iso_8583_exos/lib/unpack/unpack_0_127.js

A javascript library for messaging in iso 8583 messaging format by Roy Salgado.

const T = require('../tools');
const formats = require('../formats');
const cptable = require('exos_codepage');

/**
 * Unpack fields 0-127 from an ISO 8583 encoded string into a JSON
 * @method unpack_0_127
 * @memberof module:Message-UnPackage
 */
module.exports = function (incoming, isoJSON, config, encoding) {
  if (Buffer.isBuffer(incoming)) {
    let ASCII = "ASCII";

    let mti = encoding === ASCII
      ? new Buffer.from(incoming.slice(0, 4), 'utf8')
      : new Buffer.from(cptable.utils.decode(500, incoming.slice(0, 4)), 'utf8');

    mti = mti.toString('utf8');
    isoJSON['0'] = mti;

    if (!this._checkMTI(mti)) {
      return T.toErrorObject('failed to unpack at get mti');
    }

    let bitmapEnd;

    // Does data contain a secondary bitmap?
    const secondaryBitmap = this.hasSecondaryBitmap(
      incoming.slice(4, 8),
      config
    );
    if (secondaryBitmap === false) bitmapEnd = 12;
    else bitmapEnd = 20;

    if (config.bitmapEncoding === 'utf8') bitmapEnd = 36;

    const slice = incoming
      .slice(4, bitmapEnd)
      .toString(config.bitmapEncoding || 'hex');
    const bitmap = T.getHex(slice)
      .split('')
      .map(Number);

    let thisBuff = incoming.slice(bitmapEnd, incoming.byteLength);
    for (let i = 1; i < bitmap.length; i++) {
      if (bitmap[i] === 1) {
        //format defined
        let field = i + 1;
        let this_format = this.formats[field] || formats[field];
        if (field === 127) {
          let get127Exts = this.unpack_127_1_63(thisBuff, isoJSON);
          if (get127Exts.error) {
            return get127Exts;
          } else {
            isoJSON = get127Exts.json;
            thisBuff = get127Exts.remSlice;
            continue;
          }
        }
        if (this_format) {
          if (this_format.LenType === 'fixed') {
            if (this_format.ContentType === 'b') {
              isoJSON[field] = thisBuff
                .slice(0, this_format.MaxLen / 2)
                .toString('hex');
              thisBuff = thisBuff.slice(
                this_format.MaxLen / 2,
                thisBuff.byteLength
              );
            } else {
              let dataOfField = encoding === ASCII
                ? new Buffer.from(thisBuff.slice(0, this_format.MaxLen), 'utf8')
                : new Buffer.from(cptable.utils.decode(500, thisBuff.slice(0, this_format.MaxLen)), 'utf8');


              isoJSON[field] = dataOfField.toString('utf8');
              thisBuff = thisBuff.slice(
                this_format.MaxLen,
                thisBuff.byteLength
              );
            }
          } else {
            let thisLen = T.getLenType(this_format.LenType);
            if (!this_format.MaxLen)
              return T.toErrorObject([
                'max length not implemented for ',
                this_format.LenType,
                field
              ]);
            if (
              this.Msg[field] &&
              this.Msg[field].length > this_format.MaxLen
            ) {
              return T.toErrorObject([
                'invalid length of data on field ',
                field
              ]);
            }
            if (thisLen === 0) {
              return T.toErrorObject([
                'field ',
                field,
                ' format not implemented'
              ]);
            } else {

              let len = encoding === ASCII
                ? new Buffer.from(thisBuff.slice(0, thisLen), 'utf8')
                : new Buffer.from(cptable.utils.decode(500, thisBuff.slice(0, thisLen)), 'utf8');

              len = len.toString();
              thisBuff = thisBuff.slice(thisLen, thisBuff.byteLength);

              if (this_format.ContentType === 'b') {

                let binaryData = thisBuff.slice(0, len);
                isoJSON[field] = binaryData.toString('hex');

                thisBuff = thisBuff.slice(
                  len,
                  thisBuff.byteLength
                );
              } else {
                let dataOfField = encoding === ASCII
                ? new Buffer.from(thisBuff.slice(0, Number(len)), 'utf8')
                : new Buffer.from(cptable.utils.decode(500, thisBuff.slice(0, Number(len))), 'utf8');

                isoJSON[field] = dataOfField.toString();
                thisBuff = thisBuff.slice(Number(len), thisBuff.byteLength);
              }


            }
          }
        } else
          return T.toErrorObject(['field ', field, ' format not implemented']);
      }
    }

    return {
      json: isoJSON,
      remSlice: thisBuff
    };
  } else return T.toErrorObject(['expecting buffer but got ', typeof incoming]);
};