Implement basic decoding

encoding/gsm7.go

@@ -65,29 +65,41 @@ func (c *GSM7Coder) Encode(s string, buf *bytes.Buffer) error {
 func (c *GSM7Coder) Decode(buf *bytes.Buffer) (string, error) {
 	gsm7 := buf.Bytes()
 	var (
-		output      []byte = make([]byte, len(gsm7)*8/7)
 		offset      int    = (len(gsm7) / 8) + 1
 		bitshift    byte   = 0
 		leap, shift bool
 	)
-	log.Println(len(output))
+	outLength := len(gsm7)*8/7
+	lengthDiff := outLength - len(gsm7)
+	gsm7 = append(gsm7, make([]byte, lengthDiff)...)
 
+	// We don't care about the last byte
+	// Unless it's the %8.......
+	// We'll deal with that later
 	for index := len(gsm7) - 2; index >= 0; index-- {
 		octet := gsm7[index]
 		bitshift = byte((index + 1) % 8)
 		if bitshift == 7 {
 			leap = true
 		}
-		log.Printf("Index:%-3d Offset:%-3d Bitshift:%-3d CurrentByte:%08b (%-3d) Output(%-3d):%08b (%-3d) Leap:%5v", index, offset, bitshift, gsm7[index], gsm7[index], index+offset, output[index+offset], output[index+offset], leap)
+		log.Printf("Index:%-3d Offset:%-3d Bitshift:%-3d CurrentByte:%08b (%-3d) OffsetByte(%-3d):%08b (%-3d) Leap:%5v", index, offset, bitshift, gsm7[index], gsm7[index], index+offset, gsm7[index+offset], gsm7[index+offset], leap)
 
 		mask := byte(255 << (8 - bitshift))
 		masked := (mask & octet) >> (8 - bitshift)
 		log.Printf("Index:%-3d Offset:%-3d Bitshift:%-3d Mask:%08b Masked:%08b", index, offset, bitshift, mask, masked)
-		output[index+offset] |= masked
-
-		continue
+		if leap {
+			InsertAt(&gsm7, index+offset, masked)
+		} else {
 			gsm7[index+offset] |= masked
+		}
+		// Remove last bitshift bits
 		gsm7[index] <<= bitshift
+		// Move the remaining bit once to the right to form septet instead of octet
+		gsm7[index] >>= 1
+
+		log.Printf("Index:%-3d Offset:%-3d Bitshift:%-3d CurrentByte:%08b (%-3d) OffsetByte(%-3d):%08b (%-3d) Leap:%5v", index, offset, bitshift, gsm7[index], gsm7[index], index+offset, gsm7[index+offset], gsm7[index+offset], leap)
+		leap = false
+		continue
 
 		if !leap {
 			buf.WriteByte(gsm7[index+offset])
@@ -113,7 +125,11 @@ func (c *GSM7Coder) Decode(buf *bytes.Buffer) (string, error) {
 			offset = 1
 		}
 	}
-	return "", nil
+	log.Printf("Result: %+v", gsm7)
+	for _, v := range gsm7 {
+		log.Printf("%08b", v)
+	}
+	return string(gsm7), nil
 }
 
 // Allocation free