enc: fromHexChar -> HexCharToDec

* enc/b64.go (fromHexChar): Move and rename this function to...
* enc/hex.go (HexCharToDec): ...this.

1 files changed, 16 insertions, 0 deletions

diff --git a/enc/hex.go b/enc/hex.go
new file mode 100644
index 0000000..0d19538
--- /dev/null
+++ b/enc/hex.go
@@ -0,0 +1,16 @@
+// Copyright © 2020 rsiddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package enc
+
+// Adapted from
+// https://go.googlesource.com/go/+/refs/tags/go1.15/src/encoding/hex/hex.go#83
+func HexCharToDec(c byte) uint16 {
+	switch {
+	case '0' <= c && c <= '9':
+		return uint16(c - '0')
+	case 'a' <= c && c <= 'f':
+		return uint16(c - 'a' + 10)
+	}
+	return 0
+}