Clean out the BigInt interface

doc/api_ref/bigint.rst

@@ -13,16 +13,17 @@ declarations in ``botan/bigint.h`` and ``botan/numthry.h``.
 
       Create a BigInt with value zero
 
-   .. cpp:function:: BigInt(uint64_t n)
+   .. cpp:function:: BigInt::from_u64(uint64_t n)
 
       Create a BigInt with value *n*
 
-   .. cpp:function:: BigInt(const std::string& str)
+   .. cpp:function:: BigInt(std::string_view str)
 
       Create a BigInt from a string. By default decimal is expected. With an 0x
-      prefix instead it is treated as hexadecimal.
+      prefix instead it is treated as hexadecimal. A ``-`` prefix to indicate
+      negative numbers is also accepted.
 
-   .. cpp:function:: BigInt(const uint8_t buf[], size_t length)
+   .. cpp:function:: BigInt(std::span<const uint8_t> buf)
 
       Create a BigInt from a binary array (big-endian encoding).
 
@@ -199,18 +200,15 @@ declarations in ``botan/bigint.h`` and ``botan/numthry.h``.
 
       Return absolute value of ``*this``
 
-   .. cpp:function:: void binary_encode(uint8_t buf[]) const
+   .. cpp:function:: void serialize_to(std::span<uint8_t> buf)
 
       Encode this BigInt as a big-endian integer. The sign is ignored.
 
-   .. cpp:function:: void binary_encode(uint8_t buf[], size_t len) const
+      There must be sufficient space to encode the entire integer in ``buf``.
+      If ``buf`` is larger than required, sufficient zero bytes will be
+      prefixed.
 
-      Encode this BigInt as a big-endian integer. The sign is ignored.
-      If ``len`` is less than ``bytes()`` then only the low ``len``
-      bytes are output. If ``len`` is greater than ``bytes()`` then
-      the output is padded with leading zeros.
-
-   .. cpp:function:: void binary_decode(uint8_t buf[])
+   .. cpp:function:: void assign_from_bytes(std::span<const uint8_t> buf)
 
       Decode this BigInt as a big-endian integer.
 

src/lib/asn1/ber_dec.cpp

@@ -387,7 +387,7 @@ BER_Decoder& BER_Decoder::decode_null() {
 BER_Decoder& BER_Decoder::decode_octet_string_bigint(BigInt& out) {
    secure_vector<uint8_t> out_vec;
    decode(out_vec, ASN1_Type::OctetString);
-   out = BigInt::decode(out_vec.data(), out_vec.size());
+   out = BigInt::from_bytes(out_vec);
    return (*this);
 }
 
@@ -474,10 +474,10 @@ BER_Decoder& BER_Decoder::decode(BigInt& out, ASN1_Type type_tag, ASN1_Class cla
          for(size_t i = 0; i != obj.length(); ++i) {
             vec[i] = ~vec[i];
          }
-         out = BigInt(vec.data(), vec.size());
+         out.assign_from_bytes(vec);
          out.flip_sign();
       } else {
-         out = BigInt(obj.bits(), obj.length());
+         out.assign_from_bytes(obj.data());
       }
    }
 

src/lib/asn1/der_enc.cpp

@@ -296,8 +296,8 @@ DER_Encoder& DER_Encoder::encode(const BigInt& n, ASN1_Type type_tag, ASN1_Class
    }
 
    const size_t extra_zero = (n.bits() % 8 == 0) ? 1 : 0;
-   secure_vector<uint8_t> contents(extra_zero + n.bytes());
-   n.binary_encode(&contents[extra_zero]);
+
+   auto contents = n.serialize(n.bytes() + extra_zero);
    if(n < 0) {
       for(unsigned char& content : contents) {
          content = ~content;

src/lib/codec/base58/base58.cpp

@@ -158,9 +158,7 @@ std::vector<uint8_t> base58_decode(const char input[], size_t input_length) {
       v += idx;
    }
 
