• Brad Fitzpatrick's avatar
    bytes, strings: add Reader.Size methods · c264c873
    Brad Fitzpatrick authored
    As noted on recently on golang-nuts, there's currently no way to know
    the total size of a strings.Reader or bytes.Reader when using ReadAt
    on them. Most callers resort to wrapping it in an io.SectionReader to
    retain that information.
    
    The SizeReaderAt abstraction (an io.ReaderAt with a Size() int64
    method) has proven useful as a way of expressing a concurrency-safe
    read-only number of bytes.
    
    As one example, see http://talks.golang.org/2013/oscon-dl.slide#49 and
    the rest of that presentation for its use in dl.google.com.
    
    SizeReaderAt is also used in the open source google-api-go-client, and
    within Google's internal codebase, where it exists in a public package
    created in 2013 with the package comment: "These may migrate to the
    standard library after we have enough experience with their feel."
    
    I'm still as happy with the SizeReaderAt abstraction and its
    composabilty as I was in 2013, so I'd like to make these two Readers
    also be SizeReaderAts.
    
    Fixes #9667
    
    Change-Id: Ie6f145ada419dd116280472d8c029f046d5edf70
    Reviewed-on: https://go-review.googlesource.com/3199Reviewed-by: 's avatarAndrew Gerrand <adg@golang.org>
    Reviewed-by: 's avatarRuss Cox <rsc@golang.org>
    Reviewed-by: 's avatarRob Pike <r@golang.org>
    c264c873
reader_test.go 4.09 KB