Refactor PDF formats

neilharvey · Nov 19, 2024 · fc30460 · fc30460
1 parent bee2cef
commit fc30460
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Showing 4 changed files with 26 additions and 59 deletions.
diff --git a/src/FileSignatures/FileFormatInspector.cs b/src/FileSignatures/FileFormatInspector.cs
@@ -57,12 +57,12 @@ public FileFormatInspector(IEnumerable<FileFormat> formats)
                 RemoveBaseFormats(matches);
             }
 
-            if (matches.Count > 0)
+            if (matches.Count > 1)
             {
                 return matches.OrderByDescending(m => m.HeaderLength).First();
             }
 
-            return null;
+            return matches.Count == 1 ? matches[0] : null;
         }
 
         private List<FileFormat> FindMatchingFormats(Stream stream)

diff --git a/src/FileSignatures/FileSignatures.csproj b/src/FileSignatures/FileSignatures.csproj
@@ -13,13 +13,13 @@
     <GenerateAssemblyConfigurationAttribute>false</GenerateAssemblyConfigurationAttribute>
     <GenerateAssemblyCompanyAttribute>false</GenerateAssemblyCompanyAttribute>
     <GenerateAssemblyProductAttribute>false</GenerateAssemblyProductAttribute>
-    <Version>5.0.2</Version>
+    <Version>5.0.3-rc1</Version>
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
-    <AssemblyVersion>5.0.2</AssemblyVersion>
+    <AssemblyVersion>5.0.3</AssemblyVersion>
     <LangVersion>Latest</LangVersion>
     <Nullable>enable</Nullable>
-    <FileVersion>5.0.2</FileVersion>
+    <FileVersion>5.0.3</FileVersion>
     <SignAssembly>True</SignAssembly>
     <AssemblyOriginatorKeyFile>..\..\FileSignatures.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>

diff --git a/src/FileSignatures/Formats/AdobePdf.cs b/src/FileSignatures/Formats/AdobePdf.cs
@@ -11,19 +11,16 @@ public AdobePdf() : base([
     ])
     {
     }
-
-    protected override bool CompareFileByteToSignatureAt(byte fileByte, int signatureIndex)
-    {
-        return base.CompareFileByteToSignatureAt(fileByte, signatureIndex) || IsVersionNumber(fileByte, Signature[signatureIndex]);
-    }
-
-    private static bool IsVersionNumber(byte fileByte, byte signatureByte)
+
+    protected override bool IsSignatureByte(byte value, int signatureIndex)
     {
-        return signatureByte == VersionNumberPlaceholder && IsNumber(fileByte);
+        return IsVersionNumber(value, Signature[signatureIndex]) 
+               || base.IsSignatureByte(value, signatureIndex);
     }
 
-    private static bool IsNumber(byte @byte)
+    private static bool IsVersionNumber(byte value, byte signatureByte)
     {
-        return @byte is >= 0x30 and <= 0x39;
+        var isNumber = value is >= 0x30 and <= 0x39;
+        return signatureByte == VersionNumberPlaceholder && isNumber;
     }
 }
diff --git a/src/FileSignatures/Formats/Pdf.cs b/src/FileSignatures/Formats/Pdf.cs
@@ -19,64 +19,34 @@ protected Pdf(byte[] signature) : base(signature, "application/pdf", "pdf", 0)
 
         public override bool IsMatch(Stream stream)
         {
-            if (stream == null || stream.Length < HeaderLength)
+            if (stream == null || (stream.Length < HeaderLength && HeaderLength < int.MaxValue) || Offset > stream.Length)
             {
                 return false;
             }
 
-            stream.Position = 0;
-            var signatureValidationIndex = 0;
-            int fileByte;
+            stream.Position = Offset;
 
-            while (stream.Position < MaxFileHeaderSize && (fileByte = stream.ReadByte()) != -1)
+            var signatureIndex = 0;
+            while (stream.Position < MaxFileHeaderSize && stream.Position < stream.Length)
             {
-                if (CompareFileByteToSignatureAt((byte)fileByte, signatureValidationIndex))
+                var b = (byte)stream.ReadByte();
+                if (IsSignatureByte(b, signatureIndex))
                 {
-                    signatureValidationIndex++;
+                    signatureIndex++;
                 }
                 else
                 {
-                    signatureValidationIndex = 0;
+                    signatureIndex = 0;
                 }
-
-                if (signatureValidationIndex == Signature.Count)
-                    return true;
+                
+                if (signatureIndex == Signature.Count)
+                    return true; 
             }
-
+            
             return false;
         }
 
-        protected virtual bool CompareFileByteToSignatureAt(byte fileByte, int signatureIndex)
-        {
-            return fileByte == Signature[signatureIndex];
-        }
-    }
-
-    public class AdobePdf : Pdf
-    {
-        private const byte VersionNumberPlaceholder = 0x00;
-
-        public AdobePdf() : base([
-            0x25, 0x21, 0x50, 0x53, 0x2D, 0x41, 0x64, 0x6F, 0x62, 0x65, 0x2D, VersionNumberPlaceholder, 0x2E,
-            VersionNumberPlaceholder, 0x20, 0x50, 0x44,
-            0x46, 0x2D, VersionNumberPlaceholder, 0x2E, VersionNumberPlaceholder
-        ])
-        {
-        }
-
-        protected override bool CompareFileByteToSignatureAt(byte fileByte, int signatureIndex)
-        {
-            return base.CompareFileByteToSignatureAt(fileByte, signatureIndex) || IsVersionNumber(fileByte, Signature[signatureIndex]);
-        }
-
-        private static bool IsVersionNumber(byte fileByte, byte signatureByte)
-        {
-            return signatureByte == VersionNumberPlaceholder && IsNumber(fileByte);
-        }
-
-        private static bool IsNumber(byte @byte)
-        {
-            return @byte is >= 0x30 and <= 0x39;
-        }
+        protected virtual bool IsSignatureByte(byte value, int signatureIndex)
+           => value == Signature[signatureIndex];
     }
 }