-   std::vector<uint8_t> output(v.bytes() + leading_zeros);
-   v.binary_encode(output.data() + leading_zeros);
-   return output;
+   return v.serialize(v.bytes() + leading_zeros);
 }
 
 std::vector<uint8_t> base58_check_decode(const char input[], size_t input_length) {

src/lib/ffi/ffi_mp.cpp

@@ -77,7 +77,7 @@ int botan_mp_flip_sign(botan_mp_t mp) {
 }
 
 int botan_mp_from_bin(botan_mp_t mp, const uint8_t bin[], size_t bin_len) {
-   return BOTAN_FFI_VISIT(mp, [=](auto& bn) { bn.binary_decode(bin, bin_len); });
+   return BOTAN_FFI_VISIT(mp, [=](auto& bn) { bn.assign_from_bytes({bin, bin_len}); });
 }
 
 int botan_mp_to_hex(const botan_mp_t mp, char* out) {
@@ -99,7 +99,7 @@ int botan_mp_to_str(const botan_mp_t mp, uint8_t digit_base, char* out, size_t*
 }
 
 int botan_mp_to_bin(const botan_mp_t mp, uint8_t vec[]) {
-   return BOTAN_FFI_VISIT(mp, [=](const auto& bn) { bn.binary_encode(vec); });
+   return BOTAN_FFI_VISIT(mp, [=](const auto& bn) { bn.serialize_to(std::span{vec, bn.bytes()}); });
 }
 
 int botan_mp_to_uint32(const botan_mp_t mp, uint32_t* val) {

src/lib/ffi/ffi_srp6.cpp

@@ -76,9 +76,9 @@ int botan_srp6_server_session_step1(botan_srp6_server_session_t srp6,
       }
       try {
          Botan::RandomNumberGenerator& rng = safe_get(rng_obj);
-         auto v_bn = Botan::BigInt::decode(verifier, verifier_len);
+         auto v_bn = Botan::BigInt::from_bytes(std::span{verifier, verifier_len});
          auto b_pub_bn = s.step1(v_bn, group_id, hash_id, rng);
-         return write_vec_output(b_pub, b_pub_len, Botan::BigInt::encode(b_pub_bn));
+         return write_vec_output(b_pub, b_pub_len, b_pub_bn.serialize());
       } catch(Botan::Decoding_Error&) {
          return BOTAN_FFI_ERROR_BAD_PARAMETER;
       } catch(Botan::Lookup_Error&) {
@@ -99,7 +99,7 @@ int botan_srp6_server_session_step2(
          return BOTAN_FFI_ERROR_NULL_POINTER;
       }
       try {
-         Botan::BigInt a_bn = Botan::BigInt::decode(a, a_len);
+         Botan::BigInt a_bn = Botan::BigInt::from_bytes({a, a_len});
          auto key_sk = s.step2(a_bn);
          return write_vec_output(key, key_len, key_sk.bits_of());
       } catch(Botan::Decoding_Error&) {
@@ -128,7 +128,7 @@ int botan_srp6_generate_verifier(const char* username,
       try {
          std::vector<uint8_t> salt_vec(salt, salt + salt_len);
          auto verifier_bn = Botan::srp6_generate_verifier(username, password, salt_vec, group_id, hash_id);
-         return write_vec_output(verifier, verifier_len, Botan::BigInt::encode(verifier_bn));
+         return write_vec_output(verifier, verifier_len, verifier_bn.serialize());
       } catch(Botan::Lookup_Error&) {
          return BOTAN_FFI_ERROR_BAD_PARAMETER;
       }
@@ -161,9 +161,9 @@ int botan_srp6_client_agree(const char* identity,
       try {
          std::vector<uint8_t> saltv(salt, salt + salt_len);
          Botan::RandomNumberGenerator& rng = safe_get(rng_obj);
-         auto b_bn = Botan::BigInt::decode(b, b_len);
+         auto b_bn = Botan::BigInt::from_bytes({b, b_len});
          auto [A_bn, K_sk] = Botan::srp6_client_agree(identity, password, group_id, hash_id, saltv, b_bn, rng);
-         auto ret_a = write_vec_output(A, A_len, Botan::BigInt::encode(A_bn));
+         auto ret_a = write_vec_output(A, A_len, A_bn.serialize());
          auto ret_k = write_vec_output(K, K_len, K_sk.bits_of());
          if(ret_a != BOTAN_FFI_SUCCESS) {
             return ret_a;

src/lib/math/bigint/big_code.cpp

@@ -87,7 +87,7 @@ std::string BigInt::to_hex_string() const {
    std::vector<uint8_t> bits(std::max<size_t>(1, this_bytes));
 
    if(this_bytes > 0) {
-      this->binary_encode(bits.data());
+      this->serialize_to(bits);
    }
 
    std::string hrep;
@@ -99,36 +99,6 @@ std::string BigInt::to_hex_string() const {
    return hrep;
 }
 
