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feat(big): add ExtractLowPartLargeSum

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fallenoak 2023-02-03 00:43:20 -06:00
parent 4d3651134c
commit f01c906aa1
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3 changed files with 57 additions and 0 deletions
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8
storm/big/Ops.cpp
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@ -58,6 +58,14 @@ uint32_t ExtractLowPart(uint64_t& value) {
return low; return low;
} }
uint32_t ExtractLowPartLargeSum(uint64_t& value, uint64_t add) {
auto carry = (value += add) < add;
auto low = ExtractLowPart(value);
value += static_cast<uint64_t>(carry) << 32;
return low;
}
uint32_t ExtractLowPartSx(uint64_t& value) { uint32_t ExtractLowPartSx(uint64_t& value) {
auto low = static_cast<uint32_t>(value); auto low = static_cast<uint32_t>(value);
value >>= 32; value >>= 32;

2
storm/big/Ops.hpp
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@ -15,6 +15,8 @@ void Div(BigBuffer& a, uint32_t* b, const BigBuffer& c, uint64_t d);
uint32_t ExtractLowPart(uint64_t& value); uint32_t ExtractLowPart(uint64_t& value);
uint32_t ExtractLowPartLargeSum(uint64_t& value, uint64_t add);
uint32_t ExtractLowPartSx(uint64_t& value); uint32_t ExtractLowPartSx(uint64_t& value);
void FromBinary(BigBuffer& buffer, const void* value, uint32_t bytes); void FromBinary(BigBuffer& buffer, const void* value, uint32_t bytes);

47
test/Big.cpp
View file

@ -288,6 +288,53 @@ TEST_CASE("ExtractLowPart", "[big]") {
} }
} }
TEST_CASE("ExtractLowPartLargeSum", "[big]") {
SECTION("extracts low part after adding 2 and 4") {
uint64_t value = 2;
uint64_t add = 4;
auto low = ExtractLowPartLargeSum(value, add);
CHECK(low == 6);
CHECK(value == 0);
}
SECTION("extracts low part after adding 0x1111111122222222 and 0x3333333344444444") {
uint64_t value = 0x1111111122222222;
uint64_t add = 0x3333333344444444;
auto low = ExtractLowPartLargeSum(value, add);
CHECK(low == 0x66666666);
CHECK(value == 0x44444444);
}
SECTION("extracts low part after adding 0xCCCCCCCCCCCCCCCC and 0x5555555555555555") {
uint64_t value = 0xCCCCCCCCCCCCCCCC;
uint64_t add = 0x5555555555555555;
auto low = ExtractLowPartLargeSum(value, add);
CHECK(low == 0x22222221);
CHECK(value == 0x122222222);
}
SECTION("extracts low part after adding 0xFFFFFFFFFFFFFFFF and 0") {
uint64_t value = 0xFFFFFFFFFFFFFFFF;
uint64_t add = 0;
auto low = ExtractLowPartLargeSum(value, add);
CHECK(low == 0xFFFFFFFF);
CHECK(value == 0xFFFFFFFF);
}
SECTION("extracts low part after adding 0xFFFFFFFFFFFFFFFF and 0xFFFFFFFFFFFFFFFF") {
uint64_t value = 0xFFFFFFFFFFFFFFFF;
uint64_t add = 0xFFFFFFFFFFFFFFFF;
auto low = ExtractLowPartLargeSum(value, add);
CHECK(low == 0xFFFFFFFE);
CHECK(value == 0x1FFFFFFFF);
}
}
TEST_CASE("ExtractLowPartSx", "[big]") { TEST_CASE("ExtractLowPartSx", "[big]") {
SECTION("extracts low part of 0") { SECTION("extracts low part of 0") {
uint64_t value = 0; uint64_t value = 0;