The SeekableBuffer type is similar to a bytes.Buffer in that you can perform both reads and writes against it, but has the following two main differences:

1. You can seek on it.
2. After writing to it, the current position will be on the byte following whatever you wrote. This is the typical behavior for a file resource on almost any platform but not for a bytes.Buffer.

Eccentric usage of seek, read, and write behavior, such as the following, will work as expected:

• seeking but not writing
• seeking past the end of the file and writing
• seeking past the end of the file and reading
• writing N+M bytes when positioned only N bytes from the end of the file

Usage (from the unit-tests):

sb := NewSeekableBuffer()

// Write first string.

data := []byte("word1-word2")

_, err := sb.Write(data)
log.PanicIf(err)

// Seek and replace partway through, and replace more data than we
// currently have.

_, err = sb.Seek(6, os.SEEK_SET)
log.PanicIf(err)

data2 := []byte("word3-word4")

_, err = sb.Write(data2)
log.PanicIf(err)

// Read contents.

_, err = sb.Seek(0, os.SEEK_SET)
log.PanicIf(err)

buffer := make([]byte, 20)

_, err = sb.Read(buffer)
log.PanicIf(err)

// `buffer` currently has "word1-word3-word4".