rename package enc -> hex

* Makefile (fmt): fmt lib instead of enc
* challenge/c01.go: Use lib instead of enc
* challenge/c02.go: Use lib instead of enc
* enc/b64.go -> lib/b64.go
* enc/hex.go -> lib/hex.go
* enc/xor.go -> lib/xor.go

3 files changed, 72 insertions, 0 deletions

diff --git a/lib/b64.go b/lib/b64.go
new file mode 100644
index 0000000..d37f710
--- /dev/null
+++ b/lib/b64.go
@@ -0,0 +1,24 @@
+// Copyright © 2020 rsiddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package lib
+
+const b64_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+
+func HexToBase64(hex string) string {
+	hb := []byte(hex)
+
+	b64 := ""
+	for i := 0; i <= len(hb)-3; i = i + 3 {
+		a := (HexCharToDec(hb[i])<<8 |
+			HexCharToDec(hb[i+1])<<4 |
+			HexCharToDec(hb[i+2]))
+		b64 += encode(a >> 6)
+		b64 += encode(a & 0b111111)
+	}
+	return b64
+}
+
+func encode(b uint16) string {
+	return string(b64_table[b])
+}
diff --git a/lib/hex.go b/lib/hex.go
new file mode 100644
index 0000000..bf539bc
--- /dev/null
+++ b/lib/hex.go
@@ -0,0 +1,26 @@
+// Copyright © 2020 rsiddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package lib
+
+// 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
+}
+
+func DecToHexChar(i uint16) byte {
+	switch {
+	case 0 <= i && i <= 9:
+		return byte(48 + i)
+	case 10 <= i && i <= 15:
+		return byte(97 + (i - 10))
+	}
+	return 0
+}
diff --git a/lib/xor.go b/lib/xor.go
new file mode 100644
index 0000000..270999c
--- /dev/null
+++ b/lib/xor.go
@@ -0,0 +1,22 @@
+// Copyright © 2020 rsiddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package lib
+
+func FixedXOR(a, b string) string {
+	cs := ""
+	if len(a) != len(b) {
+		return cs
+	}
+
+	ab := []byte(a)
+	bb := []byte(b)
+	for i := 0; i < len(ab); i++ {
+		p := HexCharToDec(ab[i])
+		q := HexCharToDec(bb[i])
+		r := DecToHexChar(p ^ q)
+
+		cs += string(r)
+	}
+	return cs
+}