From 74928d9f7a20b6544e2c4fbf802e6828f17200f0 Mon Sep 17 00:00:00 2001 From: PhatPhuckDave Date: Tue, 30 Jul 2024 22:02:46 +0200 Subject: [PATCH] Add some sort of work on decode --- encoding/gsm7.go | 68 +++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 64 insertions(+), 4 deletions(-) diff --git a/encoding/gsm7.go b/encoding/gsm7.go index 4dfd2e5..688524a 100644 --- a/encoding/gsm7.go +++ b/encoding/gsm7.go @@ -3,6 +3,7 @@ package encoding import ( "bytes" "fmt" + "log" ) type GSM7Coder struct{} @@ -10,9 +11,11 @@ type GSM7Coder struct{} func (c *GSM7Coder) Encode(s string, buf *bytes.Buffer) error { // utf8 := *(*[]byte)(unsafe.Pointer(&s)) utf8 := []byte(s) - var offset int = 1 - var bitshift byte = 0 - var leap, shift bool + var ( + offset int = 1 + bitshift byte = 0 + leap, shift bool + ) for index, septet := range utf8 { if septet > 0b01111111 { @@ -60,5 +63,62 @@ func (c *GSM7Coder) Encode(s string, buf *bytes.Buffer) error { } func (c *GSM7Coder) Decode(buf *bytes.Buffer) (string, error) { - return buf.String(), nil + 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)) + + 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) + + 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 + gsm7[index+offset] |= masked + gsm7[index] <<= bitshift + + if !leap { + buf.WriteByte(gsm7[index+offset]) + } + if index == len(gsm7)-1 && gsm7[index] > 0 { + buf.WriteByte(gsm7[index]) + } + log.Printf("Index:%-3d Offset:%-3d Bitshift:%-3d CurrentByte:%08b (%-3d) OffsetByte:%08b (%-3d) Leap:%5v", index, offset, bitshift, gsm7[index], gsm7[index], gsm7[index-offset], gsm7[index-offset], leap) + if bitshift >= 7 { + if leap { + log.Printf("Shift at Index:%-3d Offset:%-3d Bitshift:%-3d", index, offset, bitshift) + leap = false + bitshift = 0 + offset++ + shift = true + continue + } + log.Printf("Leap at Index:%-3d Offset:%-3d Bitshift:%-3d", index, offset, bitshift) + leap = true + bitshift = 6 + } + if shift { + offset = 1 + } + } + return "", nil +} + +// Allocation free +// Which means data MUST have space for value +func InsertAt(data *[]byte, index int, value byte) { + copy((*data)[index+1:], (*data)[index:]) + (*data)[index] = value }