Some Node utility functions for aggregating byte information about Buffers

buffer-utils.ts

const enum UTF8_STATUS {
    ACCEPT = 0,
    REJECT = 1
}

export interface MyBufAggs {
    allNonNull: boolean;
    allAsciiChar: boolean;
    all7Bit: boolean;
    validUtf8: boolean;
}

// From https://stackoverflow.com/questions/1031645/how-to-detect-utf-8-in-plain-c
const utf8d = Buffer.from([
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 00..1f
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 20..3f
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 40..5f
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 60..7f
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, // 80..9f
    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, // a0..bf
    8, 8, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // c0..df
    0xa, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x4, 0x3, 0x3, // e0..ef
    0xb, 0x6, 0x6, 0x6, 0x5, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, // f0..ff
    0x0, 0x1, 0x2, 0x3, 0x5, 0x8, 0x7, 0x1, 0x1, 0x1, 0x4, 0x6, 0x1, 0x1, 0x1, 0x1, // s0..s0
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, // s1..s2
    1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, // s3..s4
    1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, // s5..s6
    1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // s7..s8
]);

export function checkStringBuf(b: Buffer): MyBufAggs {
    let utf8State = UTF8_STATUS.ACCEPT;
    let allNonNull = true;
    let allAsciiChar = true;
    let all7Bit = true;

    const len = b.length;
    for (let i = 0; i < len; ++i) {
        const byte = b[i];
        if (utf8State !== UTF8_STATUS.REJECT) {
            // We don't care about the codepoint, so this is
            // a simplified version of the decode function.
            const type = utf8d[byte];
            utf8State = utf8d[256 + utf8State * 16 + type];
        }

        if (byte === 0) {
            allNonNull = false;
            allAsciiChar = false;
        } else if (byte >= 128) {
            allAsciiChar = false;
            all7Bit = false;
        } else if (byte < 32 || byte >= 127) {
            allAsciiChar = false;
        }
    }

    return {
        allNonNull,
        allAsciiChar,
        all7Bit,
        validUtf8: utf8State === UTF8_STATUS.ACCEPT
    };
}

export function checkStringBufs(bufs: Buffer[]): MyBufAggs {
    const aggs: MyBufAggs = {
        allNonNull: true,
        allAsciiChar: true,
        all7Bit: true,
        validUtf8: true
    };

    for (const buf of bufs) {
        const aggs2 = checkStringBuf(buf);
        aggs.allNonNull = aggs.allNonNull && aggs2.allNonNull;
        aggs.allAsciiChar = aggs.allAsciiChar && aggs2.allAsciiChar;
        aggs.all7Bit = aggs.all7Bit && aggs2.all7Bit;
        aggs.validUtf8 = aggs.validUtf8 && aggs2.validUtf8;
    }

    return aggs;
}