mdb-reader/lib/browser/data/ole.js

JavaScript library to read data from Access databases

import { Database } from "../Database.js";
/**
 * @see https://github.com/brianb/mdbtools/blob/d6f5745d949f37db969d5f424e69b54f0da60b9b/src/libmdb/data.c#L626-L688
 */
export function readOLE(buffer, _col, database) {
    const memoLength = buffer.readUIntLE(0, 3);
    const bitmask = buffer.readUInt8(3);
    if (bitmask & 0x80) {
        // inline
        return buffer.slice(12, 12 + memoLength);
    }
    else if (bitmask & 0x40) {
        // single page
        const pageRow = buffer.readUInt32LE(4);
        const rowBuffer = database.findPageRow(pageRow);
        return rowBuffer.slice(0, memoLength);
    }
    else if (bitmask === 0) {
        // multi page
        let pageRow = buffer.readInt32LE(4);
        let memoDataBuffer = Buffer.alloc(0);
        do {
            const rowBuffer = database.findPageRow(pageRow);
            if (memoDataBuffer.length + rowBuffer.length - 4 > memoLength) {
                break;
            }
            if (rowBuffer.length === 0) {
                break;
            }
            memoDataBuffer = Buffer.concat([memoDataBuffer, rowBuffer.slice(4, buffer.length)]);
            pageRow = rowBuffer.readUInt32LE(0);
        } while (pageRow !== 0);
        return memoDataBuffer.slice(0, memoLength);
    }
    else {
        throw new Error(`Unknown memo type ${bitmask}`);
    }
}