introduced and used bigint datatype

src/big_int.cpp

@@ -0,0 +1,108 @@
+#include "big_int.hpp"
+#include "tl/expected.hpp"
+#include <iostream>
+#include <charconv>
+#include <vector>
+
+inline uint8_t hex(char c) {
+  switch(c) {
+    case '0': return 0; 
+    case '1': return 1;
+    case '2': return 2;
+    case '3': return 3;
+    case '4': return 4;
+    case '5': return 5;
+    case '6': return 6;
+    case '7': return 7;
+    case '8': return 8;
+    case '9': return 9;
+    case 'a': return 10;
+    case 'b': return 11;
+    case 'c': return 12;
+    case 'd': return 13;
+    case 'e': return 14;
+    case 'f': return 15;
+    case 'A': return 10;
+    case 'B': return 11;
+    case 'C': return 12;
+    case 'D': return 13;
+    case 'E': return 14;
+    case 'F': return 15;
+    default:
+      return 0xff;
+  }
+}
+  
+tl::expected<BigInt,BigInt::eError>
+BigInt::from_string(const std::string& str) {
+  BigInt b;
+  // std::cout << str << std::endl;
+
+  uint8_t hval=0;
+  uint8_t nibble;
+  size_t i = str.size()+1;
+
+  for(auto c : str) {
+    nibble = hex(c);
+    if (nibble ==0xFF) {
+      return tl::make_unexpected(eError::PARSE_ERROR);
+    }
+    if (i%2) {
+      hval = nibble << 4;
+    } else {
+      hval |= nibble;
+      b.data[256 - (i/2)]= hval;
+      hval = 0;
+    }
+    i--;
+  }
+
+  // std::cout << std::hex;
+  // for (auto b: b.data)
+  //   {
+  //     std::cout << (int)b;
+  //   }
+  // std::cout << std::dec << std::endl;
+  return b;
+}
+
+BigInt BigInt::from_int(uint64_t value)
+{
+  BigInt b;
+  b.data[248]=(value >> 56 & 0xff);
+  b.data[249]=(value >> 48 & 0xff);
+  b.data[250]=(value >> 40 & 0xff);
+  b.data[251]=(value >> 32 & 0xff);
+  b.data[252]=(value >> 24 & 0xff);
+  b.data[253]=(value >> 16 & 0xff);
+  b.data[254]=(value >> 8 & 0xff);
+  b.data[255]=(value & 0xff);
+  return b;
+}
+
+constexpr char hex_char [] = "0123456789abcdef";
+std::string BigInt::to_string() const
+{
+  std::string s;
+  uint8_t b;
+  uint8_t first_digit = 0;
+  for (size_t i = 0; i<256;i++) {
+    b = data[i];
+    if (first_digit==0) {
+      if (b==0) {
+	continue;
+      } else if (b>0xf) {
+	s.push_back(hex_char[b >> 4]);
+      }
+      s.push_back(hex_char[b & 0xf]);
+      first_digit = b;
+    } else {
+      s.push_back(hex_char[b >> 4]);
+      s.push_back(hex_char[b & 0xf]);
+    }
+  }
+  return s;
+}
+
+bool operator == (const BigInt& rhs, const BigInt& lhs)
+{ return rhs.data == lhs.data; }