From 328bbf61d8552f32882f43042e1c70e02cacbfe4 Mon Sep 17 00:00:00 2001
From: Adam Heinermann <aheinerm@gmail.com>
Date: Fri, 15 Nov 2024 07:52:35 -0800
Subject: [PATCH] feat(big): add SBigDiv

---
 storm/Big.cpp     |  9 ++++++
 storm/Big.hpp     |  2 ++
 storm/big/Ops.cpp |  2 +-
 test/Big.cpp      | 72 ++++++++++++++++++++++++++++++++++++++++++++---
 4 files changed, 80 insertions(+), 5 deletions(-)

diff --git a/storm/Big.cpp b/storm/Big.cpp
index 12b3234..c04e91a 100644
--- a/storm/Big.cpp
+++ b/storm/Big.cpp
@@ -44,6 +44,15 @@ void SBigDel(BigData* num) {
     delete num;
 }
 
+void SBigDiv(BigData* a, BigData* b, BigData* c) {
+    uint32_t allocCount = 0;
+    BigBuffer &buf = a->Stack().Alloc(&allocCount);
+
+    Div(a->Primary(), buf, b->Primary(), c->Primary(), a->Stack());
+
+    a->Stack().Free(allocCount);
+}
+
 void SBigFromBinary(BigData* num, const void* data, uint32_t bytes) {
     FromBinary(num->Primary(), data, bytes);
 }
diff --git a/storm/Big.hpp b/storm/Big.hpp
index eb9281c..bd7dac7 100644
--- a/storm/Big.hpp
+++ b/storm/Big.hpp
@@ -18,6 +18,8 @@ void SBigDec(BigData* a, BigData* b);
 
 void SBigDel(BigData* num);
 
+void SBigDiv(BigData* a, BigData* b, BigData* c);
+
 void SBigFromBinary(BigData* num, const void* data, uint32_t bytes);
 
 void SBigFromStr(BigData* num, const char* str);
diff --git a/storm/big/Ops.cpp b/storm/big/Ops.cpp
index 61a783c..4b2cdea 100644
--- a/storm/big/Ops.cpp
+++ b/storm/big/Ops.cpp
@@ -409,7 +409,7 @@ void Sub(BigBuffer& a, const BigBuffer& b, uint32_t c) {
 
     uint32_t i = 0;
     for (; b.IsUsed(i); i++) {
-        borrow += b[i] - static_cast<uint64_t>(c);;
+        borrow += b[i] - c;
         a[i] = ExtractLowPartSx(borrow);
     }
 
diff --git a/test/Big.cpp b/test/Big.cpp
index fdd0776..d6f93bf 100644
--- a/test/Big.cpp
+++ b/test/Big.cpp
@@ -1,5 +1,6 @@
 #include "storm/Big.hpp"
 #include "test/Test.hpp"
+#include <string>
 
 TEST_CASE("SBigAdd", "[big]") {
     SECTION("adds 0 and 1") {
@@ -214,8 +215,7 @@ TEST_CASE("SBigCompare", "[big]") {
 }
 
 TEST_CASE("SBigCopy", "[big]") {
-    BigDataTest a;
-    BigDataTest b;
+    BigDataTest a, b;
 
     SECTION("copies data") {
         uint8_t num[] = { 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9 };
@@ -232,8 +232,7 @@ TEST_CASE("SBigCopy", "[big]") {
 }
 
 TEST_CASE("SBigDec", "[big]") {
-    BigDataTest a;
-    BigDataTest b;
+    BigDataTest a, b;
 
     SECTION("decrements value by 1") {
         SBigFromUnsigned(b, 5);
@@ -254,6 +253,71 @@ TEST_CASE("SBigDec", "[big]") {
     }
 }
 
+TEST_CASE("SBigDiv", "[big]") {
+    BigDataTest a, b, c;
+
+    SECTION("divides 2 by 1") {
+        SBigFromUnsigned(b, 2);
+        SBigFromUnsigned(c, 1);
+
+        SBigDiv(a, b, c);
+
+        CHECK(a->Primary().Count() == 1);
+        CHECK(a->Primary()[0] == 2);
+    }
+
+    SECTION("divides 5 by 2") {
+        SBigFromUnsigned(b, 5);
+        SBigFromUnsigned(c, 2);
+
+        SBigDiv(a, b, c);
+
+        CHECK(a->Primary().Count() == 1);
+        CHECK(a->Primary()[0] == 2);
+    }
+
+    SECTION("divides 7 by 4") {
+        SBigFromUnsigned(b, 7);
+        SBigFromUnsigned(c, 4);
+
+        SBigDiv(a, b, c);
+
+        CHECK(a->Primary().Count() == 1);
+        CHECK(a->Primary()[0] == 1);
+    }
+
+    SECTION("divides 0x9999444488885555 by 0x2222") {
+        SBigFromStr(b, std::to_string(0x9999444488885555ULL).c_str());
+        SBigFromUnsigned(c, 0x2222);
+
+        SBigDiv(a, b, c);
+
+        CHECK(a->Primary().Count() == 2);
+        CHECK(a->Primary()[0] == 0x00040002);
+        CHECK(a->Primary()[1] == 0x48002);
+    }
+
+    SECTION("divides 0x9999444488885555 by 0xFFFFFFFF") {
+        SBigFromStr(b, std::to_string(0x9999444488885555ULL).c_str());
+        SBigFromUnsigned(c, 0xFFFFFFFF);
+
+        SBigDiv(a, b, c);
+
+        CHECK(a->Primary().Count() == 1);
+        CHECK(a->Primary()[0] == 0x99994445);
+    }
+
+    SECTION("divides 0x9999444488885555 by 0x1111222233334444 (buffer divisor)") {
+        SBigFromStr(b, std::to_string(0x9999444488885555ULL).c_str());
+        SBigFromStr(c, std::to_string(0x1111222233334444ULL).c_str());
+
+        SBigDiv(a, b, c);
+
+        CHECK(a->Primary().Count() == 1);
+        CHECK(a->Primary()[0] == 8);
+    }
+}
+
 TEST_CASE("SBigFromBinary", "[big]") {
     SECTION("creates bigdata from 0") {
         BigData* num;