From 6c830703802ea0281abfc1a19967a259d111238f Mon Sep 17 00:00:00 2001
From: fallenoak <git@fallenoak.me>
Date: Sun, 29 Jan 2023 20:37:09 -0600
Subject: [PATCH] feat(big): add SBigFromBinary

---
 storm/Big.cpp           |  4 ++++
 storm/Big.hpp           |  2 ++
 storm/big/BigBuffer.cpp |  4 ++++
 storm/big/BigBuffer.hpp |  1 +
 storm/big/Ops.cpp       | 10 ++++++++++
 storm/big/Ops.hpp       |  2 ++
 test/Big.cpp            | 43 +++++++++++++++++++++++++++++++++++++++++
 7 files changed, 66 insertions(+)

diff --git a/storm/Big.cpp b/storm/Big.cpp
index a6db9da..89a94be 100644
--- a/storm/Big.cpp
+++ b/storm/Big.cpp
@@ -7,6 +7,10 @@ void SBigDel(BigData* num) {
     delete num;
 }
 
+void SBigFromBinary(BigData* num, const void* data, uint32_t bytes) {
+    FromBinary(num->Primary(), data, bytes);
+}
+
 void SBigFromUnsigned(BigData* num, uint32_t val) {
     FromUnsigned(num->Primary(), val);
 }
diff --git a/storm/Big.hpp b/storm/Big.hpp
index 55b7a3e..c1d42e5 100644
--- a/storm/Big.hpp
+++ b/storm/Big.hpp
@@ -6,6 +6,8 @@
 
 void SBigDel(BigData* num);
 
+void SBigFromBinary(BigData* num, const void* data, uint32_t bytes);
+
 void SBigFromUnsigned(BigData* num, uint32_t val);
 
 void SBigNew(BigData** num);
diff --git a/storm/big/BigBuffer.cpp b/storm/big/BigBuffer.cpp
index c2280f2..4bafa49 100644
--- a/storm/big/BigBuffer.cpp
+++ b/storm/big/BigBuffer.cpp
@@ -13,6 +13,10 @@ uint32_t BigBuffer::operator[](uint32_t index) const {
     return 0;
 }
 
+void BigBuffer::Clear() {
+    this->m_data.SetCount(this->m_offset);
+}
+
 uint32_t BigBuffer::Count() const {
     return this->m_data.Count() - this->m_offset;
 }
diff --git a/storm/big/BigBuffer.hpp b/storm/big/BigBuffer.hpp
index 9f6919c..0266996 100644
--- a/storm/big/BigBuffer.hpp
+++ b/storm/big/BigBuffer.hpp
@@ -13,6 +13,7 @@ class BigBuffer {
     // Member functions
     uint32_t& operator[](uint32_t index);
     uint32_t operator[](uint32_t index) const;
+    void Clear();
     uint32_t Count() const;
     void GrowToFit(uint32_t index);
     int32_t IsUsed(uint32_t index) const;
diff --git a/storm/big/Ops.cpp b/storm/big/Ops.cpp
index cc15f64..efd3db3 100644
--- a/storm/big/Ops.cpp
+++ b/storm/big/Ops.cpp
@@ -19,6 +19,16 @@ uint32_t ExtractLowPartSx(uint64_t& value) {
     return low;
 }
 
+void FromBinary(BigBuffer& buffer, const void* data, uint32_t bytes) {
+    buffer.Clear();
+
+    for (uint32_t i = 0; i < bytes; i++) {
+        auto byte = static_cast<const uint8_t*>(data)[i];
+        auto v7 = (i & 3) ? buffer[i / 4] : 0;
+        buffer[i / 4] = v7 + (byte << (8 * (i & 3)));
+    }
+}
+
 void FromUnsigned(BigBuffer& buffer, uint32_t value) {
     buffer[0] = value;
     buffer.SetCount(1);
diff --git a/storm/big/Ops.hpp b/storm/big/Ops.hpp
index 096ca48..880a5df 100644
--- a/storm/big/Ops.hpp
+++ b/storm/big/Ops.hpp
@@ -8,6 +8,8 @@ uint32_t ExtractLowPart(uint64_t& value);
 
 uint32_t ExtractLowPartSx(uint64_t& value);
 
+void FromBinary(BigBuffer& buffer, const void* value, uint32_t bytes);
+
 void FromUnsigned(BigBuffer& buffer, uint32_t value);
 
 uint64_t MakeLarge(uint32_t low, uint32_t high);
diff --git a/test/Big.cpp b/test/Big.cpp
index 146ccf0..5897afc 100644
--- a/test/Big.cpp
+++ b/test/Big.cpp
@@ -68,6 +68,33 @@ TEST_CASE("MakeLarge", "[big]") {
     }
 }
 
+TEST_CASE("SBigFromBinary", "[big]") {
+    SECTION("creates bigdata from 0") {
+        BigData* num;
+        SBigNew(&num);
+        uint32_t data = 0;
+        SBigFromBinary(num, reinterpret_cast<uint8_t*>(&data), sizeof(data));
+
+        CHECK(num->Primary().Count() == 1);
+        CHECK(num->Primary()[0] == 0);
+
+        SBigDel(num);
+    }
+
+    SECTION("creates bigdata from 0x123456789ABCDEF0") {
+        BigData* num;
+        SBigNew(&num);
+        uint64_t data = 0x123456789ABCDEF0;
+        SBigFromBinary(num, reinterpret_cast<uint8_t*>(&data), sizeof(data));
+
+        CHECK(num->Primary().Count() == 2);
+        CHECK(num->Primary()[0] == 0x9ABCDEF0);
+        CHECK(num->Primary()[1] == 0x12345678);
+
+        SBigDel(num);
+    }
+}
+
 TEST_CASE("SBigFromUnsigned", "[big]") {
     SECTION("creates bigdata from 0") {
         BigData* num;
@@ -121,4 +148,20 @@ TEST_CASE("SBigToBinaryBuffer", "[big]") {
 
         SBigDel(num);
     }
+
+    SECTION("returns expected buffer for bigdata representing 0x123456789ABCDEF0") {
+        BigData* num;
+        SBigNew(&num);
+        uint64_t data = 0x123456789ABCDEF0;
+        SBigFromBinary(num, reinterpret_cast<uint8_t*>(&data), sizeof(data));
+
+        uint8_t buffer[8];
+        uint32_t bytes;
+        SBigToBinaryBuffer(num, buffer, sizeof(buffer), &bytes);
+
+        CHECK(bytes == 8);
+        CHECK(*reinterpret_cast<uint64_t*>(buffer) == 0x123456789ABCDEF0);
+
+        SBigDel(num);
+    }
 }