee included

To transfer ~5 XMR to an address such that your balance drops by exactly 5 XMR, provide a `subtractfeefrom` flag to the `transfer` command. For example:

    transfer 76bDHojqFYiFCCYYtzTveJ8oFtmpNp3X1TgV2oKP7rHmZyFK1RvyE4r8vsJzf7SyNohMnbKT9wbcD3XUTgsZLX8LU5JBCfm 5 subtractfeefrom=all

If my walet balance was exactly 30 XMR before this transaction, it will be exactly 25 XMR afterwards and the destination address will receive slightly
less than 5 XMR. You can manually select which destinations fund the transaction fee and which ones do not by providing the destination index.
For example:

    transfer 75sr8AAr... 3 74M7W4eg... 4 7AbWqDZ6... 5 subtractfeefrom=0,2

This will drop your balance by exactly 12 XMR including fees and will spread the fee cost proportionally (3:5 ratio) over destinations with addresses
`75sr8AAr...` and `7AbWqDZ6...`, respectively.

Disclaimer: This feature was paid for by @LocalMonero.

1 files changed, 57 insertions, 0 deletions

diff --git a/tests/unit_tests/epee_utils.cpp b/tests/unit_tests/epee_utils.cpp
index 1c756e77c..110cebf6a 100644
--- a/tests/unit_tests/epee_utils.cpp
+++ b/tests/unit_tests/epee_utils.cpp
@@ -1836,3 +1836,60 @@ TEST(parsing, unicode)
   epee::misc_utils::parse::match_string2(si, s.end(), bs);
   EXPECT_EQ(bs, "あまやかす");
 }
+
+TEST(parsing, strtoul)
+{
+  long ul;
+  const char* p;
+  const char* endp;
+
+  errno = 0; // Some libc's only set errno on failure, some set it to 0 on success
+
+  p = "0";
+  endp = nullptr;
+  ul = std::strtoul(p, const_cast<char**>(&endp), 10);
+  EXPECT_EQ(0, errno);
+  EXPECT_EQ(0, ul);
+  EXPECT_EQ(p + 1, endp);
+
+  p = "000000";
+  endp = nullptr;
+  ul = std::strtoul(p, const_cast<char**>(&endp), 10);
+  EXPECT_EQ(0, errno);
+  EXPECT_EQ(0, ul);
+  EXPECT_EQ(p + 6, endp);
+
+  p = "1";
+  endp = nullptr;
+  ul = std::strtoul(p, const_cast<char**>(&endp), 10);
+  EXPECT_EQ(0, errno);
+  EXPECT_EQ(1, ul);
+  EXPECT_EQ(p + 1, endp);
+
+  p = "0q";
+  endp = nullptr;
+  ul = std::strtoul(p, const_cast<char**>(&endp), 10);
+  EXPECT_EQ(0, errno);
+  EXPECT_EQ(0, ul);
+  EXPECT_EQ(p + 1, endp);
+
+  p = "    \t   0";
+  endp = nullptr;
+  ul = std::strtoul(p, const_cast<char**>(&endp), 10);
+  EXPECT_EQ(0, errno);
+  EXPECT_EQ(0, ul);
+  EXPECT_EQ(p + 9, endp);
+
+  p = "q";
+  endp = nullptr;
+  ul = std::strtoul(p, const_cast<char**>(&endp), 10);
+  EXPECT_EQ(0, errno);
+  EXPECT_EQ(0, ul);
+  EXPECT_EQ(p, endp);
+
+  p = "999999999999999999999999999999999999999";
+  endp = nullptr;
+  ul = std::strtoul(p, const_cast<char**>(&endp), 10);
+  EXPECT_EQ(ERANGE, errno);
+  EXPECT_EQ(ULLONG_MAX, ul);
+}