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// Returns a writer that delegates calls to Write(...) while ensuring
// that it is never called with less bytes than the specified amount.
//
// Calls with fewer bytes are buffered while a call with a nil slice
// causes the buffer to be flushed to the underlying writer.
func SizedWriter(writer io.Writer, size int) io.Writer {
var buffer []byte = make([]byte, 0, size)
var write WriterFunc
write = func(input []byte) (int, error) {
var (
count int
err error
)
// Flush the buffer when called with no bytes to write
if input == nil {
// Call the writer with whatever we have in store..
count, err = writer.Write(buffer)
// Advance the buffer
buffer = buffer[:copy(buffer, buffer[count:])]
return 0, err
}
// Delegate to the writer if the size is right
if len(buffer) == 0 && len(input) >= size {
reduced := (len(input) / size) * size
count, err = writer.Write(input[:reduced])
if count < reduced || err != nil {
return count, err
}
// Stage any remaining data in the buffer
buffer = append(buffer, input[count:]...)
return len(input), nil
}
// Append data to the buffer
count = copy(buffer[len(buffer):size], input)
buffer = buffer[:len(buffer)+count]
// Return if we don't have enough bytes to write
if len(buffer) < size {
return len(input), nil
}
// Flush the buffer as it is filled
_, err = write(nil)
if err != nil {
return count, err
}
// Handle the rest of the input
return write(input[count:])
}
return write
}
type sizedReader struct {
reader io.Reader
buffer []byte
from, to, size int
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// Returns a writer that delegates calls to Write(...) while ensuring
// that it is never called with less bytes than the specified amount.
//
// Calls with fewer bytes are buffered while a call with a nil slice
// causes the buffer to be flushed to the underlying writer.
func SizedWriter(writer io.Writer, size int) io.Writer {
var sw sizedWriter
sw.writer = writer
sw.buffer = make([]byte, 0, size)
sw.size = size
return &sw
}
type sizedWriter struct {
writer io.Writer
buffer []byte
size int
}
func (sw *sizedWriter) Write(input []byte) (int, error) {
var (
count int
err error
)
// Flush the buffer when called with no bytes to write
if input == nil {
// Call the writer with whatever we have in store..
count, err = sw.writer.Write(sw.buffer)
// Advance the buffer
sw.buffer = sw.buffer[:copy(sw.buffer, sw.buffer[count:])]
return 0, err
}
// Delegate to the writer if the size is right
if len(sw.buffer) == 0 && len(input) >= sw.size {
reduced := (len(input) / sw.size) * sw.size
count, err = sw.writer.Write(input[:reduced])
if count < reduced || err != nil {
return count, err
}
// Stage any remaining data in the buffer
sw.buffer = append(sw.buffer, input[count:]...)
return len(input), nil
}
// Append data to the buffer
count = copy(sw.buffer[len(sw.buffer):sw.size], input)
sw.buffer = sw.buffer[:len(sw.buffer)+count]
// Return if we don't have enough bytes to write
if len(sw.buffer) < sw.size {
return len(input), nil
}
// Flush the buffer as it is filled
_, err = sw.Write(nil)
if err != nil {
return count, err
}
// Handle the rest of the input
return sw.Write(input[count:])
}
// 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 sr sizedReader
sr.reader = reader
sr.buffer = make([]byte, size)
sr.size, sr.from, sr.to = size, 0, 0
return &sr
}
type sizedReader struct {
reader io.Reader
buffer []byte
from, to, size int
}
func (sr *sizedReader) Read(output []byte) (int, error) {
var (
count int
err error
)
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