当我编码/解码SMS PDU(GSM 7位)的用户数据,是否需要第一预先设置UDH?(When I

2019-07-30 10:15发布

虽然我可以成功地进行编码和解码的SMS消息的用户数据部分时,UDH 存在时,我无法这样做时,UDH 存在 (在这种情况下,连锁信息)。

当我解码或编码的用户数据,我需要在这样做之前预先设置UDH的文字?

本文提供了用于补偿与填充比特的UDH(我仍然不完全理解)的编码常规样品,但它不给出被传递给该例程的数据的一例,所以我不具有明确的用例(我不能在网站上找到的解码样本): http://mobiletidings.com/2009/07/06/how-to-pack-gsm7-into-septets/ 。

到目前为止,我已经能够得到一些结果,如果我解码之前预先考虑UDH用户数据,但我怀疑这只是一个巧合。

作为一个实例(使用值从https://en.wikipedia.org/wiki/Concatenated_SMS ):

UDH := '050003000302';
ENCODED_USER_DATA_PART := 'D06536FB0DBABFE56C32'; // with padding, evidently
DecodedUserData := Decode7Bit(UDH + ENCODED_USER_DATA_PART);
Writeln(DecodedUserData);

输出: “SS @ø¿Æ@hello世界”

EncodedUserData := Encode7Bit(DecodedUserData);
DecodedUserData := Decode7Bit(EncodedEncodedUserData);
Writeln(DecodedUserData);

相同的输出:“SS @ø¿Æ@hello世界”

如果没有前面加上UDH我得到的垃圾:

DecodedUserData := Decode7Bit(ENCODED_USER_DATA_PART);
Writeln(DecodedUserData);

输出: “PKYY§An§eYI”

什么是处理这个正确的方式?

我应该包括与用户数据进行编码时的文字UDH?

我应该解码后剥去乱码,或者是I(如我怀疑)完全脱落碱与这种假设?

虽然解码算法在这里似乎没有UDH工作似乎没有任何UDH信息考虑: 寻找GSM 7位编码/解码算法 。

我会永远感激,如果有人可以把我直接就进行正确的方法。 任何明显的例子/码样本将是非常赞赏。 ;-)

我也将提供包括算法,如果有人认为这将有助于解开这个谜,一个小样本应用程序。

编辑1:

我使用的是德尔福XE2更新4修补程序1

编辑2:

由于从@whosrdaddy帮助,我是能够成功地让我的编码/解码程序工作。

作为一个方面说明,我很好奇,为什么需要的用户数据是7位的边界上时,UDH不使用它编码的,而是从ETSI规范的段落中的最后一句被引用@whosrdaddy回答:

如果使用7位数据和TP-UD-头并不一个七重峰边界上完成然后填充比特的最后一个信息单元的数据八位字节之后插入,使得有七重峰整个TP-UD头的整数倍。 这是为了确保该SM本身八位字节边界开始的,使得较早的相位移动将是能够显示SM本身虽然TP-UD头在TP-UD字段可能不被理解

我的代码是基于对来自以下资源部分实例:

寻找GSM 7位编码/解码算法

https://en.wikipedia.org/wiki/Concatenated_SMS

http://mobiletidings.com/2009/02/18/combining-sms-messages/

http://mobiletidings.com/2009/07/06/how-to-pack-gsm7-into-septets/

http://mobileforensics.files.wordpress.com/2007/06/understanding_sms.pdf

http://www.dreamfabric.com/sms/

http://www.mediaburst.co.uk/blog/concatenated-sms/

下面是为别人谁是有麻烦的短信编码/解码的代码。 我敢肯定,它可以简化/优化(和意见,欢迎),但我已经与几个不同的排列和UDH头部长度成功进行了测试。 我希望它能帮助。

unit SmsUtils;

interface

uses Windows, Classes, Math;

function Encode7Bit(const AText: string; AUdhLen: Byte;
  out ATextLen: Byte): string;

function Decode7Bit(const APduData: string; AUdhLen: Integer): string;

implementation

var
  g7BitToAsciiTable: array [0 .. 127] of Byte;
  gAsciiTo7BitTable: array [0 .. 255] of Byte;

