const parseUIntLE = function(buffer, offset, size) {
let result;
switch(size) {
case 1:
result = buffer.readUInt8(offset);
break;
case 2:
result = buffer.readUInt16LE(offset);
break;
case 4:
result = buffer.readUInt32LE(offset);
break;
case 8:
result = Number(buffer.readBigUInt64LE(offset));
break;
default:
throw new Error('Unsupported UInt LE size!');
}
return result;
};
/**
* Parses sequential unsigned little endian numbers from the head of the passed buffer according to
* the specified format passed. If the buffer is not large enough to satisfy the full format,
* null values will be assigned to the remaining keys.
* @param {*} buffer The buffer to sequentially extract numbers from.
* @param {*} format Expected format to follow when extrcting values from the buffer. A list of list entries
* with the following structure:
* [
* [
* <key>, // Name of the key to assign the extracted number to.
* <size> // The size in bytes of the number to extract. possible values are 1, 2, 4, 8.
* ],
* ...
* ]
* @returns An object with keys set to their associated extracted values.
*/
const parse = function(buffer, format) {
const result = {};
let offset = 0;
for(const [key, size] of format) {
if(buffer.length >= offset + size) {
result[key] = parseUIntLE(buffer, offset, size);
}
else {
result[key] = null;
}
offset += size;
}
return result;
};
module.exports = {
parse
};