NAME
cpl_complete_word, cfc_file_start, cfc_literal_escapes,
cfc_set_check_fn, cpl_add_completion, cpl_file_completions,
cpl_last_error, cpl_list_completions, cpl_record_error,
del_CplFileConf, del_WordCompletion, new_CplFileConf,
new_WordCompletion - lookup possible completions for a word
SYNOPSIS
#include <stdio.h>
#include <libtecla.h>
WordCompletion *new_WordCompletion(void);
WordCompletion *del_WordCompletion(WordCompletion *cpl);
#define CPL_MATCH_FN(fn) int (fn)(WordCompletion *cpl, \
void *data, \
const char *line, \
int word_end)
typedef CPL_MATCH_FN(CplMatchFn);
CPL_MATCH_FN(cpl_file_completions);
CplMatches *cpl_complete_word(WordCompletion *cpl,
const char *line,
int word_end, void *data,
CplMatchFn *match_fn);
int cpl_list_completions(CplMatches *result, FILE *fp,
int term_width);
int cpl_add_completion(WordCompletion *cpl,
const char *line, int word_start,
int word_end, const char *suffix,
const char *type_suffix,
const char *cont_suffix);
void cpl_record_error(WordCompletion *cpl,
const char *errmsg);
const char *cpl_last_error(WordCompletion *cpl);
DESCRIPTION
The cpl_complete_word() function is part of the tecla
library (see the libtecla(3) man page). It is usually called
behind the scenes by gl_get_line(3), but can also be called
separately.
Given an input line containing an incomplete word to be com-
pleted, it calls a user-provided callback function (or the
provided file-completion callback function) to look up all
possible completion suffixes for that word. The callback
function is expected to look backward in the line, starting
from the specified cursor position, to find the start of the
word to be completed, then to look up all possible comple-
tions of that word and record them, one at a time by calling
cpl_add_completion().
Descriptions of the functions of this module are as follows:
CompleteWord *new_CompleteWord(void)
This function creates the resources used by the
cpl_complete_word() function. In particular, it maintains
the memory that is used to return the results of calling
cpl_complete_word().
CompleteWord *del_CompleteWord(CompleteWord *cpl)
This function deletes the resources that were returned by a
previous call to new_CompleteWord(). It always returns NULL
(ie. a deleted object). It does nothing if the cpl argument
is NULL.
The callback functions which lookup possible completions
should be defined with the following macro (which is defined
in libtecla.h).
#define CPL_MATCH_FN(fn) int (fn)(WordCompletion *cpl, \
void *data, \
const char *line, \
int word_end)
Functions of this type are called by cpl_complete_word(),
and all of the arguments of the callback are those that were
passed to said function. In particular, the line argument
contains the input line containing the word to be completed,
and word_end is the index of the character that follows the
last character of the incomplete word within this string.
The callback is expected to look backwards from word_end for
the start of the incomplete word. What constitutes the start
of a word clearly depends on the application, so it makes
sense for the callback to take on this responsibility. For
example, the builtin filename completion function looks
backwards until it hits an unescaped space, or the start of
the line. Having found the start of the word, the callback
should then lookup all possible completions of this word,
and record each completion via separate calls to
cpl_add_completion(). If the callback needs access to an
application-specific symbol table, it can pass it and any
other data that it needs, via the data argument. This
removes any need for globals.
The callback function should return 0 if no errors occur. On
failure it should return 1, and register a terse description
of the error by calling cpl_record_error().
void cpl_record_error(WordCompletion *cpl,
const char *errmsg);
The last error message recorded by calling
cpl_record_error(), can subsequently be queried by calling
cpl_last_error(), as described later.
int cpl_add_completion(WordCompletion *cpl,
const char *line, int word_start,
int word_end, const char *suffix,
const char *type_suffix,
const char *cont_suffix);
The cpl_add_completion() function is called zero or more
times by the completion callback function to record each
possible completion in the specified WordCompletion object.
