Michael McGuinness
152 lines
3.2 KiB
Go
152 lines
3.2 KiB
Go
package documentclean
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import (
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"context"
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"io"
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"github.com/pdfcpu/pdfcpu/pkg/pdfcpu"
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"github.com/pdfcpu/pdfcpu/pkg/pdfcpu/model"
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"github.com/pdfcpu/pdfcpu/pkg/pdfcpu/types"
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)
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type PDF struct {
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pdf io.ReadSeeker
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config *model.Configuration
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maxPages int
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maxBytes int64
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maxDimension int
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minDimension int
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minDPI int
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}
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const (
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TEXTRACT_SYNC_LIMIT int64 = 10 * 1024 * 1024
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TEXTRACT_ASYNC_LIMIT int64 = 500 * 1024 * 1024
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TEXTRACT_PAGE_LIMIT = 3000
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TEXTRACT_MAX_DIMENSION = 10000
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TEXTRACT_MIN_DIMENSION = 50
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TEXTRACT_MIN_DPI = 72
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PDF_DEFAULT_DPI = 72
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)
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func NewPDF(buf io.ReadSeeker) *PDF {
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config := &model.Configuration{
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ValidationMode: model.ValidationRelaxed,
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Reader15: true,
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Offline: true,
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}
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return &PDF{
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pdf: buf,
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config: config,
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maxPages: TEXTRACT_PAGE_LIMIT,
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maxBytes: TEXTRACT_SYNC_LIMIT,
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maxDimension: TEXTRACT_MAX_DIMENSION,
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minDimension: TEXTRACT_MIN_DIMENSION,
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minDPI: TEXTRACT_MIN_DPI,
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}
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}
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func (s *PDF) isCorrupt(ctx context.Context) *InvalidDocumentReason {
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pdfCtx, err := pdfcpu.ReadWithContext(ctx, s.pdf, s.config)
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if err != nil {
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reason := InvalidDocumentRead
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return &reason
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}
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if int64(pdfCtx.Read.ReadFileSize()) > s.maxBytes {
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reason := InvalidDocumentLargeFile
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return &reason
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}
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docErr := s.isValidPageCount(pdfCtx)
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if docErr != nil {
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return docErr
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}
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docErr = s.isValidDimensions(pdfCtx)
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if docErr != nil {
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return docErr
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}
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return nil
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}
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func (s *PDF) isValidPageCount(pdfCtx *model.Context) *InvalidDocumentReason {
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err := pdfCtx.EnsurePageCount()
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if err != nil {
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reason := InvalidDocumentRead
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return &reason
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}
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if pdfCtx.PageCount > s.maxPages {
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reason := InvalidDocumentLargePageCount
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return &reason
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}
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return nil
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}
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func (s *PDF) isValidDimensions(pdfCtx *model.Context) *InvalidDocumentReason {
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err := pdfCtx.EnsurePageCount()
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if err != nil {
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reason := InvalidDocumentRead
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return &reason
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}
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_, err = s.pdf.Seek(0, io.SeekStart)
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if err != nil {
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reason := InvalidDocumentRead
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return &reason
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}
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pageSet := types.IntSet{}
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for pageNum := 1; pageNum <= pdfCtx.PageCount; pageNum++ {
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pageSet[pageNum] = true
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}
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boxes, err := pdfCtx.PageBoundaries(pageSet)
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if err != nil {
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reason := InvalidDocumentRead
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return &reason
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}
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for _, box := range boxes {
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mediaBox := box.MediaBox()
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if mediaBox == nil {
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continue
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}
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dims := mediaBox.Dimensions()
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if dims.Height > float64(s.maxDimension) ||
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dims.Width > float64(s.maxDimension) {
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reason := InvalidDocumentLargeDimensions
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return &reason
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} else if dims.Height < float64(s.minDimension) ||
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dims.Width < float64(s.minDimension) {
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reason := InvalidDocumentSmallDimensions
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return &reason
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}
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dpiErr := s.isValidDPI(mediaBox, dims)
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if dpiErr != nil {
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return dpiErr
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}
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}
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return nil
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}
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func (s *PDF) isValidDPI(mediaBox *types.Rectangle, dims types.Dim) *InvalidDocumentReason {
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widthDPI := mediaBox.Width() / dims.ToInches().Width
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heightDPI := mediaBox.Height() / dims.ToInches().Height
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if widthDPI < float64(s.minDPI) || heightDPI < float64(s.minDPI) {
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reason := InvalidDocumentSmallDPI
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return &reason
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}
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return nil
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}
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