New comment on issue#10884

[产学红]

go version: 1.5beta1

i have commit a new comment to issue#10884:

https://github.com/golang/go/issues/10884

Please review, thanks a lot

I think there are still a little problem:

1. if maxBytesReader initialized with n<0, it will have a problem

2. I think that this will never trigger
   see https://github.com/golang/go/blob/master/src/net/http/request.go#L740

func (l *maxBytesReader) Read(p []byte) (n int, err error) {
    toRead := l.n
    if l.n == 0 {
        if l.sawEOF {
            return l.tooLarge()  // -------> I think that this will never trigger
        }
        // The underlying io.Reader may not return (0, io.EOF)
        // at EOF if the requested size is 0, so read 1 byte
        // instead. The io.Reader docs are a bit ambiguous
        // about the return value of Read when 0 bytes are
        // requested, and {bytes,strings}.Reader gets it wrong
        // too (it returns (0, nil) even at EOF).
        toRead = 1
    }
    if int64(len(p)) > toRead {
        p = p[:toRead]
    }
    n, err = l.r.Read(p)
    if err == io.EOF {
        l.sawEOF = true
    }
    if l.n == 0 {
        // If we had zero bytes to read remaining (but hadn't seen EOF)
        // and we get a byte here, that means we went over our limit.
        if n > 0 {
            return l.tooLarge()
        }
        return 0, err
    }
    l.n -= int64(n)
    if l.n < 0 {
        l.n = 0
    }
    return
}

Here is my code:

type maxBytesReader struct {
    w       ResponseWriter
    r       io.ReadCloser // underlying reader
    n       int64         // max bytes remaining
    stopped bool
}

func (l *maxBytesReader) tooLarge() (n int, err error) {
    if !l.stopped {
        l.stopped = true
        if res, ok := l.w.(*response); ok {
            res.requestTooLarge()
        }
    }
    return 0, errors.New("http: request body too large")
}

func (l *maxBytesReader) Read(p []byte) (n int, err error) {
    if l.n < 0 {
        return l.tooLarge() // Reached if and only if maxBytesReader initialized with n<0
    }

    toRead := l.n
    if l.n == 0 {
        // The underlying io.Reader may not return (0, io.EOF)
        // at EOF if the requested size is 0, so read 1 byte
        // instead. The io.Reader docs are a bit ambiguous
        // about the return value of Read when 0 bytes are
        // requested, and {bytes,strings}.Reader gets it wrong
        // too (it returns (0, nil) even at EOF).
        toRead = 1
    }
    if int64(len(p)) > toRead {
        p = p[:toRead]
    }
    n, err = l.r.Read(p)
    if l.n == 0 {
        // If we had zero bytes to read remaining (but hadn't seen EOF)
        // and we get a byte here, that means we went over our limit.
        if n > 0 {
            return l.tooLarge()
        }
        return 0, err // Usually 0, io.EOF
    }
    l.n -= int64(n)
    return
}

[Andrew Gerrand]

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[产学红]

ok, thanks

在 2015年7月8日星期三 UTC+8下午9:11:57，Andrew Gerrand写道：