From f30b0f1017c2b8ecaf4e02e334ee5a8e234f27b9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Silvan=20B=C3=BCdenbender?=
 <42788329+SilvanCodes@users.noreply.github.com>
Date: Wed, 13 Nov 2019 17:48:00 +0100
Subject: [PATCH] bitfield: add from_bytes() function

---
 vlib/bitfield/bitfield.v      | 26 ++++++++++++++++++++++++++
 vlib/bitfield/bitfield_test.v | 14 ++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/vlib/bitfield/bitfield.v b/vlib/bitfield/bitfield.v
index 85cd4b33c2..f0fd188af8 100644
--- a/vlib/bitfield/bitfield.v
+++ b/vlib/bitfield/bitfield.v
@@ -77,6 +77,32 @@ fn cleartail(instance mut BitField) {
 
 // public functions
 
+// from_bytes() converts a byte arry into a bitfield.
+// Be aware of possible trailing zeroes being added
+// due to the underlying 32bit int containers.
+pub fn from_bytes(input []byte) BitField {
+	mut output := new(input.len * 8)
+	for i, b in input {
+		pos := i / 4
+		match i % 4 {
+			0 {
+				output.field[pos] = output.field[pos] | (u32(b) << 24)
+			}
+			1 {
+				output.field[pos] = output.field[pos] | (u32(b) << 16)
+			}
+			2 {
+				output.field[pos] = output.field[pos] | (u32(b) << 8)
+			}
+			3 {
+				output.field[pos] = output.field[pos] | u32(b)
+			}
+		}
+	}
+
+	return output
+}
+
 // str2bf() converts a string of characters ('0' and '1') to a bit
 // array. Any character different from '0' is treated as '1'.
 
diff --git a/vlib/bitfield/bitfield_test.v b/vlib/bitfield/bitfield_test.v
index 4c091eb9f3..e7a6d456a6 100644
--- a/vlib/bitfield/bitfield_test.v
+++ b/vlib/bitfield/bitfield_test.v
@@ -122,6 +122,20 @@ fn test_hamming() {
 	assert count == bitfield.hamming(input1, input2)
 }
 
+fn test_bf_from_bytes() {
+	input := [byte(0xF0), byte(0x0F), byte(0xF0), byte(0xFF)]
+	output := bitfield.from_bytes(input)
+	mut result := 1
+	for i := 0; i < input.len * 8; i++ {
+		expected := input[input.len - 1 - i / 8] >> i % 8 & 1
+		actual := output.getbit(i)
+		if expected != actual {
+			result = 0
+		}
+	}
+	assert result == 1
+}
+
 fn test_bf_str2bf() {
 	rand.seed(time.now().uni)
 	len := 80