demo2.c

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/*
 * Copyright (c) 2000, 2001 by Martin C. Shepherd.
 * 
 * All rights reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, and/or sell copies of the Software, and to permit persons
 * to whom the Software is furnished to do so, provided that the above
 * copyright notice(s) and this permission notice appear in all copies of
 * the Software and that both the above copyright notice(s) and this
 * permission notice appear in supporting documentation.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
 * OF THIRD PARTY RIGHTS. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
 * HOLDERS INCLUDED IN THIS NOTICE BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL
 * INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING
 * FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
 * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 * 
 * Except as contained in this notice, the name of a copyright holder
 * shall not be used in advertising or otherwise to promote the sale, use
 * or other dealings in this Software without prior written authorization
 * of the copyright holder.
 */

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <errno.h>
#include <locale.h>

#include <unistd.h>
#include <sys/stat.h>

#include "libtecla.h"

/*
 * Encapsulate the resources needed by this demo.
 */
typedef struct {
  GetLine *gl;      /* The line editor */
  PathCache *pc;    /* A cache of executables in the user's path */
  PcaPathConf *ppc; /* The configuration argument of pca_path_completions() */
} DemoRes;

/*
 * The following functions allocate and free instances of the above
 * structure.
 */
static DemoRes *new_DemoRes(void);
static DemoRes *del_DemoRes(DemoRes *res);

/*
 * Search backwards for the start of a pathname.
 */
static char *start_of_path(const char *string, int back_from);

/*
 * Find the array indexes of the first character of the first
 * space-delimited word in the specified string, and of the character
 * that follows it.
 */
static int get_word_limits(const char *string, int *wa, int *wb);

/*
 * This is the demonstration completion callback function (defined below).
 */
static CPL_MATCH_FN(demo_cpl_fn);

/*.......................................................................
 * This demo takes no arguments. It reads lines of input until the
 * word 'exit' is entered, or C-d is pressed. It replaces the default
 * tab-completion callback with one which when invoked at the start of
 * a line, looks up completions of commands in the user's execution
 * path, and when invoked in other parts of the line, reverts to
 * normal filename completion. Whenever a new line is entered, it
 * extracts the first word on the line, looks it up in the user's
 * execution path to see if it corresponds to a known executable file,
 * and if so, displays the full pathname of the file, along with the
 * remaining arguments.
 */
int main(int argc, char *argv[])
{
  char *line;             /* A line of input */
  DemoRes *res;           /* The resources of the demo */
  int wa,wb;              /* The delimiting indexes of a word in line[] */
  int major,minor,micro;  /* The version number of the library */
/*
 * Allocate the resources needed by this demo.
 */
  res = new_DemoRes();
  if(!res)
    return 1;
/*
 * If the user has the LC_CTYPE or LC_ALL environment variables set,
 * enable display of characters corresponding to the specified locale.
 */
  (void) setlocale(LC_CTYPE, "");
/*
 * Lookup and display the version number of the library.
 */
  libtecla_version(&major, &minor, &micro);
  printf("Welcome to the demo2 program of libtecla version %d.%d.%d\n",
	 major, minor, micro);
/*
 * Read lines of input from the user and print them to stdout.
 */
  do {
/*
 * Get a new line from the user.
 */
    line = gl_get_line(res->gl, "$ ", NULL, 0);
    if(!line)
      break;
/*
 * Work out the extent of the first word in the input line, and
 * try to identify this as a command in the path, displaying the
 * full pathname of the match if found.
 */
    if(get_word_limits(line, &wa, &wb) == 0) {
      char *cmd = pca_lookup_file(res->pc, line + wa, wb-wa, 0);
      if(cmd) {
	printf("Command=%s\n", cmd);
	printf("Arguments=%s", line+wb);
      } else {
	printf("Command not found\n");
      };
    };
/*
 * If the user types "exit", quit the program.
 */
    if(strcmp(line, "exit\n")==0)
      break;
  } while(1);
/*
 * Clean up.
 */
  res = del_DemoRes(res);
  return 0;
}

/*.......................................................................
 * This completion callback searches for completions of executables in
 * the user's path when invoked on a word at the start of the path, and
 * performs normal filename completion elsewhere.
 */
static CPL_MATCH_FN(demo_cpl_fn)
{
/*
 * Get the resource object that was passed to gl_customize_completion().
 */
  DemoRes *res = (DemoRes *) data;
/*
 * Find the start of the filename prefix to be completed, searching
 * backwards for the first unescaped space, or the start of the line.
 */
  char *start = start_of_path(line, word_end);
/*
 * Skip spaces preceding the start of the prefix.
 */
  while(start > line && isspace((int)(unsigned char) start[-1]))
    start--;
/*
 * If the filename prefix is at the start of the line, attempt
 * to complete the filename as a command in the path. Otherwise
 * perform normal filename completion.
 */
  return (start == line) ?
    pca_path_completions(cpl, res->ppc, line, word_end) :
    cpl_file_completions(cpl, NULL, line, word_end);
}

