Satoshis, Not Doubles — Java Bug Hunt

Briefing

Inspired by the precision bugs that plague crypto exchanges: parse "0.29" of a coin through a double, multiply by 10^8, truncate — and you just destroyed one satoshi. Multiply that by a million trades a day.

AmountParser.java converts a decimal string into satoshis (8 decimal places). It must use integer math end to end.

Bug report

BUG-1SAT · Priority: High · Reported by: reconciliation

parseToSatoshis(amount) — up to 8 decimal places:

• "0.29" -> 29000000
• "1" -> 100000000
• "123.45678901"-> 12345678901

Observed: "0.29" parses to 28999999. The books never balance.

Logs

[ledger] daily reconciliation drift: -412 sat

The code as shipped

AmountParser.java (editable)

class AmountParser {
    // Parses a decimal coin amount (max 8 dp) into satoshis.
    static long parseToSatoshis(String amount) {
        double value = Double.parseDouble(amount);
        return (long) (value * 100000000);
    }
}