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