procedure InitializeTables;
var
  AsciiValue: Integer;
  i: Integer;
begin
  // create 7-bit to ascii table
  g7BitToAsciiTable[0] := 64; // @
  g7BitToAsciiTable[1] := 163;
  g7BitToAsciiTable[2] := 36;
  g7BitToAsciiTable[3] := 165;
  g7BitToAsciiTable[4] := 232;
  g7BitToAsciiTable[5] := 223;
  g7BitToAsciiTable[6] := 249;
  g7BitToAsciiTable[7] := 236;
  g7BitToAsciiTable[8] := 242;
  g7BitToAsciiTable[9] := 199;
  g7BitToAsciiTable[10] := 10;
  g7BitToAsciiTable[11] := 216;
  g7BitToAsciiTable[12] := 248;
  g7BitToAsciiTable[13] := 13;
  g7BitToAsciiTable[14] := 197;
  g7BitToAsciiTable[15] := 229;
  g7BitToAsciiTable[16] := 0;
  g7BitToAsciiTable[17] := 95;
  g7BitToAsciiTable[18] := 0;
  g7BitToAsciiTable[19] := 0;
  g7BitToAsciiTable[20] := 0;
  g7BitToAsciiTable[21] := 0;
  g7BitToAsciiTable[22] := 0;
  g7BitToAsciiTable[23] := 0;
  g7BitToAsciiTable[24] := 0;
  g7BitToAsciiTable[25] := 0;
  g7BitToAsciiTable[26] := 0;
  g7BitToAsciiTable[27] := 0;
  g7BitToAsciiTable[28] := 198;
  g7BitToAsciiTable[29] := 230;
  g7BitToAsciiTable[30] := 223;
  g7BitToAsciiTable[31] := 201;
  g7BitToAsciiTable[32] := 32;
  g7BitToAsciiTable[33] := 33;
  g7BitToAsciiTable[34] := 34;
  g7BitToAsciiTable[35] := 35;
  g7BitToAsciiTable[36] := 164;
  g7BitToAsciiTable[37] := 37;
  g7BitToAsciiTable[38] := 38;
  g7BitToAsciiTable[39] := 39;
  g7BitToAsciiTable[40] := 40;
  g7BitToAsciiTable[41] := 41;
  g7BitToAsciiTable[42] := 42;
  g7BitToAsciiTable[43] := 43;
  g7BitToAsciiTable[44] := 44;
  g7BitToAsciiTable[45] := 45;
  g7BitToAsciiTable[46] := 46;
  g7BitToAsciiTable[47] := 47;
  g7BitToAsciiTable[48] := 48;
  g7BitToAsciiTable[49] := 49;
  g7BitToAsciiTable[50] := 50;
  g7BitToAsciiTable[51] := 51;
  g7BitToAsciiTable[52] := 52;
  g7BitToAsciiTable[53] := 53;
  g7BitToAsciiTable[54] := 54;
  g7BitToAsciiTable[55] := 55;
  g7BitToAsciiTable[56] := 56;
  g7BitToAsciiTable[57] := 57;
  g7BitToAsciiTable[58] := 58;
  g7BitToAsciiTable[59] := 59;
  g7BitToAsciiTable[60] := 60;
  g7BitToAsciiTable[61] := 61;
  g7BitToAsciiTable[62] := 62;
  g7BitToAsciiTable[63] := 63;
  g7BitToAsciiTable[64] := 161;
  g7BitToAsciiTable[65] := 65;
  g7BitToAsciiTable[66] := 66;
  g7BitToAsciiTable[67] := 67;
  g7BitToAsciiTable[68] := 68;
  g7BitToAsciiTable[69] := 69;
  g7BitToAsciiTable[70] := 70;
  g7BitToAsciiTable[71] := 71;
  g7BitToAsciiTable[72] := 72;
  g7BitToAsciiTable[73] := 73;
  g7BitToAsciiTable[74] := 74;
  g7BitToAsciiTable[75] := 75;
  g7BitToAsciiTable[76] := 76;
  g7BitToAsciiTable[77] := 77;
  g7BitToAsciiTable[78] := 78;
  g7BitToAsciiTable[79] := 79;
  g7BitToAsciiTable[80] := 80;
  g7BitToAsciiTable[81] := 81;
  g7BitToAsciiTable[82] := 82;
  g7BitToAsciiTable[83] := 83;
  g7BitToAsciiTable[84] := 84;
  g7BitToAsciiTable[85] := 85;
  g7BitToAsciiTable[86] := 86;
  g7BitToAsciiTable[87] := 87;
  g7BitToAsciiTable[88] := 88;
  g7BitToAsciiTable[89] := 89;
  g7BitToAsciiTable[90] := 90;
  g7BitToAsciiTable[91] := 196;
  g7BitToAsciiTable[92] := 204;
  g7BitToAsciiTable[93] := 209;
  g7BitToAsciiTable[94] := 220;
  g7BitToAsciiTable[95] := 167;
  g7BitToAsciiTable[96] := 191;
  g7BitToAsciiTable[97] := 97;
  g7BitToAsciiTable[98] := 98;
  g7BitToAsciiTable[99] := 99;
  g7BitToAsciiTable[100] := 100;
  g7BitToAsciiTable[101] := 101;
  g7BitToAsciiTable[102] := 102;
  g7BitToAsciiTable[103] := 103;
  g7BitToAsciiTable[104] := 104;
  g7BitToAsciiTable[105] := 105;
  g7BitToAsciiTable[106] := 106;
  g7BitToAsciiTable[107] := 107;
  g7BitToAsciiTable[108] := 108;
  g7BitToAsciiTable[109] := 109;
  g7BitToAsciiTable[110] := 110;
  g7BitToAsciiTable[111] := 111;
  g7BitToAsciiTable[112] := 112;
  g7BitToAsciiTable[113] := 113;
  g7BitToAsciiTable[114] := 114;
  g7BitToAsciiTable[115] := 115;
  g7BitToAsciiTable[116] := 116;
  g7BitToAsciiTable[117] := 117;
  g7BitToAsciiTable[118] := 118;
  g7BitToAsciiTable[119] := 119;
  g7BitToAsciiTable[120] := 120;
  g7BitToAsciiTable[121] := 121;
  g7BitToAsciiTable[122] := 122;
  g7BitToAsciiTable[123] := 228;
  g7BitToAsciiTable[124] := 246;
  g7BitToAsciiTable[125] := 241;
  g7BitToAsciiTable[126] := 252;
  g7BitToAsciiTable[127] := 224;

