/
7bit.go
338 lines (315 loc) · 10.1 KB
/
7bit.go
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package Data
// Below source code belongs to github.com/xlab/at/pdu/7bit.go
import (
"bytes"
"errors"
"fmt"
)
// Esc code.
const Esc byte = 0x1B
// Ctrl+Z code.
const Sub byte = 0x1A
// <CR> code.
const CR byte = 0x0D
var crcr = []byte{CR, CR}
var cr = []byte{CR}
const (
max byte = 0x7F
unknown rune = '?'
)
// ErrUnexpectedByte happens when someone tries to decode non GSM 7-bit encoded string.
var ErrUnexpectedByte = errors.New("7bit decode: met an unexpected byte")
// Encode7Bit encodes the given UTF-8 text into GSM 7-bit (3GPP TS 23.038) encoding with packing.
func Encode7Bit(str string) []byte {
raw7 := make([]byte, 0, len(str))
for _, r := range str {
i := gsmTable.Index(r)
if i < 0 {
b := gsmEscapes.to7Bit(r)
if b != byte(unknown) {
raw7 = append(raw7, Esc, b)
} else {
raw7 = append(raw7, b)
}
continue
}
raw7 = append(raw7, byte(i))
}
return pack7Bit(raw7)
}
// Decode7Bit decodes the given GSM 7-bit packed octet data (3GPP TS 23.038) into a UTF-8 encoded string.
func Decode7Bit(octets []byte) (str string, err error) {
raw7 := unpack7Bit(octets)
var escaped bool
var r rune
for _, b := range raw7 {
if b > max {
err = ErrUnexpectedByte
return
} else if escaped {
r = gsmEscapes.from7Bit(b)
escaped = false
} else if b == Esc {
escaped = true
continue
} else {
r = gsmTable.Rune(int(b))
}
str += string(r)
}
return
}
func pad(n, block int) int {
if n%block == 0 {
return n
}
return (n/block + 1) * block
}
func blocks(n, block int) int {
if n%block == 0 {
return n / block
}
return n/block + 1
}
func pack7Bit(raw7 []byte) []byte {
pack7 := make([]byte, blocks(len(raw7)*7, 8))
pack := func(out []byte, b byte, oct int, bit uint8) (int, uint8) {
for i := uint8(0); i < 7; i++ {
out[oct] |= b >> i & 1 << bit
bit++
if bit == 8 {
oct++
bit = 0
}
}
return oct, bit
}
var oct int // current octet in pack7
var bit uint8 // current bit in octet
var b byte // current byte in raw7
for i := range raw7 {
b = raw7[i]
oct, bit = pack(pack7, b, oct, bit)
}
// N.B. in order to not confuse 7 zero-bits with @
// <CR> code is added to the packed bits.
if 8-bit == 7 {
oct, bit = pack(pack7, CR, oct, bit)
} else if bit == 0 && b == CR {
// and if data ends with <CR> on the octet boundary,
// then we add an additional octet with <CR>. See (3GPP TS 23.038).
