xstr(1)
NAME
xstr − extract strings from C programs to implement shared strings
SYNTAX
xstr [ −c ] [ − ] [ file ]
DESCRIPTION
The xstr command 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, most useful if they are also read-only.
The following command will extract the strings from the C source in file1, replacing string references by expressions of the form (&xstr[number]) for some number.
xstr −c file1
An appropriate declaration of xstr is prepended to the file. The resulting C text is placed in the file x.c, to then be compiled. The strings from this file are placed in the strings data base if they are not there already. Repeated strings and strings which are suffices 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 a command of the form:
xstr
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.
The xstr command can also be used on a single file. The following command: creates files x.c and xs.c as before, without using or affecting any strings file in the same directory.
xstr name
It may be useful to run xstr after the C preprocessor if any macro definitions yield strings or if there is conditional code which contains strings which may not, in fact, be needed. If a − is specified in place of file, xstr reads standard input. 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
The xstr program does not touch the file strings unless new items are added, thus make can avoid remaking xs.o unless truly necessary.
RESTRICTIONS
If a string is a suffix of another string in the data base, but the shorter string is seen first by xstr both strings will be placed in the data base, when just placing the longer one there will do.
FILES
stringsData base of strings
x.cmassaged C source
xs.cC source for definition of array ’xstr’
/tmp/xs*temporary file for ’xstr name’ strings