These completions are subsequently returned by
cpl_complete_word(), as described later. The cpl, line, and
word_end arguments should be those that were passed to the
callback function. The word_start argument should be the
index within the input line string of the start of the word
that is being completed. This should equal word_end if a
zero-length string is being completed. The suffix argument
is the string that would have to be appended to the incom-
plete word to complete it. If this needs any quoting (eg.
the addition of backslashes before special charaters) to be
valid within the displayed input line, this should be
included. A copy of the suffix string is allocated inter-
nally, so there is no need to maintain your copy of the
string after cpl_add_completion() returns.
Note that in the array of possible completions which the
cpl_complete_word() function returns, the suffix recorded by
cpl_add_completion() is listed along with the concatentation
of this suffix with the word that lies between word_start
and word_end in the input line.
The type_suffix argument specifies an optional string to be
appended to the completion if it is displayed as part of a
list of completions by cpl_list_completions(). The intention
is that this indicate to the user the type of each comple-
tion. For example, the file completion function places a
directory separator after completions that are directories,
to indicate their nature to the user. Similary, if the com-
pletion were a function, you could indicate this to the user
by setting type_suffix to "()". Note that the type_suffix
string isn't copied, so if the argument isn't a literal
string between speech marks, be sure that the string remains
valid for at least as long as the results of
cpl_complete_word() are needed.
The cont_suffix is a continuation suffix to append to the
completed word in the input line if this is the only comple-
tion. This is something that isn't part of the completion
itself, but that gives the user an indication about how they
might continue to extend the token. For example, the file-
completion callback function adds a directory separator if
the completed word is a directory. If the completed word
were a function name, you could similarly aid the user by
arranging for an open parenthesis to be appended.
CplMatches *cpl_complete_word(WordCompletion *cpl,
const char *line,
int word_end, void *data,
CplMatchFn *match_fn);
The cpl_complete_word() is normally called behind the scenes
by gl_get_line(3), but can also be called separately if you
separately allocate a WordCompletion object. It performs
word completion, as described at the beginning of this sec-
tion. Its first argument is a resource object previously
returned by new_CompleteWord(). The line argument is the
input line string, containing the word to be completed. The
word_end argument contains the index of the character in the
input line, that just follows the last character of the word
to be completed. When called by gl_get_line(), this is the
character over which the user pressed TAB. The match_fn
argument is the function pointer of the callback function
which will lookup possible completions of the word, as
described above, and the data argument provides a way for
the application to pass arbitrary data to the callback func-
tion.
If no errors occur, the cpl_complete_word() function returns
a pointer to a CplMatches container, as defined below. This
container is allocated as part of the cpl object that was
passed to cpl_complete_word(), and will thus change on each
call which uses the same cpl argument.
typedef struct {
char *completion; /* A matching completion */
/* string */
char *suffix; /* The part of the */
/* completion string which */
/* would have to be */
/* appended to complete the */
/* original word. */
const char *type_suffix; /* A suffix to be added when */
/* listing completions, to */
/* indicate the type of the */
/* completion. */
} CplMatch;
typedef struct {
char *suffix; /* The common initial part */
/* of all of the completion */
/* suffixes. */
const char *cont_suffix; /* Optional continuation */
/* string to be appended to */
/* the sole completion when */
/* nmatch==1. */
CplMatch *matches; /* The array of possible */
/* completion strings, */
/* sorted into lexical */
/* order. */
int nmatch; /* The number of elements in */
/* the above matches[] */
/* array. */
} CplMatches;
If an error occurs during completion, cpl_complete_word()
returns NULL. A description of the error can be acquired by
calling the cpl_last_error() function.
const char *cpl_last_error(WordCompletion *cpl);
The cpl_last_error() function returns a terse description of
the error which occurred on the last call to
cpl_complete_word() or cpl_add_completion().
int cpl_list_completions(CplMatches *result, FILE *fp,
int terminal_width);
When the cpl_complete_word() function returns multiple pos-
sible completions, the cpl_list_completions() function can
be called upon to list them, suitably arranged across the
available width of the terminal. It arranges for the
displayed columns of completions to all have the same width,
set by the longest completion. It also appends the
type_suffix strings that were recorded with each completion,
thus indicating their types to the user.