pack7 = append(pack7, 0x00)
oct, bit = pack(pack7, CR, oct, bit)
}
return pack7
}
func unpack7Bit(pack7 []byte) []byte {
raw7 := make([]byte, 0, len(pack7))
var sep byte // current septet
var bit uint8 // current bit in septet
for _, oct := range pack7 {
for i := uint8(0); i < 8; i++ {
sep |= oct >> i & 1 << bit
bit++
if bit == 7 {
raw7 = append(raw7, sep)
sep = 0
bit = 0
}
}
}
if bytes.HasSuffix(raw7, crcr) || bytes.HasSuffix(raw7, cr) {
raw7 = raw7[:len(raw7)-1]
}
return raw7
}
func displayPack(buf []byte) (out string) {
for i := 0; i < len(buf)*8; i++ {
b := buf[i/8]
if i%8 == 0 {
out += fmt.Sprintf("\n%02X:", b)
}
off := 7 - uint8(i%8)
out += fmt.Sprintf("%4d", b>>off&1)
}
return out
}
type escape struct {
from byte
to rune
}
type escapeTable [0x0A]escape
func (et *escapeTable) to7Bit(r rune) byte {
for _, esc := range et {
if esc.to == r {
return esc.from
}
}
return byte(unknown)
}
func (et *escapeTable) from7Bit(b byte) rune {
for _, esc := range et {
if esc.from == b {
return esc.to
}
}
return unknown
}
var gsmEscapes = escapeTable{
{0x0A, 0x000C}, /* FORM FEED */
{0x14, 0x005E}, /* CIRCUMFLEX ACCENT */
{0x28, 0x007B}, /* LEFT CURLY BRACKET */
{0x29, 0x007D}, /* RIGHT CURLY BRACKET */
{0x2F, 0x005C}, /* REVERSE SOLIDUS */
{0x3C, 0x005B}, /* LEFT SQUARE BRACKET */
{0x3D, 0x007E}, /* TILDE */
{0x3E, 0x005D}, /* RIGHT SQUARE BRACKET */
{0x40, 0x007C}, /* VERTICAL LINE */
{0x65, 0x20AC}, /* EURO SIGN */
}
type runeTable [0x80]rune
func (rt *runeTable) Index(r rune) int {
for i := range rt {
if rt[i] == r {
return i
}
}
return -1
}
func (rt *runeTable) Rune(idx int) rune {
if idx >= 0 && idx < len(rt) {
return rt[idx]
}
return unknown
}
// Thanks, Jeroen @ Mobile Tidings
var gsmTable = runeTable{
/* 0x00 */ 0x0040, /* COMMERCIAL AT */
/* 0x01 */ 0x00A3, /* POUND SIGN */
/* 0x02 */ 0x0024, /* DOLLAR SIGN */
/* 0x03 */ 0x00A5, /* YEN SIGN */
/* 0x04 */ 0x00E8, /* LATIN SMALL LETTER E WITH GRAVE */
/* 0x05 */ 0x00E9, /* LATIN SMALL LETTER E WITH ACUTE */
/* 0x06 */ 0x00F9, /* LATIN SMALL LETTER U WITH GRAVE */
/* 0x07 */ 0x00EC, /* LATIN SMALL LETTER I WITH GRAVE */
/* 0x08 */ 0x00F2, /* LATIN SMALL LETTER O WITH GRAVE */
/* 0x09 */ 0x00E7, /* LATIN SMALL LETTER C WITH CEDILLA */
/* 0x0A */ 0x000A, /* LINE FEED */
/* 0x0B */ 0x00D8, /* LATIN CAPITAL LETTER O WITH STROKE */
/* 0x0C */ 0x00F8, /* LATIN SMALL LETTER O WITH STROKE */
/* 0x0D */ 0x000D, /* CARRIAGE RETURN */
/* 0x0E */ 0x00C5, /* LATIN CAPITAL LETTER A WITH RING ABOVE */
/* 0x0F */ 0x00E5, /* LATIN SMALL LETTER A WITH RING ABOVE */
