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// Handle the rest of the input
return write(input[count:])
}
return write
}
type sizedReader struct {
reader io.Reader
buffer []byte
from, to, size int
}
// Returns a reader that delegates calls to Read(...) while ensuring
// that the output buffer is never smaller than the required size
// and is downsized to a multiple of the required size if larger.
func SizedReader(reader io.Reader, size int) io.Reader {
var (
buffer []byte = make([]byte, size)
from, to int = 0, 0
var sr sizedReader
sr.reader = reader
sr.buffer = make([]byte, size)
sr.size, sr.from, sr.to = size, 0, 0
)
return ReaderFunc(func(output []byte) (int, error) {
var (
count int
err error
)
start:
// Reply with the buffered data if there is any
if to-from > 0 {
count = copy(output, buffer[from:to])
// Advance the data in the buffer
from += count
// Check whether we have reached the end of the buffer
if to-from == 0 {
// Reset the buffer
from, to = 0, 0
return count, err
}
// Do not propagate an error until the buffer is exhausted
return count, nil
}
// Delegate if the buffer is empty and the destination buffer is large enough
if len(output) >= size {
return reader.Read(output[:(len(output)/size)*size])
}
// Perform a read into the buffer
count, err = reader.Read(buffer)
// Size the buffer down to the read data size
// and restart if we have successfully read some bytes
from, to = 0, count
if to-from > 0 {
goto start
}
// Returning on err/misbehaving noop reader
return 0, err
})
|