swift CGPDFDocument parsing

Question

I'm trying to use Swift to parse the contents of PDF documents, following Apple's programming guide (in which all the examples are ObjC...)

let filepath = "/Users/ben/Desktop/Test.pdf"
let localUrl  = filepath as CFString
if let pdfURL = CFURLCreateWithFileSystemPath(nil, localUrl, CFURLPathStyle.cfurlposixPathStyle, false) {
    if let pdf = CGPDFDocument(pdfURL) {
        if let inf = pdf.info {
            CGPDFDictionaryApplyFunction(inf, { (key, object, info) -> Void in
                print("\(key), \(object), \(info)")
            }, nil)
        }
        if let cat = pdf.catalog {

            CGPDFDictionaryApplyFunction(cat, { (key, object, info) -> Void in
                print("\(key), \(object), \(info)")
            }, nil)

        }
}
}

While this seems to produce some results, it's just strings of hex digits.

0x00007ff29f43ce00, 0x00007ff29f492bd0, nil
0x00007ff29f443b60, 0x00007ff29f492cd0, nil
0x00007ff29f482590, 0x00007ff29f492dd0, nil
0x00007ff29f482a40, 0x00007ff29f492ed0, nil
0x00007ff29f482e30, 0x00007ff29f492fe0, nil
0x00007ff29f47da20, 0x00007ff29f4930e0, nil
0x00007ff29f474ac0, 0x00007ff29f842b50, nil
0x00007ff29f43f5d0, 0x00007ff29f842bf0, nil
0x00007ff29f485eb0, 0x00007ff29f842a60, nil
0x00007ff29f482f70, 0x00007ff29f842ab0, nil
0x00007ff29f48b1c0, 0x00007ff29f48f6d0, nil

So how do I get the actual data? Ideally, I'm trying to get at the document metadata and things like fonts contained.

Answer 1

Your parsing retrieving high level dictionary and info data is correct, but you need to expand the decoding in CGPDFDictionaryApplyFunction to display the values of PDF data according their types (integer, string, array, dictionary, and so on). The syntax of the CGPDFDictionaryApplierFunction you are calling is:

typealias CGPDFDictionaryApplierFunction = (UnsafePointer<Int8>, COpaquePointer, UnsafeMutablePointer<()>) -> Void

Your program is displaying the pointers to the data, you could access the data values according their types as below (Swift 2):

    let filepath = "/Users/ben/Desktop/Test.pdf"
    let urlDocument = NSURL(fileURLWithPath: filepath)
    let myDocument = CGPDFDocumentCreateWithURL(urlDocument)
    if myDocument != nil {
        let numPages = CGPDFDocumentGetNumberOfPages(myDocument)
        print("Number of pages: \(numPages)")
        // Get complete catalog
        let myCatalog = CGPDFDocumentGetCatalog(myDocument)
        CGPDFDictionaryApplyFunction(myCatalog, printPDFKeys, nil)
        let myInfo = CGPDFDocumentGetInfo(myDocument)
        CGPDFDictionaryApplyFunction(myInfo, printPDFKeys, nil)
    } else {
        print("Cannot open PDF document")
    }

In order to be called from the CGPDFDictionaryApplyFunction, the printPDFKeys is to be called as a global function (outside your main class), alternately you could insert the code in a closure of CGPDFDictionaryApplyFunction as in your example above. The below code is shortened and is not including complete protection against errors and null values.

