DWG文件的设计规范 V4.5.1（中英对照版）

DWG文件的设计规范 V4.5.1

Open Design Specification for .dwg files

(资料图)

Version 5.4.1

liability英[ˌlaɪəˈbɪləti]美[ˌlaɪəˈbɪləti]n. 责任；倾向；债务；妨碍

assumesv. 取得（权力）( assume的第三人称单数 )；假设；假定；呈现

is subject to英[iz ˈsʌbdʒikt tu:]美[ɪz ˈsʌbdʒekt tu]受支配，从属于；有…倾向的

furnished英[ˈfɜːnɪʃt]美[ˈfɜːrnɪʃt]adj. 家具，有家具的v. 陈设，布置( furnish的过去式和过去分词)；提供，装备

commitment英[kəˈmɪtmənt]美[kəˈmɪtmənt]n. 信奉，忠诚；承诺；已许诺的事；献身；投入；花费

Information in these materials is furnished for informational use only, is subject tochange without notice and does not represent a

commitment on the part of Open Design Alliance. Open Design Alliance assumes no responsibility or liability for any errors or

inaccuracies that may appear in these materials. Use these materials at your own risk. 这些材料仅仅用于获取信息，如有更改恕不通知，并不代表ODA的承诺；ODA不为材料中的错误或者不准确的说法承担任何责任；使用这些材料，风险自负；

permittedv. 允许（ permit的过去式和过去分词 ）；许可；许用adj. . 被允许的

disclaim英[dɪsˈkleɪm]美[dɪsˈkleɪm]vt. 否认

either英[ˈaɪðə(r)]美[ˈiː.ðər]pron. （两者之中）任意一个；两者都(不)adv. 也（不）；而且，还

express英[ɪkˈspres]美[ɪkˈspres]v. 表达，表示；不言自明；挤出；快递adj. 明确的；特快的；用快递寄送的

implied英[ɪm"plaɪd]美[ɪm"plaɪd]adj. 暗指的，含蓄的v. 暗示，暗指( imply的过去式和过去分词 )；必然包含；说明，表明

merchantability英[ˌmɜ:tʃəntə"bɪlɪtɪ]美[ˌmɜtʃəntə"bɪlɪtɪ][经] 有销路，可销售

infringement英[ɪn"frɪndʒmənt]美[ɪnˈfrɪndʒmənt]n. 侵权；违反；违背

arisingv. 呈现，出现，发生( arise的现在分词 )；（由…）引起；起身

dealing英[ˈdiːlɪŋ]美[ ˈdiːlɪŋ]n. （商业）活动；经营方式；交易v. 经营，买卖； 贩毒

concerning英[kənˈsɜːnɪŋ]美[kənˈsɜːrnɪŋ]prep. 关于，涉及adj. 令人担忧的v. 与…相关；

warranty英[ˈwɒrənti]美[ˈwɔːrənti]n. 保证，保修单

applicable英[əˈplɪkəbl , ˈæplɪkəbl]美[ˈæplɪkəbl , əˈplɪkəbl]adj. 适当的；可应用的；适用的

ANY AND ALL任何和所有；

INCLUDING,WITHOUT LIMITATION包括但不限于；

TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW, OPEN DESIGN ALLIANCE AND ITS SUPPLIERS

DISCLAIM ANY AND ALL WARRANTIES AND CONDITIONS, EITHER EXPRESS OR IMPLIED, INCLUDING,

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DEALING, CONCERNING THESE MATERIALS. THESE MATERIALS ARE PROVIDED “AS IS” WITHOUT

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whatsoever英[ˌwɒtsəʊ"evə(r)]美[ˌhwɑtsoʊ"evər]adv. 丝毫，任何

incidental英[ˌɪnsɪˈdentl]美[ˌɪnsɪˈdɛntl]adj. 附属的；易发生的，偶然发生的；伴随发生的

however英[haʊˈevə(r)]美[haʊˈevər]adv. 然而；不管怎样；…左右conj. 不管怎样

whether英[ˈweðə(r)]美[ˈweðər]conj. (表示选择或怀疑)是否；无论，不管

tort英[tɔ:t]美[tɔrt]n. 民事侵权行为

claim英[kleɪm]美[kleɪm]v. 声称；索取；赢得；需要；夺去（生命）n. 声称，主张；权利；索赔

jurisdictionsn. 司法权( jurisdiction的名词复数 )；裁判权；管辖区域；管辖范围

consequential英[ˌkɒnsɪˈkwenʃl]美[ˌkɑnsəˈkwenʃl]adj. 作为结果的，间接的；重要的

TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW, IN NO EVENT SHALL OPEN DESIGN ALLIANCE

OR ITS SUPPLIERS (OR THEIR RESPECTIVE AGENTS, DIRECTORS, EMPLOYEES OR REPRESENTATIVES) BE

LIABLE FOR ANY DAMAGES WHATSOEVER(INCLUDING, WITHOUT LIMITATION, CONSEQUENTIAL,

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LOSS OF BUSINESS PROFITS, LOSS OF GOODWILL, BUSINESS INTERRUPTION, COMPUTER FAILURE OR

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the above limitation may not apply to you.

herein英[ˌhɪərˈɪn]美[ˌhɪrˈɪn]adv. 此中，本文中，于此；焉

identification英[aɪˌdentɪfɪˈkeɪʃn]美[aɪˌdentɪfɪˈkeɪʃn]n. 识别；身份证明；密切关联；认同；同情

respective英[rɪˈspektɪv]美[rɪˈspektɪv]adj. 各自的，分别的

Teigha® is a trademark of Open Design Alliance in the United States and/or other countries. All other trademarks, trade names or

company names referenced herein are used for identification only and are the property of their respective owners.Teigha是ODA在美国和/或其他国家使用的商标；本文中引用的 其他的商标、商品名称公司名称 仅仅用于标识，他们都是各自所有者的财产；

restricted英[rɪˈstrɪktɪd]美[rɪˈstrɪktɪd]adj. 有受限制的；（土地）对公众不完全开放的；保密的

disclosure英[dɪsˈkləʊʒə(r)]美[dɪsˈkloʊʒə(r)]n. 公开；泄露，揭露

set forth英[set fɔ:θ]美[sɛt fɔrθ]起程；出发；详尽地解释；展示

applicable英[əˈplɪkəbl , ˈæplɪkəbl]美[ˈæplɪkəbl , əˈplɪkəbl]adj. 适当的；可应用的；适用的

is subject to restrictions受到限制；

contractor英[kənˈtræktə(r)]美[ˈkɑnˌtræktɚ, kənˈtræk-]n. 订约人；承包商

US Government Restricted Rights: These materials are provided with RESTRICTED RIGHTS. Use, duplication or disclosure by

the Government is subject to restrictionsas set forthin subparagraph (c)(1)(ii) of The Rights in Technical Data and Computer

Software clause at DFARS 252.227-7013 or subparagraphs (c)(1) and (2) of the Commercial Computer Software-Restricted

Rights at 48 CFR 52.227-19, as applicable. The contractor/manufacturer is Open Design Alliance, 5025 N Central Ave #602,

Phoenix, AZ, USA.美国政府的有限权利，这些材料具有有限权利；政府使用、复制或者披露这些材料都要受到限制，如下面条款所展示的那样：技术数据和电脑软件条款、商业电脑软件有限权利，都适用；承包商、制造商是ODA；

proprietary英[prəˈpraɪətri]美[prəˈpraɪəteri]adj. 专有的，专利的；所有（人）的；（商品）专卖的

native 原生的，本地的；

* DWG is the native and proprietary file format for AutoCAD® and a trademark of Autodesk, Inc. The Open Design Alliance is

not associated with Autodesk.dwg是欧特克公司的原生格式，并且拥有专利权；ODA和欧特克公司没有任何关系；

Table of Contents目录

1 Introduction .........................................................................................................................6简介

2 BIT CODES AND DATA DEFINITIONS...........................................................................7位编码和数据定义

3 R13-R15 DWG FILE FORMAT ORGANIZATION ..........................................................20文件格式的组织

4 R2004 DWG FILE FORMAT ORGANIZATION..............................................................23文件格式的组织

5 R2007 DWG FILE FORMAT ORGANIZATION..............................................................36文件格式的组织

6 R2010 DWG FILE FORMAT ORGANIZATION..............................................................69文件格式的组织

7 R2013 DWG FILE FORMAT ORGANIZATION..............................................................70文件格式的组织

8 R2018 DWG FILE FORMAT ORGANIZATION..............................................................71文件格式的组织

9 Data section AcDb:Header (HEADER VARIABLES) .......................................................72头部变量

10 Data section AcDb:Classes ............................................................................................86类

11 PADDING (R13C3 AND LATER)................................................................................89填充补齐

12 Data section: “”..............................................................................................................90数据部分-“”.

13 Data section AcDb:SummaryInfo Section ......................................................................91数据部分-摘要

14 Data section AcDb:Preview ...........................................................................................93数据部分-概述

15 Data section AcDb:VBAProject Section.........................................................................95数据部分-VBA

16 Data section AcDb:AppInfo...........................................................................................96数据部分-APP信息

17 Data section AcDb:FileDepList......................................................................................98数据部分-文件数据库

18 Data section AcDb:RevHistory ....................................................................................100数据部分-修订历史

19 Data section AcDb:Security .........................................................................................101数据部分-安全

20 Data section AcDb:AcDbObjects.................................................................................103数据部分-数据库对象

21 Data section AcDb:ObjFreeSpace ................................................................................249数据部分-自由空间

Open Design Specification for .dwg files 5

22 Data section: AcDb:Template.......................................................................................250数据部分-模版

23 Data section AcDb:Handles (OBJECT MAP) ..............................................................251数据部分-句柄

24 Section AcDb:AcDsPrototype_1b (DataStorage)..........................................................252数据存储

25 UNKNOWN SECTION...............................................................................................263未知部分

26 SECOND FILE HEADER (R13-R15) .........................................................................264第二个文件头

27 Data section: AcDb:AuxHeader (Auxiliary file header) ................................................267辅助标题

28 Extended Entity Data (Extended Object Data).......................................................269扩展数据

29 PROXY ENTITY GRAPHICS ....................................................................................270实体图形代理

1 Introduction简介

originating英[ə"rɪdʒɪneɪtɪŋ]美[ə"rɪdʒɪneɪtɪŋ]v. 起源于，来自，产生( originate的现在分词 )；创造；创始；开创

undocumented英[ˌʌn"dɒkjʊmentɪd]美[ˌʌn"dɑkjʊmentɪd]adj. 无正式文件的，无事实证明的

proprietary英[prəˈpraɪətri]美[prəˈpraɪəteri]adj. 专有的，专利的；所有（人）的；（商品）专卖的

Originating in the late 1970s, drawing files created with microcomputer-based computer-aided design

software were saved with the .dwg extension. In the early 1980s, Autodesk® released AutoCAD® which

eventually became the most used CAD software in the world and which used Autodesk’s undocumented

and proprietary DWG™ file format (using the .dwg extension).