/*.......................................................................
 * Search backwards for the potential start of a filename. This
 * looks backwards from the specified index in a given string,
 * stopping at the first unescaped space or the start of the line.
 *
 * Input:
 *  string  const char *  The string to search backwards in.
 *  back_from      int    The index of the first character in string[]
 *                        that follows the pathname.
 * Output:
 *  return        char *  The pointer to the first character of
 *                        the potential pathname, or NULL on error.
 */
static char *start_of_path(const char *string, int back_from)
{
  int i, j;
/*
 * Search backwards from the specified index.
 */
  for(i=back_from-1; i>=0; i--) {
    int c = string[i];
/*
 * Stop on unescaped spaces.
 */
    if(isspace((int)(unsigned char)c)) {
/*
 * The space can't be escaped if we are at the start of the line.
 */
      if(i==0)
        break;
/*
 * Find the extent of the escape characters which precedes the space.
 */
      for(j=i-1; j>=0 && string[j]=='\\'; j--)
	;
/*
 * If there isn't an odd number of escape characters before the space,
 * then the space isn't escaped.
 */
      if((i - 1 - j) % 2 == 0)
	break;
    };
  };
  return (char *)string + i + 1;
}

/*.......................................................................
 * Create a new DemoRes object containing the resources needed by the
 * demo.
 *
 * Output:
 *  return  DemoRes *  The new object, or NULL on error.
 */
static DemoRes *new_DemoRes(void)
{
  DemoRes *res;  /* The object to be returned */
/*
 * Allocate the container.
 */
  res = (DemoRes *)malloc(sizeof(DemoRes));
  if(!res) {
    fprintf(stderr, "new_DemoRes: Insufficient memory.\n");
    return NULL;
  };
/*
 * Before attempting any operation that might fail, initialize the
 * container at least up to the point at which it can safely be passed
 * to del_DemoRes().
 */
  res->gl = NULL;
  res->pc = NULL;
  res->ppc = NULL;
/*
 * Create the line editor, specifying a max line length of 500 bytes,
 * and 10000 bytes to allocate to storage of historical input lines.
 */
  res->gl = new_GetLine(500, 10000);
  if(!res->gl)
    return del_DemoRes(res);
/*
 * Enable text attribute formatting directives in prompt strings.
 */
  gl_prompt_style(res->gl, GL_FORMAT_PROMPT);
/*
 * Allocate a cache of the executable files found in the user's path.
 */
  res->pc = new_PathCache();
  if(!res->pc)
    return del_DemoRes(res);
/*
 * Populate the cache with the contents of the user's path.
 */
  if(pca_scan_path(res->pc, getenv("PATH")))
    return del_DemoRes(res);
/*
 * Arrange for susequent calls to pca_lookup_file() and pca_path_completions()
 * to only report files that are executable by the user.
 */
  pca_set_check_fn(res->pc, cpl_check_exe, NULL);
/*
 * Allocate a configuration object for use with pca_path_completions().
 */
  res->ppc = new_PcaPathConf(res->pc);
  if(!res->ppc)
    return del_DemoRes(res);
/*
 * Replace the builtin filename completion callback with one which
 * searches for completions of executables in the user's path when
 * invoked on a word at the start of the path, and completes files
 * elsewhere.
 */
  if(gl_customize_completion(res->gl, res, demo_cpl_fn))
    return del_DemoRes(res);
  return res;
}

/*.......................................................................
 * Delete a DemoRes object.
 *
 * Input:
 *  res     DemoRes *  The object to be deleted.
 * Output:
 *  return  DemoRes *  The deleted object (always NULL).
 */
static DemoRes *del_DemoRes(DemoRes *res)
{
  if(res) {
    res->gl = del_GetLine(res->gl);
    res->pc = del_PathCache(res->pc);
    res->ppc = del_PcaPathConf(res->ppc);
    free(res);
  };
  return NULL;
}

/*.......................................................................
 * Return the limits of the word at the start of a given string, ignoring
 * leading white-space, and interpretting the first unescaped space, tab or
 * the end of the line, as the end of the word.
 *
 * Input:
 *  string   const char *  The string to tokenize.
 * Input/Output:
 *  wa,wb           int *  The indexes of the first character of the word,
 *                         and the character which follows the last
 *                         character of the word, will be assigned to
 *                         *wa and *wb, respectively.
 * Output:
 *  return          int    0 - A word was found.
 *                         1 - No word was found before the end of the
 *                             string.
 */
static int get_word_limits(const char *string, int *wa, int *wb)
{
  int escaped = 0;  /* True if the next character is escaped */
/*
 * Skip leading white-space.
 */
  for(*wa=0; isspace((int)(unsigned char)string[*wa]); (*wa)++)
    ;
/*
 * Find the first unescaped space, stopping early if the end of the
 * string is reached.
 */
  for(*wb = *wa; ; (*wb)++) {
    int c = string[*wb];
    if(c=='\\')
      escaped = !escaped;
    else if((!escaped && isspace((int)(unsigned char)c)) || c=='\0')
      break;
  };
  return *wa == *wb;
}