  // create ascii to 7-bit table
  ZeroMemory(@gAsciiTo7BitTable, SizeOf(gAsciiTo7BitTable));
  for i := 0 to High(g7BitToAsciiTable) do
  begin
    AsciiValue := g7BitToAsciiTable[i];
    gAsciiTo7BitTable[AsciiValue] := i;
  end;
end;

function ConvertAsciiTo7Bit(const AText: string; AUdhLen: Byte): AnsiString;
const
  ESC = #27;
  ESCAPED_ASCII_CODES = [#94, #123, #125, #92, #91, #126, #93, #124, #164];
var
  Septet: Byte;
  Ch: AnsiChar;
  i: Integer;
begin
  for i := 1 to Length(AText) do
  begin
    Ch := AnsiChar(AText[i]);
    if not(Ch in ESCAPED_ASCII_CODES) then
      Septet := gAsciiTo7BitTable[Byte(Ch)]
    else
    begin
      Result := Result + ESC;
      case (Ch) of
        #12: Septet := 10;
        #94: Septet := 20;
        #123: Septet := 40;
        #125: Septet := 41;
        #92: Septet := 47;
        #91: Septet := 60;
        #126: Septet := 61;
        #93: Septet := 62;
        #124: Septet := 64;
        #164: Septet := 101;
      else Septet := 0;
      end;
    end;
    Result := Result + AnsiChar(Septet);
  end;
end;

function Convert7BitToAscii(const AText: AnsiString): string;
const
  ESC = #27;
var
  TextLen: Integer;
  Ch: Char;
  i: Integer;
begin
  Result := '';
  TextLen := Length(AText);
  i := 1;
  while (i <= TextLen) do
  begin
    Ch := Char(AText[i]);
    if (Ch <> ESC) then
      Result := Result + Char(g7BitToAsciiTable[Ord(Ch)])
    else
    begin
      Inc(i); // skip ESC
      if (i <= TextLen) then
      begin
        Ch := Char(AText[i]);
        case (Ch) of
          #10: Ch := #12;
          #20: Ch := #94;
          #40: Ch := #123;
          #41: Ch := #125;
          #47: Ch := #92;
          #60: Ch := #91;
          #61: Ch := #126;
          #62: Ch := #93;
          #64: Ch := #124;
          #101: Ch := #164;
        end;
        Result := Result + Ch;
      end;
    end;
    Inc(i);
  end;
end;

function StrToHex(const AText: AnsiString): AnsiString; overload;
var
  TextLen: Integer;
begin
  // set the text buffer size
  TextLen := Length(AText);
  // set the length of the result to double the string length
  SetLength(Result, TextLen * 2);
  // convert the string to hex
  BinToHex(PAnsiChar(AText), PAnsiChar(Result), TextLen);
end;

function StrToHex(const AText: string): string; overload;
begin
  Result := string(StrToHex(AnsiString(AText)));
end;

