@li0ard/tinytlv/dist/index.js

Tiny TLV decoder and encoder

import { adjustTag, adjustValue, bytesToHex, getBufferLength, hexToBytes } from "./utils.js";
/** TLV class */
export class TLV {
    /** Tag (as hex) */
    tag;
    /** Length */
    length;
    /** Value (as hex) */
    value;
    /** Value (as Uint8Array) */
    byteValue;
    /** Childs */
    childs;
    /** Parent object */
    parent = null;
    /** Is constructed or primitive? */
    isConstructed;
    /** Combined length of tag, length and value field */
    size;
    /**
     * Initialize TLV object
     * @param tag Tag
     * @param value Value
     * @example new TLV('84', '325041592E5359532E4444463031');
     */
    constructor(tag, value) {
        this.tag = adjustTag(tag);
        this.value = adjustValue(value);
        this.length = this.value.length / 2;
        this.byteValue = hexToBytes(this.value);
        this.childs = [];
        const bTag = hexToBytes(this.tag);
        this.size = bTag.length + getBufferLength(this.length).length + this.byteValue.length;
        if ((bTag[0] & 0x20) === 0x00)
            this.isConstructed = false;
        else
            this.isConstructed = true;
        let offset = 0;
        if (this.isConstructed) {
            while (offset < this.length) {
                let child = TLV.parse(this.byteValue.slice(offset));
                child.parent = this;
                offset += child.size;
                this.childs.push(child);
            }
        }
    }
    /**
     * Encode TLV as string
     * @returns {string}
     */
    toString() {
        return `${this.tag}${bytesToHex(getBufferLength(this.length))}${this.value}`.toLowerCase();
    }
    /**
     * Encode TLV as Uint8Array
     * @returns {Uint8Array}
     */
    toBytes() {
        return hexToBytes(`${this.tag}${bytesToHex(getBufferLength(this.length))}${this.value}`);
    }
    /**
     * Find `tag` in childs of main object
     * @param tag Tag to find
     * @returns {TLV | undefined}
     */
    find(tag) {
        const upperTAG = adjustTag(tag);
        for (let child of this.childs) {
            if (child.tag === upperTAG)
                return child;
            if (child.isConstructed) {
                const tlv = child.find(tag);
                if (tlv !== undefined)
                    return tlv;
            }
        }
    }
    /**
     * Find all `tag`'s in childs of main object
     * @param tag Tag to find
     * @returns {TLV[]}
     */
    findAll(tag) {
        const upperTAG = adjustTag(tag);
        let results = [];
        for (let child of this.childs) {
            if (child.tag === upperTAG)
                results.push(child);
            if (child.isConstructed) {
                const tlv = child.findAll(tag);
                if (tlv.length !== 0)
                    results = results.concat(tlv);
            }
        }
        return results;
    }
    /**
     * Parse TLV from string or Uint8Array
     * @param data Data to parse
     * @returns {TLV}
     */
    static parse(data) {
        let buf;
        if (typeof data === 'string')
            buf = hexToBytes(data);
        else
            buf = data;
        let tag;
        let tagLength = 1;
        let length;
        let byteLength;
        if ((buf[0] & 0x1f) === 0x1f) {
            let idx = 1;
            do {
                tagLength++;
                if (idx > 4)
                    throw Error("Invalid tag length");
            } while ((buf[idx++] & 0x80) === 0x80);
        }
        tag = bytesToHex(buf.slice(0, tagLength));
        let lenOffset = tagLength;
        if ((buf[lenOffset] & 0x80) === 0x80)
            byteLength = (buf[lenOffset] & 0x7f) + 1;
        else
            byteLength = 1;
        if (byteLength === 1)
            length = buf[lenOffset];
        else if (byteLength === 2)
            length = buf[lenOffset + 1];
        else if (byteLength === 3)
            length = (buf[lenOffset + 1] << 8) | buf[lenOffset + 2];
        else if (byteLength === 4)
            length = (buf[lenOffset + 1] << 16) | (buf[lenOffset + 2] << 8) | buf[lenOffset + 3];
        else if (byteLength === 5)
            length = (buf[lenOffset + 1] << 24) | (buf[lenOffset + 2] << 16) | (buf[lenOffset + 3] << 8) | buf[lenOffset + 4];
        else
            throw Error("Invalid length: " + byteLength);
        return new TLV(tag, buf.slice(tagLength + byteLength, tagLength + byteLength + length));
    }
}