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31 lines
757 B
Go
31 lines
757 B
Go
package file
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import (
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"bytes"
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"errors"
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"fmt"
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"io"
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)
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// pdfMagic is the [file signature][1] (or magic bytes) for PDF
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//
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// [1]: https://en.wikipedia.org/wiki/List_of_file_signatures
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var pdfMagic = []byte{0x25, 0x50, 0x44, 0x46}
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// CheckPDF checks if the provided bytes are a PDF file.
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func CheckPDF(pdf io.Reader) error {
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buf := make([]byte, len(pdfMagic))
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if _, err := io.ReadFull(pdf, buf); err != nil {
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// ReadFull returns ErrUnexpectedEOF if it can't read enough bytes, or EOF
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// if it cannot read a single byte.
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if errors.Is(err, io.ErrUnexpectedEOF) || errors.Is(err, io.EOF) {
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return ErrInvalidType
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}
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return fmt.Errorf("reading magic bytes: %w", err)
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}
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if !bytes.Equal(buf, pdfMagic) {
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return ErrInvalidType
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}
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return nil
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}
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