@aokiapp/tlv/dist/parser/basic-parser.js

Tag-Length-Value (TLV) parser and builder library with schema support. Provides both parsing and building APIs as submodules.

import { TagClass } from "../common/types.js";
export class BasicTLVParser {
    /**
     * Parse a buffer containing a single TLV structure.
     * @param buffer - The TLV data buffer to parse.
     * @returns The parsed result including tag, length, and value.
     */
    static parse(buffer) {
        const view = new DataView(buffer);
        let offset = 0;
        const tagInfo = this.readTagInfo(view, offset);
        offset = tagInfo.newOffset;
        const lengthInfo = this.readLength(view, offset);
        offset = lengthInfo.newOffset;
        const valueInfo = this.readValue(buffer, offset, lengthInfo.length);
        offset = valueInfo.newOffset;
        return {
            tag: tagInfo.tag,
            length: lengthInfo.length,
            value: valueInfo.value,
            endOffset: offset,
        };
    }
    /**
     * Read the tag portion from the DataView and update the offset.
     * @param view - The DataView representing the TLV buffer.
     * @param offset - The current read position within the buffer.
     * @returns An object containing the parsed tag information and the new offset.
     */
    static readTagInfo(view, offset) {
        const firstByte = view.getUint8(offset++);
        const tagClassBits = (firstByte & 0xc0) >> 6;
        const tagClass = this.getTagClass(tagClassBits);
        const isConstructed = !!(firstByte & 0x20);
        let tagNumber = firstByte & 0x1f;
        if (tagNumber === 0x1f) {
            tagNumber = 0;
            let b;
            do {
                b = view.getUint8(offset++);
                tagNumber = (tagNumber << 7) | (b & 0x7f);
            } while (b & 0x80);
        }
        return {
            tag: { tagClass, constructed: isConstructed, tagNumber },
            newOffset: offset,
        };
    }
    /**
     * Convert tag class bits into a TagClass enum value.
     * @param {number} bits - The bits extracted from the tag byte.
     * @returns {TagClass} The corresponding TagClass.
     */
    static getTagClass(bits) {
        switch (bits) {
            case 0:
                return TagClass.Universal;
            case 1:
                return TagClass.Application;
            case 2:
                return TagClass.ContextSpecific;
            case 3:
                return TagClass.Private;
        }
        throw new Error("Invalid tag class");
    }
    /**
     * Read the length portion from the DataView and update the offset.
     * @param view - The DataView representing the TLV buffer.
     * @param offset - The current read position within the buffer.
     * @returns An object containing the parsed length and the new offset.
     */
    static readLength(view, offset) {
        let length = view.getUint8(offset++);
        if (length & 0x80) {
            const numBytes = length & 0x7f;
            length = 0;
            for (let i = 0; i < numBytes; i++) {
                length = (length << 8) | view.getUint8(offset++);
            }
        }
        return { length, newOffset: offset };
    }
    /**
     * Read the value portion from the buffer based on the specified length.
     * @param buffer - The original TLV data buffer.
     * @param offset - The current read position within the buffer.
     * @param length - The length of the TLV value.
     * @returns An object containing the raw value slice and the new offset.
     */
    static readValue(buffer, offset, length) {
        const value = buffer.slice(offset, offset + length);
        return { value, newOffset: offset + length };
    }
}