new_WordCompletion

cpl_complete_word(3)       Library Functions Manual       cpl_complete_word(3)



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_recall_matches,
       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);

       CplMatches *cpl_recall_matches(WordCompletion *cpl);

       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);


       #define CPL_CHECK_FN(fn) int (fn)(void *data, \
                                         const char *pathname)

       typedef CPL_CHECK_FN(CplCheckFn);

       CPL_CHECK_FN(cpl_check_exe);

       CplFileConf *new_CplFileConf(void);

       CplFileConf *del_CplFileConf(CplFileConf *cfc);

       void cfc_literal_escapes(CplFileConf *cfc, int literal);

       void cfc_file_start(CplFileConf *cfc, int start_index);

       void cfc_set_check_fn(CplFileConf *cfc, CplCheckFn *chk_fn,
                             void *chk_data);



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 completed, 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 completions 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:

         WordCompletion *new_WordCompletion(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().

         WordCompletion *del_WordCompletion(WordCompletion *cpl)

       This function deletes the resources that were returned by a previous
       call to new_WordCompletion(). 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
       incomplete 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 internally, 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 completion. 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 completion 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 completion. 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 section. Its first argument is a
       resource object previously returned by new_WordCompletion().  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 function.

       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().

         CplMatches *cpl_recall_matches(WordCompletion *cpl);

       As a convenience, the return value of the last call to
       cpl_complete_word() can be recalled at a later time by calling
       cpl_recall_matches(). If cpl_complete_word() returned NULL, so will
       cpl_recall_matches().

         int cpl_list_completions(CplMatches *result, FILE *fp,
                                  int terminal_width);

       When the cpl_complete_word() function returns multiple possible
       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. Otherwise it should be a pointer to a
       CplFileConf object, previously 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 completed, looking for
       the first un-escaped space or the start of the input line. If you wish
       to specify a different location, 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 function, 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 readable, 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 normal file that the user has
       execute permission to. You could use this to have
       cpl_file_completions() only list completions 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 completion 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, provided that each
       thread uses a separately allocated WordCompletion 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)




                                                          cpl_complete_word(3)