早在70年代，DWG就作为计算机绘图和辅助设计软件的保存文件后缀；在80年代，Autodesk发布了CAD这个全世界使用最广泛的软件，CAD使用了这个没有文件证明并且专有的DWG文件格式；

The Open Design Specification for .dwg files serves AutoCAD’s undocumented and proprietary DWG

file format. This specification includes DWG file format versions 13 up to and including version 2013.

Further, the Open Design Specification for .dwg files serves the Teigha® software development platform

of the Open Design Alliance.

DWG的公开设计规范用于CAD文件格式；设计规范包括版本13和2013；另外，DWG文件设计规范也用于ODA的Teigha开发平台；

compatibility英[kəmˌpætəˈbɪləti] 美[kəmˌpætəˈbɪlətɪ]n. 并存，相容；兼容性

While our Open Design Specification for .dwg files is able to read and write .dwg files with excellent

AutoCAD compatibility, we continue to work to improve our understanding of all the data in a .dwg file.

If you find information which will help us to understand any unknown values, please contact us at

http://www.opendesign.com/contact.

DWG的公开设计规范能够读写DWG文件，并且兼容CAD；我们将继续深入理解DWG文件数据；如果你发现了什么有价值的信息，请联系我们；

2 BIT CODES AND DATA DEFINITIONS位编码和数据定义

otherwise英[ˈʌðəwaɪz]美[ˈʌðərwaɪz]adv. 否则；除此以外；与之不同地；以其他方式

NOTE: Unless otherwise stated, all data in this manual is in little-endianorder, with the least significant

byte first.

说明：除非另做声明，本手册中的所有 数据都以小端排序，最不重要的数据排在最前面；

Much of the data in the DWG file format versions 13/14/2000/2004/2007/2010 must be read at the bit

level. Various parts of the drawing use data in compressed forms, which are explained below. Here are

the abbreviations used in this document for the various compressed forms:

B : bit (1 or 0)一个比特位

BB : special 2 bit code (entmode in entities, for instance)两个比特位

3B : bit triplet (1-3 bits) (R24)1-3个比特位

BS : bitshort (16 bits)16位

BL : bitlong (32 bits)32位

BLL : bitlonglong (64 bits) (R24)64位

BD : bitdouble浮点型

2BD : 2D point (2 bitdoubles)2个浮点型

3BD : 3D point (3 bitdoubles)3个浮点型

RC : raw char (not compressed)字符 未压缩

RS : raw short (not compressed)16位 未压缩

RD : raw double (not compressed)浮点型 未压缩

RL : raw long (not compressed)长整型 未压缩

2RD : 2 raw doubles2个浮点型

3RD : 3 raw doubles3个浮点型

MC : modular char模字符？

MS : modular short模短整型

H : handle reference (see the HANDLE REFERENCES section)句柄

T : text (bitshort length, followed by the string).文本

TU : Unicode text (bitshort character length, followed by Unicode string, 2 bytes per；Unicode文本

character). Unicode text is read from the “string stream” within the object data,

see the main Object description section for details.

TV : Variable text, T for 2004 and earlier files, TU for 2007+ files.文本变量；

X : special form特殊表格；

U : unknown未知；

SN : 16 byte sentinel16字节序列号；

BE : BitExtrusion位挤出？

DD : BitDouble With Default默认浮点型16字节

BT : BitThickness位厚度？

3DD : 3D point as 3 DD, needing 3 default values3D点，有三个默认值；

Open Design Specification for .dwg files 8

CMC : CmColor value颜色值；

TC : True Color: this is the same format as CMC in R2004+. OT : Object颜色；

type

A “seeker” is an RL-type object which indicates either an absolute address in the file or an offset from

some known address.搜索器可以表明一个绝对地址或者一个相对于已知地址的偏移量；

sentinel英[ˈsentɪnl]美[ˈsɛntənəl]n. 岗哨，哨兵vt. . 守卫，放哨

recovery英[rɪˈkʌvəri]美[rɪˈkʌvəri]n. 恢复；改善；失而复得；

A “sentinel” is 16 bytes of data used for file recovery purposes.

“哨兵”有16个字节，用来恢复文件；

Generally, the compressed forms are used to allow for compression of common data, usually values like

0.0 and 1.0 for doubles, 0 and 256 for shorts. The method for interpreting the code is to read the first two

bits, which indicate either the size of the data to follow, or the actual value for the common values. Here

are the compressed formats and some examples of how they appear in the file:

通常，压缩表格用来压缩数据；压缩数据的解析方法是，先读取前2位，这2位表明数据的长度，或者就是数据本身的值；下面是压缩数据的格式，以及他们如何在文件中呈现的例子：

2.2 BITSHORT:短整形（16位）

1st 2 bits : what it is数据前两位的含义

00 : A short (2 bytes) follows, little-endian order (LSB first)00表示这是一个短整形数据，2字节；

01 : An unsigned char (1 byte) follows；01表示这是一个字符型数据，1字节；

10 : 0；10表示0

11 : 256；11表示256

The char size is used when positive shorts less than 256 are being stored. The short size is used when

values <0 or >=256 are being stored. Obviously the special cases for 0 and 256 are used when those

values are being stored.

小于256的正短整形（2字节）将用一个字节存储；当值小于0或者大于256时，用短整型存储（2字节）；

特殊的两个值是0和256

Negative numbers use the short form, not the char form. That is, -1 is 00.11111111.11111111, not

01.11111111.负数用短整型而不是字节型；

For instance, if we were known to be reading 5 shorts from the following stream of bits:

0000000001000000011011010000111110

It would be parsed like this:这一串bit可以解析成：

00 00000001 00000001 (short 257)

10 (0)

11 (256)

01 00001111 (15)

10 (0)

2.3 BITLONG:

1st 2 bits : what it is

00 : A long (4 bytes) follows, little-endian order (LSB first)长整形，4字节；

01 : An unsigned char (1 byte) follows无符号字节，1字节；

10 : 0

11 : not used

The char size is used when positive longs less than 256 are being stored. The long size is used when

values <0 or >=256 are being stored. Obviously the special case for 0 is used when storing 0.

小于256的正整数用1字节表示；long适用于负数和超过255的数；

Negative numbers use the short form, not the char form. That is, -1 is负数用4字节表示，而不是1字节；

00.11111111.11111111.11111111.11111111, not 01.11111111.

For instance, if we were known to be reading 5 longs from the following stream of bits:

000000000100000001000000000000000010010000111110

It would be parsed like this:

00 00000001 00000001 00000000 00000000 (long 257)不是257吧？？

10 (0)

01 00001111 (15)

10 (0)

2.4 BITLONGLONG（64位 8字节）

The first 1-3 bits indicate the length l (see paragraph 2.1). Then l bytes follow, which represent the

number (the least significant byte is first).

前3位表示数据长度，后面的对应位数才是数据值；

2.5 BITDOUBLE:浮点型（）

1st 2 bits : what it is

00 : A double follows

01 : 1.0

10 : 0.0

11 : not used

Doubles are eight byte IEEE standard floating point values.

IEEE 标准中，double是8字节；

2.6 MODULAR CHARS:模字符

Modular characters are a method of storing compressed integer values. They are used in the object map to

indicate both handle offsets and file location offsets. They consist of a stream of bytes, terminating when

the high bit of the byte is 0.

模字符用来存储整形数据；他被用来表示句柄偏移和文件位置偏移；他由字节流组成，当遇到最高位为0的字节时，表示该字节流的结束；

In each byte, the high bit is a flag; when set, it indicates that another byte follows. The concept is not

difficult to understand, but is a little difficult to explain. Let’s look at an example.

在每个字节中，最高位都是标志位；当最高位置1时，表示后面还有字节；这个概念不难理解，但是难于解释，看个例子；

Assume the next two bytes in the file are:

10000010 00100100

We read bytes until we reach a byte with a high bit of 0. Obviously the second byte meets that criterion.

Since we are reading from least significant to most significant, let"s reverse the order of the bytes so that

they read MSB to LSB from left to right.

我们读取字节，直到遇到一个高位（标志位）是0的字节；显然，第二个字节就是结束标志；

MSB:Most Significant Bit(最高有效位),也就是最高位,最左侧的bit。

LSB:Least Significant Bit(最低有效位),最低位,最右侧的bit。

2.8 Bit Extrusion位挤出

For R13-R14 this is 3BD. For R2000, this is a single bit, followed optionally by 3BD. If the single bit is

1, the extrusion value is assumed to be 0,0,1 and no explicit extrusion is stored. If the single bit is 0, then

it will be followed by 3BD.单独的1位如果是1，表示0,0,1；如果是0表示后面有一个3BD类型数据，3个浮点型，表示3D点数据；

2.9 BitDouble With Default有默认值的浮点型

opcode英[ˈɒpkəʊd]美[ˈɑpkoʊd]n. 操作码

This is a 2 bit opcode followed optionally by data, and it requires a default value. The different opcodes

are described as follows:

2位的操作码，后面可能有数据，他需要有一个默认值；

00 No more data present, use the value of the default double.

00表示后面没有数据，使用double的默认值；

patched英["pætʃt]美["pætʃt]v. 补( patch的过去式和过去分词 )；修理；调停；解决

01 4 bytes of data are present. The result is the default double, with the 4 data bytes patched in

replacing the first 4 bytes of the default double (assuming little endian).

01表示后面有4字节的数据；结果是double的默认值，用4字节数据代替4字节默认值；

10 6 bytes of data are present. The result is the default double, with the first 2 data bytes patched in

replacing bytes 5 and 6 of the default double, and the last 4 data bytes patched in replacing the first 4

bytes of the default double (assuming little endian).

