Hi,

I have an uncompressed PDF file. I'm trying to find all locations/positions that contain the following format: <digit> 0 obj at the beginning of a line. E.g.: 3 0 obj.
Once I found an occurrence, I want to know how much bytes are "occupied" from the beginning of the file until that position found.

The file also contains, next to regular ASCII characters, binary data. A snippet is shown here below:

/CapHeight 667
>>
endobj 
1 0 obj 
<<
/Subtype /Type1C
/Length 1194
2 0 obj 
>>
stream
3 0 obj 
  BXTBMO+URWTypewriterTOT-LigNar %øøøûûúNú% Lm
÷/÷>¦ 7D(URW)++,Copyright 2003 by (URW)++ Design & Developmen
+t/FSType 4 def    - B F H J O S    r ¡S»OÑûb싸øÕ¸÷Å÷°À
+ø÷KŸ—{zwû
}†…}ûŠ}†‘™ø­™‘™Ô›”“š™‚“{ûp{ƒ|}•ƒ›¾™…}ü­}†…}X{ƒ|}•ƒ›
+øMœ’’Å}µ÷g°÷4µµÄ÷¢Áø£z’„œÜš”“˜˜‚’|k}†‘š÷΃ªr¨°m\\œH
+^f„|oaviZb{—~™™–•›È”¸¬×¶©‚v¡¤t‘uJˆ„„‰ƒ‹Œ„YŒ<Z„{hYso^P4Ç
+UîἬڬ.÷!±´‰‰ˆŽ†„e~L~u^r^sPDa±ÊÕį÷º}µ÷V´÷Aµ±ÆøN÷rš“’›
+¥ƒº¨àoH¹+û8.û.û-Þ/÷ÖÀ¢º®Ÿ¥š­œ›‚–}…„w†H{Ue?T^Ÿ±lr©zº±–’‘
+˜´‚†•«Ÿ¼¥©©¤´œº·±|p¤¨lž^d……òûIµ÷#µø
´oµ±Ã÷ÐÁ¬ø.…uƒovat_wJ>Y¨¾ˆ„’{{~~zužj¤vo¬º~ÑÛ»¸¯§­—¶Ïø
+™‘™²š”’˜™‚’|3{„„zI\\ÎsO°8û=1û\'û#Ý-÷¹ž¯®œ‘–’£û-÷Ø·®|l
+©­g–fAG‚fsken^uZ+JÛ÷÷ÊÖï‹´ø´öÜÞÜKÁè÷.øLœ„’z4|‚ƒ~”ƒš±
+™…}ûê}†…}e|‚ƒ~”ƒš÷6š”“—˜‚“|k}†‘™ðløãuyyuužx¡¡¡¢ytñ‹
+´ø´oµðÁ÷–ÁØ÷/øLœ„’z3|‚ƒ~”ƒš²™…}ûê}†…}d|‚ƒ~”ƒš÷=š”“—˜
+‚“|e}†‘™÷i¸ïÀÉàÙµ_9û}†…}e|‚ƒ~”ƒš÷=š”“—˜‚“|d}†‘™÷œîSÁ
+%>TfIu ‹´ø´oµðÁÐ÷/øLœ„’z3|‚ƒ~”ƒš²™…}ûê}†…}d|‚ƒ~”ƒš÷
+Mš”“—˜‚“|U}†‘™÷\\ۥº¢0”ž©“œŽ‹‰‘Š’Ž‹”‘’—›}•rec{rqyy‚{‚i
+wŸødŸ÷KŸ¶
öŽÃ’
÷Œø\\
endstream 
endobj 
4 0 obj 
<<
/Length 422
>>

[download]

To find the locations in the above code snippet, I'm using a regex like so: qr/^\d+ 0 obj/m.

This is the test code I'm using ($pdf contains the string and \d is replace with a fixed number as a test): 

my $result = $pdf=~qr/^1 0 obj/m;
say "Finding first item at start position  [$-[0]]" if $result;
say "Finding first item at start position  [$+[0]]\n" if $result;

$result = $pdf=~qr/^2 0 obj/m;
say "Finding second item at start position [$-[0]]" if $result;
say "Finding second item at start position [$+[0]]\n" if $result;

$result = $pdf=~qr/^3 0 obj/m;
say "Finding third item at start position  [$-[0]]" if $result;
say "Finding third item at start position  [$+[0]]\n" if $result;

 $result = $pdf=~qr/^4 0 obj/m;
say "Finding fourth item at start position [$-[0]]" if $result;
say "Finding fourth item at start position [$+[0]]\n" if $result;

[download]
This results in the following output: 
Finding first item at start position  [26]
Finding first item at start position  [33]

Finding second item at start position [68]
Finding second item at start position [75]

Finding third item at start position  [87]
Finding third item at start position  [94]

Finding fourth item at start position [2035]
Finding fourth item at start position [2042]

[download]

The first 3 results are correct, the 4th result is not. Reason: the first 3 results were found in "pure ASCII" text while the 4th match (4 0 obj) is in a section that's behind the section that contains the binary content. The result should be 1315 and 1322 instead of 2035 and 2042.

I'm afraid there's a problem with my regex when the text file also contains binary data.

In Python, you can tell the regex to "behave" binary by adding a b in front of the regex, like so: re.search(b'^\d+ 0 obj'... and that works perfect. The locations found are spot on.

How can this be done in Perl?

Best,
Geert

In reply to Calculated position incorrect when using regex in text file that also contains binary info by geertvc

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