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Code Issues Packages Projects Releases Wiki Activity

Small Fixes (#3951)

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This commit is contained in:
Joe Milazzo
2025-07-24 13:37:17 -06:00
committed by GitHub
parent 152f7ad00e
commit 032b8f54b7
23 changed files with 459 additions and 285 deletions
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API/Helpers/PdfMetadataExtractor.cs
+131 -101
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@@ -1,23 +1,51 @@
/**
* Contributed by https://github.com/microtherion
*
* All references to the "PDF Spec" (section numbers, etc) refer to the
* PDF 1.7 Specification a.k.a. PDF32000-1:2008
* https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf
*/
using System;
using System.Collections.Generic;
using System.IO.Compression;
using System.Text;
using System.Xml;
using System.IO;
using Microsoft.Extensions.Logging;
using API.Services;
using Microsoft.Extensions.Logging;
namespace API.Helpers;
#nullable enable
/**
* Contributed by https://github.com/microtherion
*
* All references to the "PDF Spec" (section numbers, etc.) refer to the
* PDF 1.7 Specification a.k.a. PDF32000-1:2008
* https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf
*/
/**
* Reference for PDF Metadata Format
%PDF-1.4 ← Header
Object 1 0 obj ← Objects containing content
<< /Type /Catalog ... >>
endobj
Object 2 0 obj
<< /Type /Info ... >>
endobj
...more objects...
xref ← Cross-reference table
0 6
0000000000 65535 f
0000000015 00000 n ← Object 1 is at byte offset 15
0000000109 00000 n ← Object 2 is at byte offset 109
...
trailer ← Trailer dictionary
<< /Size 6 /Root 1 0 R /Info 2 0 R >>
startxref
1234 ← Byte offset where xref starts
%%EOF
*/
/// <summary>
/// Parse PDF file and try to extract as much metadata as possible.
/// Supports both text based XRef tables and compressed XRef streams (Deflate only).
@@ -41,17 +69,17 @@ public class PdfMetadataExtractorException : Exception
}
}
public interface IPdfMetadataExtractor
public interface IPdfMetadataExtractor : IDisposable
{
Dictionary<String, String> GetMetadata();
Dictionary<string, string> GetMetadata();
}
class PdfStringBuilder
internal class PdfStringBuilder
{
private readonly StringBuilder _builder = new();
private bool _secondByte = false;
private byte _prevByte = 0;
private bool _isUnicode = false;
private bool _secondByte;
private byte _prevByte;
private bool _isUnicode;
// PDFDocEncoding defined in PDF Spec D.1
@@ -71,11 +99,11 @@ class PdfStringBuilder
private void AppendPdfDocByte(byte b)
{
if (b >= 0x18 && b < 0x20)
if (b is >= 0x18 and < 0x20)
{
_builder.Append(_pdfDocMappingLow[b - 0x18]);
}
else if (b >= 0x80 && b < 0xA1)
else if (b is >= 0x80 and < 0xA1)
{
_builder.Append(_pdfDocMappingHigh[b - 0x80]);
}
@@ -95,28 +123,24 @@ class PdfStringBuilder
// PDF Spec 7.9.2.1: Strings are either UTF-16BE or PDFDocEncoded
if (_builder.Length == 0 && !_isUnicode)
{
// Unicode strings are prefixed by a big endian BOM \uFEFF
if (_secondByte)
switch (_secondByte)
{
if (b == 0xFF)
{
// Unicode strings are prefixed by a big endian BOM \uFEFF
case true when b == 0xFF:
_isUnicode = true;
_secondByte = false;
}
else
{
break;
case true:
AppendPdfDocByte(_prevByte);
AppendPdfDocByte(b);
}
}
else if (!_secondByte && b == 0xFE)
{
_secondByte = true;
_prevByte = b;
}
else
{
AppendPdfDocByte(b);
break;
case false when b == 0xFE:
_secondByte = true;
_prevByte = b;
break;
default:
AppendPdfDocByte(b);
break;
}
}
else if (_isUnicode)
@@ -138,7 +162,7 @@ class PdfStringBuilder
}
}
override public string ToString()
public override string ToString()
{
if (_builder.Length == 0 && _secondByte)
{
@@ -153,8 +177,8 @@ internal class PdfLexer(Stream stream)
{
private const int BufferSize = 1024;
private readonly byte[] _buffer = new byte[BufferSize];
private int _pos = 0;
private int _valid = 0;
private int _pos;
private int _valid;
