114 lines
4.2 KiB
Go
114 lines
4.2 KiB
Go
package sign
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import (
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"strconv"
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"strings"
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)
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func (context *SignContext) createCatalog() (string, error) {
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var catalogBuilder strings.Builder
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// Start the catalog object
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catalogBuilder.WriteString(strconv.Itoa(int(context.CatalogData.ObjectId)) + " 0 obj\n")
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catalogBuilder.WriteString("<< /Type /Catalog")
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// (Optional; PDF 1.4) The version of the PDF specification to which
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// the document conforms (for example, 1.4) if later than the version
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// specified in the file’s header (see 7.5.2, "File header"). If the header
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// specifies a later version, or if this entry is absent, the document
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// shall conform to the version specified in the header. This entry
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// enables a PDF processor to update the version using an incremental
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// update; see 7.5.6, "Incremental updates".
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// The value of this entry shall be a name object, not a number, and
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// therefore shall be preceded by a SOLIDUS (2Fh) character (/) when
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// written in the PDF file (for example, /1.4).
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//
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// If an incremental upgrade requires a version that is higher than specified by the document.
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// if context.PDFReader.PDFVersion < "2.0" {
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// catalogBuilder.WriteString(" /Version /2.0")
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// }
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// Retrieve the root and check for necessary keys in one loop
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root := context.PDFReader.Trailer().Key("Root")
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rootPtr := root.GetPtr()
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context.CatalogData.RootString = strconv.Itoa(int(rootPtr.GetID())) + " " + strconv.Itoa(int(rootPtr.GetGen())) + " R"
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foundPages, foundNames := false, false
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for _, key := range root.Keys() {
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switch key {
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case "Pages":
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foundPages = true
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case "Names":
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foundNames = true
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}
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if foundPages && foundNames {
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break
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}
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}
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// Add Pages and Names references if they exist
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if foundPages {
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pages := root.Key("Pages").GetPtr()
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catalogBuilder.WriteString(" /Pages " + strconv.Itoa(int(pages.GetID())) + " " + strconv.Itoa(int(pages.GetGen())) + " R")
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}
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if foundNames {
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names := root.Key("Names").GetPtr()
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catalogBuilder.WriteString(" /Names " + strconv.Itoa(int(names.GetID())) + " " + strconv.Itoa(int(names.GetGen())) + " R")
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}
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// Start the AcroForm dictionary with /NeedAppearances
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catalogBuilder.WriteString(" /AcroForm << /Fields [")
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// Add existing signatures to the AcroForm dictionary
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for i, sig := range context.SignData.ExistingSignatures {
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if i > 0 {
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catalogBuilder.WriteString(" ")
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}
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catalogBuilder.WriteString(strconv.Itoa(int(sig.ObjectId)) + " 0 R")
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}
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// Add the visual signature field to the AcroForm dictionary
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if len(context.SignData.ExistingSignatures) > 0 {
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catalogBuilder.WriteString(" ")
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}
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catalogBuilder.WriteString(strconv.Itoa(int(context.VisualSignData.ObjectId)) + " 0 R")
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catalogBuilder.WriteString("]") // close Fields array
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catalogBuilder.WriteString(" /NeedAppearances false")
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// Signature flags (Table 225)
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//
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// Bit position 1: SignaturesExist
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// If set, the document contains at least one signature field. This
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// flag allows an interactive PDF processor to enable user
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// interface items (such as menu items or push-buttons) related to
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// signature processing without having to scan the entire
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// document for the presence of signature fields.
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//
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// Bit position 2: AppendOnly
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// If set, the document contains signatures that may be invalidated
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// if the PDF file is saved (written) in a way that alters its previous
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// contents, as opposed to an incremental update. Merely updating
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// the PDF file by appending new information to the end of the
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// previous version is safe (see H.7, "Updating example").
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// Interactive PDF processors may use this flag to inform a user
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// requesting a full save that signatures will be invalidated and
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// require explicit confirmation before continuing with the
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// operation.
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//
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// Set SigFlags and Permissions based on Signature Type
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switch context.SignData.Signature.CertType {
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case CertificationSignature, ApprovalSignature, TimeStampSignature:
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catalogBuilder.WriteString(" /SigFlags 3")
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case UsageRightsSignature:
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catalogBuilder.WriteString(" /SigFlags 1")
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}
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// Finalize the AcroForm and Catalog object
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catalogBuilder.WriteString(" >>") // Close AcroForm
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catalogBuilder.WriteString(" >>\nendobj\n") // Close catalog object
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return catalogBuilder.String(), nil
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}
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