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randombit / botan / 16511306696

25 Jul 2025 01:07AM UTC coverage: 90.698% (+0.005%) from 90.693%
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Merge pull request #5017 from randombit/jack/mp-cleanup

Clean up low level mp interfaces

99956 of 110208 relevant lines covered (90.7%)

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90.23
/src/lib/math/bigint/big_ops2.cpp
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/*
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* (C) 1999-2007,2018 Jack Lloyd
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*     2016 Matthias Gierlings
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*
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* Botan is released under the Simplified BSD License (see license.txt)
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*/
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#include <botan/bigint.h>
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#include <botan/internal/bit_ops.h>
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#include <botan/internal/mp_core.h>
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#include <algorithm>
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namespace Botan {
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BigInt& BigInt::add(const word y[], size_t y_words, Sign y_sign) {
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   const size_t x_sw = sig_words();
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   grow_to(std::max(x_sw, y_words) + 1);
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   if(sign() == y_sign) {
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      word carry = bigint_add2(mutable_data(), size() - 1, y, y_words);
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      mutable_data()[size() - 1] += carry;
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   } else {
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      const int32_t relative_size = bigint_cmp(_data(), x_sw, y, y_words);
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      if(relative_size >= 0) {
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         // *this >= y
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         bigint_sub2(mutable_data(), x_sw, y, y_words);
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      } else {
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         // *this < y: compute *this = y - *this
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         bigint_sub2_rev(mutable_data(), y, y_words);
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      }
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      if(relative_size < 0) {
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         set_sign(y_sign);
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      } else if(relative_size == 0) {
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         set_sign(Positive);
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      }
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   }
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   return (*this);
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}
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BigInt& BigInt::mod_add(const BigInt& s, const BigInt& mod, secure_vector<word>& ws) {
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   if(this->is_negative() || s.is_negative() || mod.is_negative()) {
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      throw Invalid_Argument("BigInt::mod_add expects all arguments are positive");
×
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   }
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   BOTAN_DEBUG_ASSERT(*this < mod);
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   BOTAN_DEBUG_ASSERT(s < mod);
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   /*
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   t + s or t + s - p == t - (p - s)
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   So first compute ws = p - s
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   Then compute t + s and t - ws
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   If t - ws does not borrow, then that is the correct valued
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   */
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   const size_t mod_sw = mod.sig_words();
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   BOTAN_ARG_CHECK(mod_sw > 0, "BigInt::mod_add modulus must be positive");
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   this->grow_to(mod_sw);
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   s.grow_to(mod_sw);
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   // First mod_sw for p - s, 2*mod_sw for bigint_addsub workspace
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   if(ws.size() < 3 * mod_sw) {
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      ws.resize(3 * mod_sw);
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   }
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   // NOLINTBEGIN(readability-container-data-pointer)
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   word borrow = bigint_sub3(&ws[0], mod._data(), mod_sw, s._data(), mod_sw);
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   BOTAN_DEBUG_ASSERT(borrow == 0);
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   BOTAN_UNUSED(borrow);
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   // Compute t - ws
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   borrow = bigint_sub3(&ws[mod_sw], this->_data(), mod_sw, &ws[0], mod_sw);
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   // Compute t + s
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   bigint_add3(&ws[mod_sw * 2], this->_data(), mod_sw, s._data(), mod_sw);
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   CT::conditional_copy_mem(borrow, &ws[0], &ws[mod_sw * 2], &ws[mod_sw], mod_sw);
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   set_words(&ws[0], mod_sw);
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   // NOLINTEND(readability-container-data-pointer)
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   return (*this);
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}
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BigInt& BigInt::mod_sub(const BigInt& s, const BigInt& mod, secure_vector<word>& ws) {
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   if(this->is_negative() || s.is_negative() || mod.is_negative()) {
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      throw Invalid_Argument("BigInt::mod_sub expects all arguments are positive");
×
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   }
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   // We are assuming in this function that *this and s are no more than mod_sw words long
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   BOTAN_DEBUG_ASSERT(*this < mod);
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   BOTAN_DEBUG_ASSERT(s < mod);
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   const size_t mod_sw = mod.sig_words();
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   this->grow_to(mod_sw);
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   s.grow_to(mod_sw);
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   if(ws.size() < mod_sw) {
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      ws.resize(mod_sw);
×
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   }
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   const word borrow = bigint_sub3(ws.data(), mutable_data(), mod_sw, s._data(), mod_sw);
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   // Conditionally add back the modulus
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   bigint_cnd_add(borrow, ws.data(), mod._data(), mod_sw);
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   copy_mem(mutable_data(), ws.data(), mod_sw);
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   return (*this);
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}
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BigInt& BigInt::mod_mul(uint8_t y, const BigInt& mod, secure_vector<word>& ws) {
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   BOTAN_ARG_CHECK(this->is_negative() == false, "*this must be positive");
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   BOTAN_ARG_CHECK(y < 16, "y too large");
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   BOTAN_DEBUG_ASSERT(*this < mod);
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   *this *= static_cast<word>(y);
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   this->reduce_below(mod, ws);
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   return (*this);
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}
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BigInt& BigInt::rev_sub(const word y[], size_t y_sw, secure_vector<word>& ws) {
×
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   BOTAN_UNUSED(ws);
×
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   BigInt y_bn;