public enum TokenType
{
@@ -353,10 +377,8 @@ internal class PdfLexer(Stream stream)
{
return (long)token.Value;
}
else
{
throw new PdfMetadataExtractorException("Expected integer after startxref keyword");
}
throw new PdfMetadataExtractorException("Expected integer after startxref keyword");
}
continue;
@@ -367,10 +389,18 @@ internal class PdfLexer(Stream stream)
}
}
public bool NextXRefEntry(ref long obj, ref int generation)
/// <summary>
///
/// </summary>
/// <example>
/// 0000000015 00000 n ← offset=15, generation=0, in-use
/// 0000000109 00000 n ← offset=109, generation=0, in-use
/// 0000000000 65535 f ← offset=0, generation=65535, free
/// </example>
/// <remarks>Cross-reference table entry as per PDF Spec 7.5.4</remarks>
/// <exception cref="PdfMetadataExtractorException"></exception>
public bool NextXRefEntry(out long offset, out int generation)
{
// Cross-reference table entry as per PDF Spec 7.5.4
WantLookahead(20);
if (_valid - _pos < 20)
@@ -378,14 +408,11 @@ internal class PdfLexer(Stream stream)
throw new PdfMetadataExtractorException("End of stream");
}
var inUse = true;
// Parse the 20-byte XRef entry: "nnnnnnnnnn ggggg n/f \r\n"
offset = Convert.ToInt64(Encoding.ASCII.GetString(_buffer, _pos, 10).Trim());
generation = Convert.ToInt32(Encoding.ASCII.GetString(_buffer, _pos + 11, 5).Trim());
if (obj == 0)
{
obj = Convert.ToInt64(Encoding.ASCII.GetString(_buffer, _pos, 10));
generation = Convert.ToInt32(Encoding.ASCII.GetString(_buffer, _pos + 11, 5));
inUse = _buffer[_pos + 17] == 'n';
}
var inUse = _buffer[_pos + 17] == 'n';
_pos += 20;
@@ -503,7 +530,7 @@ internal class PdfLexer(Stream stream)
{
StringBuilder sb = new();
var hasDot = LastByte() == '.';
var followedBySpace = false;
bool followedBySpace;
sb.Append((char)LastByte());
@@ -647,7 +674,8 @@ internal class PdfLexer(Stream stream)
case '(':
parenLevel++;
goto default;
sb.AppendByte(b);
break;
case ')':
if (--parenLevel == 0)
@@ -655,7 +683,8 @@ internal class PdfLexer(Stream stream)
return new Token(TokenType.String, sb.ToString());
}
goto default;
sb.AppendByte(b);
break;
case '\\':
b = NextByte();
@@ -688,7 +717,6 @@ internal class PdfLexer(Stream stream)
break;
case >= '0' and <= '7':
var b1 = b;
var b2 = NextByte();
var b3 = NextByte();
@@ -697,7 +725,7 @@ internal class PdfLexer(Stream stream)
throw new PdfMetadataExtractorException("Invalid octal escape, got {b1}{b2}{b3}");
}
sb.AppendByte((byte)((b1 - '0') << 6 | (b2 - '0') << 3 | (b3 - '0')));
sb.AppendByte((byte)((b - '0') << 6 | (b2 - '0') << 3 | (b3 - '0')));
break;
}
@@ -763,26 +791,15 @@ internal class PdfLexer(Stream stream)
}
}
switch (sb.ToString())
return sb.ToString() switch
{
case "true":
return new Token(TokenType.Bool, true);
case "false":
return new Token(TokenType.Bool, false);
case "stream":
return new Token(TokenType.StreamStart, true);
case "endstream":
return new Token(TokenType.StreamEnd, true);
case "endobj":
return new Token(TokenType.ObjectEnd, true);
default:
return new Token(TokenType.Keyword, sb.ToString());
}
"true" => new Token(TokenType.Bool, true),
"false" => new Token(TokenType.Bool, false),
"stream" => new Token(TokenType.StreamStart, true),
"endstream" => new Token(TokenType.StreamEnd, true),
"endobj" => new Token(TokenType.ObjectEnd, true),
_ => new Token(TokenType.Keyword, sb.ToString())
};
}
}
@@ -791,9 +808,10 @@ internal class PdfMetadataExtractor : IPdfMetadataExtractor
private readonly ILogger<BookService> _logger;
private readonly PdfLexer _lexer;
private readonly FileStream _stream;
private long[] _objectOffsets = new long[0];
private readonly Dictionary<long, long> _objectOffsets = [];
private readonly Dictionary<string, string> _metadata = [];
private readonly Stack<MetadataRef> _metadataRef = new();
private bool _disposed;
private struct MetadataRef(long root, long info)
{
@@ -801,7 +819,7 @@ internal class PdfMetadataExtractor : IPdfMetadataExtractor
