# Shapefile C Library V1.2

## Purpose

The Shapefile C Library provides the ability to write simple C programs for reading, writing and updating (to a limited extent) ESRI Shapefiles, and the associated attribute file (.dbf).

## Manifest

- shapelib.html: This file - general documentation on the Shapefile C Library.

- shp_api.html: Documentation for the API for accessing the .shp/.shx files.

- dbf_api.html: Documentation for the API for accessing the .dbf attribute files.

- shpopen.c: C code for access to .shp/.shx vertex files.

- dbfopen.c: C code for access to .dbf attribute file.

- shapefil.h: Include file defining all the services of dbfopen.c and shpopen.c.

- contrib/: A directory of "in progress" contributed programs from Carl Anderson.

- dbfcreate.c: Simple example program for creating a new .dbf file.

- dbfadd.c: Simple example program for adding a record to a .dbf file.

- dbfdump.c: Simple example program for displaying the contents of a .dbf file.

- shpcreate.c: Simple example program for creating a new .shp and .shx file.

- shpadd.c: Simple example program for adding a shape to an existing shape file.

- shpdump.c: Simple program for dumping all the vertices in a shapefile with an indicating of the parts.

- shputils.c: Complex contributed program capable of clipping and appending shapefiles as well as a few other things. Type shputils after building to get a full usage message.

- Makefile: A simple makefile to compile the library and example programs.

- makeshape.sh: A simple script for running some of the example programs.

- shptest.c: A simple test harnass to generate each of the supported types of shapefiles.

- shptree.c: Implements a simple quadtree algorithm for fast spatial searches of shapefiles.

- shptreedump.c: A simple mainly showing information on quad trees build using the quad tree api.

- stream1.sh - A test script, which should produce stream1.out. Note this will only work if you have the example data downloaded.

- stream1.out: Expected output of stream1.sh test script.

- stream2.sh: A test script, which should produce stream2.out.

- stream2.out: Expected output of stream2.sh test script.

- pyshapelib-0.1: Prototype contributed Python bindings.

## What is a Shapefile?

If you don't know, you probably don't need this library. The Shapefile format is a new working and interchange format promulagated by ESRI (http://www.esri.com/) for simple vector data with attributes. It is apparently the only file format that can be edited in ARCView 2/3, and can also be exported and imported in Arc/Info.

An excellent white paper on the shapefile format is available from ESRI, but it is .pdf format, so you will need Adobe Acrobat to browse it.

The file format actually consists of three files.

    XXX.shp - holds the actual vertices.
    XXX.shx - hold index data pointing to the structures in the .shp file.
    XXX.dbf - holds the attributes in xBase (dBase) format.

## Release Notes

To get notification of new releases of Shapelib subscribe to the project at www.freshmeat.net. This is currently the only reliable way of finding out about new releases since there is no shapelib specific mailing list.

Release 1.2.10: Added SHPRewindObject() function, and shprewind utility program. Release 1.2.9: Good support for reading and writing NULL fields in .dbf files, good support for NULL shapes and addition of the DBFGetFieldIndex() functions (all contributed by Jim Matthews).

An upgraded shputils.c has been contributed by Bill Miller. Daniel Morissette contributed DBFGetNativeFieldType(). Better error checking for disk errors in dbfopen.c. Various other bug fixes and safety improvements.

Release 1.2.8: Added hacked libtool support (supplied by Jan) and "rpm ready" install logic.

Release 1.2.7: Fix record size (was 4 bytes too long). Modify SHPReadObject() to handle null shapes properly. Use atof() instead of sscanf(). Support .DBF as well as .dbf.

Release 1.2.6: Now available under old MIT style license, or at the users option, LGPL. Added the contrib directory of stuff from Carl Anderson and the shptree.c API for quadtree based spatial searches.

Release 1.2.5: SHPOpen() now forcably uses "rb" or "r+b" access string to avoid common mistakes on Windows. Also fixed a serious bug with .dbf files with a 'F' field type.

Release 1.2.4: DBFOpen() will now automatically translate a .shp extension to .dbf for convenience. SHPOpen() will try datasets with lower and uppercase extension. DBFAddField() now returns the field number, not TRUE/FALSE.

Release 1.2.3: Disable writing measures to multi-patches as ArcView seems to puke on them (as reported by Monika Sester). Add white space trimming, and string/numeric attribute interchangability in DBF API as suggested by Steve Lime. Dbfdump was updated to include several reporting options.

Release 1.2.2: Added proper support for multipatch (reading and writing) - this release just for testing purposes.

Release 1.2 is mostly a rewrite of the .shp/.shx access API to account for ArcView 3.x 3D shapes, and to encapsulate the shapes in a structure. Existing code using the shapefile library will require substantial changes to use release 1.2.

