From 16b382f1cd9226d4efadbca7e637683b79a1881e Mon Sep 17 00:00:00 2001
From: Lee ByeongJun <lbj199874@gmail.com>
Date: Thu, 29 Feb 2024 16:54:32 +0900
Subject: [PATCH] uint256 to words

---
 main.go           | 18 ++++++++++++++
 word/word.go      | 26 ++++++++++++++++++++
 word/word_test.go | 62 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 106 insertions(+)
 create mode 100644 main.go
 create mode 100644 word/word.go
 create mode 100644 word/word_test.go

diff --git a/main.go b/main.go
new file mode 100644
index 0000000..f9d3c92
--- /dev/null
+++ b/main.go
@@ -0,0 +1,18 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/gnoswap-labs/int256/word"
+	"github.com/holiman/uint256"
+)
+
+func main() {
+	num, _ := uint256.FromHex("0x1234567890abcdef1234567890abcdef1234567890abcdef1234544440abcdef")
+
+	w := word.ToWords(num)
+
+	for i := 0; i < 8; i++ {
+		fmt.Printf("%d: %x\n", i, w.Words[i])
+	}
+}
diff --git a/word/word.go b/word/word.go
new file mode 100644
index 0000000..a299498
--- /dev/null
+++ b/word/word.go
@@ -0,0 +1,26 @@
+package word
+
+import (
+	"encoding/binary"
+
+	"github.com/holiman/uint256"
+)
+
+type Uint32Words struct {
+	Words [8]uint32
+}
+
+func ToWords(num *uint256.Int) *Uint32Words {
+	// convert uint256 to bytes
+	bytes := num.Bytes()
+
+	// convert byte array to 32bit size words
+	words := new(Uint32Words)
+	for i := 0; i < 8; i++ {
+		// Extract each 32-bit word.
+		// The binary.BigEndian.Uint32 function reads 4 bytes from the byte slice and converts it to uint32.
+		words.Words[i] = binary.BigEndian.Uint32(bytes[i*4 : (i+1)*4])
+	}
+
+	return words
+}
\ No newline at end of file
diff --git a/word/word_test.go b/word/word_test.go
new file mode 100644
index 0000000..d980904
--- /dev/null
+++ b/word/word_test.go
@@ -0,0 +1,62 @@
+package word
+
+import (
+	"testing"
+
+	"github.com/holiman/uint256"
+)
+
+func TestToWords(t *testing.T) {
+	tests := []struct {
+		name   string
+		hex    string // Hexadecimal representation of the uint256 value
+		expect [8]uint32
+	}{
+		{
+			name: "HalfMaxUint256",
+			hex:  "0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+			expect: [8]uint32{
+				0x7fffffff, 0xffffffff, 0xffffffff, 0xffffffff,
+				0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff,
+			},
+		},
+		{
+			name: "RandomNumber",
+			hex:  "0x1a2b3c4d5e6f708192a3b4c5d6e7f8091a2b3c4d5e6f708192a3b4c5d6e7f809",
+			expect: [8]uint32{
+				0x1a2b3c4d, 0x5e6f7081, 0x92a3b4c5, 0xd6e7f809,
+				0x1a2b3c4d, 0x5e6f7081, 0x92a3b4c5, 0xd6e7f809,
+			},
+		},
+		{
+			name: "MaxUint256",
+			hex:  "0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+			expect: [8]uint32{
+				0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff,
+				0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff,
+			},
+		},
+		{
+			name: "ArbitraryNumber",
+			hex:  "0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef",
+			expect: [8]uint32{
+				0x12345678, 0x90abcdef, 0x12345678, 0x90abcdef,
+				0x12345678, 0x90abcdef, 0x12345678, 0x90abcdef,
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			num, _ := uint256.FromHex(tc.hex)
+
+			result := ToWords(num)
+
+			for i, word := range result.Words {
+				if word != tc.expect[i] {
+					t.Errorf("Test %s failed: word %d is 0x%x, want 0x%x", tc.name, i, word, tc.expect[i])
+				}
+			}
+		})
+	}
+}