public long Info = info;
}
private struct XRefSection(long first, long count)
private readonly struct XRefSection(long first, long count)
{
public readonly long First = first;
public readonly long Count = count;
@@ -822,7 +840,9 @@ internal class PdfMetadataExtractor : IPdfMetadataExtractor
return _metadata;
}
#pragma warning disable S1144
private void LogMetadata(string filename)
#pragma warning restore S1144
{
_logger.LogTrace("Metadata for {Path}:", filename);
@@ -854,14 +874,11 @@ internal class PdfMetadataExtractor : IPdfMetadataExtractor
if (!_lexer.TestByte((byte)'x'))
{
// Cross-reference stream (PDF Spec 7.5.8)
ReadXRefStream();
return;
}
// Cross-reference table (PDF Spec 7.5.4)
var token = _lexer.NextToken();
if (token.Type != PdfLexer.TokenType.Keyword || (string)token.Value != "xref")
@@ -885,23 +902,17 @@ internal class PdfMetadataExtractor : IPdfMetadataExtractor
var numObj = (long)token.Value;
if (_objectOffsets.Length < startObj + numObj)
{
Array.Resize(ref _objectOffsets, (int)(startObj + numObj));
}
_lexer.ExpectNewline();
var generation = 0;
for (var obj = startObj; obj < startObj + numObj; ++obj)
{
var inUse = _lexer.NextXRefEntry(ref _objectOffsets[obj], ref generation);
var inUse = _lexer.NextXRefEntry(out var offset, out var generation);
if (!inUse)
if (inUse && offset > 0)
{
_objectOffsets[obj] = 0;
_objectOffsets[obj] = offset ;
}
// Free objects (inUse == false) are not stored in the dictionary
}
}
else if (token.Type == PdfLexer.TokenType.Keyword && (string)token.Value == "trailer")
@@ -1105,11 +1116,6 @@ internal class PdfMetadataExtractor : IPdfMetadataExtractor
{
var section = sections.Dequeue();
if (_objectOffsets.Length < size)
{
Array.Resize(ref _objectOffsets, (int)size);
}
for (var i = section.First; i < section.First + section.Count; ++i)
{
long type = 0;
@@ -1136,9 +1142,9 @@ internal class PdfMetadataExtractor : IPdfMetadataExtractor
generation = (generation << 8) | (ushort)stream.ReadByte();
}
if (type == 1 && _objectOffsets[i] == 0)
if (type == 1)
{
_objectOffsets[i] = offset;
_objectOffsets.TryAdd(i, offset);
}
}
}
@@ -1253,7 +1259,7 @@ internal class PdfMetadataExtractor : IPdfMetadataExtractor
{
var meta = _metadataRef.Pop();
//_logger.LogTrace("DocumentCatalog for {Path}: {Root}, Info: {Info}", filename, meta.root, meta.info);
_logger.LogTrace("DocumentCatalog for {Path}: {Root}, Info: {Info}", filename, meta.Root, meta.Info);
ReadMetadataFromInfo(meta.Info);
ReadMetadataFromXml(MetadataObjInObjectCatalog(meta.Root));
@@ -1265,7 +1271,7 @@ internal class PdfMetadataExtractor : IPdfMetadataExtractor
// Document information dictionary (PDF Spec 14.3.3)
// We treat this as less authoritative than the Metadata stream.
if (infoObj < 1 || infoObj >= _objectOffsets.Length || _objectOffsets[infoObj] == 0)
if (!HasObject(infoObj))
{
return;
}
@@ -1338,7 +1344,7 @@ internal class PdfMetadataExtractor : IPdfMetadataExtractor
{
// Look for /Metadata entry in document catalog (PDF Spec 7.7.2)
if (rootObj < 1 || rootObj >= _objectOffsets.Length || _objectOffsets[rootObj] == 0)
if (!HasObject(rootObj))
{
return -1;
}
@@ -1416,7 +1422,7 @@ internal class PdfMetadataExtractor : IPdfMetadataExtractor
private void ReadMetadataFromXml(long meta)
{
if (meta < 1 || meta >= _objectOffsets.Length || _objectOffsets[meta] == 0) return;
if (!HasObject(meta)) return;
_stream.Seek(_objectOffsets[meta], SeekOrigin.Begin);
_lexer.ResetBuffer();
@@ -1634,4 +1640,28 @@ internal class PdfMetadataExtractor : IPdfMetadataExtractor
SkipValue();
}
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool disposing)
{
if (_disposed || !disposing) return;
_stream.Dispose();
_disposed = true;
}
private bool HasObject(long objNum)
{
return _objectOffsets.ContainsKey(objNum) && _objectOffsets[objNum] > 0;
}
private long GetObjectOffset(long objNum)
{
return _objectOffsets.TryGetValue(objNum, out var offset) ? offset : 0;
}
}