4. struct:: namespace — structure and metadata

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23 functions about the file itself: metadata, internal objects, security and traceability.

Functions from list_objects onwards read the internal structure of the file. That analysis runs exactly once, on first use, and is cached.

4.1 Metadata

Direct reads

All return an empty string when the field is missing.

check "Required metadata" {
  assert struct::get_title() != "", "PDF has no title"
  assert struct::get_author() != "", "PDF has no author"

  // Producer reveals the originating tool — useful for tracing problems
  print("produced by:", struct::get_producer())
  print("authored in:", struct::get_creator())
}

check "Trusted origin" {
  // Some workflows only accept PDFs from approved tools
  producer = struct::get_producer()
  assert producer.contains("Adobe") || producer.contains("Ghostscript"),
    "PDF produced by an unapproved tool: #{producer}"
}

struct::get_creation_date() and struct::get_modification_date()

Dates already converted from the PDF internal format (D:20260802173622-03'00') to YYYY-MM-DD HH:MM:SS.

check "File dates" {
  created = struct::get_creation_date()
  assert created != "", "PDF has no creation date"
  print("created:", created)
  print("modified:", struct::get_modification_date())

  // String comparison works because the format sorts correctly
  assert created > "2026-01-01", "file is too old for this campaign"
}

struct::list_metadata_entries()

List of all non-empty entries, formatted as "Key: value".

check "Metadata inventory" {
  entries = struct::list_metadata_entries()
  print("metadata:", entries.join(" | "))
  require entries.length >= 2
}

struct::extract_xmp()

XMP (XML) metadata from the catalog. Empty string when absent.

check "XMP present" {
  xmp = struct::extract_xmp()
  assert xmp != "", "PDF has no XMP metadata"

  // XMP is XML — you can look for specific fields
  assert xmp.contains("pdfaid"), "no PDF/A identification in the XMP"
  print("XMP has", xmp.length, "characters")
}

4.2 File and traceability

struct::file_size()

Size in bytes.

check "Size for e-mail delivery" {
  mb = struct::file_size() / 1024 / 1024
  assert mb < 10, "file is #{round(mb)} MB (10 MB e-mail limit)"
}

struct::calculate_sha256()

SHA-256 hash of the file — the fingerprint for an audit trail.

check "Audit record" {
  // The hash goes into the report and proves exactly which file was approved
  hash = struct::calculate_sha256()
  print("SHA-256:", hash)
  require hash.length == 64
}

struct::detect_file_bloat([kb_per_page])

True when the file is bloated — above the KB-per-page limit (default 1024).

check "Lean file" {
  assert !struct::detect_file_bloat(1024),
    "heavy file: #{struct::file_size() / 1024} KB for #{doc.page_count} pages"

  // Stricter limit for web publishing
  assert !struct::detect_file_bloat(200),
    "too heavy for web publishing"
}

4.3 Internal objects

struct::count_objects()

Number of content objects (text, images, strokes) across the pages.

check "Document is not empty" {
  require struct::count_objects() > 0
  print("content objects:", struct::count_objects())
}

struct::list_objects()

Lists every object in the file as "number: type".

check "File inventory" {
  objects = struct::list_objects()
  print("total objects:", objects.length)

  // How many are fonts?
  fonts = objects.filter { |o| o.contains("Font") }
  print("font objects:", fonts.length)
}

struct::detect_unreferenced_objects()

Objects unreachable from the trailer — dead weight in the file.

Infrastructure objects (ObjStm, XRef) are excluded: by definition they are never referenced from the trailer, and reporting them would be a false alarm.

check "No junk in the file" {
  loose = struct::detect_unreferenced_objects()
  assert loose.length == 0,
    "#{loose.length} unreferenced object(s): #{loose.join(", ")}"
}

struct::detect_orphaned_resources()

Same as above but limited to resources (fonts, images, XObjects) — the kind of leftover that weighs the most.

check "Orphaned resources" {
  orphans = struct::detect_orphaned_resources()
  assert orphans.length == 0,
    "unused embedded resources: #{orphans.join(", ")} — run 'pdfl fix' with remove_unused_resources()"
}

struct::measure_object_size(number)

Approximate size of a specific object, in bytes.

check "Heaviest object" {
  // Combine with list_objects to investigate what takes up space
  struct::list_objects().each { |entry| print(entry) }
  print("size of object 5:", struct::measure_object_size(5), "bytes")
}

4.4 Security

struct::detect_javascript()

True when the PDF has embedded JavaScript.

check "No executable code" {
  // JavaScript in a PDF is a common attack vector and unnecessary
  // in production print documents
  assert !struct::detect_javascript(),
    "PDF contains embedded JavaScript"
}

struct::detect_suspicious_actions()

Lists risky actions found: JavaScript, Launch (runs a program), URI, SubmitForm, ImportData, GoToR — each with its originating object.

check "Document actions" {
  actions = struct::detect_suspicious_actions()
  assert actions.length == 0,
    "suspicious actions in the PDF: #{actions.join("; ")}"
}

check "Only links are acceptable" {
  // If external links are allowed, filter down to what actually worries you
  dangerous = struct::detect_suspicious_actions().filter { |a|
    a.contains("Launch") || a.contains("JavaScript")
  }
  assert dangerous.length == 0, "dangerous actions: #{dangerous.join("; ")}"
}

struct::check_encryption()

True when the document is encrypted.

check "File open for production" {
  // An encrypted PDF can fail at the print shop's RIP
  assert !struct::check_encryption(),
    "PDF is encrypted — remove protection before sending it to print"
}

struct::validate_permissions()

True when there are no permission restrictions (document free to process).

check "Permissions" {
  assert struct::validate_permissions(),
    "PDF has permission restrictions that may block processing"
}

struct::validate_signatures()

True when the document has digital signature fields.

This function detects the presence of those fields. Cryptographic validation of the certificate chain is not performed in this version.

check "Signed document" {
  assert struct::validate_signatures(),
    "document has no digital signature field"
}

4.5 Complete example

// audit.pdfl — compliance and security verification
profile "file-audit" {

  check "Identification" tags: ["metadata"] {
    assert struct::get_title() != "", "no title"
    assert struct::get_author() != "", "no author"
    assert struct::get_creation_date() != "", "no creation date"
    print("document:", struct::get_title())
    print("produced by:", struct::get_producer())
  }

  check "Traceability" tags: ["audit"] {
    // The hash proves exactly which file was validated
    print("SHA-256:", struct::calculate_sha256())
    print("size:", struct::file_size() / 1024, "KB")
  }

  check "Security" tags: ["security"] {
    assert !struct::detect_javascript(), "embedded JavaScript"
    assert !struct::check_encryption(), "encrypted file"
    actions = struct::detect_suspicious_actions()
    assert actions.length == 0, "suspicious actions: #{actions.join("; ")}"
  }

  check "File hygiene" tags: ["optimization"] {
    orphans = struct::detect_orphaned_resources()
    assert orphans.length == 0, "unused resources: #{orphans.join(", ")}"
    assert !struct::detect_file_bloat(1024), "bloated file"
  }
}

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