func printPDFKeys( key: UnsafePointer<Int8>, object: COpaquePointer, info: UnsafeMutablePointer<()>) {
    let contentDict: CGPDFDictionaryRef = CGPDFDictionaryRef(info)
    let keyString = String(CString: UnsafePointer<CChar>(key), encoding: NSISOLatin1StringEncoding)
    let objectType = CGPDFObjectGetType(object)
    if keyString == nil {
        return
    }
    print("key \(keyString!) is present in dictionary, type \(objectType.rawValue)")
    var ptrObjectValue = UnsafePointer<Int8>()
    switch objectType {
    // ObjectType is enum of:
    //   Null
    //   Boolean
    //   Integer
    //   Real
    //   Name
    //   String
    //   Array
    //   Dictionary
    //   Stream
    case .Boolean:
        // Boolean
        var objectBoolean = CGPDFBoolean()
        if CGPDFObjectGetValue(object, objectType, &objectBoolean) {
            let testbool = NSNumber(unsignedChar: objectBoolean)
            print("Boolean value \(testbool)")
        }
    case .Integer:
        // Integer
        var objectInteger = CGPDFInteger()
        if CGPDFObjectGetValue(object, objectType, &objectInteger) {
            print("Integer value \(objectInteger)")
        }
    case .Real:
        // Real
        var objectReal = CGPDFReal()
        if CGPDFObjectGetValue(object, objectType, &objectReal) {
            print("Real value \(objectReal)")
        }
    case .Name:
        // Name
        if (CGPDFObjectGetValue(object, objectType, &ptrObjectValue)) {
            let stringName = String(CString: UnsafePointer<CChar>(ptrObjectValue), encoding: NSISOLatin1StringEncoding)
            print("Name value: \(stringName!)")
        }
    case .String:
        // String
        let valueFound = CGPDFObjectGetValue(object, objectType, &ptrObjectValue)
        let stringValue = CGPDFStringCopyTextString(COpaquePointer(ptrObjectValue))
        print("String value: \(stringValue!)")
    case .Array:
        // Array
        print("Array")
        var objectArray = CGPDFArrayRef()
        if (CGPDFObjectGetValue(object, objectType, &objectArray))
        {
            print("array: \(arrayFromPDFArray(objectArray))")
        }
    case .Dictionary:
        // Dictionary
        var objectDictionary = CGPDFDictionaryRef()
        if (CGPDFObjectGetValue(object, objectType, &objectDictionary)) {
            let count = CGPDFDictionaryGetCount(objectDictionary)
            print("Found dictionary with \(count) entries")
            if !(keyString == "Parent") && !(keyString == "P") {
                //catalogLevel = catalogLevel + 1
                CGPDFDictionaryApplyFunction(objectDictionary, printPDFKeys, nil)
                //catalogLevel = catalogLevel - 1
            }
        }
case .Stream:
    // Stream
    print("Stream")
    var objectStream = CGPDFStreamRef()
    if (CGPDFObjectGetValue(object, objectType, &objectStream)) {
        let dict: CGPDFDictionaryRef = CGPDFStreamGetDictionary( objectStream )
        var fmt: CGPDFDataFormat = .Raw
        let streamData: CFDataRef = CGPDFStreamCopyData(objectStream, &fmt)!;
        let data = NSData(data: streamData)
        let dataString = NSString(data: data, encoding: NSUTF8StringEncoding)
        let dataLength: Int = CFDataGetLength(streamData)
        print("data stream (length=\(dataLength)):")
        if dataLength < 400 {
            print(dataString)
        }
    }
default:
    print("Null")
}
}

// convert a PDF array into an objC one
func arrayFromPDFArray(pdfArray: CGPDFArrayRef ) -> NSMutableArray {
var i:Int = 0
var tmpArray: NSMutableArray = NSMutableArray()

let count = CGPDFArrayGetCount(pdfArray)
for i in 0..<count {
    var value = CGPDFObjectRef()
    if (CGPDFArrayGetObject(pdfArray, i, &value)) {
        if let object = objectForPDFObject(value) {
            tmpArray.addObject(object)
        }
    }
}

