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79 lines
1.7 KiB
Go
79 lines
1.7 KiB
Go
package gzip
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import (
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"bytes"
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"compress/gzip"
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"io"
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)
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// DefaultBufferSize is the default buffer size used by the Compressor.
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const DefaultBufferSize = 65536
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// Compressor is a wrapper around a gzip.Writer that reads from an io.Reader
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// and writes to an internal buffer. The internal buffer is used to store
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// compressed data until it is read by the caller.
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type Compressor struct {
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r io.Reader
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bufSz int
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buf *bytes.Buffer
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gzw *gzip.Writer
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nRx int64
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nTx int64
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}
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// NewCompressor returns an instantiated Compressor that reads from r and
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// compresses the data using gzip.
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func NewCompressor(r io.Reader, bufSz int) (*Compressor, error) {
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buf := new(bytes.Buffer)
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gzw, err := gzip.NewWriterLevel(buf, gzip.DefaultCompression)
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if err != nil {
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return nil, err
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}
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return &Compressor{
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r: r,
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bufSz: bufSz,
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buf: buf,
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gzw: gzw,
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}, nil
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}
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// Read reads compressed data.
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func (c *Compressor) Read(p []byte) (n int, err error) {
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if c.buf.Len() == 0 && c.gzw != nil {
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nn, err := io.CopyN(c.gzw, c.r, int64(c.bufSz))
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c.nRx += nn
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c.nTx += int64(len(p))
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if err != nil {
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// Time to write the footer.
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if err := c.Close(); err != nil {
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return 0, err
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}
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if err != io.EOF {
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// Actual error, let caller handle
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return 0, err
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}
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} else if nn > 0 {
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// We read some data, but didn't hit any error.
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// Just flush the data in the buffer, ready
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// to be read.
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if err := c.gzw.Flush(); err != nil {
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return 0, err
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}
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}
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}
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return c.buf.Read(p)
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}
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// Close closes the Compressor.
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func (c *Compressor) Close() error {
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if c.gzw == nil {
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return nil
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}
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if err := c.gzw.Close(); err != nil {
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return err
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}
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c.gzw = nil
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return nil
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}
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