function HexToStr(const AText: AnsiString): AnsiString; overload;
var
  ResultLen: Integer;
begin
  // set the length of the result to half the Text length
  ResultLen := Length(AText) div 2;
  SetLength(Result, ResultLen);
  // convert the hex back into a string
  if (HexToBin(PAnsiChar(AText), PAnsiChar(Result), ResultLen) <> ResultLen) then
    Result := 'Error Converting Hex To String: ' + AText;
end;

function HexToStr(const AText: string): string; overload;
begin
  Result := string(HexToStr(AnsiString(AText)));
end;

function Encode7Bit(const AText: string; AUdhLen: Byte;
  out ATextLen: Byte): string;
// AText: Ascii text
// AUdhLen: Length of UDH including UDH Len byte (e.g. '050003CC0101' = 6 bytes)
// ATextLen: returns length of text that was encoded.  This can be different
// than Length(AText) due to escape characters
// Returns text as encoded PDU hex string
var
  Text7Bit: AnsiString;
  Pdu: AnsiString;
  PduIdx: Integer;
  PduLen: Byte;
  PaddingBits: Byte;
  BitsToMove: Byte;
  Septet: Byte;
  Octet: Byte;
  PrevOctet: Byte;
  ShiftedOctet: Byte;
  i: Integer;
begin
  Result := '';
  Text7Bit := ConvertAsciiTo7Bit(AText, AUdhLen);
  ATextLen := Length(Text7Bit);
  BitsToMove := 0;
  // determine how many padding bits needed based on the UDH
  if (AUdhLen > 0) then
    PaddingBits := 7 - ((AUdhLen * 8) mod 7)
  else
    PaddingBits := 0;
  // calculate the number of bytes needed to store the 7-bit text
  // along with any padding bits that are required
  PduLen := Ceil(((ATextLen * 7) + PaddingBits) / 8);
  // reserve space for the PDU bytes
  Pdu := AnsiString(StringOfChar(#0, PduLen));
  PduIdx := 1;
  for i := 1 to ATextLen do
  begin
    if (BitsToMove = 7) then
      BitsToMove := 0
    else
    begin
      // convert the current character to a septet (7-bits) and make room for
      // the bits from the next one
      Septet := (Byte(Text7Bit[i]) shr BitsToMove);
      if (i = ATextLen) then
        Octet := Septet
      else
      begin
        // convert the next character to a septet and copy the bits from it
        // to the octet (PDU byte)
        Octet := Septet or
          Byte((Byte(Text7Bit[i + 1]) shl Byte(7 - BitsToMove)));
      end;
      Byte(Pdu[PduIdx]) := Octet;
      Inc(PduIdx);
      Inc(BitsToMove);
    end;
  end;
  // The following code pads the pdu on the *right* by shifting it to the *left*
  // by <PaddingBits>. It does this by using the same bit storage convention as
  // the 7-bit compression routine above, by taking the most significant
  // <PaddingBits> from each PDU byte and moving them to the least significant
  // bits of the next PDU byte. If there is no room in the last PDU byte for the
  // high bits of the previous byte that were removed, then those bits are
  // placed into an additional byte reserved for this purpose.
  // Note: <PduLen> has already been set to account for the reserved byte if
  // it is required.
  if (PaddingBits > 0) then
  begin
    SetLength(Result, (PduLen * 2));
    PrevOctet := 0;
    for PduIdx := 1 to PduLen do
    begin
      Octet := Byte(Pdu[PduIdx]);
      if (PduIdx = 1) then
        ShiftedOctet := Byte(Octet shl PaddingBits)
      else
        ShiftedOctet := Byte(Octet shl PaddingBits) or
          Byte(PrevOctet shr (8 - PaddingBits));
      Byte(Pdu[PduIdx]) := ShiftedOctet;
      PrevOctet := Octet;
    end;
  end;
  Result := string(StrToHex(Pdu));
end;