return tmpArray
}

func objectForPDFObject( object: CGPDFObjectRef) -> AnyObject? {
let objectType: CGPDFObjectType = CGPDFObjectGetType(object)
var ptrObjectValue = UnsafePointer<Int8>()
switch (objectType) {
case .Boolean:
    // Boolean
    var objectBoolean = CGPDFBoolean()
    if CGPDFObjectGetValue(object, objectType, &objectBoolean) {
        let testbool = NSNumber(unsignedChar: objectBoolean)
        return testbool
    }
case .Integer:
    // Integer
    var objectInteger = CGPDFInteger()
    if CGPDFObjectGetValue(object, objectType, &objectInteger) {
        return objectInteger
    }
case .Real:
    // Real
    var objectReal = CGPDFReal()
    if CGPDFObjectGetValue(object, objectType, &objectReal) {
        return objectReal
    }
case .String:
    let valueFound = CGPDFObjectGetValue(object, objectType, &ptrObjectValue)
    let stringValue = CGPDFStringCopyTextString(COpaquePointer(ptrObjectValue))
    return stringValue
case .Dictionary:
    // Dictionary
    var objectDictionary = CGPDFDictionaryRef()
    if (CGPDFObjectGetValue(object, objectType, &objectDictionary)) {
        let count = CGPDFDictionaryGetCount(objectDictionary)
        print("In array, found dictionary with \(count) entries")
        CGPDFDictionaryApplyFunction(objectDictionary, printPDFKeys, nil)
    }
case .Stream:
    // Stream
    var objectStream = CGPDFStreamRef()
    if (CGPDFObjectGetValue(object, objectType, &objectStream)) {
        let dict: CGPDFDictionaryRef = CGPDFStreamGetDictionary( objectStream )
        var fmt: CGPDFDataFormat = .Raw
        let streamData: CFDataRef = CGPDFStreamCopyData(objectStream, &fmt)!;
        let data = NSData(data: streamData)
        let dataString = NSString(data: data, encoding: NSUTF8StringEncoding)
        print("data stream (length=\(CFDataGetLength(streamData))):")
        return dataString
    }
default:
    return nil
}
return nil
}

Answer 2

Swift 4 - Here is an updated version of Daniel's excellent example which compiles in Swift 4.

import Foundation
import Quartz

print("Hello, World!")

func printPDFKeys( key: UnsafePointer<Int8>, object: CGPDFObjectRef) { //, info: UnsafeMutableRawPointer) {
    // let _: CGPDFDictionaryRef = CGPDFDictionaryRef(info)
    let keyString = String(cString: UnsafePointer<CChar>(key), encoding: .isoLatin1)
    let objectType = CGPDFObjectGetType(object)
    if keyString == nil {
        return
    }
    print("key \(keyString!) is present in dictionary, type \(objectType.rawValue)")
    var ptrObjectValue:UnsafePointer<Int8>? = nil
    switch objectType {
        // ObjectType is enum of:
        //   Null
        //   Boolean
        //   Integer
        //   Real
        //   Name
        //   String
        //   Array
        //   Dictionary
    //   Stream
    case .boolean:
        // Boolean
        var objectBoolean:CGPDFBoolean = 0
        if CGPDFObjectGetValue(object, objectType, &objectBoolean) {
            let testbool = NSNumber(value: objectBoolean)
            print("Boolean value \(testbool)")
        }
    case .integer:
        // Integer
        var objectInteger:CGPDFInteger? = nil
        if CGPDFObjectGetValue(object, objectType, &objectInteger) {
            print("Integer value \(objectInteger)")
        }
    case .real:
        // Real
        var objectReal:CGPDFReal? = nil
        if CGPDFObjectGetValue(object, objectType, &objectReal) {
            print("Real value \(objectReal)")
        }
    case .name:
        // Name
        if (CGPDFObjectGetValue(object, objectType, &ptrObjectValue)) {
            let stringName = String(cString: UnsafePointer<CChar>(ptrObjectValue!), encoding: String.Encoding.isoLatin1)
            print("Name value: \(stringName!)")
        }
    case .string:
        // String
        _ = CGPDFObjectGetValue(object, objectType, &ptrObjectValue)
        let stringValue = CGPDFStringCopyTextString(OpaquePointer(ptrObjectValue!))
        print("String value: \(stringValue!)")
    case .array:
        // Array
        print("Array")
        var objectArray:CGPDFArrayRef? = nil
        if (CGPDFObjectGetValue(object, objectType, &objectArray))
        {
            print("array: \(arrayFromPDFArray(pdfArray: objectArray!))")
        }
    case .dictionary:
        // Dictionary
        var objectDictionary:CGPDFDictionaryRef? = nil
        if (CGPDFObjectGetValue(object, objectType, &objectDictionary)) {
            let count = CGPDFDictionaryGetCount(objectDictionary!)
            print("Found dictionary with \(count) entries")
            if !(keyString == "Parent") && !(keyString == "P") {
                //catalogLevel = catalogLevel + 1
                CGPDFDictionaryApplyFunction(objectDictionary!, { (key, object, info) -> Void in
                    printPDFKeys(key: key, object: object) // , info: info)
                }, nil)

