Generalize ConvertBits

src/test/convertbits_tests.cpp

@@ -16,8 +16,8 @@ BOOST_AUTO_TEST_CASE(convertbits_deterministic)
         std::vector<unsigned char> input(32, i);
         std::vector<unsigned char> data;
         std::vector<unsigned char> output;
-        ConvertBits<8, 5, true>(data, input.begin(), input.end());
-        ConvertBits<5, 8, false>(output, data.begin(), data.end());
+        ConvertBits<8, 5, true>([&](unsigned char c) { data.push_back(c); }, input.begin(), input.end());
+        ConvertBits<5, 8, false>([&](unsigned char c) { output.push_back(c); }, data.begin(), data.end());
         BOOST_CHECK_EQUAL(data.size(), 52);
         BOOST_CHECK_EQUAL(output.size(), 32);
         BOOST_CHECK(input == output);
@@ -27,8 +27,8 @@ BOOST_AUTO_TEST_CASE(convertbits_deterministic)
         std::vector<unsigned char> input(43, i);
         std::vector<unsigned char> data;
         std::vector<unsigned char> output;
-        ConvertBits<8, 5, true>(data, input.begin(), input.end());
-        ConvertBits<5, 8, false>(output, data.begin(), data.end());
+        ConvertBits<8, 5, true>([&](unsigned char c) { data.push_back(c); }, input.begin(), input.end());
+        ConvertBits<5, 8, false>([&](unsigned char c) { output.push_back(c); }, data.begin(), data.end());
         BOOST_CHECK_EQUAL(data.size(), 69);
         BOOST_CHECK_EQUAL(output.size(), 43);
         BOOST_CHECK(input == output);
@@ -41,8 +41,8 @@ BOOST_AUTO_TEST_CASE(convertbits_random)
         auto input = libzcash::random_uint256();
         std::vector<unsigned char> data;
         std::vector<unsigned char> output;
-        ConvertBits<8, 5, true>(data, input.begin(), input.end());
-        ConvertBits<5, 8, false>(output, data.begin(), data.end());
+        ConvertBits<8, 5, true>([&](unsigned char c) { data.push_back(c); }, input.begin(), input.end());
+        ConvertBits<5, 8, false>([&](unsigned char c) { output.push_back(c); }, data.begin(), data.end());
         BOOST_CHECK_EQUAL(data.size(), 52);
         BOOST_CHECK_EQUAL(output.size(), 32);
         BOOST_CHECK(input == uint256(output));

src/utilstrencodings.h

@@ -135,7 +135,7 @@ bool ParseFixedPoint(const std::string &val, int decimals, int64_t *amount_out);
 
 /** Convert from one power-of-2 number base to another. */
 template<int frombits, int tobits, bool pad, typename O, typename I>
-bool ConvertBits(O& out, I it, I end) {
+bool ConvertBits(const O& outfn, I it, I end) {
     size_t acc = 0;
     size_t bits = 0;
     constexpr size_t maxv = (1 << tobits) - 1;
@@ -145,12 +145,12 @@ bool ConvertBits(O& out, I it, I end) {
         bits += frombits;
         while (bits >= tobits) {
             bits -= tobits;
-            out.push_back((acc >> bits) & maxv);
+            outfn((acc >> bits) & maxv);
         }
         ++it;
     }
     if (pad) {
-        if (bits) out.push_back((acc << (tobits - bits)) & maxv);
+        if (bits) outfn((acc << (tobits - bits)) & maxv);
     } else if (bits >= frombits || ((acc << (tobits - bits)) & maxv)) {
         return false;
     }