#71 ignore malformed dates in true type header table. fix reading of dates from bytes

src/UglyToad.PdfPig.Tests/Fonts/TrueType/Parser/TrueTypeFontParserTests.cs

@@ -48,15 +48,15 @@
             Assert.Equal(2048, font.TableRegister.HeaderTable.UnitsPerEm);
 
             Assert.Equal(2008, font.TableRegister.HeaderTable.Created.Year);
-            Assert.Equal(10, font.TableRegister.HeaderTable.Created.Month);
+            Assert.Equal(09, font.TableRegister.HeaderTable.Created.Month);
-            Assert.Equal(13, font.TableRegister.HeaderTable.Created.Day);
+            Assert.Equal(12, font.TableRegister.HeaderTable.Created.Day);
             Assert.Equal(12, font.TableRegister.HeaderTable.Created.Hour);
             Assert.Equal(29, font.TableRegister.HeaderTable.Created.Minute);
             Assert.Equal(34, font.TableRegister.HeaderTable.Created.Second);
 
             Assert.Equal(2011, font.TableRegister.HeaderTable.Modified.Year);
-            Assert.Equal(12, font.TableRegister.HeaderTable.Modified.Month);
+            Assert.Equal(11, font.TableRegister.HeaderTable.Modified.Month);
-            Assert.Equal(31, font.TableRegister.HeaderTable.Modified.Day);
+            Assert.Equal(30, font.TableRegister.HeaderTable.Modified.Day);
             Assert.Equal(5, font.TableRegister.HeaderTable.Modified.Hour);
             Assert.Equal(13, font.TableRegister.HeaderTable.Modified.Minute);
             Assert.Equal(10, font.TableRegister.HeaderTable.Modified.Second);
@@ -158,6 +158,20 @@
             var name = font.Name;
 
             Assert.Equal("Andada Regular", name);
+
+            Assert.Equal(1.001999m, font.TableRegister.HeaderTable.Revision);
+
+            Assert.Equal(11, font.TableRegister.HeaderTable.Flags);
+
+            Assert.Equal(1000, font.TableRegister.HeaderTable.UnitsPerEm);
+
+            Assert.Equal(2011, font.TableRegister.HeaderTable.Created.Year);
+            Assert.Equal(9, font.TableRegister.HeaderTable.Created.Month);
+            Assert.Equal(30, font.TableRegister.HeaderTable.Created.Day);
+
+            Assert.Equal(2017, font.TableRegister.HeaderTable.Modified.Year);
+            Assert.Equal(5, font.TableRegister.HeaderTable.Modified.Month);
+            Assert.Equal(4, font.TableRegister.HeaderTable.Modified.Day);
         }
 
         [Fact]

src/UglyToad.PdfPig/Fonts/TrueType/Tables/HeaderTable.cs

@@ -2,6 +2,7 @@
 {
     using System;
     using Geometry;
+    using PdfPig.Exceptions;
 
     /// <summary>
     /// The 'head' table contains global information about the font. 
@@ -99,8 +100,26 @@
                 throw new InvalidOperationException($"The units per em for this TrueType font was incorrect, value should be between 16 and 16384 but found {unitsPerEm} istead.");
             }
 
-            var created = data.ReadInternationalDate();
+            DateTime created;
-            var modified = data.ReadInternationalDate();
+            try
+            {
+                created = data.ReadInternationalDate();
+            }
+            catch (PdfDocumentFormatException)
+            {
+                created = DateTime.MinValue;
+            }
+
+            DateTime modified;
+            try
+            {
+                modified = data.ReadInternationalDate();
+            }
+            catch (PdfDocumentFormatException)
+            {
+                modified = DateTime.MinValue;
+            }
+
             var xMin = data.ReadSignedShort();
             var yMin = data.ReadSignedShort();
             var xMax = data.ReadSignedShort();

src/UglyToad.PdfPig/Fonts/TrueType/TrueTypeDataBytes.cs

@@ -4,6 +4,7 @@
     using System.IO;
     using System.Text;
     using IO;
+    using PdfPig.Exceptions;
 
     internal class TrueTypeDataBytes
     {
@@ -99,43 +100,35 @@
 
         public long ReadLong()
         {
-            ReadBuffered(internalBuffer, 8);
+            var upper = (long)ReadSignedInt();
-
+            var lower = ReadSignedInt();
-            var result = FromBytes(internalBuffer, 0, 8);
+            var result = (upper << 32) + (lower & 0xFFFFFFFF);
-
             return result;
         }
 
         public DateTime ReadInternationalDate()
         {
-            // TODO: this returns the wrong value, investigate...
+            var secondsSince1904 = ReadLong();
-            long secondsSince1904 = ReadLong();
 
             var date = new DateTime(1904, 1, 1, 0, 0, 0, DateTimeKind.Utc);
 
+            try
+            {
                 var result = date.AddSeconds(secondsSince1904);
-            result = result.AddMonths(1);
-            result = result.AddDays(1);
 
                 return result;
             }
+            catch (ArgumentOutOfRangeException)
+            {
+                throw new PdfDocumentFormatException($"Invalid date offset ({secondsSince1904} seconds) encountered in TrueType header table.");
+            }
+        }
 
         public void Seek(long position)
         {
             inputBytes.Seek(position);
         }
 
-        private long FromBytes(byte[] buffer, int startIndex, int bytesToConvert)
-        {
-            long ret = 0;
-            for (int i = 0; i < bytesToConvert; i++)
-            {
-                ret = unchecked((ret << 8) | buffer[startIndex + i]);
-            }
-
-            return ret;
-        }
-
         public int ReadSignedByte()
         {
             ReadBuffered(internalBuffer, 1);