                // CGPDFDictionaryApplyFunction(objectDictionary!, printPDFKeys as! CGPDFDictionaryApplierFunction, nil)
                //catalogLevel = catalogLevel - 1
            }
        }
    case .stream:
        // Stream
        print("Stream")
        var objectStream:CGPDFStreamRef? = nil
        if (CGPDFObjectGetValue(object, objectType, &objectStream)) {
            let _: CGPDFDictionaryRef = CGPDFStreamGetDictionary( objectStream! )!
            var fmt: CGPDFDataFormat = .raw
            let streamData: CFData = CGPDFStreamCopyData(objectStream!, &fmt)!;
            let data = NSData(data: streamData as Data)
            let dataString = NSString(data: data as Data, encoding: String.Encoding.utf8.rawValue)
            let dataLength: Int = CFDataGetLength(streamData)
            print("data stream (length=\(dataLength)):")
            if dataLength < 400 {
                print(dataString)
            }
        }
    default:
        print("Null")
    }
}

// convert a PDF array into an objC one
func arrayFromPDFArray(pdfArray: CGPDFArrayRef ) -> NSMutableArray {
    var _:Int = 0
    let tmpArray: NSMutableArray = NSMutableArray()

    let count = CGPDFArrayGetCount(pdfArray)
    for i in 0..<count {
        var value:CGPDFObjectRef? = nil
        if (CGPDFArrayGetObject(pdfArray, i, &value)) {
            if let object = objectForPDFObject(object: value!) {
                tmpArray.add(object)
            }
        }
    }

    return tmpArray
}

func objectForPDFObject( object: CGPDFObjectRef) -> AnyObject? {
    let objectType: CGPDFObjectType = CGPDFObjectGetType(object)
    var ptrObjectValue:UnsafePointer<Int8>? = nil
    switch (objectType) {
    case .boolean:
        // Boolean
        var objectBoolean = CGPDFBoolean()
        if CGPDFObjectGetValue(object, objectType, &objectBoolean) {
            let testbool = NSNumber(value: objectBoolean)
            return testbool
        }
    case .integer:
        // Integer
        var objectInteger = CGPDFInteger()
        if CGPDFObjectGetValue(object, objectType, &objectInteger) {
            return objectInteger as AnyObject
        }
    case .real:
        // Real
        var objectReal = CGPDFReal()
        if CGPDFObjectGetValue(object, objectType, &objectReal) {
            return objectReal as AnyObject
        }
    case .string:
        _ = CGPDFObjectGetValue(object, objectType, &ptrObjectValue)
        let stringValue = CGPDFStringCopyTextString(OpaquePointer(ptrObjectValue!))
        return stringValue
    case .dictionary:
        // Dictionary
        var objectDictionary:CGPDFDictionaryRef? = nil
        if (CGPDFObjectGetValue(object, objectType, &objectDictionary)) {
            let count = CGPDFDictionaryGetCount(objectDictionary!)
            print("In array, found dictionary with \(count) entries")
            CGPDFDictionaryApplyFunction(objectDictionary!, { (key, object, info) -> Void in
                printPDFKeys(key: key, object: object) // , info: info)
            }, nil)

