Closer file structure to desired

lib/challenge/inline/hex.go

@@ -0,0 +1,95 @@
+package inline
+
+import (
+	"errors"
+)
+
+const (
+	hextable        = "0123456789abcdef"
+	reverseHexTable = "" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\xff\xff\xff\xff\xff\xff" +
+		"\xff\x0a\x0b\x0c\x0d\x0e\x0f\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\x0a\x0b\x0c\x0d\x0e\x0f\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
+)
+
+// EncodedLen returns the length of an encoding of n source bytes.
+// Specifically, it returns n * 2.
+func EncodedLen(n int) int { return n * 2 }
+
+// Encode encodes src into [EncodedLen](len(src))
+// bytes of dst. As a convenience, it returns the number
+// of bytes written to dst, but this value is always [EncodedLen](len(src)).
+// Encode implements hexadecimal encoding.
+func Encode(dst, src []byte) int {
+	j := 0
+	for _, v := range src {
+		dst[j] = hextable[v>>4]
+		dst[j+1] = hextable[v&0x0f]
+		j += 2
+	}
+	return len(src) * 2
+}
+
+// ErrLength reports an attempt to decode an odd-length input
+// using [Decode] or [DecodeString].
+// The stream-based Decoder returns [io.ErrUnexpectedEOF] instead of ErrLength.
+var ErrLength = errors.New("encoding/hex: odd length hex string")
+
+// InvalidByteError values describe errors resulting from an invalid byte in a hex string.
+type InvalidByteError byte
+
+func (e InvalidByteError) Error() string {
+	return "encoding/hex: invalid byte"
+}
+
+// DecodedLen returns the length of a decoding of x source bytes.
+// Specifically, it returns x / 2.
+func DecodedLen(x int) int { return x / 2 }
+
+// Decode decodes src into [DecodedLen](len(src)) bytes,
+// returning the actual number of bytes written to dst.
+//
+// Decode expects that src contains only hexadecimal
+// characters and that src has even length.
+// If the input is malformed, Decode returns the number
+// of bytes decoded before the error.
+func Decode(dst, src []byte) (int, error) {
+	i, j := 0, 1
+	for ; j < len(src); j += 2 {
+		p := src[j-1]
+		q := src[j]
+
+		a := reverseHexTable[p]
+		b := reverseHexTable[q]
+		if a > 0x0f {
+			return i, InvalidByteError(p)
+		}
+		if b > 0x0f {
+			return i, InvalidByteError(q)
+		}
+		dst[i] = (a << 4) | b
+		i++
+	}
+	if len(src)%2 == 1 {
+		// Check for invalid char before reporting bad length,
+		// since the invalid char (if present) is an earlier problem.
+		if reverseHexTable[src[j-1]] > 0x0f {
+			return i, InvalidByteError(src[j-1])
+		}
+		return i, ErrLength
+	}
+	return i, nil
+}