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cajparser.py
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from os import remove
from struct import unpack
from subprocess import run,PIPE
from utils import add_outlines, fnd, fnd_all, fnd_rvrs, fnd_unuse_no
class CAJParser(object):
def __init__(self, filename):
self.filename = filename
try:
with open(filename, "rb") as caj:
fmt = unpack("4s", caj.read(4))[0].replace(b'\x00', b'').decode("gb18030")
if fmt == "CAJ":
self.format = "CAJ"
self._PAGE_NUMBER_OFFSET = 0x10
self._TOC_NUMBER_OFFSET = 0x110
elif fmt == "HN":
self.format = "HN"
self._PAGE_NUMBER_OFFSET = 0x90
self._TOC_NUMBER_OFFSET = 0x158
else:
self.format = None
raise Exception("Unknown file type.")
except UnicodeDecodeError:
raise Exception("Unknown file type.")
@property
def page_num(self):
with open(self.filename, "rb") as caj:
caj.seek(self._PAGE_NUMBER_OFFSET)
[page_num] = unpack("i", caj.read(4))
return page_num
@property
def toc_num(self):
with open(self.filename, "rb") as caj:
caj.seek(self._TOC_NUMBER_OFFSET)
[toc_num] = unpack("i", caj.read(4))
return toc_num
def get_toc(self):
toc = []
with open(self.filename, "rb") as caj:
for i in range(self.toc_num):
caj.seek(self._TOC_NUMBER_OFFSET + 4 + 0x134 * i)
toc_bytes = unpack("256s24s12s12si", caj.read(0x134))
ttl_end = toc_bytes[0].find(b"\x00")
title = toc_bytes[0][0:ttl_end].decode("gb18030").encode("utf-8")
pg_end = toc_bytes[2].find(b"\x00")
page = int(toc_bytes[2][0:pg_end])
level = toc_bytes[4]
toc_entry = {"title": title, "page": page, "level": level}
toc.append(toc_entry)
return toc
def output_toc(self, dest):
toc_items = self.get_toc()
with open(dest, "wb") as f:
for toc in toc_items:
f.write(b' ' * (toc["level"] - 1) + toc["title"]
+ b' ' + str(toc["page"]).encode("utf-8") + b'\n')
def convert(self, dest):
if self.format == "CAJ":
self._convert_caj(dest)
elif self.format == "HN":
self._convert_hn(dest)
def _convert_caj(self, dest):
caj = open(self.filename, "rb")
# Extract original PDF data (and add header)
caj.seek(self._PAGE_NUMBER_OFFSET + 4)
[pdf_start_pointer] = unpack("i", caj.read(4))
caj.seek(pdf_start_pointer)
[pdf_start] = unpack("i", caj.read(4))
pdf_end = fnd_all(caj, b"endobj")[-1] + 6
pdf_length = pdf_end - pdf_start
caj.seek(pdf_start)
pdf_data = b"%PDF-1.3\r\n" + caj.read(pdf_length) + b"\r\n"
with open("pdf.tmp", 'wb') as f:
f.write(pdf_data)
pdf = open("pdf.tmp", "rb")
# deal with disordered PDF data
endobj_addr = fnd_all(pdf, b"endobj")
pdf_data = b"%PDF-1.3\r\n"
obj_no = []
for addr in endobj_addr:
startobj = fnd_rvrs(pdf, b" 0 obj", addr)
startobj1 = fnd_rvrs(pdf, b"\r", startobj)
startobj2 = fnd_rvrs(pdf, b"\n", startobj)
startobj = max(startobj1, startobj2)
length = fnd(pdf, b" ", startobj) - startobj
pdf.seek(startobj)
[no] = unpack(str(length) + "s", pdf.read(length))
if int(no) not in obj_no:
obj_no.append(int(no))
obj_len = addr - startobj + 6
pdf.seek(startobj)
[obj] = unpack(str(obj_len) + "s", pdf.read(obj_len))
pdf_data += (b"\r" + obj)
pdf_data += b"\r\n"
with open("pdf.tmp", 'wb') as f:
f.write(pdf_data)
pdf = open("pdf.tmp", "rb")
# Add Catalog (find obj_no of pages)
inds_addr = [i + 8 for i in fnd_all(pdf, b"/Parent")]
inds = []
for addr in inds_addr:
length = fnd(pdf, b" ", addr) - addr
pdf.seek(addr)
[ind] = unpack(str(length) + "s", pdf.read(length))
inds.append(int(ind))
# get pages_obj_no list containing distinct elements
# & find missing pages object(s) -- top pages object(s) in pages_obj_no
pages_obj_no = []
top_pages_obj_no = []
for ind in inds:
if (ind not in pages_obj_no) and (ind not in top_pages_obj_no):
if fnd(pdf, bytes("\r{0} 0 obj".format(ind), "utf-8")) == -1:
top_pages_obj_no.append(ind)
else:
pages_obj_no.append(ind)
