nearfs/src/util/is-binary.js

NEARFS is a distributed file system compatible with IPFS that uses the NEAR blockchain as a backend.

// NOTE: Lifted from https://github.com/gjtorikian/isBinaryFile/blob/main/src/index.ts
function isBinary(fileBuffer) {
    const bytesRead = fileBuffer.length;
    const totalBytes = bytesRead;

    // empty file. no clue what it is.
    if (bytesRead === 0) {
        return false;
    }

    let suspiciousBytes = 0;

    // UTF-8 BOM
    if (bytesRead >= 3 && fileBuffer[0] === 0xef && fileBuffer[1] === 0xbb && fileBuffer[2] === 0xbf) {
        return false;
    }

    // UTF-32 BOM
    if (
        bytesRead >= 4 &&
        fileBuffer[0] === 0x00 &&
        fileBuffer[1] === 0x00 &&
        fileBuffer[2] === 0xfe &&
        fileBuffer[3] === 0xff
    ) {
        return false;
    }

    // UTF-32 LE BOM
    if (
        bytesRead >= 4 &&
        fileBuffer[0] === 0xff &&
        fileBuffer[1] === 0xfe &&
        fileBuffer[2] === 0x00 &&
        fileBuffer[3] === 0x00
    ) {
        return false;
    }

    // GB BOM
    if (
        bytesRead >= 4 &&
        fileBuffer[0] === 0x84 &&
        fileBuffer[1] === 0x31 &&
        fileBuffer[2] === 0x95 &&
        fileBuffer[3] === 0x33
    ) {
        return false;
    }

    if (totalBytes >= 5 && fileBuffer.slice(0, 5).toString() === '%PDF-') {
        /* PDF. This is binary. */
        return true;
    }

    // UTF-16 BE BOM
    if (bytesRead >= 2 && fileBuffer[0] === 0xfe && fileBuffer[1] === 0xff) {
        return false;
    }

    // UTF-16 LE BOM
    if (bytesRead >= 2 && fileBuffer[0] === 0xff && fileBuffer[1] === 0xfe) {
        return false;
    }

    for (let i = 0; i < totalBytes; i++) {
        if (fileBuffer[i] === 0) {
            // NULL byte--it's binary!
            return true;
        } else if ((fileBuffer[i] < 7 || fileBuffer[i] > 14) && (fileBuffer[i] < 32 || fileBuffer[i] > 127)) {
            // UTF-8 detection
            if (fileBuffer[i] > 193 && fileBuffer[i] < 224 && i + 1 < totalBytes) {
                i++;
                if (fileBuffer[i] > 127 && fileBuffer[i] < 192) {
                    continue;
                }
            } else if (fileBuffer[i] > 223 && fileBuffer[i] < 240 && i + 2 < totalBytes) {
                i++;
                if (fileBuffer[i] > 127 && fileBuffer[i] < 192 && fileBuffer[i + 1] > 127 && fileBuffer[i + 1] < 192) {
                    i++;
                    continue;
                }
            }

            suspiciousBytes++;
            // Read at least 32 fileBuffer before making a decision
            if (i >= 32 && (suspiciousBytes * 100) / totalBytes > 10) {
                return true;
            }
        }
    }

    if ((suspiciousBytes * 100) / totalBytes > 10) {
        return true;
    }

    return false;
}

module.exports = { isBinary };