/* 0x10 */ 0x0394, /* GREEK CAPITAL LETTER DELTA */
/* 0x11 */ 0x005F, /* LOW LINE */
/* 0x12 */ 0x03A6, /* GREEK CAPITAL LETTER PHI */
/* 0x13 */ 0x0393, /* GREEK CAPITAL LETTER GAMMA */
/* 0x14 */ 0x039B, /* GREEK CAPITAL LETTER LAMDA */
/* 0x15 */ 0x03A9, /* GREEK CAPITAL LETTER OMEGA */
/* 0x16 */ 0x03A0, /* GREEK CAPITAL LETTER PI */
/* 0x17 */ 0x03A8, /* GREEK CAPITAL LETTER PSI */
/* 0x18 */ 0x03A3, /* GREEK CAPITAL LETTER SIGMA */
/* 0x19 */ 0x0398, /* GREEK CAPITAL LETTER THETA */
/* 0x1A */ 0x039E, /* GREEK CAPITAL LETTER XI */
/* 0x1B */ 0x00A0, /* ESCAPE TO EXTENSION TABLE */
/* 0x1C */ 0x00C6, /* LATIN CAPITAL LETTER AE */
/* 0x1D */ 0x00E6, /* LATIN SMALL LETTER AE */
/* 0x1E */ 0x00DF, /* LATIN SMALL LETTER SHARP S (German) */
/* 0x1F */ 0x00C9, /* LATIN CAPITAL LETTER E WITH ACUTE */
/* 0x20 */ 0x0020, /* SPACE */
/* 0x21 */ 0x0021, /* EXCLAMATION MARK */
/* 0x22 */ 0x0022, /* QUOTATION MARK */
/* 0x23 */ 0x0023, /* NUMBER SIGN */
/* 0x24 */ 0x00A4, /* CURRENCY SIGN */
/* 0x25 */ 0x0025, /* PERCENT SIGN */
/* 0x26 */ 0x0026, /* AMPERSAND */
/* 0x27 */ 0x0027, /* APOSTROPHE */
/* 0x28 */ 0x0028, /* LEFT PARENTHESIS */
/* 0x29 */ 0x0029, /* RIGHT PARENTHESIS */
/* 0x2A */ 0x002A, /* ASTERISK */
/* 0x2B */ 0x002B, /* PLUS SIGN */
/* 0x2C */ 0x002C, /* COMMA */
/* 0x2D */ 0x002D, /* HYPHEN-MINUS */
/* 0x2E */ 0x002E, /* FULL STOP */
/* 0x2F */ 0x002F, /* SOLIDUS */
/* 0x30 */ 0x0030, /* DIGIT ZERO */
/* 0x31 */ 0x0031, /* DIGIT ONE */
/* 0x32 */ 0x0032, /* DIGIT TWO */
/* 0x33 */ 0x0033, /* DIGIT THREE */
/* 0x34 */ 0x0034, /* DIGIT FOUR */
/* 0x35 */ 0x0035, /* DIGIT FIVE */
/* 0x36 */ 0x0036, /* DIGIT SIX */
/* 0x37 */ 0x0037, /* DIGIT SEVEN */
/* 0x38 */ 0x0038, /* DIGIT EIGHT */
/* 0x39 */ 0x0039, /* DIGIT NINE */
/* 0x3A */ 0x003A, /* COLON */
/* 0x3B */ 0x003B, /* SEMICOLON */
/* 0x3C */ 0x003C, /* LESS-THAN SIGN */
/* 0x3D */ 0x003D, /* EQUALS SIGN */
/* 0x3E */ 0x003E, /* GREATER-THAN SIGN */
/* 0x3F */ 0x003F, /* QUESTION MARK */
/* 0x40 */ 0x00A1, /* INVERTED EXCLAMATION MARK */
/* 0x41 */ 0x0041, /* LATIN CAPITAL LETTER A */
/* 0x42 */ 0x0042, /* LATIN CAPITAL LETTER B */
/* 0x43 */ 0x0043, /* LATIN CAPITAL LETTER C */
/* 0x44 */ 0x0044, /* LATIN CAPITAL LETTER D */
/* 0x45 */ 0x0045, /* LATIN CAPITAL LETTER E */
/* 0x46 */ 0x0046, /* LATIN CAPITAL LETTER F */
/* 0x47 */ 0x0047, /* LATIN CAPITAL LETTER G */
/* 0x48 */ 0x0048, /* LATIN CAPITAL LETTER H */
/* 0x49 */ 0x0049, /* LATIN CAPITAL LETTER I */
/* 0x4A */ 0x004A, /* LATIN CAPITAL LETTER J */
/* 0x4B */ 0x004B, /* LATIN CAPITAL LETTER K */
