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uint64 what and why

Ashwini Gaddagi

Ashwini Gaddagi

— 1 min read

uint = unsigned integer, no negative numbers. Range is 0 to a very large positive number.

var x int    // -9,223,372,036,854,775,808  to  +9,223,372,036,854,775,807
var x uint64 //  0  to  18,446,744,073,709,551,615

In a commit log specifically:

type Record struct {
    Value  []byte
    Offset uint64   // position in the log
}

Offset is the index of a record in the log... It answers "where is this record?"

uint64 makes perfect sense here for two reasons:

1. An offset can never be negative i.e. index -3 makes no sense
2. Logs can get HUGE, uint64 gives you 18 quintillion records
   before you run out of space. Amazing!

It's intentional type choice, encoding a business rule ("offsets are never negative") directly into the type. If someone passes -1, the compiler refuses. The compiler becomes your first line of defence!

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