Teach fixup_pdf_template.py to automatically calculate stream length.

BUG=pdfium:1008

Change-Id: I5136d57bd401d44b56ac19e5cfb52702afa32200
Reviewed-on: https://pdfium-review.googlesource.com/26651
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>

5 files changed, 43 insertions, 4 deletions

diff --git a/testing/resources/bug_921.in b/testing/resources/bug_921.in
index 9c48b2004e..a0c2e73cc8 100644
--- a/testing/resources/bug_921.in
+++ b/testing/resources/bug_921.in
@@ -43,7 +43,7 @@ endobj
 >>
 endobj
 {{object 6 0}} <<
-/Length 2784
+{{streamlen}}
 >>
 stream
 BT
diff --git a/testing/resources/combobox_form.in b/testing/resources/combobox_form.in
index 6c9f914023..77085f2861 100644
--- a/testing/resources/combobox_form.in
+++ b/testing/resources/combobox_form.in
@@ -33,7 +33,7 @@ endobj
 >>
 endobj
 {{object 7 0}}
-<< /Length 51 >>
+<< {{streamlen}} >>
 stream
 BT
 0 0 0 rg
diff --git a/testing/resources/text_form.in b/testing/resources/text_form.in
index c30f0bac4e..12ea13a3e2 100644
--- a/testing/resources/text_form.in
+++ b/testing/resources/text_form.in
@@ -42,7 +42,7 @@ endobj
 >>
 endobj
 {{object 8 0}}
-<< /Length 51 >>
+<< {{streamlen}} >>
 stream
 BT
 0 0 0 rg
diff --git a/testing/resources/text_form_multiple.in b/testing/resources/text_form_multiple.in
index 576e15597c..066ab202df 100644
--- a/testing/resources/text_form_multiple.in
+++ b/testing/resources/text_form_multiple.in
@@ -42,7 +42,7 @@ endobj
 >>
 endobj
 {{object 8 0}}
-<< /Length 51 >>
+<< {{streamlen}} >>
 stream
 BT
 0 0 0 rg
diff --git a/testing/tools/fixup_pdf_template.py b/testing/tools/fixup_pdf_template.py
index 0f31eccada..19f75e0263 100755
--- a/testing/tools/fixup_pdf_template.py
+++ b/testing/tools/fixup_pdf_template.py
@@ -13,13 +13,20 @@ script replaces {{name}}-style variables in the input with calculated results
   {{trailer}}    - expands to a standard trailer with "1 0 R" as the /Root.
   {{startxref}   - expands to a startxref directive followed by correct offset.
   {{object x y}} - expands to |x y obj| declaration, noting the offset.
+  {{streamlen}}  - expands to |/Length n|.
 """
 
+import cStringIO
 import optparse
 import os
 import re
 import sys
 
+class StreamLenState:
+  START = 1
+  FIND_STREAM = 2
+  FIND_ENDSTREAM = 3
+
 class TemplateProcessor:
   HEADER_TOKEN = '{{header}}'
   HEADER_REPLACEMENT = '%PDF-1.7\n%\xa0\xf2\xa4\xf4'
@@ -41,7 +48,12 @@ class TemplateProcessor:
   OBJECT_PATTERN = r'\{\{object\s+(\d+)\s+(\d+)\}\}'
   OBJECT_REPLACEMENT = r'\1 \2 obj'
 
+  STREAMLEN_TOKEN = '{{streamlen}}'
+  STREAMLEN_REPLACEMENT = '/Length %d'
+
   def __init__(self):
+    self.streamlen_state = StreamLenState.START
+    self.streamlens = []
     self.offset = 0
     self.xref_offset = 0
     self.max_object_number = 0
@@ -60,9 +72,30 @@ class TemplateProcessor:
         result += self.XREF_REPLACEMENT_F
     return result
 
+  def preprocess_line(self, line):
+    if self.STREAMLEN_TOKEN in line:
+      assert(self.streamlen_state == StreamLenState.START)
+      self.streamlen_state = StreamLenState.FIND_STREAM
+      self.streamlens.append(0)
+      return
+
+    if (self.streamlen_state == StreamLenState.FIND_STREAM and
+        line.rstrip() == 'stream'):
+      self.streamlen_state = StreamLenState.FIND_ENDSTREAM
+      return
+
+    if self.streamlen_state == StreamLenState.FIND_ENDSTREAM:
+      if line.rstrip() == 'endstream':
+        self.streamlen_state = StreamLenState.START
+      else:
+        self.streamlens[-1] += len(line)
+
   def process_line(self, line):
     if self.HEADER_TOKEN in line:
       line = line.replace(self.HEADER_TOKEN, self.HEADER_REPLACEMENT)
+    if self.STREAMLEN_TOKEN in line:
+      sub = self.STREAMLEN_REPLACEMENT % self.streamlens.pop(0)
+      line = re.sub(self.STREAMLEN_TOKEN, sub, line)
     if self.XREF_TOKEN in line:
       self.xref_offset = self.offset
       line = self.generate_xref_table()
@@ -76,6 +109,7 @@ class TemplateProcessor:
     if match:
       self.insert_xref_entry(int(match.group(1)), int(match.group(2)))
       line = re.sub(self.OBJECT_PATTERN, self.OBJECT_REPLACEMENT, line)
+
     self.offset += len(line)
     return line
 
@@ -85,7 +119,12 @@ def expand_file(input_path, output_path):
   try:
     with open(input_path, 'rb') as infile:
       with open(output_path, 'wb') as outfile:
+        preprocessed = cStringIO.StringIO()
         for line in infile:
+          preprocessed.write(line)
+          processor.preprocess_line(line)
+        preprocessed.seek(0)
+        for line in preprocessed:
           outfile.write(processor.process_line(line))
   except IOError:
     print >> sys.stderr, 'failed to process %s' % input_path