10表示后面有6字节数据；结果是double默认值用前2个字节数据替代第5和6字节的默认值；最后4字节代替前面4字节默认值；

11 A full RD follows.

2.10BitThickness厚度位

For R13-R14, this is a BD. For R2000+, this is a single bit followed optionally by a BD. If the bit is one,

the thickness value is assumed to be 0.0. If the bit is 0, then a BD that represents the thickness follows.

BD : bitdouble 浮点型；对于R2000+版本，这一位后面就是一个浮点数；如果这一位是1，厚度值就是0.0,；如果这一位是0，后面就是一个浮点数；

2.11CmColor

R15 and earlier: BS color index2字节颜色索引；

R2004+: There are two types of color definitions, below named as CMC and ENC:

CMC:

BS : color index (always 0)两字节

BL : RGB value四字节

RC : Color Byte (& 1 => color name follows (TV),字符 1字节；

&2 => book name follows (TV))

ENC: This color is used by entities: this definition may contain a DBCOLOR reference and optional

transparency.

BS : color number: flags + color index

color flags: first byte of the bitshort.

0x8000: complex color (rgb).

Next value is a BS containing the RGB value (last 24 bits).

0x4000: has AcDbColor reference (0x8000 is also set in this case).

The handle to the color is written in the handle stream.

0x2000: color is followed by a transparency BL.

The first byte represents the transparency type:

0 = BYLAYER,

1 = BYBLOCK,

3 = the transparency value in the last byte.

Color index: if no flags were set, the color is looked up by the color number (ACI

color)

2.12Object type对象类型

Until R2007, the object type was a bit short. In R2010 the object type changed:

A bit pair, followed by either 1 or 2 bytes, depending on the bit pair value:

2007版本中，用2字节表示；2010版本中用2位表示，后面跟1字节或2字节；

nevertheless英[ˌnevəðəˈles]美[ˌnevərðəˈles]adv. 然而；尽管如此；不过

2.13HANDLE REFERENCES:句柄引用

referred英[rɪˈfɜːd]美[rɪˈfɜːrd]vi. (to)涉及，查阅v. 提到( refer的过去式和过去分词 )；针对；关系到；请教

All objects in R13+ .dwg files are referred to by object handles. These handles are stored in the file in the

following form:

R13+版本涉及到了对象句柄；按照如下格式存储：

|CODE (4 bits)|COUNTER (4 bits)|HANDLE or OFFSET|

In this document we write these as CODE.COUNTER.BYTE.BYTE..., such as 0101.0001.00001111 (the

usual reference to LAYER 0 for drawings created under R13, which has handle F). In abbreviated form,

we write 5.1.0F.

abbreviated英[ə"bri:vɪeɪtɪd]美[ə"brivɪeɪtɪd]adj. 简短的，仅可蔽体的，小型的v. 缩简；缩略；使用缩写词

form英[fɔːm]美[fɔːrm]n. 类型；形态，外形；表格；状态v. 形成，构成；组建，排列

4位编码，4位长度（字节数），后跟句柄或者偏移量；R13以下版本，LAYER 0的句柄是F；缩写形态就是5.1.0F；

The CODE has different meanings depending on the handle. Certain object handles in AutoCAD have

"ownership" relations with other objects. In these cases the code indicates the type of relation:

编码表示句柄类型；CAD中的对象句柄和其他对象有隶属关系；编码就表示关系类型，如下表：

We will call these TYPEDOBJHANDLEs. Often their type is fixed to some value at all times; in other

words, for instance in a certain position only a HARD_POINTER TYPEDOBJHANDLE would be

allowed.

这称为类型对象句柄；通常他们的类型是固定的；也就是说，只能使用硬指针引用；

In other cases, the handle is stored as an offset from some other handle, and the code indicates how the

offset is to be applied. These handles always represent a soft pointer reference. See the table below for the

codes and their meaning:

通常，句柄存储的是相对于其他句柄的偏移量，编码表示如何使用偏移量；这些句柄是软指针引用；如下表：

Code: Action:

0x2, 0x3, 0x4, 0x5 none - just read offset and use it as the result读取偏移量

0x6 result is reference handle + 1 (length is 0 in this case)句柄偏移1，长度 0

0x8 result is reference handle – 1 (length is 0 in this case)句柄偏移-1 长度0

0xA result is reference handle plus offset正偏移量

0xC result is reference handle minus offset负偏移量

We will call these OFFSETOBJHANDLEs. These handles are described with (CODE X), where X

indicates the code if the offset is an ABSOLUTE reference (0x2 – 0x5).

这称为偏移句柄；这些句柄在4位code后面跟1位X，表示是否是绝对引用；

COUNTER tells how many bytes of HANDLE follow.

EXAMPLE: An entity on a layer whose handle is 5E7 has the following handle reference near the end of

the entity data (its code being 5):

5 2 0 5 E 7

01010010 00000101 11100111 (0101.0010.00000101.11100111)

2.14CRCS:

2.14.1 8-bit CRC循环冗余校验

modification英[ˌmɒdɪfɪˈkeɪʃn]美[ˌmɑːdɪfɪˈkeɪʃn]n. 修改，修正，变更，改良，改进

redundancy英[rɪˈdʌndənsi]美[rɪˈdʌndənsi]n. 过多，过剩；冗长；裁员；（机器的）多余度

CAD使用修正的循环冗余校验，作为检错机制；CRC（循环冗余校验）以2字节结尾，因为表格中包含256个16位值，他们不以任何类型的位的形式存储；他们以字节存储；他们不嵌入位编码；因此在一个对象末尾可能有未被使用的位（闲置位）；例子如下：

The AutoCAD DWG file format uses a modification of a standard cyclic redundancy check as an error

detecting mechanism. The CRC ends up being 2 bytes long due to a lookup in a table containing 256 16-

bit values, and are not stored in any sort of bit code form. They also always appear on byte boundaries;

they are not embedded within the stream of bits. Thus there may be extra unused bits at the end of an

object. For instance, consider an object containing one bitshort, as follows:

01000000 11100000 01010101 01010101

This parses as:

01 bitshort with one character

00000011 the value of the bitshort (3)

100000 unused bits闲置位

01010101 01010101 the CRC校验位

whereby英[weəˈbaɪ]美[werˈbaɪ]adv. 凭此；借以

beyond英[bɪˈjɒnd]美[bɪˈjɑːnd]prep. 在…另一边；超过，超出；晚于；无法理解

The modification that is made to the CRC is that a starting value different from 0 is used. Autodesk also

uses a method whereby the result of the CRC is XORed with a "magic number". This method is used

extensively in pre-R13 files, but seems only to be used in the header for R13 and beyond.

Here is the CRC function we use; it is simply a standard 8 bit CRC calculation:

对CRC的修订是，使用一个不以0开头的数；CRC的结果是和一个魔法数进行异或运算；R13之前版本一般都用这个方法，R13及之后的版本仅仅在头部校验使用该方法；下面是CRC函数，是一个标准的8位CRC算法：

int crctable[256]= {0x0000,0xC0C1,0xC181,0x0140,0xC301,0x03C0,0x0280,0xC241,

0xC601,0x06C0,0x0780,0xC741,0x0500,0xC5C1,0xC481,0x0440,

0xCC01,0x0CC0,0x0D80,0xCD41,0x0F00,0xCFC1,0xCE81,0x0E40,

0x0A00,0xCAC1,0xCB81,0x0B40,0xC901,0x09C0,0x0880,0xC841,

0xD801,0x18C0,0x1980,0xD941,0x1B00,0xDBC1,0xDA81,0x1A40,

0x1E00,0xDEC1,0xDF81,0x1F40,0xDD01,0x1DC0,0x1C80,0xDC41,

0x1400,0xD4C1,0xD581,0x1540,0xD701,0x17C0,0x1680,0xD641,

0xD201,0x12C0,0x1380,0xD341,0x1100,0xD1C1,0xD081,0x1040,

0xF001,0x30C0,0x3180,0xF141,0x3300,0xF3C1,0xF281,0x3240,

0x3600,0xF6C1,0xF781,0x3740,0xF501,0x35C0,0x3480,0xF441,

0x3C00,0xFCC1,0xFD81,0x3D40,0xFF01,0x3FC0,0x3E80,0xFE41,

0xFA01,0x3AC0,0x3B80,0xFB41,0x3900,0xF9C1,0xF881,0x3840,

0x2800,0xE8C1,0xE981,0x2940,0xEB01,0x2BC0,0x2A80,0xEA41,

0xEE01,0x2EC0,0x2F80,0xEF41,0x2D00,0xEDC1,0xEC81,0x2C40,

0xE401,0x24C0,0x2580,0xE541,0x2700,0xE7C1,0xE681,0x2640,

0x2200,0xE2C1,0xE381,0x2340,0xE101,0x21C0,0x2080,0xE041,

0xA001,0x60C0,0x6180,0xA141,0x6300,0xA3C1,0xA281,0x6240,

0x6600,0xA6C1,0xA781,0x6740,0xA501,0x65C0,0x6480,0xA441,

0x6C00,0xACC1,0xAD81,0x6D40,0xAF01,0x6FC0,0x6E80,0xAE41,

0xAA01,0x6AC0,0x6B80,0xAB41,0x6900,0xA9C1,0xA881,0x6840,

0x7800,0xB8C1,0xB981,0x7940,0xBB01,0x7BC0,0x7A80,0xBA41,

0xBE01,0x7EC0,0x7F80,0xBF41,0x7D00,0xBDC1,0xBC81,0x7C40,

0xB401,0x74C0,0x7580,0xB541,0x7700,0xB7C1,0xB681,0x7640,

0x7200,0xB2C1,0xB381,0x7340,0xB101,0x71C0,0x7080,0xB041,

0x5000,0x90C1,0x9181,0x5140,0x9301,0x53C0,0x5280,0x9241,

0x9601,0x56C0,0x5780,0x9741,0x5500,0x95C1,0x9481,0x5440,

0x9C01,0x5CC0,0x5D80,0x9D41,0x5F00,0x9FC1,0x9E81,0x5E40,

0x5A00,0x9AC1,0x9B81,0x5B40,0x9901,0x59C0,0x5880,0x9841,

0x8801,0x48C0,0x4980,0x8941,0x4B00,0x8BC1,0x8A81,0x4A40,

0x4E00,0x8EC1,0x8F81,0x4F40,0x8D01,0x4DC0,0x4C80,0x8C41,

0x4400,0x84C1,0x8581,0x4540,0x8701,0x47C0,0x4680,0x8641,

0x8201,0x42C0,0x4380,0x8341,0x4100,0x81C1,0x8081,0x4040 };

short crc8(unsigned short dx,char *p,long n)

{

register unsigned char al;

while (n-- > 0) {

al = (unsigned char)((*p) ^ ((char)(dx & 0xFF)));

dx = (dx>>8) & 0xFF;

dx = dx ^ crctable[al & 0xFF];

p++;

}

return(dx);

}

This function takes as its input an initial CRC value, a pointer to the data to be CRC"d, and the number of

bytes of data. The return value is the new CRC. This function can be used to accumulate a CRC by

running the first set of bytes with an initial value of 0 (or the "starting value" for this type of object), and

subsequent calls with the initial value equal to the last returned CRC.