            // CGPDFDictionaryApplyFunction(objectDictionary!, printPDFKeys as! CGPDFDictionaryApplierFunction, nil)
        }
    case .stream:
        // Stream
        var objectStream:CGPDFStreamRef? = nil
        if (CGPDFObjectGetValue(object, objectType, &objectStream)) {
            let _: CGPDFDictionaryRef = CGPDFStreamGetDictionary( objectStream! )!
            var fmt: CGPDFDataFormat = .raw
            let streamData: CFData = CGPDFStreamCopyData(objectStream!, &fmt)!;
            let data = NSData(data: streamData as Data)
            let dataString = NSString(data: data as Data, encoding: String.Encoding.utf8.rawValue)
            print("data stream (length=\(CFDataGetLength(streamData))):")
            return dataString
        }
    default:
        return nil
    }
    return nil
}

func parse () {
    let filepath = ("~/Desktop/doc.pdf" as NSString).expandingTildeInPath
    let urlDocument = NSURL(fileURLWithPath: filepath)
    let myDocument = CGPDFDocument(urlDocument)
    if myDocument != nil {
        let numPages = myDocument?.numberOfPages
        print("Number of pages: \(numPages)")
        // Get complete catalog
        let myCatalog = myDocument?.catalog

        CGPDFDictionaryApplyFunction(myCatalog!, { (key, object, info) -> Void in
            printPDFKeys(key: key, object: object) // , info: info)
        }, nil)

        // CGPDFDictionaryApplyFunction(myCatalog!, printPDFKeys, nil)
        let myInfo = myDocument?.info

        CGPDFDictionaryApplyFunction(myInfo!, { (key, object, info) -> Void in
            printPDFKeys(key: key, object: object) // , info: info)
        }, nil)

        // CGPDFDictionaryApplyFunction(myInfo!, printPDFKeys, nil)
    } else {
        print("Cannot open PDF document")
    }
}

parse()

Answer 3

Made a parser (based on previous answers) that crawls the PDF hierarchy and gives you a JSON.

// Parse PDF into JSON.
PDFParser.parse(pdfUrl: pdfFileURL, into: jsonFileURL)

// Parse PDF into Dictionary.
let pdf: [String:Any?] = PDFParser.parse(pdfUrl: pdfFileURL)

Gives you:

{
  "Catalog" : {
    "Pages<Dictionary>" : {
      "MediaBox<Array>" : [
        0,
        0,
        612,
        792
      ],
      "Type<Name>" : "Pages",
      "Kids<Array>" : [
        {
          "Rotate<Integer>" : 0,
          "MediaBox<Array>" : [
            0,
            0,
            595.27499999999998,
            841.88999999999999
          ],
          "Parent<Dictionary>" : "<PARENT_NOT_SERIALIZED>",
          "Resources<Dictionary>" : {
            "ColorSpace<Dictionary>" : {
              "Cs1<Array>" : [
                "ICCBased",
                {
                  "N<Integer>" : 3,
                  "Filter<Name>" : "FlateDecode",
                  "Alternate<Name>" : "DeviceRGB",
                  "Length<Integer>" : 2612
                }
              ]
            }
...

To get from CGPDFDocument (like original question):

// Get document catalog.
guard
    let document = CGPDFDocument(pdfFileURL as CFURL),
    let catalog = document.catalog
else { return }

// Parse into dictionary.
let catalogDictionary = PDFParser.value(from: catalog)

Gives you a pretty usual Swift dictionary. Console output:

Optional(["Pages<Dictionary>": Optional({
    "Count<Integer>" = 1;
    "Kids<Array>" =     (
                {
            "ArtBox<Array>" =             (
                "28.3465",
                "325.193",
                "393.389",
                "813.543"
            );
            "Contents<Stream>" =             {
                Data = "q Q q 0 0 595.276 841.89 re W n 1 0 1 0 k /Gs1 gs 201.8862 420.9449 m 201.8862\n473.8269 244.7562 516.6959 297.6372 516.6959 c 350.5192 516.6959 393.3892\n473.8269 393.3892 420.9449 c 393.3892 368.0629 350.5192 325.1939 297.6372\n325.1939 c 244.7562 325.1939 201.8862 368.0629 201.8862 420.9449 c f Q q 28.346 530.078 283.464 283.465\nre W n 0 0 0 1 k /Gs1 gs BT 12 0 0 12 28.3467 803.499 Tm /Tc1 1 Tf [ (h) 4\n(ttp://epp) 7 (z.eu) ] TJ ET Q";
                "Filter<Name>" = FlateDecode;
                "Length<Integer>" = 237;
            };
            "MediaBox<Array>" =             (
                0,
                0,
                "595.2760000000001",
                "841.89"
            );
            "Parent<Dictionary>" = "<PARENT_NOT_SERIALIZED>";
            "Resources<Dictionary>" =             {
                "ExtGState<Dictionary>" =                 {
                    "Gs1<Dictionary>" =                     {
                        "OPM<Integer>" = 1;
                        "Type<Name>" = ExtGState;
                    };
                };
...

