dwg file format
an attempt to specify the dwg (r12) file format using the bff grammar for
binary files.
acknowledgements
i would like to thank reini urban <rurban@sbox.tu-graz.ac.at> 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).
definition of the whole file
root dwg_file :=
[begin : end](
char[12] : version,
byte, word, word, word, byte,
longp : p_entities, longp : p_entend,
longp : p_blocksec, byte[4], longp : p_bsend, byte[4],
tablepos : block_table,
tablepos : layer_table,
tablepos : style_table,
tablepos : ltype_table,
tablepos : view_table,
header, [cur : 0x3ef]byte*,
tablepos : ucs_table, [cur : 0x500]byte*,
tablepos : vport_table, byte[8],
tablepos : appid_table, byte[6],
tablepos : dimstyle_table, [cur : 0x69f]byte*,
tablepos : p13_table, bytes[38],
[p_entities : p_entend]entities : ents, byte[19],
[block_table.start : ]blocks : block_table,
[layer_table.start : ]layers : layer_table,
[style_table.start : ]styles : style_table,
[ltype_table.start : ]ltypes : ltype_table,
[view_table.start : ]table : view_table,
[ucs_table.start : ]table : ucs_table,
[vport_table.start : vport_table.end]table : vport_table,
[appid_table.start : ]appids : appid_table,
[dimstyle_table.start : ]table : dimstyle_table,
[p13_table.start : ]table : p13_table,
[p_blocksec : p_bsend]entities : blocks, bytes[36],
longp = p_entities, longp = p_entend,
longp = blocksec, longp = bsend,
bytes[12],
bytes[6],
longp = block_table.start, bytes[6],
longp = layer_table.start, bytes[6],
longp = style_table.start, bytes[6],
longp = ltype_table.start, bytes[6]
longp = view_table.start, bytes[6],
longp = ucs_table.start, bytes[6],
longp = vport_table.start, bytes[6],
longp = appid_table.start, bytes[6],
longp = dimstyle_table.start, bytes[6],
longp = p13_table.start, bytes[6],
longp bytes*,
).
a table position
tablepos :=
word : size,
long : nr,
long : start,
the header
header :=
word,
point(true) : inbase,
point(true) : extmin,
point(true) : extmax,
point(false) : limmin,
point(false) : limmax,
double[4],
byte[2],
double[2],
byte[56],
double[3],
byte[18],
double .
the block table
blocks :=
( [size](
byte : flag,
char[32] : name,
word : used,
byte, word, byte, word,
check_2
)
)[nr] : blocks_info,
check_32.
check_2 := byte[2].
check_32 := byte[32].
the layer table
layers :=
( [size](
byte : flag,
char[32] : name,
word : used,
word : color,
word : style,
check_2
)
)[nr] : layer_info,
check_32.
the style table
styles :=
( [size](
byte : flag,
char[32] : name,
word, double[3], byte, double, char[128],
check_2
)
)[nr] : style_info,
check_32.
the line-type table
ltypes :=
( [size](
byte : flag,
char[32] : name,
word, char[48], byte,
byte, double[13],
check_2
)
)[nr] : ltype_info,
check_32 .
the application identifier table
appids :=
( [size](
byte : flag,
char[32] : name,
word,
check_2
)
)[nr] : appid_info,
check_32 .
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 byte : l70 fi, /*?*/
if (opts & 0x20) then byte : 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.
