1set/starlet

// Package replacecr defines a wrapper for replacing solo carriage return characters (\r) with carriage-return + line feed (\r\n).
// Copied from https://github.com/qri-io/starlib/tree/master/util/replacecr
package replacecr

import (
    "bufio"
    "io"
)

// Reader wraps an io.Reader. on every call of Read. it looks for
// for instances of lonely \r replacing them with \r\n before returning to the end consumer
// lots of files in the wild will come without "proper" line breaks, which irritates go's
// standard csv package. This'll fix by wrapping the reader passed to csv.NewReader:
//         rdr, err := csv.NewReader(replacecr.Reader(r))
// because Reader adds '\n' characters, the number of bytes reported from the underlying
// reader can/will differ from what the underlyng reader would return
// if read from directly. This can cause issues with checksums and byte counts.
// Use with caution.
func Reader(data io.Reader) io.Reader {
    return crlfReplaceReader{
        rdr: bufio.NewReader(data),
    }
}

// crlfReplaceReader wraps a reader
type crlfReplaceReader struct {
    rdr *bufio.Reader
}

// Read implements io.Reader for crlfReplaceReader
func (c crlfReplaceReader) Read(p []byte) (n int, err error) {
    lenP := len(p)
    if lenP == 0 {
        return
    }

    for {
        if n == lenP {
            return
        }

        p[n], err = c.rdr.ReadByte()
        if err != nil {
            return
        }

        // any time we encounter \r & still have space, check to see if \n follows
        // ff next char is not \n, add it in manually
        if p[n] == '\r' && n < lenP-1 {
            if pk, err := c.rdr.Peek(1); (err == nil && pk[0] != '\n') || (err != nil && err.Error() == "EOF") {
                n++
                p[n] = '\n'
            }
        }

        n++
    }
}