The other tables
table :=
( [size](
byte : flag,
[size - 3]byte*,
check_2
)
)[nr],
check_32 .
The entities
(Experimental)
entities :=
( byte : kind,
byte : flag,
word : length,
[length - 4](
word : layer,
word : opts,
if (flag & 1) then byte : color else color = 0 fi,
if (flag & 0x40) then byte : extra else extra = 0 fi,
if (extra & 2) then xdata fi,
if (flag & 2) then word : type fi,
if (flag & 4 && kind > 2 && kind != 22) then double : z fi,
if (flag & 8) then double : th fi,
if (flag & 0x20) then handle fi,
if (extra & 4) then word : paper fi,
switch (kind)
case 1: /* LINE */
point(!(flag & 4)) : l10,
point(!(flag & 4)) : l11,
if (opts & 1) then point(TRUE) : l210 fi,
if (opts & 2) then double : l38 fi,
case 2: /* POINT */
point(!(flag & 4)) : l10,
if (opts & 1) then point(TRUE) : l210 fi,
if (opts & 2) then double : l38 fi,
case 3: /* CIRCLE */
point(FALSE) : l10,
double : l40,
if (opts & 1) then point(TRUE) : l210 fi,
if (opts & 2) then double : l38 fi,
case 4: /* SHAPE */
point(FALSE) : l10,
word : l2,
if (opts & 1) then point(TRUE) : l210 fi,
if (opts & 2) then double : l38 fi,
case 7: /* TEXT */
point(FALSE) : l10,
double : l40,
string : l1,
if (opts & 1) then double : l50 fi,
if (opts & 2) then double : l41 fi,
if (opts & 4) then double : l51 fi, /*?*/
if (opts & 8) then byte : l7 fi,
if (opts & 0x10) then byte : l71 fi,
if (opts & 0x20) then byte : l72 fi,
if (opts & 0x40) then point(FALSE) : l11 fi,
if (opts & 0x100) then byte : l73 fi,
case 8: /* ARC */
point(FALSE) : l10,
double : l40,
double : l50,
double : l51,
if (opts & 1) then point(TRUE) : l210 fi,
if (opts & 2) then double : l38 fi,
case 9: /* TRACE */
point(FALSE) : l10,
point(FALSE) : l11,
point(FALSE) : l12,
point(FALSE) : l13,
if (opts & 1) then point(TRUE) : l210 fi,
if (opts & 2) then double : l38 fi,
case 11: /* SOLID */
point(FALSE) : l11,
point(FALSE) : l12,
point(FALSE) : l13,
point(FALSE) : l14,
if (opts & 1) then point(TRUE) : l210 fi,
if (opts & 2) then double : l38 fi
case 12: /* BLOCK */
point(FALSE) : l10, /*?*/
string : l1, /* if (opts & 1) then ? */
if (opts & 2) then string : l3 fi
case 13: /* ENDBLK */
case 14: /* INSERT */
word : l1,
point(FALSE) : l10,
if (opts & 1) then double : l41 fi,
if (opts & 2) then double : l42 fi,
if (opts & 4) then double : l43 fi,
if (opts & 8) then double : l50 fi,
if (opts & 0x10) then word : l70 fi,
if (opts & 0x20) then word : l71 fi,
if (opts & 0x40) then double : l44 fi, /*?*/
if (opts & 0x80) then double : l45 fi /*?*/
case 15: /* ATTDEF */
point(FALSE) : l10,
double : l40,
string : l1,
string : l3,
string : l2,
byte : l70,
if (opts & 1) then byte : l73 fi, /*?*/
if (opts & 2) then double : l50 fi, /*?*/
if (opts & 4) then double : l41 fi,
if (opts & 8) then double : l42 fi,
if (opts & 0x10) then byte : l7 fi,
if (opts & 0x20) then byte : l71 fi,
if (opts & 0x40) then byte : l72 fi,
if (opts & 0x80) then point(FALSE) : l11 fi, /*?*/
if (opts & 0x100) then point(TRUE) : l210 fi,
