LibCrypto: Add {Signed,Unsigned}BigInteger::from_base{2, 8, 16} helpers

These can be used to create BigInteger instances from non-decimal
number strings.

Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp

@@ -27,7 +27,7 @@ size_t SignedBigInteger::export_data(Bytes data, bool remove_leading_zeros) cons
     return m_unsigned_data.export_data(bytes_view, remove_leading_zeros) + 1;
 }
 
-SignedBigInteger SignedBigInteger::from_base10(StringView str)
+static bool parse_sign(StringView& str)
 {
     bool sign = false;
     if (str.length() > 1) {
@@ -39,10 +39,37 @@ SignedBigInteger SignedBigInteger::from_base10(StringView str)
         if (maybe_sign == '+')
             str = str.substring_view(1, str.length() - 1);
     }
+    return sign;
+}
+
+SignedBigInteger SignedBigInteger::from_base10(StringView str)
+{
+    auto sign = parse_sign(str);
     auto unsigned_data = UnsignedBigInteger::from_base10(str);
     return { move(unsigned_data), sign };
 }
 
+SignedBigInteger SignedBigInteger::from_base2(StringView str)
+{
+    auto sign = parse_sign(str);
+    auto unsigned_data = UnsignedBigInteger::from_base2(str);
+    return { move(unsigned_data), sign };
+}
+
+SignedBigInteger SignedBigInteger::from_base8(StringView str)
+{
+    auto sign = parse_sign(str);
+    auto unsigned_data = UnsignedBigInteger::from_base8(str);
+    return { move(unsigned_data), sign };
+}
+
+SignedBigInteger SignedBigInteger::from_base16(StringView str)
+{
+    auto sign = parse_sign(str);
+    auto unsigned_data = UnsignedBigInteger::from_base16(str);
+    return { move(unsigned_data), sign };
+}
+
 String SignedBigInteger::to_base10() const
 {
     StringBuilder builder;

Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h

@@ -62,8 +62,11 @@ public:
 
     size_t export_data(Bytes, bool remove_leading_zeros = false) const;
 
+    static SignedBigInteger from_base2(StringView str);
+    static SignedBigInteger from_base8(StringView str);
     static SignedBigInteger from_base10(StringView str);
     String to_base10() const;
+    static SignedBigInteger from_base16(StringView str);
 
     u64 to_u64() const;
 

Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp

@@ -5,6 +5,7 @@
  */
 
 #include "UnsignedBigInteger.h"
+#include <AK/CharacterTypes.h>
 #include <AK/StringBuilder.h>
 #include <AK/StringHash.h>
 #include <LibCrypto/BigInt/Algorithms/UnsignedBigIntegerAlgorithms.h>
@@ -71,7 +72,40 @@ UnsignedBigInteger UnsignedBigInteger::from_base10(const String& str)
     UnsignedBigInteger ten { 10 };
 
     for (auto& c : str) {
-        result = result.multiplied_by(ten).plus(c - '0');
+        result = result.multiplied_by(ten).plus(parse_ascii_digit(c));
+    }
+    return result;
+}
+
+UnsignedBigInteger UnsignedBigInteger::from_base2(const String& str)
+{
+    UnsignedBigInteger result;
+    UnsignedBigInteger two { 2 };
+
+    for (auto& c : str) {
+        result = result.multiplied_by(two).plus(parse_ascii_digit(c));
+    }
+    return result;
+}
+
+UnsignedBigInteger UnsignedBigInteger::from_base8(const String& str)
+{
+    UnsignedBigInteger result;
+    UnsignedBigInteger eight { 8 };
+
+    for (auto& c : str) {
+        result = result.multiplied_by(eight).plus(parse_ascii_digit(c));
+    }
+    return result;
+}
+
+UnsignedBigInteger UnsignedBigInteger::from_base16(const String& str)
+{
+    UnsignedBigInteger result;
+    UnsignedBigInteger sixteen { 16 };
+
+    for (auto& c : str) {
+        result = result.multiplied_by(sixteen).plus(parse_ascii_hex_digit(c));
     }
     return result;
 }

Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h

@@ -53,8 +53,11 @@ public:
 
     size_t export_data(Bytes, bool remove_leading_zeros = false) const;
 
+    static UnsignedBigInteger from_base2(const String& str);
+    static UnsignedBigInteger from_base8(const String& str);
     static UnsignedBigInteger from_base10(const String& str);
     String to_base10() const;
+    static UnsignedBigInteger from_base16(const String& str);
 
     u64 to_u64() const;