Avoid truncating inline images, where the data and the "EI" marker is glued together (issue 10388) (#10436)

Thanks to the *excellent* debugging done by @janpe2, this was easy to fix!

src/core/parser.js

@@ -222,7 +222,18 @@ var Parser = (function ParserClosure() {
           stream.skip(-(stream.pos - maybeEIPos)); // Reset the stream position.
         }
       }
-      return ((stream.pos - 4) - startPos);
+
+      let endOffset = 4;
+      stream.skip(-endOffset); // Set the stream position to just before "EI".
+      ch = stream.peekByte();
+      stream.skip(endOffset); // ... and remember to reset the stream position.
+
+      // Ensure that we don't accidentally truncate the inline image, when the
+      // data is immediately followed by the "EI" marker (fixes issue10388.pdf).
+      if (!isSpace(ch)) {
+        endOffset--;
+      }
+      return ((stream.pos - endOffset) - startPos);
     },
     /**
      * Find the EOI (end-of-image) marker 0xFFD9 of the stream.

test/pdfs/.gitignore

@@ -72,6 +72,7 @@
 !issue9458.pdf
 !issue9915_reduced.pdf
 !issue9940.pdf
+!issue10388_reduced.pdf
 !issue10438_reduced.pdf
 !bad-PageLabels.pdf
 !decodeACSuccessive.pdf

test/test_manifest.json

@@ -739,6 +739,13 @@
        "link": true,
        "type": "load"
     },
+    {  "id": "issue10388",
+       "file": "pdfs/issue10388_reduced.pdf",
+       "md5": "62a6b2adbea1535432bd94a3516e2d4c",
+       "rounds": 1,
+       "link": false,
+       "type": "eq"
+    },
     {  "id": "issue7507",
        "file": "pdfs/issue7507.pdf",
        "md5": "f7aeaafe0c89b94436e94eaa63307303",