3 R13-R15 DWG FILE FORMAT ORGANIZATION

R13-R15版本的文件格式

3.1 FILE STRUCTURE文件结构

notations英[nəʊ"teɪʃnz]美[noʊ"teɪʃnz]n. 记号，标记法

regarding英[rɪˈɡɑːdɪŋ]美[rɪˈɡɑːrdɪŋ]prep. 关于；就…而论；至于

arrangement英[əˈreɪndʒmənt]美[əˈreɪndʒmənt]n. 安排；筹划；布置

The structure of the DWG file format changed between R13 C2 and R13 C3. Notations regarding C3

below indicate the differences.

R13 C2和R13 C3版本的文件格式有变化；C3的不同之处后面有说明；

R13-R15的一般文件布局如下：

The general arrangement of data in an R13/R14/R15 file is as follows:

HEADER头部

FILE HEADER文件头

DWG HEADER VARIABLES头部变量

CRC循环冗余校验

CLASS DEFINITIONS类定义

TEMPLATE (R13 only, optional)模版（只有R13有，并且是可选的）

PADDING (R13C3 AND LATER, 200 bytes, minutes the template section above if present)填充位

IMAGE DATA (PRE-R13C3)图片数据

OBJECT DATA对象数据

All entities, table entries, dictionary entries, etc. go in thissection.所有的实体、表格、字典等；

OBJECT MAP对象图；

OBJECT FREE SPACE (optional)对象的自由空间（可选）；

TEMPLATE (R14-R15, optional)模版（可选）；

SECOND HEADER第二个头；

IMAGE DATA (R13C3 AND LATER)图片数据；

3.2 FILE HEADER文件头

3.2.1 VERSION ID:版本ID

The first 6 bytes are:

The next 7 starting at offset 0x06 are to be six bytes of 0 (in R14, 5 0’s and the ACADMAINTVER

variable) and a byte of 1. We have occasionally seen other values here but their meaning (and importance)

is unclear.

从第7位开始的6位是0，然后是1个字节的1；有时也会看到其他数据，不过其含义和重要性暂不清楚；

6+6+8=20

3.2.2 IMAGE SEEKER:图片查找器；

At 0x0D is a seeker (4 byte long absolute address) for the beginning sentinel of the image data.

0x0D 是一个图片查找器（4字节的绝对地址），表示图片数据的开始位置；

3.2.3 OBJECT FREE SPACE对象的自由空间

TODO.

3.2.4 TEMPLATE模版（可选）

This section is optional, see chapter 22.

3.2.5 DWGCODEPAGE:编码页

Bytes at 0x13 and 0x14 are a raw short indicating the value of the code page for this drawing file.

表示本文件的代码页；

3.2.6 SECTION-LOCATOR RECORDS:节定位记录

At 0x15 is a long that tells how many sets of recno/seeker/length records follow. Each record has the

following format:

0x15 开始的4字节表示记录个数（后面有多少条记录）；每个记录的格式如下：

Record number (raw byte) | Seeker (raw long) | Size (raw long)

记录编号（1字节）查找器（4字节）大小（4字节）

The records are as follows:

0 : Header variables (covers beginning and ending sentinels).头部变量

1 : Class section.类

2 : Object map.对象图

3 : (C3 and later.) A special table (no sentinels). See unknown section (R13 C3 and

later). The presence of the 4th record (3) indicates that the C3 file format

applies. Just look at the long at 21; if it"s 4 or greater, it"s the C3-and-later

format.一个特殊的表格；

4 : In R13-R15, points to a location where there may be data stored. Currently we

have seen only the MEASUREMENT variable stored here. See chapter 22. This section

is optional.一个指针，只想数据存储位置；目前我们只看到测量变量存储在这里；这部分是可选的；

Remarks:

We have seen files with up to 6 sets in this section; the meaning of the sixth one

is unknown. The Open Design Toolkit emits files with the first 5 sets only.

这里最多有6套数据，第6套数据含义未知；我们的工具包只使用前5套数据；

RS : CRC for BOF to this point. Use 0 for the initial value, and depending on the

number of sets of section-locators, XOR the result with one of the following:

文件开始的循环冗余校验；用0作为初始值，依赖于有多少套数据，并和下面其中一个进行异或运算；

3 : 0xA598

4 : 0x8101

5 : 0x3CC4

6 : 0x8461

The following 16 byte sentinel appears after the CRC:后面的16字节如下所示：

0x95,0xA0,0x4E,0x28,0x99,0x82,0x1A,0xE5,0x5E,0x41,0xE0,0x5F,0x9D,0x3A,0x4D,0x00

4 R2004 DWG FILE FORMAT ORGANIZATION

4.1 R2004 File Header

exclusive英[ɪkˈskluːsɪv]美[ɪkˈskluːsɪv]adj. 独有的；高档的；排外的；不含…的

The encrypted data at 0x80 can be decrypted by exclusive or’ing the 0x6c bytes of data from the file with

the following magic number sequence:可以使用下面的魔术数字进行解密；

29 23 BE 84 E1 6C D6 AE 52 90 49 F1 F1 BB E9 EB

B3 A6 DB 3C 87 0C 3E 99 24 5E 0D 1C 06 B7 47 DE

B3 12 4D C8 43 BB 8B A6 1F 03 5A 7D 09 38 25 1F

5D D4 CB FC 96 F5 45 3B 13 0D 89 0A 1C DB AE 32

20 9A 50 EE 40 78 36 FD 12 49 32 F6 9E 7D 49 DC

AD 4F 14 F2 44 40 66 D0 6B C4 30 B7

This magic sequence can be generated by the following code, which generates the sequence and stores it

in the data vector:

OdUInt8* p = data.asArrayPtr();

OdUInt32 sz = 0x6c;

int randseed = 1;

while (sz--)

{

randseed *= 0x343fd;

randseed += 0x269ec3;

*p++ = (OdUInt8)(randseed >> 0x10);

}

throughout英[θruːˈaʊt]美[θruːˈaʊt]prep. 自始至终；遍及adv. 自始至终；遍及

remainder英[rɪˈmeɪndə(r)]美[rɪˈmeɪndər]n. 剩余物；其他人员；差数；廉价出售的图书

Once decrypted, this sequence of bytes consists of the following data (we will call this data the 2004 File

Header Data throughout the remainder of this document). The file header data is repeated at the end of the

file (this is the second header data).

一旦解密，字节序列将由下面的数据组成（也就是文件头数据，这个数据遍布在文件的其他部分）；文件头会在文件尾部再次出现，我们叫他第二文件头；

maintenance 英[ˈmeɪntənəns]美[ˈmeɪntənəns]n. 维修; 维护; 保养; 维持; 保持; 抚养费;

The next 0x14 bytes will be copied from the magic number sequence, starting at 0x100 – 0x14. These

0x14 bytes are present in the file header at the beginning of the file, but not at the copy at the end of the

file.后面的20个字节将被拷贝到文件开始文件头，而不会拷贝到文件结尾的文件头；

The remaining data in the file is broken up into sections. There are 2 types of sections, System Sections

and Data Sections. A data section consists of 1 or more section pages, a system section consists of just 1

section page. System sections contain maps to navigate through the data sections and pages. System and

data section pages have different page headers.

剩余的数据将被划分成很多小节；有2种不同的节，系统节和数据节；数据节包括若干页，系统节只有1页；系统节用来导航到所有的数据节和数据页；系统节和数据节的页面有不同的页面标题；

checksum英[ˈtʃeksʌm]校验和

4.2 Section page checksum节页面的校验和

The following function (pseudocode) is used to calculate system and data page checksums as stored in the

page header (note that system and data page headers are different).

下面的函数用来计算系统页和数据页的校验和，并存储到页面的头部；注意，系统页和数据页的头部是不同的；

OdUInt32 checksum(OdUInt32 seed, OdUInt8* data, OdUInt32 size)

{

OdUInt32 sum1 = seed & 0xffff;

OdUInt32 sum2 = seed >> 0x10;

while (size != 0)

{

OdUInt32 chunkSize = min(0x15b0, size);

size -= chunkSize;

for (int i = 0; i < chunkSize; i++)

{

sum1 += *data++;

sum2 += sum1;

}

sum1 %= 0xFFF1;

sum2 %= 0xFFF1;

}

return (sum2 << 0x10) | (sum1 & 0xffff);

}

4.3 System section page系统节页面

A System Section page starts with of the following 0x14 bytes of header data:

Immediately following this data, there will be CompDataSize bytes of compressed data, which is the

actual data for the section. See the Compression section later in this document for details on the

compression algorithm used. After the compressed data there is second header chunk, but fields

decompressed size, compressed size and checksum are set to zero.

压缩数据大小是这个节的真实大小；后面会介绍压缩算法；压缩数据后面是第二标题数据块，但是压缩大小、解压大小、校验和等字段被设置为0；

chunk英[tʃʌŋk]美[tʃʌŋk]n. 厚块；大量；

The section page checksum is calculated in two stages. First the checksum (using the data page checksum

function) is calculated from the header data, using a seed of 0. The header data’s checksum being 0 at this

stage, but all other fields should be filled. In the second stage the final checksum is calculated from the

compressed data, using the first checksum as the seed.

