96f0b64a11
Add a specialised bytes.Buffer variant with seeking capabilities. This allows writers without seeking support to serialize using NodeSerializerStreamed.
90 lines
1.6 KiB
Go
90 lines
1.6 KiB
Go
/*
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SeekableBuffer
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Copyright (c) 2023 aler9
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Copyright (c) 2025 Zervó Zadachin
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Implementation based on code from "bluenviron/mediacommon".
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See: https://github.com/bluenviron/mediacommon/blob/main/pkg/formats/fmp4/seekablebuffer/seekablebuffer.go
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Original code was licensed under the MIT License.
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See: https://github.com/bluenviron/mediacommon/blob/main/LICENSE
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*/
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package seekablebuffer
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import (
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"bytes"
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"fmt"
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"io"
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)
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// Buffer is a bytes.Buffer with an additional Seek() method.
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type Buffer struct {
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bytes.Buffer
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pos int64
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}
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// Write implements io.Writer.
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func (b *Buffer) Write(p []byte) (int, error) {
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var n int
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if b.pos < int64(b.Len()) {
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n = copy(b.Bytes()[b.pos:], p)
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p = p[n:]
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}
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if len(p) > 0 {
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// Buffer.Write should never return an error here.
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nn, _ := b.Buffer.Write(p)
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n += nn
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}
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b.pos += int64(n)
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return n, nil
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}
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// Read (almost) implements io.Reader.
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func (b *Buffer) Read(_ []byte) (int, error) {
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return 0, fmt.Errorf("read not implemented")
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}
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// Seek implements io.Seeker.
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func (b *Buffer) Seek(offset int64, whence int) (int64, error) {
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var pos2 int64
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switch whence {
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case io.SeekStart:
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pos2 = offset
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case io.SeekCurrent:
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pos2 = b.pos + offset
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case io.SeekEnd:
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pos2 = int64(b.Len()) + offset
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default:
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return 0, fmt.Errorf("invalid seek whence")
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}
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if pos2 < 0 {
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return 0, fmt.Errorf("negative position")
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}
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b.pos = pos2
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// Expand buffer if needed
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diff := b.pos - int64(b.Len())
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if diff > 0 {
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// Buffer.Write should never return an error here.
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b.Buffer.Write(make([]byte, diff))
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}
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return pos2, nil
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}
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// Reset resets the buffer state.
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func (b *Buffer) Reset() {
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b.Buffer.Reset()
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b.pos = 0
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}
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