/* 0x4C */ 0x004C, /* LATIN CAPITAL LETTER L */
/* 0x4D */ 0x004D, /* LATIN CAPITAL LETTER M */
/* 0x4E */ 0x004E, /* LATIN CAPITAL LETTER N */
/* 0x4F */ 0x004F, /* LATIN CAPITAL LETTER O */
/* 0x50 */ 0x0050, /* LATIN CAPITAL LETTER P */
/* 0x51 */ 0x0051, /* LATIN CAPITAL LETTER Q */
/* 0x52 */ 0x0052, /* LATIN CAPITAL LETTER R */
/* 0x53 */ 0x0053, /* LATIN CAPITAL LETTER S */
/* 0x54 */ 0x0054, /* LATIN CAPITAL LETTER T */
/* 0x55 */ 0x0055, /* LATIN CAPITAL LETTER U */
/* 0x56 */ 0x0056, /* LATIN CAPITAL LETTER V */
/* 0x57 */ 0x0057, /* LATIN CAPITAL LETTER W */
/* 0x58 */ 0x0058, /* LATIN CAPITAL LETTER X */
/* 0x59 */ 0x0059, /* LATIN CAPITAL LETTER Y */
/* 0x5A */ 0x005A, /* LATIN CAPITAL LETTER Z */
/* 0x5B */ 0x00C4, /* LATIN CAPITAL LETTER A WITH DIAERESIS */
/* 0x5C */ 0x00D6, /* LATIN CAPITAL LETTER O WITH DIAERESIS */
/* 0x5D */ 0x00D1, /* LATIN CAPITAL LETTER N WITH TILDE */
/* 0x5E */ 0x00DC, /* LATIN CAPITAL LETTER U WITH DIAERESIS */
/* 0x5F */ 0x00A7, /* SECTION SIGN */
/* 0x60 */ 0x00BF, /* INVERTED QUESTION MARK */
/* 0x61 */ 0x0061, /* LATIN SMALL LETTER A */
/* 0x62 */ 0x0062, /* LATIN SMALL LETTER B */
/* 0x63 */ 0x0063, /* LATIN SMALL LETTER C */
/* 0x64 */ 0x0064, /* LATIN SMALL LETTER D */
/* 0x65 */ 0x0065, /* LATIN SMALL LETTER E */
/* 0x66 */ 0x0066, /* LATIN SMALL LETTER F */
/* 0x67 */ 0x0067, /* LATIN SMALL LETTER G */
/* 0x68 */ 0x0068, /* LATIN SMALL LETTER H */
/* 0x69 */ 0x0069, /* LATIN SMALL LETTER I */
/* 0x6A */ 0x006A, /* LATIN SMALL LETTER J */
/* 0x6B */ 0x006B, /* LATIN SMALL LETTER K */
/* 0x6C */ 0x006C, /* LATIN SMALL LETTER L */
/* 0x6D */ 0x006D, /* LATIN SMALL LETTER M */
/* 0x6E */ 0x006E, /* LATIN SMALL LETTER N */
/* 0x6F */ 0x006F, /* LATIN SMALL LETTER O */
/* 0x70 */ 0x0070, /* LATIN SMALL LETTER P */
/* 0x71 */ 0x0071, /* LATIN SMALL LETTER Q */
/* 0x72 */ 0x0072, /* LATIN SMALL LETTER R */
/* 0x73 */ 0x0073, /* LATIN SMALL LETTER S */
/* 0x74 */ 0x0074, /* LATIN SMALL LETTER T */
/* 0x75 */ 0x0075, /* LATIN SMALL LETTER U */
/* 0x76 */ 0x0076, /* LATIN SMALL LETTER V */
/* 0x77 */ 0x0077, /* LATIN SMALL LETTER W */
/* 0x78 */ 0x0078, /* LATIN SMALL LETTER X */
/* 0x79 */ 0x0079, /* LATIN SMALL LETTER Y */
/* 0x7A */ 0x007A, /* LATIN SMALL LETTER Z */
/* 0x7B */ 0x00E4, /* LATIN SMALL LETTER A WITH DIAERESIS */
/* 0x7C */ 0x00F6, /* LATIN SMALL LETTER O WITH DIAERESIS */
/* 0x7D */ 0x00F1, /* LATIN SMALL LETTER N WITH TILDE */
/* 0x7E */ 0x00FC, /* LATIN SMALL LETTER U WITH DIAERESIS */
/* 0x7F */ 0x00E0, /* LATIN SMALL LETTER A WITH GRAVE */
}