1Copyright (c) 1993-1994 by Xerox Corporation. All rights reserved. 2 3THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED 4OR IMPLIED. ANY USE IS AT YOUR OWN RISK. 5 6Permission is hereby granted to use or copy this program 7for any purpose, provided the above notices are retained on all copies. 8Permission to modify the code and to distribute modified code is granted, 9provided the above notices are retained, and a notice that the code was 10modified is included with the above copyright notice. 11 12Please send bug reports to Hans-J. Boehm (Hans_Boehm@hp.com or 13boehm@acm.org). 14 15This is a string packages that uses a tree-based representation. 16See cord.h for a description of the functions provided. Ec.h describes 17"extensible cords", which are essentially output streams that write 18to a cord. These allow for efficient construction of cords without 19requiring a bound on the size of a cord. 20 21More details on the data structure can be found in 22 23Boehm, Atkinson, and Plass, "Ropes: An Alternative to Strings", 24Software Practice and Experience 25, 12, December 1995, pp. 1315-1330. 25 26A fundamentally similar "rope" data structure is also part of SGI's standard 27template library implementation, and its descendents, which include the 28GNU C++ library. That uses reference counting by default. 29There is a short description of that data structure at 30http://reality.sgi.com/boehm/ropeimpl.html . (The more official location 31http://www.sgi.com/tech/stl/ropeimpl.html is missing a figure.) 32 33All of these are descendents of the "ropes" in Xerox Cedar. 34 35de.c is a very dumb text editor that illustrates the use of cords. 36It maintains a list of file versions. Each version is simply a 37cord representing the file contents. Nonetheless, standard 38editing operations are efficient, even on very large files. 39(Its 3 line "user manual" can be obtained by invoking it without 40arguments. Note that ^R^N and ^R^P move the cursor by 41almost a screen. It does not understand tabs, which will show 42up as highlighred "I"s. Use the UNIX "expand" program first.) 43To build the editor, type "make cord/de" in the gc directory. 44 45This package assumes an ANSI C compiler such as gcc. It will 46not compile with an old-style K&R compiler. 47 48Note that CORD_printf iand friends use C functions with variable numbers 49of arguments in non-standard-conforming ways. This code is known to 50break on some platforms, notably PowerPC. It should be possible to 51build the remainder of the library (everything but cordprnt.c) on 52any platform that supports the collector. 53 54