Refactor `QPDF` pattern-finding methods: relocate `findHeader`, `findStartxref`,…

… and `findEndstream` to `Objects`, remove `QPDF::PatternFinder` class, and update related logic for improved encapsulation.

Refactor `QPDF` pattern-finding methods: relocate `findHeader`, `findStartxref`,…
… and `findEndstream` to `Objects`, remove `QPDF::PatternFinder` class, and update related logic for improved encapsulation.
m-holger
1 parent 8ded7ff5
Showing 5 changed files with 59 additions and 63 deletions
include/qpdf/QPDF.hh
libqpdf/QPDF.cc
libqpdf/QPDF_objects.cc
libqpdf/qpdf/QPDF_private.hh
qpdf/qpdf.testcov
@@ -791,13 +791,7 @@ class QPDF
         bool is_root_metadata,
         std::unique_ptr<Pipeline>& heap);
  
-    class PatternFinder;
-
-    // Methods to support pattern finding
     static bool validatePDFVersion(char const*&, std::string& version);
-    bool findHeader();
-    bool findStartxref();
-    bool findEndstream();
  
     // JSON import
     void importJSON(std::shared_ptr<InputSource>, bool must_be_complete);
@@ -334,33 +334,6 @@ QPDF::validatePDFVersion(char const*&amp; p, std::string&amp; version)
     return true;
 }
  
-bool
-QPDF::findHeader()
-{
-    qpdf_offset_t global_offset = m->file->tell();
-    std::string line = m->file->readLine(1024);
-    char const* p = line.data();
-    if (strncmp(p, "%PDF-", 5) != 0) {
-        throw std::logic_error("findHeader is not looking at %PDF-");
-    }
-    p += 5;
-    std::string version;
-    // Note: The string returned by line.data() is always null-terminated. The code below never
-    // overruns the buffer because a null character always short-circuits further advancement.
-    if (!validatePDFVersion(p, version)) {
-        return false;
-    }
-    m->pdf_version = version;
-    if (global_offset != 0) {
-        // Empirical evidence strongly suggests (codified in PDF 2.0 spec) that when there is
-        // leading material prior to the PDF header, all explicit offsets in the file are such that
-        // 0 points to the beginning of the header.
-        QTC::TC("qpdf", "QPDF global offset");
-        m->file = std::make_shared<OffsetInputSource>(m->file, global_offset);
-    }
-    return true;
-}
-
 void
 QPDF::warn(QPDFExc const& e)
 {
@@ -3,6 +3,7 @@
 #include <qpdf/QPDF_private.hh>
  
 #include <qpdf/InputSource_private.hh>
+#include <qpdf/OffsetInputSource.hh>
 #include <qpdf/Pipeline.hh>
 #include <qpdf/QPDFExc.hh>
 #include <qpdf/QPDFLogger.hh>
@@ -101,11 +102,54 @@ class QPDF::ResolveRecorder final
     std::set<QPDFObjGen>::const_iterator iter;
 };
  
+class Objects::PatternFinder final: public InputSource::Finder
+{
+  public:
+    PatternFinder(Objects& o, bool (Objects::*checker)()) :
+        o(o),
+        checker(checker)
+    {
+    }
+    ~PatternFinder() final = default;
+    bool
+    check() final
+    {
+        return (this->o.*checker)();
+    }
+
+  private:
+    Objects& o;
+    bool (Objects::*checker)();
+};
+
+bool
+Objects::findHeader()
+{
+    qpdf_offset_t global_offset = m->file->tell();
+    std::string line = m->file->readLine(1024);
+    char const* p = line.data();
+    util::assertion(strncmp(p, "%PDF-", 5) == 0, "findHeader is not looking at %PDF-");
+    p += 5;
+    std::string version;
+    // Note: The string returned by line.data() is always null-terminated. The code below never
+    // overruns the buffer because a null character always short-circuits further advancement.
+    if (!validatePDFVersion(p, version)) {
+        return false;
+    }
+    m->pdf_version = version;
+    if (global_offset != 0) {
+        // Empirical evidence strongly suggests (codified in PDF 2.0 spec) that when there is
+        // leading material prior to the PDF header, all explicit offsets in the file are such that
+        // 0 points to the beginning of the header.
+        m->file = std::make_shared<OffsetInputSource>(m->file, global_offset);
+    }
+    return true;
+}
+
 bool
-QPDF::findStartxref()
+Objects ::findStartxref()
 {
-    if (m->objects.readToken(*m->file).isWord("startxref") &&
-        m->objects.readToken(*m->file).isInteger()) {
+    if (readToken(*m->file).isWord("startxref") && readToken(*m->file).isInteger()) {
         // Position in front of offset token
         m->file->seek(m->file->getLastOffset(), SEEK_SET);
         return true;
@@ -121,7 +165,7 @@ Objects::parse(char const* password)
     }
  