校验和计算分2步；首先使用校验和函数，对头部数据进行计算，使用种子数据为0；此时校验和的值是0，但是其他字段将被填充数据；第二步，用第一步的校验和作为种子，使用压缩数据进行计算，得到最终的校验和；

Each section page must start on a 0x20 byte boundary of the raw data stream. The empty bytes between

the start of this section and then end of the previous section are filled with as many bytes as needed from

the magic number sequence.

每个节都以0x20 开始，作为数据流的边界；本节开始和上一节结束位置之间的字节，用魔术数字序列进行填充；

System Sections includeSection page map and Section map. These 2 sections serve as a table of contents

for the remaining sections of the file and their pages. Once these 2 sections have been processed, all other

sections in the file can be accessed randomly.

系统节包含页面地图和节地图；这2个节作为后续节和页面的索引表；只有这两个节处理完成后，后续的节才可以访问；

4.4 2004 Section page map

The uncompressed (global) section page map contains the following data:

未压缩的页面地图包含如下数据：

This repeats, with one number and size for each section page in the file, until the end of the section page

map. Note that this map also contains a reference to the section map, which is a system section. All other

pages are data section pages. The address of each section can be calculated as 0x100 for the first section,

and for each subsequent section the address is the previous section address plus the previous section size.

页面编号和页面编码的数据结构不断重复，直到页面地图结尾的地方；注意，这个地图也包含节地图的引用，也就是系统节的引用；其他页面都是数据页面；以0x100 作为第一个节的地址，后续节的地址只需用该节的地址加上该节的大小即可算出来；

If the section number is negative, this represents a gap in the sections (unused data). For a negative

section number, the following data will be present after the section size:

如果有负数的节编号，表示一个节缺口（无用数据）；对于编号是负数的节，其后将会是如下数据：

Taken together, these units of file section information form a vector (1 indexed) of all sections in the file,

and this vector will be referred to asthe SectionPageMap throughout the remainder of this document.

taken together英[ˈteɪkən təˈɡeðə]美[ˈtekən təˈɡɛðɚ]一并考虑

be referred to as被称为；

consecutively英[kən"sekjətɪvlɪ]美[kən"sekjətɪvlɪ]adv. 连续地

sections英["sekʃənz]美["sekʃənz]n. 部分( section的名词复数 )；节；部件；部门

Section pages are numbered consecutively. The system section pages are the last pages, with a gap of 1

between the page numbers for the data sections and system sections.

页面编号是连续编号的；系统页面是最后一个页面，使用1个间隔，来区分数据节和系统节；

4.5 2004 Data section map

The data section map is a map for locating all data sections (i.e. system sections are not present in this

map).数据节地图用来定位所有数据节，系统节不会出现在这个地图上；

The uncompressed Section Info section contains the following data:

未压缩的节信息包含如下内容：

Next, the following data is repeated NumDescriptions times:

Following this, the following (local) section page map data will be present, repeated PageCount times:

Maximum section page size appears to be 0x7400 bytes in the normal case. If a logical section of the file

(the database objects, for example) exceeds this size, then it is broken up into pages of size 0x7400. In

this case, the PageCount value above will contain the number of 0x7400 byte pages, and the data from the

pages can be appended together in order and treated as a single logical section.

Section Types seen so far in 2004 files include (sections are present in the section map in this order):

The section order in the stream is different than the order in the section map. The order in the stream is as

follows:节的排序

auxiliary英[ɔːɡˈzɪliəri]美[ɔːɡˈzɪliəri]adj. 辅助的；备用的

免责声明disclaimer

13 Data section AcDb:SummaryInfo Section摘要节

This section contains summary information about the drawing. Strings are encoded as a 16-bit length,

followed by the character bytes (0-terminated).这个节包括图纸的摘要信息，字符串编码成2字节，并以0作为结尾；

14 Data section AcDb:Preview

14.1PRE-R13C3

The BMP (or, sometimes, WMF) image of this file, if any. Only stored here for pre-R13C3 files. Later

files place the data at the end. The format of this data is discussed in the section illustrating where R13C4

and beyond store it.

缩略图可以使bmp或者wmf格式；在pre-R13C3中在这个节存储缩略图；后续的版本中都存储在文件的最后；数据格式将在R13C4及以后版本中讨论，这些版本中存储了这些数据；

illustratingv. 给…加插图( illustrate的现在分词 )；说明；表明；（用示例、图画等）说明

15 Data section AcDb:VBAProject Section

The VBA project section is optional.

The contents are currently unknown.The ODA reads and writes the contents of this section as is:

这部分内容暂时未知，ODA按照如下格式进行读写；

16 Data section AcDb:AppInfo应用程序信息

Contains information about the application that wrote the .dwg file. This section is optional.

The AppInfo format depends on the application version (Acad version that wrote the file) in the file

header. So a R18 .dwg file might have an R21 AppInfo section.

程序信息取决于应用程序的版本，也就是写该文件的CAD软件；所以R18的DWG文件里面可能会有R21版本的软件信息；

16.1R18

In R18 the app info section consists of the following fields. Strings are encoded as a 16-bit length,

followed by the character bytes (0-terminated).

17 Data section AcDb:FileDepList依赖项列表

Contains file dependencies (e.g. IMAGE files, or fonts used by STYLE).

包含文件的所有依赖项（图片文件、字体文件等）；

In R18 the app info section consists of the following fields. Strings are encoded as a 32-bit length,

followed by the character bytes (without trailing 0).

R18版本包含以下字段；字符串是32位的，以0结尾；

Then follows an array of features (repeated file count times). The feature name + the full filename

constitute the lookup key of a file dependency:

后面是一个特征数据，包括文件名、完整文件名

feature英[ˈfiːtʃə(r)]美[ˈfiːtʃər]n. 特征；五官；特写；正片，故事片

constitute英[ˈkɒnstɪtjuːt]美[ˈkɑːnstɪtuːt]v. 组成，构成；被视为；设立

18 Data section AcDb:RevHistory修订历史

The contents of this section are unknown. In the following paragraphs is described what the ODA writes

in this section.

这节的内容未知；ODA在该节写入下面内容：

18.1R18

More unknown bytes may follow.

19 Data section AcDb:Security安全节

This section was introduced in R18. The AcDb:Security section is optional in the file—it is present if the

file was saved with a password.

以R18版本为例介绍该节；安全节是可选的，如果文件设置了密码，就会有安全节；

R18: The section is present in the file if the SecurityType entry at location 0x18 in the file is greater than0.

如果在0x18位置的SecurityType 值大于0，就说明有安全节；

Strings are prefixed with a 32-bit length (not zero terminated).

这里的字符串指定了一个32位的长度，而不是以0结尾；

cryptographic英["krɪptəʊ"græfɪk]美[ˌkrɪptə"græfɪk]adj. 关于暗号的，用密码写的

Using the indicated provider and algorithm (and password obtained from the client for this drawing), the

encryption password can be verified by decrypting the Test Encrypted Sequence. If the result is

"SamirBajajSamirB" (0x53, 0x61, 0x6d, 0x69, 0x72, 0x42, 0x61, 0x6a, 0x61, 0x6a, 0x53, 0x61, 0x6d,

0x69, 0x72, 0x42), then the password is correct.

indicated英["ɪndə,keɪtɪd]美[ "ɪndə,ketɪd]adj. 表明的；指示的v. 标示( indicate的过去式和过去分词 )；指示；象征；

使用明确的提供者和算法（使用绘图人员提供的密码），通过解密测试加密序列，来验证用户的密码是否有效；

如果用提供的密码解密出来的内容恰好是测试序列"SamirBajajSamirB"，就说明这个密码是正确的；

The algorithm is RC4 (this is a symmetric encryption algorithm). The algorithm is used in DWG fileformat version 2004 and 2007.

假面算法用的是RC4（这是一种对称加密算法）；在2004和2007版本的DWG文件中使用这种加密算法；

Parameters are:参数如下

- Password (provided by user).密码（用户设置）

- Provider id: e.g. 0x0d.提供者（设置密码的用户）id；

- Provider name: e.g. "Microsoft Base DSS and Diffie-Hellman Cryptographic Provider".提供者名称；

- Key length: default value is 40.键长度，默认40；

- Flags: no salt.不使用盐值；

The password bytes (convert unicode password string to bytes, 2 bytes per character) are hashed (using

MD5). A session key is derived from the password hash (using no salt). This session key is then used for

both encryption and decryption.

密码用MD5计算hash值；一个会话密钥从哈希得到；会话密钥同时用于加密和解密；

20 Data section AcDb:AcDbObjects实体对象

This region holds the actual objects in the drawing. These can be entities, table entries, dictionary entries,

and objects. This second use of objects is somewhat confusing; all items stored in the file are “objects”,

but only some of them areobject objects. Others are entities, table entries, etc. The objects in this section

can appear in any order.

该节保存绘图中实际使用的对象；这些对象可能是实体、表格、字典、对象；对象的第二种使用方法有些难以理解；所有的元素在文件中都保存为对象，但是只有其中一部分是物体对象；其他的是实体、表格等；这些对象的顺序并不固定；

confusing英[kənˈfjuːzɪŋ]美[kənˈfjuːzɪŋ]adj. 难以理解的

Not all objects present in the file are actually used. All used objects can eventually be traced back to

handle references in the Header section. So the proper way to read a file is to start reading the header and

then tracing all references from there until all references have been followed. Very occasionally a file

contains e.g. two APPID objects with the same name, of which one is used, and the other is not. Reading

both would be incorrect due to a name clash. To complicate matters more, files also exist with table

records with duplicate names. This is incorrect, and the software should rename the record to be unique

upon reading.

文件中的所有对象不一定都会使用；那些被使用的对象可以再文件头中找到相应的句柄引用；所以要读取一个DWG文件，应该首先从头部找到所有引用，然后根据引用指向的 地址找出对象；很偶然的情况下，一个文件中会出现两个同名的APPID对象，这两个对象中有一个被使用了，而另一个没有被使用；如果同时读取两个同名对象，会造成名称冲突，从而导致错误；这是不正确的，并且软件应当把重名的对象改成唯一名称；

For R18 and later the section data (right after the page header) starts with a RL value of 0x0dca (meaning

unknown).

