fenix
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cpdf-source
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This commit is contained in:
John Whitington 2023-03-19 20:04:45 +00:00
parent 2d512cc8ed
commit d6cb104d21
1 changed files with 17 additions and 20 deletions
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37
cpdfpng.ml
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@ -10,36 +10,33 @@ type t =
idat : bytes}
(* Writing *)
let crc_table =
let table =
let f n =
let c = ref (i32ofi n) in
let a = ref (i32ofi n) in
for _ = 0 to 7 do
c := lxor32 (lsr32 !c 1) (land32 0xedb88320l (i32succ (lnot32 (land32 !c 1l))))
a := lxor32 (lsr32 !a 1) (land32 0xedb88320l (i32succ (lnot32 (land32 !a 1l))))
done;
!c
!a
in
Array.init 256 f
let update_crc crc buf len =
let c = ref crc in
let update crc buf len =
let a = ref crc in
for n = 0 to len - 1 do
let e = i32ofi (int_of_char buf.[n]) in
c := lxor32 crc_table.(i32toi (land32 (lxor32 !c e) 0xffl)) (lsr32 !c 8)
a := lxor32 table.(i32toi (land32 (lxor32 !a e) 0xffl)) (lsr32 !a 8)
done;
!c
let png_crc buf len =
lnot32 (update_crc 0xffffffffl buf len)
!a
let bytes_of_word x =
i32toi (Int32.shift_right x 24),
i32toi (land32 0x000000FFl (Int32.shift_right x 16)),
i32toi (land32 0x000000FFl (Int32.shift_right x 8)),
i32toi (sr32 x 24),
i32toi (land32 0x000000FFl (sr32 x 16)),
i32toi (land32 0x000000FFl (sr32 x 8)),
i32toi (land32 0x000000FFl x)
let write_crc o ctype cdata =
let crc = update_crc 0xffffffffl ctype 4 in
let crc = update_crc crc cdata (String.length cdata) in
let crc = update 0xffffffffl ctype 4 in
let crc = update crc cdata (String.length cdata) in
let a, b, c, d = bytes_of_word crc in
o.output_byte a;
o.output_byte b;
@ -77,10 +74,10 @@ let write_png png o =
(* Reading *)
let string_of_tag t =
Printf.sprintf "%c%c%c%c"
(char_of_int (i32toi (Int32.shift_right t 24)))
(char_of_int (i32toi (Int32.logand 0x000000FFl (Int32.shift_right t 16))))
(char_of_int (i32toi (Int32.logand 0x000000FFl (Int32.shift_right t 8))))
(char_of_int (i32toi (Int32.logand 0x000000FFl t)))
(char_of_int (i32toi (sr32 t 24)))
(char_of_int (i32toi (land32 0x000000FFl (sr32 t 16))))
(char_of_int (i32toi (land32 0x000000FFl (sr32 t 8))))
(char_of_int (i32toi (land32 0x000000FFl t)))
let read_unsigned_4byte i =
let a = i32ofi (i.input_byte ()) in