Modify BigInt constructors

Add static methods for very common (eg zero, one) or very uncommon (eg
ECSDA truncated integers) construction methods, instead of using C++
constructors for all of these.

Also adds from_s32 which allows creating a negative BigInt easily,
instead of -BigInt(-x) -> BigInt::from_s32(x)

1 files changed, 3 insertions, 3 deletions

diff --git a/src/lib/pubkey/ecdsa/ecdsa.cpp b/src/lib/pubkey/ecdsa/ecdsa.cpp
index 490364f8b..2324edf85 100644
--- a/src/lib/pubkey/ecdsa/ecdsa.cpp
+++ b/src/lib/pubkey/ecdsa/ecdsa.cpp
@@ -52,7 +52,7 @@ PointGFp recover_ecdsa_public_key(const EC_Group& group,
 
    try
       {
-      const BigInt e(msg.data(), msg.size(), group.get_order_bits());
+      const BigInt e = BigInt::from_bytes_with_max_bits(msg.data(), msg.size(), group.get_order_bits());
       const BigInt r_inv = group.inverse_mod_order(r);
 
       BigInt x = r + add_order*group_order;
@@ -179,7 +179,7 @@ secure_vector<uint8_t>
 ECDSA_Signature_Operation::raw_sign(const uint8_t msg[], size_t msg_len,
                                     RandomNumberGenerator& rng)
    {
-   BigInt m(msg, msg_len, m_group.get_order_bits());
+   BigInt m = BigInt::from_bytes_with_max_bits(msg, msg_len, m_group.get_order_bits());
 
 #if defined(BOTAN_HAS_RFC6979_GENERATOR)
    const BigInt k = m_rfc6979->nonce_for(m);
@@ -241,7 +241,7 @@ bool ECDSA_Verification_Operation::verify(const uint8_t msg[], size_t msg_len,
    if(sig_len != m_group.get_order_bytes() * 2)
       return false;
 
-   const BigInt e(msg, msg_len, m_group.get_order_bits());
+   const BigInt e = BigInt::from_bytes_with_max_bits(msg, msg_len, m_group.get_order_bits());
 
    const BigInt r(sig, sig_len / 2);
    const BigInt s(sig + sig_len / 2, sig_len / 2);