The ubiquitous io.Reader interface's Read method returns a (int,
error). Surprisingly (for programmers coming from other languages with
a built-in or idiomatic Result<T, E> type), it's possible for both
return values to be non-zero. There's (often overlooked??) commentary
in https://pkg.go.dev/io#Reader that says:
> Callers should always process the n > 0 bytes returned before considering the
> error err.
So that (again, especially for programmers used to saying result? or
"try result" or similar Result<T, E> aware mechanisms in other
languages), the following Go code is incorrect:
n, err := r.Read(buffer, etc)
if err != nil {
return err
}
doStuffWith(buffer[:n])
---
Do any of the early Gophers remember the motivations for designing
Read's semantics in that way? At the libc or syscall level (and my
reading of FD.Read in internal/poll/fd_unix.go), I don't think
read(fd, etc) can return both non-zero.
Is it just that, if you've got a buffer of some sort (including the
compress/* packages), it can be more efficient (1 Read call instead of
2) to return (positiveN, io.EOF)?
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