Release V1.1 has been built on a number of platforms, and used by a number of people successfully. V1.1 is the first release with the xBase API documentation.

## Maintainer

This library is maintained by me (Frank Warmerdam) on my own time. Please send me bug patches and suggestions for the library. Email can be sent to warmerdam@pobox.com.

The current status of the Shapelib code can be found somewhere off my home page at http://pobox.com/~warmerdam.

The shputils.c module was contributed by Bill Miller (NC-DOT) who can be reached at bmiller@doh.dot.state.nc.us. I had to modify it substantially to work with the 1.2 API, and I am not sure that it works as well as it did when it was originally provided by Bill.

## Credits

I didn't start this section anywhere near soon enough, so alot of earlier contributors to Shapelib are lost in pre-history.

- Bill Miller (NY-DOT) for shputils.c
- Carl Anderson for the contents of the contrib directory, and the "tuple" additions to dbfopen.c.
- Andrea Giacomelli for patches for dbfopen.c.
- Doug Matthews for portability improvements.
- Jan-Oliver Wagner for convincing me to make it available under LGPL, shared library support, and various other patches.
- Dennis Christopher (of Avenza) for testing and bug fixes.
- Miko Syrjä (of 3D-system Oy) for a record size bug fix.
- Steven Lime and Curtis Hill for help with NULL shapes.
- Jim Matthews for support of NULL attributes in dbf files.

## In Memorium

I would like to dedicate Shapelib to the memory of Sol Katz. While I never met him in person, his generous contributions to the GIS community took many forms, including free distribution of a variety of GIS translators with source. The fact that he used this Shapelib in some of his utilities, and thanked me was a great encouragement to me. I hope I can do his memory honour by trying to contribute in a similar fashion.

## Portability

The Shapefile C Library should port easily to 32bit systems with ANSI C compilers. It should work on 64 bit architectures (such as the DEC AXP).

Care should also be taken to pass the binary access flag into SHPOpen() and DBFOpen() when operating on systems with special text file translation such as MSDOS.

The shputils.c module is contributed, and may not take the same approach to portability as the rest of the package.

On Linux, and most unix systems it should be possible to build and install shapefile support as a shared library using the "lib" and "lib_install" targets of the Makefile. Note that this Makefile doesn't use autoconf mechanisms and will generally require some hand tailoring for your environment.

## Limitations

- You can't modify the vertices of existing structures (though you can update the attributes of existing structures, and create new structures).

- Not written in such a way as to be particularly fast. This is particularly true of the 1.2 API. For applications more concerned with speed it may be worth using the V1.1 API.

- Doesn't set the last access time properly in the .dbf files.

- There is no way to synchronize information to the file except to close it.

- Poor error checking and reporting.

- Not professionally supported (well it can be, if you want to pay).

- Some aspects of xBase files not supported, though I believe they are not used by ESRI.

- The application must keep the .dbf file in sync with the .shp/.shx files through appropriate use of the DBF and SHP APIs.

- No support for the undocumented .sbn/.sbx spatial index files.

## Copyright

The source for the Shapefile C Library is (c) 1998 Frank Warmerdam, and released under the following conditions. The intent is that anyone can do anything with the code, but that I do not assume any liability, nor express any warranty for this code.

As of Shapelib 1.2.6 the core portions of the library are made available under two possible licenses. The licensee can choose to use the code under either the Library GNU Public License (LGPL) described in LICENSE.LGPL or under the following MIT style license. Any files in the Shapelib distribution without explicit copyright license terms (such as this documentation, the Makefile and so forth) should be considered to have the following licensing terms. Some auxilary portions of Shapelib, notably some of the components in the contrib directory come under slightly different license restrictions. Check the source files that you are actually using for conditions.

### Default License Terms

Copyright (c) 1999, Frank Warmerdam

This software is available under the following "MIT Style" license, or at the option of the licensee under the LGPL (see LICENSE.LGPL). This option is discussed in more detail in shapelib.html.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

### Shapelib Modifications

I am pleased to receive bug fixes, and improvements for Shapelib. Unless the submissions indicate otherwise I will assume that changes submitted to me remain under the the above "dual license" terms. If changes are made to the library with the intention that those changes should be protected by the LGPL then I should be informed upon submission. Note that I will not generally incorporate changes into the core of Shapelib that are protected under the LGPL as this would effectively limit the whole file and distribution to LGPL terms.

### Opting for LGPL

For licensee's opting to use Shapelib under LGPL as opposed to the MIT Style license above, and wishing to redistribute the software based on Shapelib, I would ask that all "dual license" modules be updated to indicate that only the LGPL (and not the MIT Style license) applies. This action represents opting for the LGPL, and thereafter LGPL terms apply to any redistribution and modification of the affected modules.