LibCrypto: Define *BigInteger::to_base to convert big integers to String

Author: https://github.com/trflynn89
Commit: https://github.com/SerenityOS/serenity/commit/3ad1f250e7
Pull-request: https://github.com/SerenityOS/serenity/pull/17014
Reviewed-by: https://github.com/linusg ✅

Tests/LibCrypto/TestBigInteger.cpp

@@ -241,9 +241,10 @@ TEST_CASE(test_unsigned_bigint_base10_from_string)
 
 TEST_CASE(test_unsigned_bigint_base10_to_string)
 {
-    auto result = Crypto::UnsignedBigInteger {
+    auto bigint = Crypto::UnsignedBigInteger {
         Vector<u32> { 3806301393, 954919431, 3879607298, 721 }
-    }.to_base_deprecated(10);
+    };
+    auto result = MUST(bigint.to_base(10));
     EXPECT_EQ(result, "57195071295721390579057195715793");
 }
 
@@ -386,10 +387,10 @@ TEST_CASE(test_bigint_random_distribution)
         "100000000000000000000000000000"_bigint);         // 10**29
     if (actual_result < "100000000000000000000"_bigint) { // 10**20
         FAIL("Too small");
-        outln("The generated number {} is extremely small. This *can* happen by pure chance, but should happen only once in a billion times. So it's probably an error.", actual_result.to_base_deprecated(10));
+        outln("The generated number {} is extremely small. This *can* happen by pure chance, but should happen only once in a billion times. So it's probably an error.", MUST(actual_result.to_base(10)));
     } else if ("99999999900000000000000000000"_bigint < actual_result) { // 10**29 - 10**20
         FAIL("Too large");
-        outln("The generated number {} is extremely large. This *can* happen by pure chance, but should happen only once in a billion times. So it's probably an error.", actual_result.to_base_deprecated(10));
+        outln("The generated number {} is extremely large. This *can* happen by pure chance, but should happen only once in a billion times. So it's probably an error.", MUST(actual_result.to_base(10)));
     }
 }
 

Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp

@@ -51,16 +51,22 @@ SignedBigInteger SignedBigInteger::from_base(u16 N, StringView str)
     return { move(unsigned_data), sign };
 }
 
-DeprecatedString SignedBigInteger::to_base_deprecated(u16 N) const
+ErrorOr<String> SignedBigInteger::to_base(u16 N) const
 {
     StringBuilder builder;
 
     if (m_sign)
-        builder.append('-');
+        TRY(builder.try_append('-'));
 
-    builder.append(m_unsigned_data.to_base_deprecated(N));
+    auto unsigned_as_base = TRY(m_unsigned_data.to_base(N));
+    TRY(builder.try_append(unsigned_as_base.bytes_as_string_view()));
 
-    return builder.to_deprecated_string();
+    return builder.to_string();
+}
+
+DeprecatedString SignedBigInteger::to_base_deprecated(u16 N) const
+{
+    return MUST(to_base(N)).to_deprecated_string();
 }
 
 u64 SignedBigInteger::to_u64() const

Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h

@@ -9,6 +9,7 @@
 
 #include <AK/Concepts.h>
 #include <AK/Span.h>
+#include <AK/String.h>
 #include <LibCrypto/BigInt/UnsignedBigInteger.h>
 
 namespace Crypto {
@@ -63,6 +64,7 @@ public:
     size_t export_data(Bytes, bool remove_leading_zeros = false) const;
 
     [[nodiscard]] static SignedBigInteger from_base(u16 N, StringView str);
+    [[nodiscard]] ErrorOr<String> to_base(u16 N) const;
     [[nodiscard]] DeprecatedString to_base_deprecated(u16 N) const;
 
     [[nodiscard]] u64 to_u64() const;

Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp

@@ -146,11 +146,11 @@ UnsignedBigInteger UnsignedBigInteger::from_base(u16 N, StringView str)
     return result;
 }
 
-DeprecatedString UnsignedBigInteger::to_base_deprecated(u16 N) const
+ErrorOr<String> UnsignedBigInteger::to_base(u16 N) const
 {
     VERIFY(N <= 36);
     if (*this == UnsignedBigInteger { 0 })
-        return "0";
+        return String::from_utf8("0"sv);
 
     StringBuilder builder;
     UnsignedBigInteger temp(*this);
@@ -160,11 +160,16 @@ DeprecatedString UnsignedBigInteger::to_base_deprecated(u16 N) const
     while (temp != UnsignedBigInteger { 0 }) {
         UnsignedBigIntegerAlgorithms::divide_u16_without_allocation(temp, N, quotient, remainder);
         VERIFY(remainder.words()[0] < N);
-        builder.append(to_ascii_base36_digit(remainder.words()[0]));
+        TRY(builder.try_append(to_ascii_base36_digit(remainder.words()[0])));
         temp.set_to(quotient);
     }
 
-    return builder.to_deprecated_string().reverse();
+    return TRY(builder.to_string()).reverse();
+}
+
+DeprecatedString UnsignedBigInteger::to_base_deprecated(u16 N) const
+{
+    return MUST(to_base(N)).to_deprecated_string();
 }
 
 u64 UnsignedBigInteger::to_u64() const

Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h

@@ -12,6 +12,7 @@
 #include <AK/Concepts.h>
 #include <AK/DeprecatedString.h>
 #include <AK/Span.h>
+#include <AK/String.h>
 #include <AK/Types.h>
 #include <AK/Vector.h>
 
@@ -63,6 +64,7 @@ public:
     size_t export_data(Bytes, bool remove_leading_zeros = false) const;
 
     [[nodiscard]] static UnsignedBigInteger from_base(u16 N, StringView str);
+    [[nodiscard]] ErrorOr<String> to_base(u16 N) const;
     [[nodiscard]] DeprecatedString to_base_deprecated(u16 N) const;
 
     [[nodiscard]] u64 to_u64() const;