对于R18版本或者更高，本节的数据从0x0dca 开始；

20.1Common non-entity object format非实体对象的格式

Objects (non-entities) have the following general format:非实体对象的格式如下所示

assign英[əˈsaɪn]美[əˈsaɪn]v. 指派(任务)；给予

unsigned英["ʌn"saɪnd]美[ʌn"saɪnd]adj. 无符号的，无正负之分的

20.2Common entity format常用实体格式

Drawing entities, which are of course objects, have the same format as objects, with some additional

standard items:

绘图实体，属于进程对象，都有相同的格式，还拥有一些标准元素：

MS : Size of object, not including the CRC 对象大小，不含CRC

R2010+:

MC : Size in bits of the handle stream (unsigned, 0x40 is not interpreted as sign).句柄流大小

Commmon:

OT : Object type对象类型

R2000+ Only:

RL : Size of object data in bits对象数据大小

Common:

H : Object’s handle对象句柄

BS : Size of extended object data, if any扩展数据大小，如有

X : Extended object data, if any扩展数据，如有

B : Flag indicating presence of graphic image.是否有图片

if (graphicimageflag is 1) {如果有图片

R13-R007:

RL: Size of graphic image in bytes图片大小

R2010+:

BLL: Size of graphic image in bytes图片大小

Common:

X: The graphic image图片

}

R13-R14 Only:

RL : Size of object data in bits对象大小

6B : Flags标志

6B : Common parameters公共参数

R2000+ Only:

B : 0 if the previous and next linkers are present; 1 if they are BOTH defaults (1

back and 1 forward).0表示有链接，1表示默认值；

ENC : Entity color颜色

BD : Linetype Scale线型

BB : Line type flags线型标志

00 – BYLAYER linetype线型（按图层）

01 – BYBLOCK linetype线型（按块）

10 – CONTINUOUS linetype线型（连续线）

11 – Indicates that a linetype handle will be stored in the handles section of the

entity.线型句柄

BB : Plotstyle flags:打印样式标志

00 – BYLAYER plotstyle打印样式（按图层）

01 – BYBLOCK plotstyle打印样式（按块）

10 – CONTINUOUS plotstyle打印样式（连续线）

11 – Indicates that a plotstyle handle will be stored in the handles section of

the entity.打印样式句柄

R2007+:

BB : Material flags:材质标志

00 – BYLAYER material材质（按图层）

01 – BYBLOCK material材质（按块）

10 – global material?全局材质

11 – Indicates that a material handle will be stored in the handles section of the

entity.材质句柄

RC : Shadow flags阴影标志

R2010+:

B : Has full visual style完全样式

B : Has face visual style面样式

B : Has edge visual style边样式

Common:

BS : Invisible flag (bit 0: 0 = visible, 1 = invisible)是否可见

R2000+:

RC : Entity lineweight flag线宽标志

Common:

X : Object data (varies by type of object)对象数据（不同对象的数据有所不同）

X : Handles associated with this object该对象的句柄

B* : Padding bits are added until the next byte boundary is reached.填充到下一个字节边界

RS : CRC校验

varies英["veərɪz]美["veərɪz]v. 变化( vary的第三人称单数 )；[生物学]变异；相应变化；呈现不同

The R13-R14 FLAGS area (6 bits) indicates which handle references are present in the HANDLE REFS

area. They are as follows:R13-R14版本中的标志，表示句柄引用，如下所示：

FEDCBA

FE : Entity mode (entmode). Generally, this indicates whether or not the owner

relative handle reference is present. The values go as follows:

实体模式，表示是否有主人的引用；这个值如下：

00 : The owner relative handle reference is present.00表示有主人句柄；

Applies to the following:适用于以下情形

VERTEX, ATTRIB, and SEQEND.顶点、特性、序列结尾；

BLOCK, ENDBLK, and the defining entities in all

block defs except *MODEL_SPACE and *PAPER_SPACE.

块、结束块和块中定义的所有实体，模型空间和图纸空间除外；

01 : PSPACE entity without a owner relative handle ref.01表示没有主人的句柄（图纸空间）；

10 : MSPACE entity without a owner relative handle ref.10表示没有主人句柄（模型空间）；

11 : Not used.未使用；

DC : This is the number of reactors attached to an entity as a bitshort. This feature

may have been dormant in R13, but it appears in R14, and in files saved as R13 by

R14.

reactors英[r"ɪæktəz]美[r"ɪæktəz]n. 起反应的人( reactor的名词复数 )；反应装置；原子炉；核反应堆

dormant英[ˈdɔːmənt]美[ˈdɔːrmənt]adj. 休眠的；蛰伏的；暂停活动的

实体上附属的反应器的个数，用2字节表示；R13中，这个属性可能无法使用，但是在R14版本中可用，用R14保存成R13的文件中也可用；

B : 0 if a linetype reference is present; 1 if it"s not (the default being BYLAYER --

even though there IS a BYLAYER linetype entity and it has a handle).

表示有没有线型的引用，0表示有1没有；默认的线型是按图层

A : 0 if the previous and next linkers are present; 1 if they are BOTH defaults (1

back and 1 forward).0表示有链接，1表示默认值；

The COMMON PARAMETERS (6 bits):

CCSSII

CC : Color bitshort

SS : Linetype scale bitdouble

II : "Invisible" flag bitshort (bit 0: 0 = visible, 1 = invisible).

The ENTITY-SPECIFIC PARAMETERS area is coded with bitcodes. Each entity has its own parameter

prescription. Some parameters ALWAYS appear in raw form -- even if bitcode abbreviations could be

used (the 10 and 11 points in TEXT, for example). Generally the raw form is used in conditions wherein

it cannot reasonably be assumed that the likely value for the particular parameter is one of the

compressible values.

prescription英[prɪˈskrɪpʃn]美[prɪˈskrɪpʃn]n. [医]药方，处方；处方药；训令，指示；法规

实体说明参数部分使用位编码；每个实体都有各自的参数；有些参数始终都会出现，即使使用了缩写；

原始数据用于可压缩的值；

One method for loading these objects is to follow the object map. Doing so will cause each object to be

loaded once and only once. Alternatively one can try to scan the objects as they are found, and replace

objects with duplicated object handles with the ones found later in the file. The Teigha Classic for .dwg

files Toolkit uses a hybrid approach, loading the control objects first, then the objects they contain.

获取对象的方式是使用对象地图；用这种方法会将对象加载一次，且只有一次；另外也可以扫描文件来获取对象，或者用一个复制的句柄来代替该对象；Teigha使用混合方式来获取对象，首先加载控制对象，然后加载其中（控制对象）包含的对象；

20.3Object types对象类型

Some object types have fixed values, others have values which vary with the drawing. Here are the fixed

values:有些对象有固定的值，有些对象有变化的值；下面是一些固定的值：

UNUSED 0未使用RAY 0x28射线

TEXT 1文本XLINE 0x29

ATTRIB 2特性DICTIONARY 0x2A

ATTDEF 3 OLEFRAME 0x2B

BLOCK 4块MTEXT 0x2C多行文本

ENDBLK 5结束块LEADER 0x2D

SEQEND 6 TOLERANCE 0x2E

INSERT 7 MLINE 0x2F多线

MINSERT 8 BLOCK CONTROL OBJ 0x30

9 BLOCK块HEADER 0x31头部

VERTEX (2D) 0x0A顶点LAYER CONTROL OBJ 0x32图层

VERTEX (3D) 0x0B顶点LAYER 0x33图层

VERTEX (MESH) 0x0C网格顶点STYLE CONTROL OBJ 0x34

VERTEX (PFACE) 0x0D面顶点STYLE 0x35

VERTEX (PFACE FACE) 0x0E 0x36

POLYLINE (2D) 0x0F 0x37多段线

POLYLINE (3D) 0x10多段线LTYPE CONTROL OBJ 0x38

ARC 0x11圆弧LTYPE 0x39线型

CIRCLE 0x12 0x3A

LINE 0x13 0x3B

DIMENSION (ORDINATE)注释0x14 VIEW CONTROL OBJ 0x3C视图

DIMENSION (LINEAR) 0x15 VIEW 0x3D

DIMENSION (ALIGNED) 0x16 UCS CONTROL OBJ 0x3E

DIMENSION (ANG 3-Pt) 0x17 UCS 0x3F坐标

DIMENSION (ANG 2-Ln) 0x18 VPORT CONTROL OBJ 0x40

DIMENSION (RADIUS) 0x19 VPORT 0x41

DIMENSION (DIAMETER) 0x1A APPID CONTROL OBJ 0x42

POINT 0x1B APPID 0x43点

3DFACE 0x1C DIMSTYLE CONTROL OBJ 0x44

POLYLINE (PFACE)多段线0x1D DIMSTYLE 0x45标注样式

POLYLINE (MESH) 0x1E VP ENT HDR CTRL OBJ 0x46

SOLID 0x1F实线VP ENT HDR 0x47

TRACE 0x20 GROUP 0x48组

SHAPE 0x21 MLINESTYLE 0x49

VIEWPORT 0x22视口OLE2FRAME 0x4A

ELLIPSE 0x23 (DUMMY) 0x4B

SPLINE 0x24 LONG_TRANSACTION 0x4C

REGION 0x25区域LWPOLYLINE 0x4D

3DSOLID 0x26三维实体HATCH 0x4E

BODY 0x27 XRECORD 0x4F

ACDBPLACEHOLDER 0x50

VBA_PROJECT 0x51

LAYOUT 0x52布局

ACAD_PROXY_ENTITY 0x1f2代理实体

ACAD_PROXY_OBJECT 0x1f3代理对象

There are a number of objects with non-fixed values. These are:非定值对象：

ACAD_TABLE表格

CELLSTYLEMAP单元格样式

DBCOLOR颜色

DICTIONARYVAR

DICTIONARYWDFLT字典

FIELD字段

GROUP组

HATCH填充

IDBUFFER缓存

IMAGE图像

IMAGEDEF图像定义

IMAGEDEFREACTOR

LAYER_INDEX图层索引

LAYOUT布局

LWPLINE

MATERIAL材质

MLEADER引线

MLEADERSTYLE引线样式

OLE2FRAME

PLACEHOLDER占位符

PLOTSETTINGS打印设置

RASTERVARIABLES

SCALE缩放

SORTENTSTABLE排序表格

SPATIAL_FILTER空间过滤器

SPATIAL_INDEX空间索引

TABLEGEOMETRY表格几何体

TABLESTYLES表格样式

VBA_PROJECT

VISUALSTYLE视觉样式

WIPEOUTVARIABLE

XRECORD

For objects with non-fixed values, taking the object type minus 500 gives an index into the class list,

which then determines the type of object. For instance, an object type of 501 means that this object is of

the class which is second in the class list; the classdxfname field determines the type of the object.

