xstr(1)

DESCRIPTION

xstr maintains a file strings into which strings in component parts of a large program are hashed. These strings are replaced with references to this common area. This serves to implement shared constant strings, which are most useful if they are also read-only.

The command:

extracts the strings from the C source in name, replacing string references with expressions of the form (&xstr[number]) for some number. An appropriate declaration of xstr is placed at the beginning of the file. The resulting C text is placed in the file x.c, for subsequent compiling. The strings from this file are placed in the strings database if they are not there already. Repeated strings and strings that are suffixes of existing strings do not cause changes to the data base.

After all components of a large program have been compiled, a file xs.c declaring the common xstr space, can be created by the command:

This xs.c file should then be compiled and loaded with the rest of the program. If possible, the array can be made read-only (shared), saving space and swap overhead.

xstr can also be used on a single file. A command:

creates files x.c and xs.c as before, without using or affecting any strings file in the same directory.

It may be useful to run xstr after the C preprocessor if any macro definitions yield strings or if there is conditional code containing strings that are not, in fact, needed. xstr reads from its standard input when the argument - is given. An appropriate command sequence for running xstr after the C preprocessor is:

xstr does not touch the file strings unless new items are added, thus make can avoid remaking xs.o unless truly necessary (see make(1)).

WARNINGS

If a string is a suffix of another string in the data base, but the shorter string is seen first by xstr, both strings are placed in the data base, when placing only the longer one there would be sufficient.

AUTHOR

xstr was developed by the University of California, Berkeley.

FILES

SEE ALSO

mkstr(1).