bitfield: add bf.from_bytes_lowest_bits_first/1 and a test for it

vlib/bitfield/bitfield.v

@@ -24,8 +24,8 @@ const (
 	slot_size = 32
 )
 
-// public functions
-// from_bytes() converts a byte array into a bitfield.
+// from_bytes converts a byte array into a bitfield.
+// [0x0F, 0x01] => 0000 1111 0000 0001
 pub fn from_bytes(input []byte) BitField {
 	mut output := new(input.len * 8)
 	for i, b in input {
@@ -59,6 +59,16 @@ pub fn from_bytes(input []byte) BitField {
 	return output
 }
 
+// from_bytes_lowest_bits_first converts a byte array into a bitfield
+// [0x0F, 0x01] => 1111 0000 1000 0000
+pub fn from_bytes_lowest_bits_first(input []byte) BitField {
+	mut output := new(input.len * 8)
+	for i, b in input {
+		output.field[i / 4] |= u32(b) << ((i % 4) * 8)
+	}
+	return output
+}
+
 // from_str converts a string of characters ('0' and '1') to a bit
 // array. Any character different from '0' is treated as '1'.
 pub fn from_str(input string) BitField {

vlib/bitfield/bitfield_test.v

@@ -126,6 +126,14 @@ fn test_bf_from_bytes() {
 	assert newoutput == output
 }
 
+fn test_bf_from_bytes_lowest_bits_first() {
+	input := [byte(0x01), 0xF0]
+	output := bitfield.from_bytes_lowest_bits_first(input).str()
+	assert output == '10000000' + '00001111'
+	newoutput := bitfield.from_str(output).str()
+	assert newoutput == output
+}
+
 fn test_bf_from_str() {
 	len := 80
 	mut input := ''