     // Find the header anywhere in the first 1024 bytes of the file.
-    PatternFinder hf(qpdf, &QPDF::findHeader);
+    PatternFinder hf(*this, &Objects::findHeader);
     if (!m->file->findFirst("%PDF-", 0, 1024, hf)) {
         warn(damagedPDF("", -1, "can't find PDF header"));
         // QPDFWriter writes files that usually require at least version 1.2 for /FlateDecode
@@ -139,7 +183,7 @@ Objects::parse(char const* password)
         m->xref_table_max_id = static_cast<int>(m->xref_table_max_offset / 3);
     }
     qpdf_offset_t start_offset = (end_offset > 1054 ? end_offset - 1054 : 0);
-    PatternFinder sf(qpdf, &QPDF::findStartxref);
+    PatternFinder sf(*this, &Objects::findStartxref);
     qpdf_offset_t xref_offset = 0;
     if (m->file->findLast("startxref", start_offset, 0, sf)) {
         xref_offset = QUtil::string_to_ll(readToken(*m->file).getValue().c_str());
@@ -1324,10 +1368,10 @@ Objects::readObjectInStream(is::OffsetBuffer&amp; input, int stream_id, int obj_id)
 }
  
 bool
-QPDF::findEndstream()
+Objects ::findEndstream()
 {
     // Find endstream or endobj. Position the input at that token.
-    auto t = m->objects.readToken(*m->file, 20);
+    auto t = readToken(*m->file, 20);
     if (t.isWord("endobj") || t.isWord("endstream")) {
         m->file->seek(m->file->getLastOffset(), SEEK_SET);
         return true;
@@ -1342,7 +1386,7 @@ Objects::recoverStreamLength(
     // Try to reconstruct stream length by looking for endstream or endobj
     warn(damagedPDF(*input, stream_offset, "attempting to recover stream length"));
  
-    PatternFinder ef(qpdf, &QPDF::findEndstream);
+    PatternFinder ef(*this, &Objects::findEndstream);
     size_t length = 0;
     if (m->file->findFirst("end", stream_offset, 0, ef)) {
         length = toS(m->file->tell() - stream_offset);
@@ -242,27 +242,6 @@ class QPDF::StringDecrypter final: public QPDFObjectHandle::StringDecrypter
     QPDF* qpdf;
     QPDFObjGen og;
 };
-// Other linearization data structures
-
-class QPDF::PatternFinder final: public InputSource::Finder
-{
-  public:
-    PatternFinder(QPDF& qpdf, bool (QPDF::*checker)()) :
-        qpdf(qpdf),
-        checker(checker)
-    {
-    }
-    ~PatternFinder() final = default;
-    bool
-    check() final
-    {
-        return (this->qpdf.*checker)();
-    }
-
-  private:
-    QPDF& qpdf;
-    bool (QPDF::*checker)();
-};
  
 // This class is used to represent a PDF document.
 //
@@ -1028,6 +1007,8 @@ class QPDF::Doc::Objects: Common
     std::vector<bool> compressible_set();
  
   private:
+    class PatternFinder;
+
     // Get a list of objects that would be permitted in an object stream.
     template <typename T>
     std::vector<T> compressible();
@@ -1071,6 +1052,11 @@ class QPDF::Doc::Objects: Common
     bool isUnresolved(QPDFObjGen og);
     void setLastObjectDescription(std::string const& description, QPDFObjGen og);
  
+    // Methods to support pattern finding
+    bool findHeader();
+    bool findStartxref();
+    bool findEndstream();
+
     Foreign foreign_;
     Streams streams_;
  
@@ -129,7 +129,6 @@ QPDFObjectHandle trailing data in parse 0
 QPDFTokenizer EOF reading token 0
 QPDFTokenizer EOF reading appendable token 0
 QPDFWriter extra header text no newline 0
-QPDF global offset 0
 QPDFWriter make Extensions direct 0
 QPDFWriter make ADBE direct 1
 QPDFWriter preserve Extensions 0