Refactor QPDFTokenizer's inline image handling

Add a version of expectInlineImage that takes an input source and
searches for EI. This is in preparation for improving the way EI is
found. This commit just refactors the code without changing the
functionality and adds tests to make sure the old and new code behave
identically.

1 files changed, 110 insertions, 7 deletions

diff --git a/libqpdf/QPDFTokenizer.cc b/libqpdf/QPDFTokenizer.cc
index c11c8218..e03f927b 100644
--- a/libqpdf/QPDFTokenizer.cc
+++ b/libqpdf/QPDFTokenizer.cc
@@ -13,6 +13,79 @@
 #include <string.h>
 #include <cstdlib>
 
+static bool is_delimiter(char ch)
+{
+    return (strchr(" \t\n\v\f\r()<>[]{}/%", ch) != 0);
+}
+
+class QPDFWordTokenFinder: public InputSource::Finder
+{
+  public:
+    QPDFWordTokenFinder(PointerHolder<InputSource> is,
+                        std::string const& str) :
+        is(is),
+        str(str)
+    {
+    }
+    virtual ~QPDFWordTokenFinder()
+    {
+    }
+    virtual bool check();
+
+  private:
+    PointerHolder<InputSource> is;
+    std::string str;
+};
+
+bool
+QPDFWordTokenFinder::check()
+{
+    // Find a word token matching the given string, preceded by a
+    // delimiter, and followed by a delimiter or EOF.
+    QPDFTokenizer tokenizer;
+    QPDFTokenizer::Token t = tokenizer.readToken(is, "finder", true);
+    qpdf_offset_t pos = is->tell();
+    if (! (t == QPDFTokenizer::Token(QPDFTokenizer::tt_word, str)))
+    {
+///        QTC::TC("qpdf", "QPDFTokenizer finder found wrong word");
+        return false;
+    }
+    qpdf_offset_t token_start = is->getLastOffset();
+    char next;
+    bool next_okay = false;
+    if (is->read(&next, 1) == 0)
+    {
+        QTC::TC("qpdf", "QPDFTokenizer inline image at EOF");
+        next_okay = true;
+    }
+    else
+    {
+        next_okay = is_delimiter(next);
+    }
+    is->seek(pos, SEEK_SET);
+    if (! next_okay)
+    {
+///        QTC::TC("qpdf", "QPDFTokenizer finder word not followed by delimiter");
+        return false;
+    }
+    if (token_start == 0)
+    {
+        // Can't actually happen...we never start the search at the
+        // beginning of the input.
+        return false;
+    }
+    is->seek(token_start - 1, SEEK_SET);
+    char prev;
+    bool prev_okay = ((is->read(&prev, 1) == 1) && is_delimiter(prev));
+    is->seek(pos, SEEK_SET);
+    if (! prev_okay)
+    {
+///        QTC::TC("qpdf", "QPDFTokenizer finder word not preceded by delimiter");
+        return false;
+    }
+    return true;
+}
+
 QPDFTokenizer::Members::Members() :
     pound_special_in_name(true),
     allow_eof(false),
@@ -31,6 +104,7 @@ QPDFTokenizer::Members::reset()
     error_message = "";
     unread_char = false;
     char_to_unread = '\0';
+    inline_image_bytes = 0;
     string_depth = 0;
     string_ignoring_newline = false;
     last_char_was_bs = false;
@@ -91,7 +165,7 @@ QPDFTokenizer::isSpace(char ch)
 bool
 QPDFTokenizer::isDelimiter(char ch)
 {
-    return (strchr(" \t\n\v\f\r()<>[]{}/%", ch) != 0);
+    return is_delimiter(ch);
 }
 
 void
@@ -470,12 +544,21 @@ QPDFTokenizer::presentCharacter(char ch)
     {
         this->m->val += ch;
         size_t len = this->m->val.length();
-        if ((len >= 4) &&
-            isDelimiter(this->m->val.at(len-4)) &&
-            (this->m->val.at(len-3) == 'E') &&
-            (this->m->val.at(len-2) == 'I') &&
-            isDelimiter(this->m->val.at(len-1)))
+        if (len == this->m->inline_image_bytes)
+        {
+            QTC::TC("qpdf", "QPDFTokenizer found EI by byte count");
+            this->m->type = tt_inline_image;
+            this->m->inline_image_bytes = 0;
+            this->m->state = st_token_ready;
+        }
+        else if ((this->m->inline_image_bytes == 0) &&
+                 (len >= 4) &&
+                 isDelimiter(this->m->val.at(len-4)) &&
+                 (this->m->val.at(len-3) == 'E') &&
+                 (this->m->val.at(len-2) == 'I') &&
+                 isDelimiter(this->m->val.at(len-1)))
         {
+            QTC::TC("qpdf", "QPDFTokenizer found EI the old way");
             this->m->val.erase(len - 1);
             this->m->type = tt_inline_image;
             this->m->unread_char = true;
@@ -562,7 +645,7 @@ QPDFTokenizer::presentEOF()
             (this->m->val.at(len-2) == 'E') &&
             (this->m->val.at(len-1) == 'I'))
         {
-            QTC::TC("qpdf", "QPDFTokenizer inline image at EOF");
+            QTC::TC("qpdf", "QPDFTokenizer inline image at EOF the old way");
             this->m->type = tt_inline_image;
             this->m->state = st_token_ready;
         }
@@ -598,6 +681,26 @@ QPDFTokenizer::presentEOF()
 void
 QPDFTokenizer::expectInlineImage()
 {
+    expectInlineImage(PointerHolder<InputSource>());
+}
+
+void
+QPDFTokenizer::expectInlineImage(PointerHolder<InputSource> input)
+{
+    if (input.getPointer())
+    {
+        qpdf_offset_t last_offset = input->getLastOffset();
+        qpdf_offset_t pos = input->tell();
+
+        QPDFWordTokenFinder f(input, "EI");
+        if (input->findFirst("EI", pos, 0, f))
+        {
+            this->m->inline_image_bytes = input->tell() - pos;
+        }
+
+        input->seek(pos, SEEK_SET);
+        input->setLastOffset(last_offset);
+    }
     if (this->m->state != st_top)
     {
         throw std::logic_error("QPDFTokenizer::expectInlineImage called"