×
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   y_bn.m_data.set_words(y, y_sw);
×
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   *this = y_bn - *this;
×
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   return (*this);
×
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}
×
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/*
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* Multiplication Operator
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*/
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BigInt& BigInt::operator*=(const BigInt& y) {
527✔
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   secure_vector<word> ws;
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   return this->mul(y, ws);
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}
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BigInt& BigInt::mul(const BigInt& y, secure_vector<word>& ws) {
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   const size_t x_sw = sig_words();
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   const size_t y_sw = y.sig_words();
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   set_sign((sign() == y.sign()) ? Positive : Negative);
10,099✔
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   if(x_sw == 0 || y_sw == 0) {
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      clear();
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      set_sign(Positive);
33✔
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   } else if(x_sw == 1 && y_sw > 0) {
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      grow_to(y_sw + 1);
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      bigint_linmul3(mutable_data(), y._data(), y_sw, word_at(0));
658✔
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   } else {
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      const size_t new_size = x_sw + y_sw + 1;
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      if(ws.size() < new_size) {
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         ws.resize(new_size);
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      }
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      secure_vector<word> z_reg(new_size);
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      bigint_mul(z_reg.data(), z_reg.size(), _data(), size(), x_sw, y._data(), y.size(), y_sw, ws.data(), ws.size());
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      this->swap_reg(z_reg);
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   }
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   return (*this);
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}
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BigInt& BigInt::square(secure_vector<word>& ws) {
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   const size_t sw = sig_words();
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   secure_vector<word> z(2 * sw);
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   ws.resize(z.size());
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   bigint_sqr(z.data(), z.size(), _data(), size(), sw, ws.data(), ws.size());
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   swap_reg(z);
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   set_sign(BigInt::Positive);
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   return (*this);
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}
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BigInt& BigInt::operator*=(word y) {
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   if(y == 0) {
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      clear();
×
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      set_sign(Positive);
×
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   }
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   const word carry = bigint_linmul2(mutable_data(), size(), y);
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   set_word_at(size(), carry);
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   return (*this);
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}
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/*
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* Division Operator
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*/
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BigInt& BigInt::operator/=(const BigInt& y) {
929✔
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   if(y.sig_words() == 1 && is_power_of_2(y.word_at(0))) {
1,620✔
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      (*this) >>= (y.bits() - 1);
85✔
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   } else {
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      (*this) = (*this) / y;
844✔
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   }
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   return (*this);
929✔
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}
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/*
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* Modulo Operator
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*/
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BigInt& BigInt::operator%=(const BigInt& mod) {
325,051✔
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   return (*this = (*this) % mod);
325,051✔
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}
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/*
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* Modulo Operator
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*/
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word BigInt::operator%=(word mod) {
33✔
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   if(mod == 0) {
33✔
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      throw Invalid_Argument("BigInt::operator%= divide by zero");
×
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   }
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   word remainder = 0;
33✔
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   if(is_power_of_2(mod)) {
33✔
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      remainder = (word_at(0) & (mod - 1));
10✔
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   } else {
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      const size_t sw = sig_words();
28✔
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      for(size_t i = sw; i > 0; --i) {
79✔
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         remainder = bigint_modop_vartime(remainder, word_at(i - 1), mod);
102✔
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      }
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   }
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   if(remainder != 0 && sign() == BigInt::Negative) {
33✔
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      remainder = mod - remainder;
12✔
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   }
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   m_data.set_to_zero();
33✔
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   m_data.set_word_at(0, remainder);
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   set_sign(BigInt::Positive);
33✔
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   return remainder;
33✔
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}
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/*
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* Left Shift Operator
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*/
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BigInt& BigInt::operator<<=(size_t shift) {
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   const size_t sw = sig_words();
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   const size_t new_size = sw + (shift + WordInfo<word>::bits - 1) / WordInfo<word>::bits;
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   m_data.grow_to(new_size);
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   bigint_shl1(m_data.mutable_data(), new_size, sw, shift);
12,142,064✔
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   return (*this);
12,142,064✔
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}
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/*
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* Right Shift Operator
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*/
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BigInt& BigInt::operator>>=(size_t shift) {
7,554,295✔
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   bigint_shr1(m_data.mutable_data(), m_data.size(), shift);
7,554,295✔
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269
   if(is_negative() && is_zero()) {
7,645,780✔
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      set_sign(Positive);
8✔
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   }
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   return (*this);
7,554,295✔
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}
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}  // namespace Botan
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