Give csv.NewReader your own *bufio.Reader.
Regarding (https://pkg.go.dev/pkg/bufio/#NewReaderSize) if the underlying
io.Reader is already a *bufio.Reader with a big enough size (and
csv.NewReader uses the default 4k),
then the underlying reader is used, no new wrapping is introduced.
This way if you use
cr := countingReader{Reader:r}
br := bufio.NewReader(cr)
csvR := csv.NewReader(br)
then cr.N - br.Buffered() is the number of bytes read by csv.Reader, the
end of the last line read.
Hope this helps.
Severyn Lisovsky a következőt írta (2020. október 31., szombat, 3:17:26
UTC+1):
> Hi,
>
> I have difficulty counting bytes that were processed by csv.Reader because
> it reads from internally created bufio.Reader. If I pass some counting
> reader to csv.NewReader it will show not the actual number bytes
> "processed" by csv.Reader to receive the output I get calling
> csv.Reader.Read method, but the number of bytes copied to bufio.Reader's
> buffer internally (some bytes may be read during next csv.Reader.Read call
> from the buffer).
>
> Is there a way I can deal with this issue by not forking encoding/csv
> package?
>
> To give you more high-level picture - I want to split remote csv file to
> chunks. Each chunk should be standalone csv file - starting from actual
> beginning of the line, ending with newline byte. So I'm trying to do the
> following - split file size by the number of chunks, and for each chunk -
> skip first bytes up to newline symbol and read to offset+chunkSize+[number
> of bytes to the next newline symbol]
>
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