From 4d3651134c17e26da551a39619b7ccfe1f8100bc Mon Sep 17 00:00:00 2001
From: fallenoak <git@fallenoak.me>
Date: Wed, 1 Feb 2023 23:27:32 -0600
Subject: [PATCH] feat(big): add Div

---
 storm/big/Ops.cpp |  17 +++++++
 storm/big/Ops.hpp |   2 +
 test/Big.cpp      | 114 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 133 insertions(+)

diff --git a/storm/big/Ops.cpp b/storm/big/Ops.cpp
index 4409e8a..3e094bc 100644
--- a/storm/big/Ops.cpp
+++ b/storm/big/Ops.cpp
@@ -34,6 +34,23 @@ int32_t Compare(const BigBuffer& a, const BigBuffer& b) {
     return result;
 }
 
+void Div(BigBuffer& a, uint32_t* b, const BigBuffer& c, uint64_t d) {
+    // TODO STORM_ASSERT(d <= SMALL_BOUND);
+
+    auto index = c.Count();
+    a.SetCount(index);
+
+    uint64_t data = 0;
+    while (index > 0) {
+        InsertLowPart(data, c[--index]);
+        a[index] = data / d;
+        data %= d;
+    }
+
+    a.Trim();
+    *b = data;
+}
+
 uint32_t ExtractLowPart(uint64_t& value) {
     auto low = static_cast<uint32_t>(value);
     value >>= 32;
diff --git a/storm/big/Ops.hpp b/storm/big/Ops.hpp
index c13548d..99fc457 100644
--- a/storm/big/Ops.hpp
+++ b/storm/big/Ops.hpp
@@ -11,6 +11,8 @@ void Add(BigBuffer& a, const BigBuffer& b, const BigBuffer& c);
 
 int32_t Compare(const BigBuffer& a, const BigBuffer& b);
 
+void Div(BigBuffer& a, uint32_t* b, const BigBuffer& c, uint64_t d);
+
 uint32_t ExtractLowPart(uint64_t& value);
 
 uint32_t ExtractLowPartSx(uint64_t& value);
diff --git a/test/Big.cpp b/test/Big.cpp
index f9f16b8..c1ba4dd 100644
--- a/test/Big.cpp
+++ b/test/Big.cpp
@@ -147,6 +147,120 @@ TEST_CASE("Compare", "[big]") {
     }
 }
 
+TEST_CASE("Div", "[big]") {
+    SECTION("divides 2 by 1") {
+        BigData* a;
+        SBigNew(&a);
+
+        uint32_t b;
+
+        BigData* c;
+        SBigNew(&c);
+        SBigFromUnsigned(c, 2);
+
+        uint64_t d = 1;
+
+        Div(a->Primary(), &b, c->Primary(), d);
+
+        CHECK(a->Primary().Count() == 1);
+        CHECK(a->Primary()[0] == 2);
+        CHECK(b == 0);
+
+        SBigDel(a);
+        SBigDel(c);
+    }
+
+    SECTION("divides 5 by 2") {
+        BigData* a;
+        SBigNew(&a);
+
+        uint32_t b;
+
+        BigData* c;
+        SBigNew(&c);
+        SBigFromUnsigned(c, 5);
+
+        uint64_t d = 2;
+
+        Div(a->Primary(), &b, c->Primary(), d);
+
+        CHECK(a->Primary().Count() == 1);
+        CHECK(a->Primary()[0] == 2);
+        CHECK(b == 1);
+
+        SBigDel(a);
+        SBigDel(c);
+    }
+
+    SECTION("divides 7 by 4") {
+        BigData* a;
+        SBigNew(&a);
+
+        uint32_t b;
+
+        BigData* c;
+        SBigNew(&c);
+        SBigFromUnsigned(c, 7);
+
+        uint64_t d = 4;
+
+        Div(a->Primary(), &b, c->Primary(), d);
+
+        CHECK(a->Primary().Count() == 1);
+        CHECK(a->Primary()[0] == 1);
+        CHECK(b == 3);
+
+        SBigDel(a);
+        SBigDel(c);
+    }
+
+    SECTION("divides 0x9999444488885555 by 0x2222") {
+        BigData* a;
+        SBigNew(&a);
+
+        uint32_t b;
+
+        BigData* c;
+        SBigNew(&c);
+        uint64_t c_ = 0x9999444488885555;
+        SBigFromBinary(c, reinterpret_cast<uint8_t*>(&c_), sizeof(c_));
+
+        uint64_t d = 0x2222;
+
+        Div(a->Primary(), &b, c->Primary(), d);
+
+        CHECK(a->Primary().Count() == 2);
+        CHECK(a->Primary()[0] == 0x00040002);
+        CHECK(a->Primary()[1] == 0x48002);
+        CHECK(b == 0x1111);
+
+        SBigDel(a);
+        SBigDel(c);
+    }
+
+    SECTION("divides 0x9999444488885555 by 0xFFFFFFFF") {
+        BigData* a;
+        SBigNew(&a);
+
+        uint32_t b;
+
+        BigData* c;
+        SBigNew(&c);
+        uint64_t c_ = 0x9999444488885555;
+        SBigFromBinary(c, reinterpret_cast<uint8_t*>(&c_), sizeof(c_));
+
+        uint64_t d = 0xFFFFFFFF;
+
+        Div(a->Primary(), &b, c->Primary(), d);
+
+        CHECK(a->Primary().Count() == 1);
+        CHECK(a->Primary()[0] == 0x99994445);
+        CHECK(b == 0x2221999A);
+
+        SBigDel(a);
+        SBigDel(c);
+    }
+}
 
 TEST_CASE("ExtractLowPart", "[big]") {
     SECTION("extracts low part of 0") {