1 files changed, 62 insertions, 0 deletions
diff --git a/v_windows/v/vlib/encoding/hex/hex.v b/v_windows/v/vlib/encoding/hex/hex.v
new file mode 100644
index 0000000..99387f1
--- /dev/null
+++ b/v_windows/v/vlib/encoding/hex/hex.v
@@ -0,0 +1,62 @@
+module hex
+
+import strings
+
+// decode converts a hex string into an array of bytes. The expected
+// input format is 2 ASCII characters for each output byte. If the provided
+// string length is not a multiple of 2, an implicit `0` is prepended to it.
+pub fn decode(s string) ?[]byte {
+	mut hex_str := s
+	if hex_str.len >= 2 {
+		if s[0] == `0` && (s[1] == `x` || s[1] == `X`) {
+			hex_str = s[2..]
+		}
+	}
+	if hex_str.len == 0 {
+		return []byte{}
+	} else if hex_str.len == 1 {
+		return [char2nibble(hex_str[0]) ?]
+	} else if hex_str.len == 2 {
+		n1 := char2nibble(hex_str[0]) ?
+		n0 := char2nibble(hex_str[1]) ?
+		return [(n1 << 4) | n0]
+	}
+	// calculate the first byte depending on if hex_str.len is odd
+	mut val := char2nibble(hex_str[0]) ?
+	if hex_str.len & 1 == 0 {
+		val = (val << 4) | char2nibble(hex_str[1]) ?
+	}
+	// set cap to hex_str.len/2 rounded up
+	mut bytes := []byte{len: 1, cap: (hex_str.len + 1) >> 1, init: val}
+	// iterate over every 2 bytes
+	// the start index depends on if hex_str.len is odd
+	for i := 2 - (hex_str.len & 1); i < hex_str.len; i += 2 {
+		n1 := char2nibble(hex_str[i]) ?
+		n0 := char2nibble(hex_str[i + 1]) ?
+		bytes << (n1 << 4) | n0
+	}
+	return bytes
+}
+
+// encode converts an array of bytes into a string of ASCII hex bytes. The
+// output will always be a string with length a multiple of 2.
+[manualfree]
+pub fn encode(bytes []byte) string {
+	mut sb := strings.new_builder(bytes.len << 1)
+	for b in bytes {
+		sb.write_string(b.hex())
+	}
+	res := sb.str()
+	unsafe { sb.free() }
+	return res
+}
+
+// char2nibble converts an ASCII hex character to it's hex value
+fn char2nibble(b byte) ?byte {
+	match b {
+		`0`...`9` { return b - byte(`0`) }
+		`A`...`F` { return b - byte(`A`) + 10 }
+		`a`...`f` { return b - byte(`a`) + 10 }
+		else { return error('invalid hex char $b.ascii_str()') }
+	}
+}