See the sections on EED a description of that areas.

对于非定值对象，可以用对象类型减去500获得类列表的索引，然后就能获取对象的类型了；

例如，一个对象的类型是501，那么类型索引就是501-500=1，也就是类型列表中的第二个成员（0开始）；

20.4OBJECT PRESCRIPTIONS对象处方？

prescriptions英[prɪsk"rɪpʃnz]美[prɪsk"rɪpʃnz]n. 规定；处方；开处方；计划

prescription英[prɪˈskrɪpʃn]美[prɪˈskrɪpʃn]n. （条例、指示、命令、法令等）规定; 处方

prescript 规定，规定规定; 处方;

The object prescriptions are given in the following form:对象处方格式如下

ITEM TYPE-CODE DXF-CODE DESCRIPTION元素 类型编码 图形交换码 处方

See the top of this document for the key to the data types used here.

20.4.1 Common Entity Data常用实体数据

The following data appears at the beginning of each entity in the file, and willbe referred toas Common

Entity Data in the subsequent entity descriptions.

下面的数据在每个实体的开头部分，被称为实体数据，这些数据在后续的实体描述信息中；

Length MS --- Entity length (not counting itself or CRC).实体长度（不含自身长度和CRC）

Type BS 0 1 (internal DWG type code).

R2000+ Only:

Obj size RL size of object in bits, not including end handles

Common:

Handle H 5 code 0, length followed by the handle bytes.

EED size BS size of extended entity data, if any

EED X -3 See EED section.

Graphic present Flag B 1 if a graphic is present

Graphics X if graphicpresentflag is 1, the graphic goes here.

See the section on Proxy Entity Graphics for the

format of this section.

R13-R14 Only:

Obj size RL size of object in bits, not including end handles

Common:

Entmode BB entity mode

Numreactors BL number of persistent reactors attached to this

object

R2004+:

XDic Missing Flag B If 1, no XDictionary handle is stored for this

object, otherwise XDictionary handle is stored as in

R2000 and earlier.

R2013+:

Has DS binary data B If 1 then this object has associated binary data

stored in the data store. See for more details

chapter 24.

R13-R14 Only:

Isbylayerlt B 1 if bylayer linetype, else 0

Common:

Nolinks B 1 if major links are assumed +1, -1, else 0

For R2004+ this always has value 1

(links are not used)

Color CMC(B) 62

Ltype scale BD 48

R2000+:

Ltype flags BB 00 = bylayer, 01 = byblock, 10 = continous, 11 =

linetype handle present at end of object

Plotstyle flags BB 00 = bylayer, 01 = byblock, 11 = plotstyle handle

present at end of object

R2007+:

Material flags BB 00 = bylayer, 01 = byblock, 11 = material handle

present at end of object

Shadow flags RC

Common:

Invisibility BS 60

R2000+:

Lineweight RC 370

20.4.2 Common Entity Handle Data常用实体句柄

be referred to as被称为…

subsequent英[ˈsʌbsɪkwənt]美[ˈsʌbsɪkwənt]adj. 后来的；随后的；作为结果而发生的；附随的

The following data appears in the handles section of each entity, and will be referred to asCommon

Entity Handle Data in the subsequent entity descriptions.

下面的数据出现在每个实体的句柄部分，被称为后面的实体描述信息的实体句柄数据；

Handle refs

[Owner ref handle (soft pointer)]

[Reactors (soft pointer)]

xdicobjhandle (hard owner)

R13-R14 Only:

8 LAYER (hard pointer)

6 [LTYPE (hard pointer)] (present if Isbylayerlt is 0)

R13-R2000 Only:

previous/next handles present if Nolinks is 0

[PREVIOUS ENTITY (relative soft pointer)]

[NEXT ENTITY (relative soft pointer)]

R2004+:

[Color book color handle (hard pointer)]

R2000+ Only:

8 LAYER (hard pointer)

6 [LTYPE (hard pointer)] present if linetype flagswere 11

R2007+:

MATERIAL present if material flags were 11

R2000+:

PLOTSTYLE (hard pointer) present if plotstyle flags

were 11

R2010+:

If has full visual style, the full visual style handle (hard pointer).

If has face visual style, the face visual style handle (hard pointer).

If has edge visual style, the full visual style handle (hard pointer).

20.4.3 TEXT (1)文本数据

elevation 高程英[ˌelɪˈveɪʃn]美[ˌelɪˈveɪʃn]n. 高程; 提升; 提拔;(某地方的)高度; (尤指)海拔; 高地; 高处;

oblique英[əˈbli:k]美[oˈblik, əˈblik]adj. 斜，倾斜的；

Common Entity Data

R13-14 Only:

Elevation BD ---高程、高度

Insertion pt 2RD 10插入点坐标

Alignment pt 2RD 11对齐点坐标

Extrusion 3BD 210挤出坐标

Thickness BD 39厚度

Oblique ang BD 51斜体字、倾斜角度

Rotation ang BD 50旋转角度

Height BD 40高度

Width factor BD 41宽度系数

Text value TV 1文本内容

Generation BS 71

Horiz align. BS 72水平对齐

Vert align. BS 73垂直对齐

R2000+ Only:

DataFlags RC Used to determine presence of subsquent data标志位，决定了是否有后续的数据

Elevation RD --- present if !(DataFlags & 0x01)高程、高度

Insertion pt 2RD 10插入点位置

Alignment pt 2DD 11 present if !(DataFlags & 0x02), use 10 & 20 values对齐点位置

for 2 default values.

Extrusion BE 210

Thickness BT 39

Oblique ang RD 51 present if !(DataFlags & 0x04)

Rotation ang RD 50 present if !(DataFlags & 0x08)

Height RD 40

Width factor RD 41 present if !(DataFlags & 0x10)

Text value TV 1

Generation BS 71 present if !(DataFlags & 0x20)

Horiz align. BS 72 present if !(DataFlags & 0x40)

Vert align. BS 73 present if !(DataFlags & 0x80)

Common:

Common Entity Handle Data实体句柄

H 7 STYLE (hard pointer)

CRC X ---

20.4.5 ATTDEF (3)属性

Common ATTRIB Entity Data属性实体数据

R2010+:

Version RC ?版本

Common:

Prompt TV 3

CRC X ---

20.4.6 BLOCK (4)块

Common Entity Data 实体数据

Block name TV 2块名

Common Entity Handle Data实体句柄

CRC X --- 校验数据

20.4.7 ENDBLK (5)结束块

Common Entity Data实体数据

Common Entity Handle Data实体句柄

CRC X ---校验数据

20.4.18 ARC (17)圆弧

Common Entity Data

Center 3BD 10圆心

Radius BD 40半径

Thickness BT 39宽度

Extrusion BE 210挤出

Start angle BD 50开始角度

End angle BD 51结束角度

Common Entity Handle Data句柄

CRC X ---校验

20.4.19 ARC_DIMENSION圆弧的标注

Class properties:类属性

maintenance 英[ˈmeɪntənəns]美[ˈmeɪntənəns]n. 维修; 维护; 保养;

The arc length dimension was introduced in AutoCAD 2004. The DXF format is slightly different from

the other dimension entities. The entity type in DXF is ARC_DIMENSION, rather than DIMENSION.

Common Entity Data

Extension line 1 point 3BD 13延伸线的点

Extension line 2 point 3BD 14延伸线的点

Arc center 3BD 15圆心

Is partial? B 70

Start angle (radians) BD 40起始角度

End angle (radians) BD 41结束角度

Has leader? B 71是否有引线

Leader point 1 3BD 16引线的点

Leader point 2 3BD 17引线的点

Common Entity Handle Data句柄

H 3 DIMSTYLE (hard pointer)标注类型

H 2 anonymous BLOCK (hard pointer)匿名块

CRC X ---校验

20.4.20 CIRCLE (18)圆

Common Entity Data

Center 3BD 10

Radius BD 40

Thickness BT 39

Extrusion BE 210

Common Entity Handle Data

CRC X ---

20.4.20.1 R14 Example:

OBJECT: circle (12H), len 2BH (43), handle: 92

20.4.21 LINE (19)直线

Common Entity Data

R13-R14 Only:

Start pt 3BD 10起始点

End pt 3BD 11结束点

R2000+:

Z’s are zero bit B

Start Point x RD 10起始点x

End Point x DD 11 Use 10 value for default结束点x

Start Point y RD 20起始点y

End Point y DD 21 Use 20 value for default结束点y

Start Point z RD 30 Present only if “Z’s are zero bit” is 0起始点z

End Point z DD 31 Present only if “Z’s are zero bit” is 0, use 30结束点z

value for default.

Common:

Thickness BT 39宽度（线宽）

Extrusion BE 210挤出

Common Entity Handle Data句柄

CRC X ---校验

20.4.33 POLYLINE (PFACE) (29)多段线

Common Entity Data

Numverts BS 71 Number of vertices in the mesh.顶点个数

Numfaces BS 72 Number of faces面个数

R2004+:

Owned Object Count BL Number of objects owned by this object.

Common:

Common Entity Handle Data句柄

R13-R2000:

H first VERTEX (soft pointer)起始顶点

H last VERTEX (soft pointer)结束顶点

R2004+:

H [VERTEX (soft pointer)] Repeats “Owned Object Count”times.

Common:

H SEQEND (hard owner)

CRC X ---校验

20.4.39 ELLIPSE (35)椭圆

Note that the 10 pt and the 11 vector are WCS -- even though an ellipse is planar and has an extrusion

vector (210-group).

Common Entity Data

Center 3BD 10 (WCS)

SM axis vec 3BD 11 Semi-major axis vector (WCS)

Extrusion 3BD 210

Axis ratio BD 40 Minor/major axis ratio

Beg angle BD 41 Starting angle (eccentric anomaly, radians)

End angle BD 42 Ending angle (eccentric anomaly, radians)

Common Entity Handle Data

CRC X ---

20.4.42 RAY (40)射线

Common Entity Data

Point 3BD 10点

Vector 3BD 11向量

Common Entity Handle Data

CRC X ---

20.4.44 DICTIONARY (42)字典

Basically a list of pairs of string/objhandle that constitute the dictionary entries.

