58 lines
1.0 KiB
Go
58 lines
1.0 KiB
Go
package streaming
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import (
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"errors"
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"io"
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)
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type Writer interface {
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io.WriteSeeker
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}
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type writer struct {
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data []byte
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offset int
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}
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func NewWriter(data []byte) Writer {
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return &writer{data, 0}
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}
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func (w *writer) Write(data []byte) (int, error) {
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length := len(data)
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if w.offset+length > len(w.data) {
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length = len(w.data) - w.offset
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}
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if length == 0 {
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return 0, errors.New("cannot write past end of buffer")
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}
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copy(w.data[w.offset:], data[:length])
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w.offset += length
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return length, nil
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}
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func (w *writer) Seek(offset int64, whence int) (int64, error) {
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result := w.offset
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switch whence {
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case io.SeekStart:
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result = int(offset)
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case io.SeekCurrent:
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result = w.offset + int(offset)
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case io.SeekEnd:
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result = len(w.data) - int(offset)
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}
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if result < 0 {
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return int64(w.offset), errors.New("cannot seek before beginning of buffer")
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}
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if result >= len(w.data) {
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return int64(w.offset), errors.New("cannot seek past end of buffer")
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}
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w.offset = result
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return int64(w.offset), nil
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}
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