function Decode7Bit(const APduData: string; AUdhLen: Integer): string;
// APduData: Hex string representation of PDU data
// AUdhLen: Length of UDH including UDH Len (e.g. '050003CC0101' = 6 bytes)
// Returns decoded Ascii text
var
  Pdu: AnsiString;
  NumSeptets: Byte;
  Septets: AnsiString;
  PduIdx: Integer;
  PduLen: Integer;
  by: Byte;
  currBy: Byte;
  left: Byte;
  mask: Byte;
  nextBy: Byte;
  Octet: Byte;
  NextOctet: Byte;
  PaddingBits: Byte;
  ShiftedOctet: Byte;
  i: Integer;
begin
  Result := '';
  PaddingBits := 0;
  // convert hex string to bytes
  Pdu := AnsiString(HexToStr(APduData));
  PduLen := Length(Pdu);
  // The following code removes padding at the end of the PDU by shifting it
  // *right* by <PaddingBits>. It does this by taking the least significant
  // <PaddingBits> from the following PDU byte and moving them to the most
  // significant the current PDU byte.
  if (AUdhLen > 0) then
  begin
    PaddingBits := 7 - ((AUdhLen * 8) mod 7);
    for PduIdx := 1 to PduLen do
    begin
      Octet := Byte(Pdu[PduIdx]);
      if (PduIdx = PduLen) then
        ShiftedOctet := Byte(Octet shr PaddingBits)
      else
      begin
        NextOctet := Byte(Pdu[PduIdx + 1]);
        ShiftedOctet := Byte(Octet shr PaddingBits) or
          Byte(NextOctet shl (8 - PaddingBits));
      end;
      Byte(Pdu[PduIdx]) := ShiftedOctet;
    end;
  end;
  // decode
  // number of septets in PDU after excluding the padding bits
  NumSeptets := ((PduLen * 8) - PaddingBits) div 7;
  Septets := AnsiString(StringOfChar(#0, NumSeptets));
  left := 7;
  mask := $7F;
  nextBy := 0;
  PduIdx := 1;
  for i := 1 to NumSeptets do
  begin
    if mask = 0 then
    begin
      Septets[i] := AnsiChar(nextBy);
      left := 7;
      mask := $7F;
      nextBy := 0;
    end
    else
    begin
      if (PduIdx > PduLen) then
        Break;
      by := Byte(Pdu[PduIdx]);
      Inc(PduIdx);
      currBy := ((by AND mask) SHL (7 - left)) OR nextBy;
      nextBy := (by AND (NOT mask)) SHR left;
      Septets[i] := AnsiChar(currBy);
      mask := mask SHR 1;
      left := left - 1;
    end;
  end; // for
  // remove last character if unused
  // this is kind of a hack, but frankly I don't know how else to compensate
  // for it.
  if (Septets[NumSeptets] = #0) then
    SetLength(Septets, NumSeptets - 1);
  // convert 7-bit alphabet to ascii
  Result := Convert7BitToAscii(Septets);
end;

initialization
  InitializeTables;
end.

Answer 1:

不,你不进行编码时包括UDH部分,但是你如果读GSM阶段2规范的第57页上,他们提到这样一个事实:“如果使用7位数据和TP-UD-头不上七重峰完成边界然后填充比特的最后一个信息单元的数据八位字节之后插入,使得有七重峰整个TP-UD头的整数倍”。 当你包括UDH部分,这可能并非如此,因此,所有你需要做的就是计算偏移(填充比特=号)

计算偏移,这个代码假定UDHPart是AnsiString类型:

Len := Length(UDHPart) shr 1;
Offset := 7 - ((Len * 8) mod 7);  // fill bits

现在编码7位数据时,则正常进行,但在结束时,你却将数据偏移位到左侧,该代码具有可变结果(AnsiString类型)的编码数据:

 // fill bits
 if Offset > 0 then
  begin
   v := Result;
   Len := Length(v);
   BytesRemain := ceil(((Len * 7)+Offset) / 8);       
   Result := StringOfChar(#0, BytesRemain);
   for InPos := 1 to BytesRemain do
    begin
     if InPos = 1 then
      Byte(Result[InPos]) := Byte(v[InPos]) shl offset
     else
      Byte(Result[InPos]) := (Byte(v[InPos]) shl offset) or (Byte(v[InPos-1]) shr (8 - offset));
    end;
  end;

解码是同样的事情真的,你第一次转移的解码前7个数据位偏移到右侧...

我希望这将设置你到正确的轨道......



Answer 2:

在你的情况的数据D06536FB0DBABFE56C32

得到第一个字符是D0 => H(在第一7位,第8位不能使用)

其余的是6536FB0DBABFE56C32

在上午

(01100101)0011011011111011000011011011101010111111111001010110110000110010

移位从右到左。 =>每个右7位是char!

001100100110110011100101101111111011101000001101111 1101100 110110(0 1100101)

我转向7左侧。 你可以从上面得到的字符串。 但我容易做显示:d

(1100101)(1101100)(1101100)(1101111)(0100000)(1110111)(1101111)(1110010)(1101100)(1100100)00

和字符串为“世界ELLO”

与第一个字符相结合你的“Hello World”



文章来源: When I encode/decode SMS PDU (GSM 7 Bit) user data, do I need prepend the UDH first?