THE BUILT-IN FILENAME-COMPLETION CALLBACK
By default the gl_get_line(3) function, passes the following
completion callback function to cpl_complete_word(). This
function can also be used separately, either by sending it
to cpl_complete_word(), or by calling it directly from your
own completion callback function.
CPL_MATCH_FN(cpl_file_completions);
Certain aspects of the behavior of this callback can be
changed via its data argument. If you are happy with its
default behavior you can pass NULL in this argument. Other-
wise it should be a pointer to a CplFileConf object, previ-
ously allocated by calling new_CplFileConf().
CplFileConf *new_CplFileConf(void);
CplFileConf objects encapsulate the configuration parameters
of cpl_file_completions(). These parameters, which start out
with default values, can be changed by calling the accessor
functions described below.
By default, the cpl_file_completions() callback function
searches backwards for the start of the filename being com-
pleted, looking for the first un-escaped space or the start
of the input line. If you wish to specify a different loca-
tion, call cfc_file_start() with the index at which the
filename starts in the input line. Passing start_index=-1
re-enables the default behavior.
void cfc_file_start(CplFileConf *cfc, int start_index);
By default, when cpl_file_completions() looks at a filename
in the input line, each lone backslash in the input line is
interpreted as being a special character which removes any
special significance of the character which follows it, such
as a space which should be taken as part of the filename
rather than delimiting the start of the filename. These
backslashes are thus ignored while looking for completions,
and subsequently added before spaces, tabs and literal
backslashes in the list of completions. To have unescaped
backslashes treated as normal characters, call
cfc_literal_escapes() with a non-zero value in its literal
argument.
void cfc_literal_escapes(CplFileConf *cfc, int literal);
By default, cpl_file_completions() reports all files who's
names start with the prefix that is being completed. If you
only want a selected subset of these files to be reported in
the list of completions, you can arrange this by providing a
callback function which takes the full pathname of a file,
and returns 0 if the file should be ignored, or 1 if the
file should be included in the list of completions. To
register such a function for use by cpl_file_completions(),
call cfc_set_check_fn(), and pass it a pointer to the func-
tion, together with a pointer to any data that you would
like passed to this callback whenever it is called. Your
callback can make its decisions based on any property of the
file, such as the filename itself, whether the file is read-
able, writable or executable, or even based on what the file
contains.
#define CPL_CHECK_FN(fn) int (fn)(void *data, \
const char *pathname)
typedef CPL_CHECK_FN(CplCheckFn);
void cfc_set_check_fn(CplFileConf *cfc,
CplCheckFn *chk_fn, void *chk_data);
The cpl_check_exe() function is a provided callback of the
above type, for use with cpl_file_completions(). It returns
non-zero if the filename that it is given represents a nor-
mal file that the user has execute permission to. You could
use this to have cpl_file_completions() only list comple-
tions of executable files.
When you have finished with a CplFileConf variable, you can
pass it to the del_CplFileConf() destructor function to
reclaim its memory.
CplFileConf *del_CplFileConf(CplFileConf *cfc);
THREAD SAFETY
In multi-threaded programs, you should use the libtecla_r.a
version of the library. This uses POSIX reentrant functions
where available (hence the _r suffix), and disables features
that rely on non-reentrant system functions. In the case of
this module, the only disabled feature is username comple-
tion in ~username/ expressions, in cpl_file_completions().
Using the libtecla_r.a version of the library, it is safe to
use the facilities of this module in multiple threads, pro-
vided that each thread uses a separately allocated WordCom-
pletion object. In other words, if two threads want to do
word completion, they should each call new_WordCompletion()
to allocate their own completion objects.
FILES
libtecla.a - The tecla library
libtecla.h - The tecla header file.
SEE ALSO
libtecla(3), gl_get_line(3), ef_expand_file(3),
pca_lookup_file(3)
AUTHOR
Martin Shepherd (mcs@astro.caltech.edu)