From 33585cb36fb452e992e6031dcdda918f7c12cdd1 Mon Sep 17 00:00:00 2001
From: fallenoak <git@fallenoak.me>
Date: Sun, 29 Jan 2023 22:12:59 -0600
Subject: [PATCH] feat(big): add SBigAdd

---
 storm/Big.cpp     |  4 +++
 storm/Big.hpp     |  2 ++
 storm/big/Ops.cpp | 11 ++++++
 storm/big/Ops.hpp |  2 ++
 test/Big.cpp      | 91 +++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 110 insertions(+)

diff --git a/storm/Big.cpp b/storm/Big.cpp
index 89a94be..5b28cfe 100644
--- a/storm/Big.cpp
+++ b/storm/Big.cpp
@@ -3,6 +3,10 @@
 #include "storm/Memory.hpp"
 #include <cstring>
 
+void SBigAdd(BigData* a, BigData* b, BigData* c) {
+    Add(a->Primary(), b->Primary(), c->Primary());
+}
+
 void SBigDel(BigData* num) {
     delete num;
 }
diff --git a/storm/Big.hpp b/storm/Big.hpp
index c1d42e5..a12566b 100644
--- a/storm/Big.hpp
+++ b/storm/Big.hpp
@@ -4,6 +4,8 @@
 #include "storm/big/BigData.hpp"
 #include <cstdint>
 
+void SBigAdd(BigData* a, BigData* b, BigData* c);
+
 void SBigDel(BigData* num);
 
 void SBigFromBinary(BigData* num, const void* data, uint32_t bytes);
diff --git a/storm/big/Ops.cpp b/storm/big/Ops.cpp
index efd3db3..5a3a36f 100644
--- a/storm/big/Ops.cpp
+++ b/storm/big/Ops.cpp
@@ -1,5 +1,16 @@
 #include "storm/big/Ops.hpp"
 
+void Add(BigBuffer& a, const BigBuffer& b, const BigBuffer& c) {
+    uint64_t carry = 0;
+    uint32_t i = 0;
+    for (i = 0; carry || b.IsUsed(i) || c.IsUsed(i); i++) {
+        carry += static_cast<uint64_t>(b[i]) + c[i];
+        a[i] = ExtractLowPart(carry);
+    }
+
+    a.SetCount(i);
+}
+
 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 880a5df..6db197b 100644
--- a/storm/big/Ops.hpp
+++ b/storm/big/Ops.hpp
@@ -4,6 +4,8 @@
 #include "storm/big/BigBuffer.hpp"
 #include <cstdint>
 
+void Add(BigBuffer& a, const BigBuffer& b, const BigBuffer& c);
+
 uint32_t ExtractLowPart(uint64_t& value);
 
 uint32_t ExtractLowPartSx(uint64_t& value);
diff --git a/test/Big.cpp b/test/Big.cpp
index 5897afc..637ea1c 100644
--- a/test/Big.cpp
+++ b/test/Big.cpp
@@ -68,6 +68,97 @@ TEST_CASE("MakeLarge", "[big]") {
     }
 }
 
+TEST_CASE("SBigAdd", "[big]") {
+    SECTION("adds 0 and 1") {
+        BigData* a;
+        SBigNew(&a);
+
+        BigData* b;
+        SBigNew(&b);
+        SBigFromUnsigned(b, 0);
+
+        BigData* c;
+        SBigNew(&c);
+        SBigFromUnsigned(c, 1);
+
+        SBigAdd(a, b, c);
+
+        CHECK(a->Primary().Count() == 1);
+        CHECK(a->Primary()[0] == 1);
+
+        SBigDel(a);
+        SBigDel(b);
+        SBigDel(c);
+    }
+
+    SECTION("adds 1 and 2") {
+        BigData* a;
+        SBigNew(&a);
+
+        BigData* b;
+        SBigNew(&b);
+        SBigFromUnsigned(b, 1);
+
+        BigData* c;
+        SBigNew(&c);
+        SBigFromUnsigned(c, 2);
+
+        SBigAdd(a, b, c);
+
+        CHECK(a->Primary().Count() == 1);
+        CHECK(a->Primary()[0] == 3);
+
+        SBigDel(a);
+        SBigDel(b);
+        SBigDel(c);
+    }
+
+    SECTION("adds 0x12345678 and 0x23456789") {
+        BigData* a;
+        SBigNew(&a);
+
+        BigData* b;
+        SBigNew(&b);
+        SBigFromUnsigned(b, 0x12345678);
+
+        BigData* c;
+        SBigNew(&c);
+        SBigFromUnsigned(c, 0x23456789);
+
+        SBigAdd(a, b, c);
+
+        CHECK(a->Primary().Count() == 1);
+        CHECK(a->Primary()[0] == 0x3579BE01);
+
+        SBigDel(a);
+        SBigDel(b);
+        SBigDel(c);
+    }
+
+    SECTION("adds 0xFFFFFFFF and 0xF0F0F0F0") {
+        BigData* a;
+        SBigNew(&a);
+
+        BigData* b;
+        SBigNew(&b);
+        SBigFromUnsigned(b, 0xFFFFFFFF);
+
+        BigData* c;
+        SBigNew(&c);
+        SBigFromUnsigned(c, 0xF0F0F0F0);
+
+        SBigAdd(a, b, c);
+
+        CHECK(a->Primary().Count() == 2);
+        CHECK(a->Primary()[0] == 0xF0F0F0EF);
+        CHECK(a->Primary()[1] == 0x1);
+
+        SBigDel(a);
+        SBigDel(b);
+        SBigDel(c);
+    }
+}
+
 TEST_CASE("SBigFromBinary", "[big]") {
     SECTION("creates bigdata from 0") {
         BigData* num;