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LibCrypto: Optimize UnsignedBigInteger import_data/export_data

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No need to do complicated math to import or export numbers,
just convert the byte stream to words and vice versa.
This commit is contained in:
Tom 2020-07-22 16:16:05 -06:00 committed by Andreas Kling
parent 08221139a5
commit 3fdacef07f
Notes: sideshowbarker 2024-07-19 04:38:05 +09:00 
Author: https://github.com/tomuta
Commit: https://github.com/SerenityOS/serenity/commit/3fdacef07f5
Pull-request: https://github.com/SerenityOS/serenity/pull/2857
2 changed files with 47 additions and 28 deletions
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66
Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp
View file

@ -29,6 +29,25 @@
namespace Crypto {
UnsignedBigInteger::UnsignedBigInteger(const u8* ptr, size_t length)
{
m_words.resize_and_keep_capacity((length + sizeof(u32) - 1) / sizeof(u32));
size_t in = length, out = 0;
while (in >= sizeof(u32)) {
in -= sizeof(u32);
u32 word = ((u32)ptr[in] << 24) | ((u32)ptr[in + 1] << 16) | ((u32)ptr[in + 2] << 8) | (u32)ptr[in + 3];
m_words[out++] = word;
}
if (in > 0) {
u32 word = 0;
for (size_t i = 0; i < in; i++) {
word <<= 8;
word |= (u32)ptr[i];
}
m_words[out++] = word;
}
}
UnsignedBigInteger UnsignedBigInteger::create_invalid()
{
UnsignedBigInteger invalid(0);
@ -36,35 +55,30 @@ UnsignedBigInteger UnsignedBigInteger::create_invalid()
return invalid;
}
// FIXME: in great need of optimisation
UnsignedBigInteger UnsignedBigInteger::import_data(const u8* ptr, size_t length)
{
UnsignedBigInteger integer { 0 };
for (size_t i = 0; i < length; ++i) {
auto part = UnsignedBigInteger { ptr[length - i - 1] }.shift_left(8 * i);
integer = integer.plus(part);
}
return integer;
}
size_t UnsignedBigInteger::export_data(AK::ByteBuffer& data) const
{
UnsignedBigInteger copy { *this };
UnsignedBigInteger quotient;
UnsignedBigInteger remainder;
size_t size = trimmed_length() * sizeof(u32);
size_t i = 0;
for (; i < size; ++i) {
if (copy.trimmed_length() == 0)
break;
data[size - i - 1] = copy.m_words[0] & 0xff;
divide_u16_without_allocation(copy, 256, quotient, remainder);
copy.set_to(quotient);
size_t word_count = trimmed_length();
size_t out = 0;
if (word_count > 0) {
ssize_t leading_zeros = -1;
u32 word = m_words[word_count - 1];
for (size_t i = 0; i < sizeof(u32); i++) {
u8 byte = (u8)(word >> ((sizeof(u32) - i - 1) * 8));
data[out++] = byte;
if (leading_zeros < 0 && byte != 0)
leading_zeros = (int)i;
}
for (size_t i = word_count - 1; i > 0; i--) {
word = m_words[i - 1];
data[out++] = (u8)(word >> 24);
data[out++] = (u8)(word >> 16);
data[out++] = (u8)(word >> 8);
data[out++] = (u8)word;
}
if (leading_zeros > 0)
out -= leading_zeros;
}
return i;
return out;
}
UnsignedBigInteger UnsignedBigInteger::from_base10(const String& str)

9
Libraries/LibCrypto/BigInt/UnsignedBigInteger.h
View file

@ -46,12 +46,17 @@ public:
{
}
explicit UnsignedBigInteger(const u8* ptr, size_t length);
UnsignedBigInteger() { }
static UnsignedBigInteger create_invalid();
static UnsignedBigInteger import_data(const AK::StringView& data) { return import_data((const u8*)data.characters_without_null_termination(), data.length()); }
static UnsignedBigInteger import_data(const u8* ptr, size_t length);
static UnsignedBigInteger import_data(const u8* ptr, size_t length)
{
return UnsignedBigInteger(ptr, length);
}
size_t export_data(AK::ByteBuffer& data) const;
size_t export_data(const u8* ptr, size_t length) const
@ -129,7 +134,7 @@ struct UnsignedDivisionResult {
}
inline const LogStream&
operator<<(const LogStream& stream, const Crypto::UnsignedBigInteger value)
operator<<(const LogStream& stream, const Crypto::UnsignedBigInteger& value)
{
if (value.is_invalid()) {
stream << "Invalid BigInt";