const { Errors } = require('./enig_error'); // // Utils for dealing with Microsoft Binary Format (MBF) used // in various BASIC languages, etc. // // - https://en.wikipedia.org/wiki/Microsoft_Binary_Format // - https://stackoverflow.com/questions/2268191/how-to-convert-from-ieee-python-float-to-microsoft-basic-float // // Number to 32bit MBF const numToMbf32 = (v) => { const mbf = Buffer.alloc(4); if (0 === v) { return mbf; } const ieee = Buffer.alloc(4); ieee.writeFloatLE(v, 0); const sign = ieee[3] & 0x80; let exp = (ieee[3] << 1) | (ieee[2] >> 7); if (exp === 0xfe) { throw Errors.Invalid(`${v} cannot be converted to mbf`); } exp += 2; mbf[3] = exp; mbf[2] = sign | (ieee[2] & 0x7f); mbf[1] = ieee[1]; mbf[0] = ieee[0]; return mbf; }; const mbf32ToNum = (mbf) => { if (0 === mbf[3]) { return 0.0; } const ieee = Buffer.alloc(4); const sign = mbf[2] & 0x80; const exp = mbf[3] - 2; ieee[3] = sign | (exp >> 1); ieee[2] = (exp << 7) | (mbf[2] & 0x7f); ieee[1] = mbf[1]; ieee[0] = mbf[0]; return ieee.readFloatLE(0); }; module.exports = { numToMbf32, mbf32ToNum, };