-/*
-* Encode a BigInt, with leading 0s if needed
-*/
-secure_vector<uint8_t> BigInt::encode_1363(const BigInt& n, size_t bytes) {
-   if(n.bytes() > bytes) {
-      throw Encoding_Error("encode_1363: n is too large to encode properly");
-   }
-
-   secure_vector<uint8_t> output(bytes);
-   n.binary_encode(output.data(), output.size());
-   return output;
-}
-
-void BigInt::encode_1363(std::span<uint8_t> output, const BigInt& n) {
-   if(n.bytes() > output.size()) {
-      throw Encoding_Error("encode_1363: n is too large to encode properly");
-   }
-
-   n.binary_encode(output.data(), output.size());
-}
-
-//static
-void BigInt::encode_1363(uint8_t output[], size_t bytes, const BigInt& n) {
-   if(n.bytes() > bytes) {
-      throw Encoding_Error("encode_1363: n is too large to encode properly");
-   }
-
-   n.binary_encode(output, bytes);
-}
-
 /*
 * Encode two BigInt, with leading 0s if needed, and concatenate
 */
@@ -140,19 +110,26 @@ secure_vector<uint8_t> BigInt::encode_fixed_length_int_pair(const BigInt& n1, co
       throw Encoding_Error("encode_fixed_length_int_pair: values too large to encode properly");
    }
    secure_vector<uint8_t> output(2 * bytes);
-   n1.binary_encode(output.data(), bytes);
-   n2.binary_encode(output.data() + bytes, bytes);
+   n1.serialize_to(std::span{output}.subspan(0, bytes));
+   n2.serialize_to(std::span{output}.subspan(bytes, bytes));
    return output;
 }
 
+BigInt BigInt::decode(std::span<const uint8_t> buf, Base base) {
+   if(base == Binary) {
+      return BigInt::from_bytes(buf);
+   }
+   return BigInt::decode(buf.data(), buf.size(), base);
+}
+
 /*
 * Decode a BigInt
 */
 BigInt BigInt::decode(const uint8_t buf[], size_t length, Base base) {
-   BigInt r;
    if(base == Binary) {
-      r.binary_decode(buf, length);
+      return BigInt::from_bytes(std::span{buf, length});
    } else if(base == Hexadecimal) {
+      BigInt r;
       secure_vector<uint8_t> binary;
 
       if(length % 2) {
@@ -166,8 +143,10 @@ BigInt BigInt::decode(const uint8_t buf[], size_t length, Base base) {
          binary = hex_decode_locked(cast_uint8_ptr_to_char(buf), length, false);
       }
 
-      r.binary_decode(binary.data(), binary.size());
+      r.assign_from_bytes(binary);
+      return r;
    } else if(base == Decimal) {
+      BigInt r;
       // This could be made faster using the same trick as to_dec_string
       for(size_t i = 0; i != length; ++i) {
          const char c = buf[i];
@@ -182,10 +161,10 @@ BigInt BigInt::decode(const uint8_t buf[], size_t length, Base base) {
          r *= 10;
          r += x;
       }
+      return r;
    } else {
       throw Invalid_Argument("Unknown BigInt decoding method");
    }
-   return r;
 }
 
 }  // namespace Botan

src/lib/math/bigint/big_io.cpp

@@ -22,16 +22,12 @@ std::ostream& operator<<(std::ostream& stream, const BigInt& n) {
 
    const size_t base = (stream_flags & std::ios::hex) ? 16 : 10;
 
-   std::string enc;
-
    if(base == 10) {
-      enc = n.to_dec_string();
+      stream << n.to_dec_string();
    } else {
-      enc = n.to_hex_string();
+      stream << n.to_hex_string();
    }
 
-   stream.write(enc.data(), enc.size());
-
    if(!stream.good()) {
       throw Stream_IO_Error("BigInt output operator has failed");
    }

src/lib/math/bigint/big_ops2.cpp

@@ -21,7 +21,7 @@ BigInt& BigInt::add(const word y[], size_t y_words, Sign y_sign) {
    if(sign() == y_sign) {
       bigint_add2(mutable_data(), size() - 1, y, y_words);
    } else {
-      const int32_t relative_size = bigint_cmp(data(), x_sw, y, y_words);
+      const int32_t relative_size = bigint_cmp(_data(), x_sw, y, y_words);
 
       if(relative_size >= 0) {
          // *this >= y
@@ -71,15 +71,15 @@ BigInt& BigInt::mod_add(const BigInt& s, const BigInt& mod, secure_vector<word>&
       ws.resize(3 * mod_sw);
    }
 
