PDFPatcher/App/Model/PdfModelHelper.cs

using System;
using System.Collections.Generic;
using System.Text;
using iTextSharp.text.pdf;
using System.IO;

namespace PDFPatcher.Model
{
	static class PdfModelHelper
	{
		internal static T Locate<T> (this PdfDictionary source, params object[] path) where T : PdfObject {
			PdfObject s = source;
			if (s == null) {
				return null;
			}
			PdfName n;
			foreach (var item in path) {
				n = item as PdfName;
				if (s == null) {
					return null;
				}
				if (n != null) {
					if (s.Type != PdfObject.DICTIONARY && s.Type != PdfObject.STREAM) {
						return null;
					}
					s = (s as PdfDictionary).GetDirectObject (n);
					continue;
				}
				if (item is Int32 == false) {
					throw new ArgumentException ("参数类型必须为 Int32 或 PdfName");
				}
				int i = (int)item;
				if (s.Type != PdfObject.ARRAY) {
					return null;
				}
				s = (s as PdfArray).GetDirectObject (i);
			}
			return s as T;
		}
		internal static T Locate<T> (this PdfDictionary source, params PdfName[] path) where T : PdfObject {
			return source.Locate<T> (true, path);
		}
		internal static T Locate<T> (this PdfDictionary source, bool resolveRef, params PdfName[] path) where T : PdfObject {
			PdfObject o = null;
			foreach (var item in path) {
				if (source == null) {
					return null;
				}
				o = resolveRef ? source.GetDirectObject (item) : source.Get (item);
				source = o as PdfDictionary;
			}
			return o as T;
		}
		internal static T Locate<T> (this PdfArray source, int index) where T : PdfObject {
			return source.Locate<T> (true, index);
		}
		internal static T Locate<T> (this PdfArray source, bool resolveRef, int index) where T : PdfObject {
			if (source == null) {
				return null;
			}
			return (resolveRef ? source.GetDirectObject (index) : source[index]) as T;
		}
		internal static T CastAs<T> (this PdfIndirectReference pdfRef) where T : PdfObject {
			return PdfReader.GetPdfObject (pdfRef) as T;
		}

		internal static bool ValueIs (this PdfNumber obj, double value) {
			return obj != null && obj.DoubleValue == value;
		}
		internal static bool ValueIs (this PdfBoolean obj, bool value) {
			return obj != null && obj.BooleanValue == value;
		}
		internal static bool ValueIs (this PdfObject obj, PdfName value) {
			return value.Equals (obj);
		}

		internal static int TryGetInt32 (this PdfDictionary source, PdfName key, int defaultValue) {
			var w = source.GetAsNumber (key);
			return (w != null ? w.IntValue : defaultValue);
		}
		internal static bool TryGetBoolean (this PdfDictionary source, PdfName key, bool defaultValue) {
			var b = source.GetAsBoolean (key);
			return (b != null ? b.BooleanValue : defaultValue);
		}

		internal static string Decode (this PdfString text, Encoding encoding) {
			if (text == null) {
				return String.Empty;
			}
			var bytes = text.GetBytes ();
			using (MemoryStream ms = new MemoryStream (bytes)) {
				if (encoding == null) {
					if (bytes.Length >= 2 && (bytes[0] == 0xFF && bytes[1] == 0xFE || bytes[0] == 0xFE && bytes[1] == 0xFF)) {
						using (TextReader r = new StreamReader (ms, true)) {
							return r.ReadToEnd ();
						}
					}
					else {
						return PdfEncodings.ConvertToString (bytes, PdfObject.TEXT_PDFDOCENCODING);
					}
				}
				else {
					// 忽略字节顺序标记
					if (bytes.Length >= 2 && (bytes[0] == 0xFF && bytes[1] == 0xFE || bytes[0] == 0xFE && bytes[1] == 0xFF)) {
						ms.Position += 2;
					}
					else if (bytes.Length >= 3 && bytes[0] == 0xef && bytes[1] == 0xbb && bytes[2] == 0xbf) {
						ms.Position += 3;
					}
					else if (bytes.Length >= 4 && bytes[0] == 0 && bytes[1] == 0 && bytes[2] == 0xfe && bytes[3] == 0xff) {
						ms.Position += 4;
					}
					using (TextReader r = new StreamReader (ms, encoding)) {
						return r.ReadToEnd ();
					}
				}
			}
		}

		internal static PdfString ToPdfString (this string text) {
			if (String.IsNullOrEmpty (text)) {
				return new PdfString ();
			}
			bool u = false;
			foreach (var c in text) {
				if (c > 127) {
					u = true;
					break;
				}
			}
			return u ? new PdfString (text, PdfObject.TEXT_UNICODE) : new PdfString (text);
		}
	}
}