include/libeosio/base58.hpp: adding base58_decode functions.

include/libeosio/base58.hpp

@@ -36,6 +36,13 @@ std::string base58_encode(const std::string& str);
 std::string base58_encode(const std::vector<unsigned char>& vch);
 std::string base58_encode(const unsigned char* pbegin, const unsigned char* pend);
 
+
+/**
+ * Base58 Decoding functions.
+ */
+bool base58_decode(const char* psz, std::string& out);
+bool base58_decode(const std::string& str, std::string& out);
+
 /**
  * Returns true if `ch` is a base58 character, false otherwise.
  */

src/base58.cpp

@@ -27,11 +27,35 @@
 #include <algorithm>
 #include <cstddef>
 #include <cassert>
+#include <cstring>
 #include <libeosio/base58.hpp>
 
 namespace libeosio {
 
 static const char charmap[59] = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
+static const int8_t table[256] = {
+	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
+	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
+	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
+	-1, 0, 1, 2, 3, 4, 5, 6,  7, 8,-1,-1,-1,-1,-1,-1,
+	-1, 9,10,11,12,13,14,15, 16,-1,17,18,19,20,21,-1,
+	22,23,24,25,26,27,28,29, 30,31,32,-1,-1,-1,-1,-1,
+	-1,33,34,35,36,37,38,39, 40,41,42,43,-1,44,45,46,
+	47,48,49,50,51,52,53,54, 55,56,57,-1,-1,-1,-1,-1,
+	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
+	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
+	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
+	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
+	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
+	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
+	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
+	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
+};
+
+bool is_space(char c) {
+	return c == ' ' || c == '\f' || c == '\n' || c == '\r' || c == '\t' || c == '\v';
+}
+
 
 std::string base58_encode(const unsigned char* pbegin, const unsigned char* pend) {
 
@@ -84,6 +108,62 @@ std::string base58_encode(const std::vector<unsigned char>& vch) {
     return base58_encode(vch.data(), vch.data() + vch.size());
 }
 
+bool base58_decode(const char* psz, std::string& out) {
+	// Skip leading spaces.
+	while (*psz && is_space(*psz))
+		psz++;
+	// Skip and count leading '1's.
+	int zeroes = 0;
+	int length = 0;
+	while (*psz == '1') {
+		zeroes++;
+		psz++;
+	}
+	// Allocate enough space in big-endian base256 representation.
+	int size = strlen(psz) * 733 /1000 + 1; // log(58) / log(256), rounded up.
+	std::vector<unsigned char> b256(size);
+	// Process the characters.
+
+	while (*psz && !is_space(*psz)) {
+		// Decode base58 character
+		int carry = table[(uint8_t)*psz];
+		if (carry == -1)  // Invalid b58 character
+			return false;
+		int i = 0;
+		for (std::vector<unsigned char>::reverse_iterator it = b256.rbegin(); (carry != 0 || i < length) && (it != b256.rend()); ++it, ++i) {
+			carry += 58 * (*it);
+			*it = carry % 256;
+			carry /= 256;
+		}
+		assert(carry == 0);
+		length = i;
+		psz++;
+	}
+
+	// Skip trailing spaces.
+	while (is_space(*psz))
+		psz++;
+
+	if (*psz != 0)
+		return false;
+
+	// Skip leading zeroes in b256.
+	std::vector<unsigned char>::iterator it = b256.begin() + (size - length);
+	while (it != b256.end() && *it == 0)
+		it++;
+
+	// Copy result into output vector.
+	out.reserve(zeroes + (b256.end() - it));
+	out.assign(zeroes, 0);
+	while (it != b256.end())
+		out.push_back(*(it++));
+	return true;
+}
+
+bool base58_decode(const std::string& str, std::string& out) {
+	return base58_decode(str.c_str(), out);
+}
+
 bool is_base58(char ch) {
 	for(unsigned int i=0; i < sizeof(charmap); i++) {
 		if (ch == charmap[i]) {

tests/CMakeLists.txt

@@ -4,6 +4,7 @@ set(TEST_SRC
 
 	# Base58
 	base58/encode.cpp
+	base58/decode.cpp
 	base58/is_base58.cpp
 
 	# WIF

tests/base58/decode.cpp

@@ -0,0 +1,48 @@
+#include <libeosio/base58.hpp>
+#include <iostream>
+#include <vector>
+#include <doctest.h>
+
+typedef struct {
+	std::string name;
+	std::string in;
+	std::string expectedOut;
+	bool expectedReturn;
+} test_t;
+
+typedef std::vector<test_t> tests;
+
+TEST_CASE("base58_decode") {
+	tests input = {
+		test_t{"empty", "","", true},
+		test_t{"invalid","OI","",false},
+		test_t{
+			"valid #1",
+			"2nPTv2DT874jRaYBN4uhM9mT2iRiwdJuCXuX5buUHyyvWUSu6cX62i8HYo8PsWqgs9DHbwhpSpV5SVUnCqyLcpxcuGanH68eXgzZTGq",
+			"Quisque ut ipsum lorem. Nullam ac justo elit. Sed gravida convallis mattis.",
+			true
+		},
+		test_t{
+			"valid #2",
+			"5yAgp6rBagDHQZ3GacZSeaEPF2jfuwVHM21aNfXETJgn3EkArxc5UWSq1RM",
+			"Cras fringilla, eros et imperdiet tincidunt",
+			true
+		},
+		test_t{
+			"valid #3",
+			"9P7SxYWTWMq5hHkri53b1CGvWKRXxq3uXWPs5RiVtYagFrsnTXDxvKnk1twkPmV7BuxcRhBHWSwFLXpXbmdfHwZrnDaTB3wrBhsjm2Dd7F95ixh5vQLxajmT8hd22yUbvXuAZci8vTgFWMUyQi5YzWwntQiK5KFDkx3oA7kxvdU5t1yJZur84a9aKTCihEWtvCJ6LoBCpxvyB16YaCKeBQWLbUqoaXvFoDM78BpKD8biYyWQhnzHonjdwAS4KNXs5ByBdBvvPK1Q2Knr8zuFZxKHEFmgZGFTt8SMSsTDjkanUjojbfpJt5gcrHh6UFrt45n7kT9sj9Xsf1UyXZG3E2H85jXSbVnKowz2VPq1TkLLUKG8CSfdH3fVRp2E3yL5cpbbFWngbMzsbBZDgr4kPPcazebvSZ8qm8taBcBmt1ry25ey9TfFbMzP4FR1q9yjvkqGusMtrrBFm8YEeRmoMugMQoXvUgpExh29j",
+			"Praesent massa nibh, feugiat ac aliquet sed, varius quis metus. Fusce auctor imperdiet purus. Vivamus elementum risus vel imperdiet condimentum. Nunc iaculis, sem eu sollicitudin tempus, nibh felis scelerisque orci, a tincidunt felis lectus in nulla. Vestibulum egestas eu elit id luctus. Vivamus eget ipsum neque. Fusce eleifend mauris a tempus vehicula.",
+			true
+		},
+	};
+
+	for(tests::const_iterator it = input.begin(); it != input.end(); it++) {
+
+		SUBCASE(it->name.c_str()) {
+			std::string result;
+
+			CHECK( libeosio::base58_decode(it->in, result) == it->expectedReturn );
+			CHECK( result == it->expectedOut );
+		}
+	}
+}