if (opts & 0x200) then double : l38 fi /*?*/
case 16: /* ATTRIB */
point(FALSE) : l10,
double : l40,
string : l1,
string : l2,
byte : l70,
if (opts & 1) then byte : l73 fi, /*?*/
if (opts & 2) then double : l50 fi, /*?*/
if (opts & 4) then double : l41 fi,
if (opts & 8) then double : l42 fi,
if (opts & 0x10) then byte : l7 fi,
if (opts & 0x20) then byte : l71 fi,
if (opts & 0x40) then byte : l72 fi,
if (opts & 0x80) then point(FALSE) : l11 fi, /*?*/
if (opts & 0x100) then point(TRUE) : l210 fi,
if (opts & 0x200) then double : l38 fi /*?*/
case 17: /* S/BEND */
long
case 19: /* PLINE */
if (opts & 1) then byte : l70 fi,
if (opts & 2) then double : l40 fi, /*?*/
if (opts & 4) then byte : l71 fi, /*?*/
if (opts & 8) then byte : l72 fi, /*?*/
if (opts & 0x10) then byte : l73 fi, /*?*/
if (opts & 0x20) then byte : l74 fi, /*?*/
if (opts & 0x40) then byte : l75 fi /*?*/
case 20: /* VERTEX */
point(FALSE) : l10,
if (opts & 1) then double : l40 fi, /*?*/
if (opts & 2) then double : l41 fi, /*?*/
if (opts & 4) then byte : l70 fi, /*?*/
if (opts & 8) then double : l50 fi /*?*/
case 22: /* 3DFACE */
point(!(flag & 4)) : l10,
point(!(flag & 4)) : l11,
point(!(flag & 4)) : l12,
point(!(flag & 4)) : l13
case 23: /* DIM */
word : l1,
point(TRUE) : l10,
point(FALSE) : l11, /*?*/
if (opts & 2) then byte : l70 fi,
if (opts & 1) then point(TRUE) : l12 fi, /*?*/
if (opts & 4) then string : l1 fi,
if (opts & 8) then point(TRUE) : l13 fi,
if (opts & 0x10) then point(TRUE) : l14 fi,
if (opts & 0x20) then point(TRUE) : l15 fi,
if (opts & 0x40) then point(TRUE) : l16 fi,
if (opts & 0x80) then double : l40 fi,
if (opts & 0x100) then double : l50 fi,
if (opts & 0x200) then double : l51 fi,
if (opts & 0x400) then double : l52 fi,
if (opts & 0x800) then double : l53 fi
case 24: /* VPORT */
point(TRUE) : l10,
double : l40,
double : l41,
word : l68
endswitch
check_2
)
)* : entities.
The AutoCAD 12 DWG file format
This page gives a description of the DWG format used by AutoCAD version 12. The description is given in the form of a Binary File Format grammer. I also wrote a C program that can parse a DWG file. AutoCAD versions up to version 12, all used the format very similar to the version described here. AutoCAD version 13, and later, started using a completely different version. I made some attempts to crack the AutoCAD R13 format.
A number of CAD vendors have decided to form the OpenDWG Alliance, which aims at making the DWG format available to everybody who joins them.
Acknowledgements
I would like to thank Reini Urban for his contributions.
Definition of the elementary elements
typedef word word :=
byte : b1, byte : b2
return (word)f | ((word)s << 8).
typedef longword longp :=
byte : b1, byte : b2, byte : b3, byte : b4
return (longword)b1 | ((longword)b2 << 8)
| ((longword)b3 << 16) | ((longword)b4 << 24).
typedef longword longword :=
byte : b1, byte : b2, byte : b3, byte : b4
return (longword)b1 | ((longword)b2 << 8)
| ((longword)b3 << 16) | ((longword)b4 << 24).