ParsePDF.swift:

//
//  PDFParser.swift
//  PDFParser
//
//  Copyright (c) 2020 Geri Borbás http://www.twitter.com/_eppz
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
//  The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

import Foundation
import PDFKit


class PDFParser
{


    /// Shorthand for type strings.
    static let namesForTypes: [CGPDFObjectType:String] =
    [
        .null : "Null",
        .boolean : "Boolean",
        .integer : "Integer",
        .real : "Real",
        .name : "Name",
        .string : "String",
        .array : "Array",
        .dictionary : "Dictionary",
        .stream : "Stream",
        CGPDFObjectTypeObject : "Object",
    ]

    struct Message
    {
        static let parentNotSerialized = "<PARENT_NOT_SERIALIZED>"
        static let couldNotParseValue = "<COULD_NOT_PARSE_VALUE>"
        static let couldNotGetStreamData = "<COULD_NOT_GET_STREAM_DATA>"
        static let unknownStreamDataFormat = "<UNKNOWN_STREAM_DATA_FORMAT>"
    }

    /// Parse a PDF file into a JSON file.
    static func parse(pdfUrl: URL, into jsonURL: URL)
    {
        do
        {
            let pdf = PDFParser.parse(pdfUrl: pdfUrl)
            let data = try JSONSerialization.data(withJSONObject: pdf, options: .prettyPrinted)
            try data.write(to: jsonURL, options: [])
        }
        catch
        { print(error) }
    }

    /// Parse a PDF file into a JSON file.
    static func parse(pdfUrl: URL) -> [String:Any?]
    {
        // Document.
        guard
            let document = CGPDFDocument(pdfUrl as CFURL),
            let catalog = document.catalog,
            let info = document.info
            else
        {
            print("Cannot open PDF.")
            return [:]
        }

        // Parse.
        return [
            "Catalog" : PDFParser.value(from: catalog),
            "Info" : PDFParser.value(from: info)
        ]
    }

    static func value(from object: CGPDFObjectRef) -> Any?
    {
        switch (CGPDFObjectGetType(object))
        {
            case .null:

                return nil

            case .boolean:

                var valueRef: CGPDFBoolean = 0
                if CGPDFObjectGetValue(object, .boolean, &valueRef)
                { return Bool(valueRef == 0x01) }

            case .integer:

                var valueRef: CGPDFInteger = 0
                if CGPDFObjectGetValue(object, .integer, &valueRef)
                { return valueRef as Int }

            case .real:

                var valueRef: CGPDFReal = 0.0
                if CGPDFObjectGetValue(object, .real, &valueRef)
                { return Double(valueRef) }

            case .name:

                var objectRefOrNil: UnsafePointer<Int8>? = nil
                if
                    CGPDFObjectGetValue(object, .name, &objectRefOrNil),
                    let objectRef = objectRefOrNil,
                    let string = String(cString: objectRef, encoding: String.Encoding.isoLatin1)
                { return string }

            case .string:

                var objectRefOrNil: UnsafePointer<Int8>? = nil
                if
                    CGPDFObjectGetValue(object, .string, &objectRefOrNil),
                    let objectRef = objectRefOrNil,
                    let stringRef = CGPDFStringCopyTextString(OpaquePointer(objectRef))
                { return stringRef as String }

            case .array:

