From c9826d2336d2493dd922d1d7ba5fa9e7128ffc66 Mon Sep 17 00:00:00 2001
From: Adam Heinermann <aheinerm@gmail.com>
Date: Fri, 15 Nov 2024 08:35:42 -0800
Subject: [PATCH] feat(big): add SBigIsOne

---
 storm/Big.cpp     |  4 ++++
 storm/Big.hpp     |  2 ++
 storm/big/Ops.cpp |  5 +++++
 storm/big/Ops.hpp |  2 ++
 test/Big.cpp      | 16 ++++++++++++++++
 5 files changed, 29 insertions(+)

diff --git a/storm/Big.cpp b/storm/Big.cpp
index c64beaf..141f3fc 100644
--- a/storm/Big.cpp
+++ b/storm/Big.cpp
@@ -77,6 +77,10 @@ int32_t SBigIsOdd(BigData* a) {
     return IsOdd(a->Primary());
 }
 
+int32_t SBigIsOne(BigData* a) {
+    return IsOne(a->Primary());
+}
+
 void SBigMod(BigData* a, BigData* b, BigData* c) {
     uint32_t allocCount = 0;
     auto& scratch = a->Stack().Alloc(&allocCount);
diff --git a/storm/Big.hpp b/storm/Big.hpp
index 5d19f38..f7968e6 100644
--- a/storm/Big.hpp
+++ b/storm/Big.hpp
@@ -32,6 +32,8 @@ int32_t SBigIsEven(BigData* a);
 
 int32_t SBigIsOdd(BigData* a);
 
+int32_t SBigIsOne(BigData* a);
+
 void SBigMod(BigData* a, BigData* b, BigData* c);
 
 void SBigMul(BigData* a, BigData* b, BigData* c);
diff --git a/storm/big/Ops.cpp b/storm/big/Ops.cpp
index 7cc3a4c..c96064c 100644
--- a/storm/big/Ops.cpp
+++ b/storm/big/Ops.cpp
@@ -220,6 +220,11 @@ int32_t IsOdd(const BigBuffer &num) {
     return num.Count() != 0 && (num[0] & 1) != 0;
 }
 
+int32_t IsOne(const BigBuffer &num) {
+    num.Trim();
+    return num.Count() == 1 && num[0] == 1;
+}
+
 uint64_t MakeLarge(uint32_t low, uint32_t high) {
     return low + (static_cast<uint64_t>(high) << 32);
 }
diff --git a/storm/big/Ops.hpp b/storm/big/Ops.hpp
index 28d3b38..84e54cb 100644
--- a/storm/big/Ops.hpp
+++ b/storm/big/Ops.hpp
@@ -37,6 +37,8 @@ int32_t IsEven(const BigBuffer &num);
 
 int32_t IsOdd(const BigBuffer &num);
 
+int32_t IsOne(const BigBuffer &num);
+
 uint64_t MakeLarge(uint32_t low, uint32_t high);
 
 void Mul(BigBuffer& a, const BigBuffer& b, uint64_t c);
diff --git a/test/Big.cpp b/test/Big.cpp
index a29cbe8..36ccac9 100644
--- a/test/Big.cpp
+++ b/test/Big.cpp
@@ -470,6 +470,22 @@ TEST_CASE("SBigIsOdd", "[big]") {
     }
 }
 
+TEST_CASE("SBigIsOne", "[big]") {
+    BigDataTest a;
+
+    SECTION("1 is 1") {
+        SBigFromUnsigned(a, 1);
+        CHECK(SBigIsOne(a));
+    }
+
+    SECTION("numbers are not 1") {
+        auto v = GENERATE(0ULL, 2ULL, 10ULL, 11ULL, 10000000000001ULL, 0xFF00000000000001ULL);
+
+        SBigFromStr(a, std::to_string(v).c_str());
+        CHECK_FALSE(SBigIsOne(a));
+    }
+}
+
 TEST_CASE("SBigMod", "[big]") {
     SECTION("mods 7 by 4") {
         BigData* a;