NAME [Toc] [Back]
xstr - extract strings from C programs to implement shared strings
SYNOPSIS [Toc] [Back]
xstr [-c] [-] [file]
DESCRIPTION [Toc] [Back]
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.
xstr -c name
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:
cc -E name.c | xstr -c -
cc -c x.c
mv x.o name.o
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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 [Toc] [Back]
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 [Toc] [Back]
xstr was developed by the University of California, Berkeley.
FILES [Toc] [Back]
strings Data base of strings
x.c Massaged C source
xs.c C source for definition of array xstr
/tmp/xs* Temp file when `xstr name' does not touch strings
SEE ALSO [Toc] [Back]
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