字符串和对象句柄组成一对，很多个这样的对组成一个列表，他们组成了字典的入口；

Length MS --- Entity length (not counting itself or CRC).

Type S 0 42 (internal DWG type code).

R2000+:

Obj size RL size of object in bits, not including end handles对象大小

Common:

Handle H 5 Length (char) followed by the handle bytes.对象句柄

EED X -3 See EED section.

R13-R14 Only:

Obj size RL size of object in bits, not including end handles对象大小

Common:

Numreactors S number of reactors in this object反应堆的个数

R2004+:

otherwise英[ˈʌðəwaɪz]美[ˈʌðərwaɪz]adv. 否则；除此以外；与之不同地；以其他方式

XDic Missing Flag B If 1, no XDictionary handle is stored for this

object, otherwise XDictionary handle is stored as in

R2000 and earlier.

Common:

Numitems L number of dictonary items字典中元素个数

R14 Only:

Unknown R14 RC Unknown R14 byte, has always been 0未知字节，始终是0

R2000+:

Cloning flag BS 281

Hard Owner flag RC 280

Common:

Text TV string name of dictionary entry, numitems entries

Handle refs H parenthandle (soft relative pointer)父亲的句柄

[Reactors (soft pointer)]

xdicobjhandle (hard owner)

20.4.46 MTEXT (44)多行文本

Common Entity (Handle) Data

Insertion pt3 BD 10 First picked point. (Location relative to text插入点坐标

depends on attachment point (71).)

Extrusion 3BD 210 Undocumented; appears in DXF and entget, but ACAD

doesn"t even bother to adjust it to unit length.

X-axis dir 3BD 11 Apparently the text x-axis vector. (Why not just a

rotation?) ACAD maintains it as a unit vector.x轴方向，单位向量

Common:

Rect width BD 41 Reference rectangle width (width picked by theuser).矩形框宽度

R2007+:

Rect height BD 46 Reference rectangle height.矩形框高度

Common:

Text height BD 40 Undocumented文本高度

Attachment BS 71 Similar to justification; see DXF doc

Drawing dir BS 72 Left to right, etc.; see DXF doc绘制方向

Extents ht BD --- Undocumented and not present in DXF or entget扩展高度

Extents wid BD --- Undocumented and not present in DXF or entget扩展宽度

Text TV 1 All text in one long string (without "\n"s

3 for line wrapping). ACAD seems to add braces ({ })

and backslash-P"s to indicate paragraphs based on

the "\r\n""s found in the imported file. But, all

the text is in this one long string -- not broken

into 1- and 3-groups as in DXF and entget.

ACAD"s entget breaks this string into 250-char

pieces (not 255 as doc"d) – even if it"s mid-word.

The 1-group always gets the tag end; therefore, the

3"s are always 250 chars long.

H 7 STYLE (hard pointer)

R2000+:

Linespacing Style BS 73

Linespacing Factor BD 44

Unknown bit B

R2004+:

frame (R2018+)

IF background flags has bit 0x01 set, or in case of R2018 bit 0x10:

Background scale factor

BL 45 default = 1.5

Background color CMC 63

Background transparency

BL 441

END IF background flags 0x01/0x10

R2018+

Is NOT annotative B

IF MTEXT is not annotative

Version BS Default 0

Default flag B Default true

BEGIN REDUNDANT FIELDS (see above for descriptions)

Registered application H Hard pointer

Attachment point BL

X-axis dir 3BD 10

Insertion point 3BD 11

Rect width BD 40

Rect height BD 41

Extents width BD 42

Extents height BD 43

END REDUNDANT FIELDS

Column type BS 71 0 = No columns, 1 = static columns, 2 = dynamic

columns

IF Has Columns data (column type is not 0)

Column height count BL 72

Columnn width BD 44

Gutter BD 45

Auto height? B 73

Flow reversed? B 74

IF not auto height and column type is dynamic columns

REPEAT Column heights

Column height BD 46

END REPEAT

END IF (has column heights)

END IF (has columns data)

END IF (not annotative)

Common:

CRC X ---

UCS用户坐标系(User Coordinate System);

20.4.96 TABLE (varies)表格

The TABLE entity (entity type ACAD_TABLE) was introduced in AutoCAD 2005 (a sub

release of R18), and a large number of changes were introduced in AutoCAD 2008 (a sub release of

R21). The table entity inherits from the INSERT entity. The geometric results, consisting of table borders,

texts and such are created in an anonymous block, similarly to the mechanism in the DIMENSION entity.

The anonymous block name prefix is “*T”. For the AutoCAD 2008 changes see paragraph 20.4.96.2.

TODO: document roundtrip data with connections to AcDbTableContent and

AcDbTableGeometry.

在CAD2005版（R18）开始引入表格，相比于2008有很大变化；表格继承自插入实体；包括表格边框、文本、匿名块，类似于标注；匿名刈名称以T为前缀；

20.4.96.1 Until R21

This paragraph describes the table DWG format until R21. In R24 the format was changed to make use of

table content to contain all data (AcDbTableContent).

21 Data section AcDb:ObjFreeSpace自由空间

The meaning of this section is not completely known. The ODA knows how to write a valid section, but

the meaning is not known of every field.

这个节的含义并不完全清楚；但是ODA直到如何写一个有效的节，只是字段的含义不清楚而已；

22 Data section: AcDb:Template模板

mandatory英[ˈmændətəri]美[ˈmændətɔːri]adj. 强制的；命令的；受委托的

This section is optional in releases 13-15. The section is mandatory in the releases 18 and newer. The

template section only contains the MEASUREMENT system variable.

R13-15版本中，这个节是可选的；在R18或者更新的版本中，这个节是必须的；模板节仅仅包含测量相关的系统变量；

23 Data section AcDb:Handles (OBJECT MAP)对象地图

23.1R13-15

The Object Map is a table which gives the location of each object in the file This table is broken into

sections. It is basically a list of handle/file loc pairs, and goes (something like) this:

对象地图是一个表格，其中列出了每个对象在文件中的位置；这个表格被拆分成多个部分；基本上是句柄/文件位置键值对，如下所示：

Set the "last handle" to all 0 and the "last loc" to 0L;

Repeat until section size==2 (the last empty (except the CRC) section):

Short: size of this section. Note this is in BIGENDIAN order (MSB

first)

Repeat until out of data for this section:

offset of this handle from last handle as modular char.句柄偏移量

offset of location in file from last loc as modular char. (note

that location offsets can be negative, if the terminating byte

has the 4 bit set).文件中的位置偏移量

End repeat.

CRC (most significant byte followed by least significant byte)

End of section

End top repeat

Note that each section is cut off at a maximum length of 2032.

24 Section AcDb:AcDsPrototype_1b (DataStorage)

数据存储

At this moment (December 2012), this sections contains information about Acis data (regions, solids).

The data is stored in a byte stream, not a bit stream like e.g. the objects section.

The data store contains several data segments, and index segments that contain lookup information for

finding the data segments and objects within these data segments. The file header contains the stream

position of the segment index file segment and the segment indexes for the schema index/data

index/search file segments. The segment index file segment is a lookup table for finding the stream

position of a file segment by its segment index.

In paragraph 24.3 the default contents of this section is shown when empty.

25 UNKNOWN SECTION未知节

This section is largely unknown. The total size of this section is 53. We simply patch in "known to be

valid" data. We first write a 0L, then the number of entries in the objmap +3, as a long. Then 45 bytes of

"known to be valid data". Then we poke in the start address for objects at offset 16.

26 SECOND FILE HEADER (R13-R15)

27 Data section: AcDb:AuxHeader (Auxiliary file

header)辅助节

The auxiliary file header contains mostly redundant information and was introduced in R15.

28 Extended Entity Data扩展实体数据

(Extended Object Data)

EED directly follows the entity handle.

Each application"s data is structured as follows:

|Length|Application handle|Data items|

Length is a bitshort indicating the length of the data for an app, not including itself, the bit-pair, or the app

table handle. The above format repeats until a length of zero is found.

The application handle is a standard table handle reference: 0101|4-bit length|handle bytes|

Each data item has a 1-byte code (DXF group code minus 1000) followed by the value. It looks like

there"s no bit-pair coding within the data; that would throw off the length value (it would need to count

bits, too). The form of the value is listed below for each type:

29 PROXY ENTITY GRAPHICS代理图形

Proxy entities (zombies prior to R14) can have associated graphics data. The presence or absence of this

data is indicated by the single bit which we call the “graphic present flag”, which mostly occurs on entitytype proxies, and very few other entities. Entity type proxies are proxies where the related class’s

itemclassid field is equal to 0x1F2.

代理实体可以拥有相关的图形数据；有一个标志位来表示是否有该部分数据，他通常出现在实体类型代理中，而很少出现在实体中；只有itemclassid 字段的值是0x1F2才能代理；

If that bit is 1, then following it, and preceding the RL which indicates the number of bits in the object, is

an RL which indicates the number of bytes of proxy entity graphic data to follow.

Graphics data is padded to 4 byte boundaries! So, for instance, strings which are too short are padded out

to the next 4 byte boundary. Similarly for lists of shorts.

In addition to the data definitions from chapter 2 there are a few additional data types:

PS : Padded string. This is a string, terminated with a zero byte. The file’s text encoding (code page)

is used to encode/decode the bytes into a string.

PUS : Padded Unicode string. The bytes are encoded using Unicode encoding. The bytes consist of

byte pairs and the string is terminated by 2 zero bytes.

We use the following defines to discriminate sub-item presence:

#define adHasPrimTraits(a) (a & 0xFFFFL)

#define adPrimsHaveColors(a) (a & 0x0001L)

#define adPrimsHaveLayers(a) (a & 0x0002L)

#define adPrimsHaveLinetypes(a) (a & 0x0004L)

#define adPrimsHaveMarkers(a) (a & 0x0020L)

#define adPrimsHaveVisibilities(a) (a & 0x0040L)

#define adPrimsHaveNormals(a) (a & 0x0080L)

#define adPrimsHaveOrientation(a) (a & 0x0400L)

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