parseSizeToBytes function

int? parseSizeToBytes(String input)

Parses a human-readable size string in input into a byte count.

Accepts an optional decimal number followed by an optional binary unit (K, M, G, T, P, E) and an optional trailing B, case-insensitive with surrounding whitespace allowed. Units use 1024-based factors. The result is rounded to the nearest whole byte. Returns null for malformed input or a negative value.

Example:

parseSizeToBytes('1.5 MB'); // 1572864
parseSizeToBytes('512K'); // 524288
parseSizeToBytes('big'); // null

Implementation

int? parseSizeToBytes(String input) {
  final RegExpMatch? m = _sizeRegex.firstMatch(input.trim());
  if (m == null) return null;
  final String? g1 = m.group(1);
  if (g1 == null) return null;
  final double? value = double.tryParse(g1);
  if (value == null || value < 0) return null;
  // The unit group may be 'K', 'KB', or 'B'; strip the trailing 'B' so that
  // 'KB' and 'K' both key into the factor table as 'K' (and 'B'/'' as bytes).
  final String unit = (m.group(2) ?? '').toUpperCase().replaceAll(_kUnitB, '');
  // 1024-based (binary) factors: callers expect '1 MB' = 1048576 bytes, not 1e6.
  const Map<String, int> factors = <String, int>{
    '': 1,
    'K': 1024,
    'M': 1048576,
    'G': 1073741824,
    'T': 1099511627776,
    'P': 1125899906842624,
    'E': 1152921504606846976,
  };
  final int? factor = factors[unit];
  if (factor == null) return null;
  return (value * factor).round();
}