                var arrayRefOrNil: CGPDFArrayRef? = nil
                if
                    CGPDFObjectGetValue(object, .array, &arrayRefOrNil),
                    let arrayRef = arrayRefOrNil
                {
                    var array: [Any] = []
                    for index in 0 ..< CGPDFArrayGetCount(arrayRef)
                    {
                        var eachObjectRef: CGPDFObjectRef? = nil
                        if
                            CGPDFArrayGetObject(arrayRef, index, &eachObjectRef),
                            let eachObject = eachObjectRef,
                            let eachValue = PDFParser.value(from: eachObject)
                        { array.append(eachValue) }
                    }
                    return array
                }

            case .stream:

                var streamRefOrNil: CGPDFStreamRef? = nil
                if
                    CGPDFObjectGetValue(object, .stream, &streamRefOrNil),
                    let streamRef = streamRefOrNil,
                    let streamDictionaryRef = CGPDFStreamGetDictionary(streamRef)
                {
                    // Get stream dictionary.
                    var streamNSMutableDictionary = NSMutableDictionary()
                    Self.collectObjects(from: streamDictionaryRef, into: &streamNSMutableDictionary)
                    var streamDictionary = streamNSMutableDictionary as! [String: Any?]

                    // Get data.
                    var dataString: String? = Message.couldNotGetStreamData
                    var streamDataFormat: CGPDFDataFormat = .raw
                    if let streamData: CFData = CGPDFStreamCopyData(streamRef, &streamDataFormat)
                    {
                        switch streamDataFormat
                        {
                            case .raw: dataString = String(data: NSData(data: streamData as Data) as Data, encoding: String.Encoding.utf8)
                            case .jpegEncoded, .JPEG2000: dataString = NSData(data: streamData as Data).base64EncodedString()
                        @unknown default: dataString = Message.unknownStreamDataFormat
                        }
                    }

                    // Add to dictionary.
                    streamDictionary["Data"] = dataString

                    return streamDictionary
                }

            case .dictionary:

                var dictionaryRefOrNil: CGPDFDictionaryRef? = nil
                if
                    CGPDFObjectGetValue(object, .dictionary, &dictionaryRefOrNil),
                    let dictionaryRef = dictionaryRefOrNil
                {
                    var dictionary = NSMutableDictionary()
                    Self.collectObjects(from: dictionaryRef, into: &dictionary)
                    return dictionary as! [String: Any?]
                }

            @unknown default:

                var dictionary = NSMutableDictionary()
                Self.collectObjects(from: object, into: &dictionary)
                return dictionary as! [String: Any?]

        }

        // No known case.
        return nil
    }

    static func collectObjects(from dictionaryRef: CGPDFDictionaryRef, into dictionaryPointer: UnsafeMutableRawPointer?)
    {

        CGPDFDictionaryApplyFunction(
            dictionaryRef,
            {
                (eachKeyPointer, eachObject, eachContextOrNil: UnsafeMutableRawPointer?) -> Void in

                // Unwrap dictionary.
                guard let dictionary = eachContextOrNil?.assumingMemoryBound(to: NSMutableDictionary.self).pointee
                else { return print("Could not unwrap dictionary.") }

                // Unwrap key.
                guard let eachKey = String(cString: UnsafePointer<CChar>(eachKeyPointer), encoding: .isoLatin1)
                else { return print("Could not unwrap key.") }

                // Type.
                guard let eachTypeName = PDFParser.namesForTypes[CGPDFObjectGetType(eachObject)]
                else { return print("Could not unwrap type.") }

                // Assemble.
                let eachDictionaryKey = "\(eachKey)<\(eachTypeName)>" as NSString

                // Skip parent.
                guard eachKey != "Parent"
                else
                {
                    dictionary.setObject(Message.parentNotSerialized, forKey: eachDictionaryKey)
                    return
                }

                // Parse value.
                guard let eachValue = PDFParser.value(from: eachObject)
                else
                {
                    dictionary.setObject(Message.couldNotParseValue, forKey: eachDictionaryKey)
                    fatalError("")
                    // return
                }

                // Set.
                dictionary.setObject(eachValue, forKey: eachDictionaryKey)
            },
            dictionaryPointer
        )
    }
}