-   word borrow = bigint_sub3(&ws[0], mod.data(), mod_sw, s.data(), mod_sw);
+   word borrow = bigint_sub3(&ws[0], mod._data(), mod_sw, s._data(), mod_sw);
    BOTAN_DEBUG_ASSERT(borrow == 0);
    BOTAN_UNUSED(borrow);
 
    // Compute t - ws
-   borrow = bigint_sub3(&ws[mod_sw], this->data(), mod_sw, &ws[0], mod_sw);
+   borrow = bigint_sub3(&ws[mod_sw], this->_data(), mod_sw, &ws[0], mod_sw);
 
    // Compute t + s
-   bigint_add3_nc(&ws[mod_sw * 2], this->data(), mod_sw, s.data(), mod_sw);
+   bigint_add3_nc(&ws[mod_sw * 2], this->_data(), mod_sw, s._data(), mod_sw);
 
    CT::conditional_copy_mem(borrow, &ws[0], &ws[mod_sw * 2], &ws[mod_sw], mod_sw);
    set_words(&ws[0], mod_sw);
@@ -106,11 +106,11 @@ BigInt& BigInt::mod_sub(const BigInt& s, const BigInt& mod, secure_vector<word>&
    }
 
    if(mod_sw == 4) {
-      bigint_mod_sub_n<4>(mutable_data(), s.data(), mod.data(), ws.data());
+      bigint_mod_sub_n<4>(mutable_data(), s._data(), mod._data(), ws.data());
    } else if(mod_sw == 6) {
-      bigint_mod_sub_n<6>(mutable_data(), s.data(), mod.data(), ws.data());
+      bigint_mod_sub_n<6>(mutable_data(), s._data(), mod._data(), ws.data());
    } else {
-      bigint_mod_sub(mutable_data(), s.data(), mod.data(), mod_sw, ws.data());
+      bigint_mod_sub(mutable_data(), s._data(), mod._data(), mod_sw, ws.data());
    }
 
    return (*this);
@@ -137,7 +137,7 @@ BigInt& BigInt::rev_sub(const word y[], size_t y_sw, secure_vector<word>& ws) {
    ws.resize(std::max(x_sw, y_sw));
    clear_mem(ws.data(), ws.size());
 
-   const int32_t relative_size = bigint_sub_abs(ws.data(), data(), x_sw, y, y_sw);
+   const int32_t relative_size = bigint_sub_abs(ws.data(), _data(), x_sw, y, y_sw);
 
    this->cond_flip_sign(relative_size > 0);
    this->swap_reg(ws);
@@ -163,7 +163,7 @@ BigInt& BigInt::mul(const BigInt& y, secure_vector<word>& ws) {
       set_sign(Positive);
    } else if(x_sw == 1 && y_sw) {
       grow_to(y_sw + 1);
-      bigint_linmul3(mutable_data(), y.data(), y_sw, word_at(0));
+      bigint_linmul3(mutable_data(), y._data(), y_sw, word_at(0));
    } else if(y_sw == 1 && x_sw) {
       word carry = bigint_linmul2(mutable_data(), x_sw, y.word_at(0));
       set_word_at(x_sw, carry);
@@ -172,7 +172,7 @@ BigInt& BigInt::mul(const BigInt& y, secure_vector<word>& ws) {
       ws.resize(new_size);
       secure_vector<word> z_reg(new_size);
 
-      bigint_mul(z_reg.data(), z_reg.size(), data(), size(), x_sw, y.data(), y.size(), y_sw, ws.data(), ws.size());
+      bigint_mul(z_reg.data(), z_reg.size(), _data(), size(), x_sw, y._data(), y.size(), y_sw, ws.data(), ws.size());
 
       this->swap_reg(z_reg);
    }
@@ -186,7 +186,7 @@ BigInt& BigInt::square(secure_vector<word>& ws) {
    secure_vector<word> z(2 * sw);
    ws.resize(z.size());
 
-   bigint_sqr(z.data(), z.size(), data(), size(), sw, ws.data(), ws.size());
+   bigint_sqr(z.data(), z.size(), _data(), size(), sw, ws.data(), ws.size());
 
    swap_reg(z);
    set_sign(BigInt::Positive);