single_pages_obj_missed = len(top_pages_obj_no) == 1
multi_pages_obj_missed = len(top_pages_obj_no) > 1
# generate catalog object
catalog_obj_no = fnd_unuse_no(obj_no, top_pages_obj_no)
obj_no.append(catalog_obj_no)
root_pages_obj_no = None
if multi_pages_obj_missed:
root_pages_obj_no = fnd_unuse_no(obj_no, top_pages_obj_no)
elif single_pages_obj_missed:
root_pages_obj_no = top_pages_obj_no[0]
top_pages_obj_no = pages_obj_no
else: # root pages object exists, then find the root pages object #
found = False
for pon in pages_obj_no:
tmp_addr = fnd(pdf, bytes("\r{0} 0 obj".format(pon), 'utf-8'))
while True:
pdf.seek(tmp_addr)
[_str] = unpack("6s", pdf.read(6))
if _str == b"Parent":
break
elif _str == b"endobj":
root_pages_obj_no = pon
found = True
break
tmp_addr = tmp_addr + 1
if found:
break
catalog = bytes("{0} 0 obj\r<</Type /Catalog\r/Pages {1} 0 R\r>>\rendobj\r".format(
catalog_obj_no, root_pages_obj_no), "utf-8")
pdf_data += catalog
with open("pdf.tmp", 'wb') as f:
f.write(pdf_data)
pdf = open("pdf.tmp", "rb")
# Add Pages obj and EOF mark
# if root pages object exist, pass
# deal with single missing pages object
if single_pages_obj_missed or multi_pages_obj_missed:
inds_str = ["{0} 0 R".format(i) for i in top_pages_obj_no]
kids_str = "[{0}]".format(" ".join(inds_str))
pages_str = "{0} 0 obj\r<<\r/Type /Pages\r/Kids {1}\r/Count {2}\r>>\rendobj\r".format(
root_pages_obj_no, kids_str, self.page_num)
pdf_data += bytes(pages_str, "utf-8")
with open("pdf.tmp", 'wb') as f:
f.write(pdf_data)
pdf = open("pdf.tmp", "rb")
# deal with multiple missing pages objects
if multi_pages_obj_missed:
kids_dict = {i: [] for i in top_pages_obj_no}
count_dict = {i: 0 for i in top_pages_obj_no}
for tpon in top_pages_obj_no:
kids_addr = fnd_all(pdf, bytes("/Parent {0} 0 R".format(tpon), "utf-8"))
for kid in kids_addr:
ind = fnd_rvrs(pdf, b"obj", kid) - 4
addr = fnd_rvrs(pdf, b"\r", ind)
length = fnd(pdf, b" ", addr) - addr
pdf.seek(addr)
[ind] = unpack(str(length) + "s", pdf.read(length))
kids_dict[tpon].append(int(ind))
type_addr = fnd(pdf, b"/Type", addr) + 5
tmp_addr = fnd(pdf, b"/", type_addr) + 1
pdf.seek(tmp_addr)
[_type] = unpack("5s", pdf.read(5))
if _type == b"Pages":
cnt_addr = fnd(pdf, b"/Count ", addr) + 7
pdf.seek(cnt_addr)
[_str] = unpack("1s", pdf.read(1))
cnt_len = 0
while _str not in [b" ", b"\r", b"/"]:
cnt_len += 1
pdf.seek(cnt_addr + cnt_len)
[_str] = unpack("1s", pdf.read(1))
pdf.seek(cnt_addr)
[cnt] = unpack(str(cnt_len) + "s", pdf.read(cnt_len))
count_dict[tpon] += int(cnt)
else: # _type == b"Page"
count_dict[tpon] += 1
kids_no_str = ["{0} 0 R".format(i) for i in kids_dict[tpon]]
kids_str = "[{0}]".format(" ".join(kids_no_str))
pages_str = "{0} 0 obj\r<<\r/Type /Pages\r/Kids {1}\r/Count {2}\r>>\rendobj\r".format(
tpon, kids_str, count_dict[tpon])
pdf_data += bytes(pages_str, "utf-8")
pdf_data += bytes("\n%%EOF\r", "utf-8")
with open("pdf.tmp", 'wb') as f:
f.write(pdf_data)
# Use mutool to repair xref
# raise CalledProcessError(code=6) after pack the gui program
# try:
# check_output(["mutool", "clean", "pdf.tmp", "pdf_toc.pdf"], stderr=STDOUT)
# except CalledProcessError as e:
# print(e.output.decode("utf-8"))
# raise Exception("Command mutool returned non-zero exit status " + str(e.returncode))
p = run(['mutool', 'clean', 'pdf.tmp', 'pdf_toc.pdf'])
# code = system('mutool clean pdf.tmp pdf_toc.pdf')
# if code != 0:
# raise Exception("Command mutool returned non-zero exit status " + str(code))
if p.returncode != 0:
raise Exception("Command mutool returned non-zero exit status " + str(p.returncode))
# Add Outlines
add_outlines(self.get_toc(), "pdf_toc.pdf", dest)
pdf.close()
remove("pdf.tmp")
remove("pdf_toc.pdf")
def _convert_hn(self, dest):
raise Exception("Unsupported file type.")