Usenet 1994 January/usenetsourcesnewsgroupsinfomagicjanuary1994.iso/sources/unix/volume20/index-db/part01/dbio.c

C/C++ Source or Header | 1989-10-23 | 5.0 KB | 266 lines

#ifndef lint
static char *RCSid = "$Header: /u5/davy/progs/index/RCS/dbio.c,v 1.1 89/08/09 11:06:36 davy Exp $";
#endif
/*
 * dbio.c - database input/output routines.
 *
 * David A. Curry
 * Research Institute for Advanced Computer Science
 * Mail Stop 230-5
 * NASA Ames Research Center
 * Moffett Field, CA 94035
 * [e-mail]
 *
 * $Log:    dbio.c,v $
 * Revision 1.1  89/08/09  11:06:36  davy
 * Initial revision
 *
 */
#include <sys/param.h>
#include <sys/stat.h>
#include <curses.h>
#include <stdio.h>
#include "defs.h"

struct    dbfile *db;        /* array of database entries        */
struct    idxfile idx;        /* description of the database file    */

int    dbmodified = 0;        /* non-zero if database needs saving    */
int    dbentries, dbsize;    /* number of entries, size of db array    */

/*
 * read_idxfile - read the database description file.
 */
read_idxfile(dbname)
char *dbname;
{
    FILE *fp;
    register int len;
    char buf[BUFSIZ], idxfile[MAXPATHLEN];

    /*
     * Construct the file name.
     */
    sprintf(idxfile, "%s/%s%s", dbasedir, dbname, IDXFILE_SUFFIX);

    /*
     * Open the file.
     */
    if ((fp = fopen(idxfile, "r")) == NULL) {
        error("%s: cannot open \"%s\".\n", pname, idxfile, 0);
        exit(1);
    }

    /*
     * Zero out the structure.
     */
    bzero(&idx, sizeof(struct idxfile));

    /*
     * Read lines from the file.
     */
    while (idx.idx_nlines < MAXDBLINES) {
        /*
         * End of file.
         */
        if (fgets(buf, sizeof(buf), fp) == NULL)
            break;

        /*
         * Strip the newline.
         */
        len = strlen(buf) - 1;
        buf[len] = '\0';

        /*
         * If the first character is '!', then this line
         * should not participate in searches.  Save the
         * stuff after the '!'.  Otherwise this line does
         * participate in searches, save the whole line.
         */
        if (*buf == '!') {
            idx.idx_lines[idx.idx_nlines] = savestr(buf+1);
            idx.idx_search[idx.idx_nlines] = 0;
            len--;
        }
        else {
            idx.idx_lines[idx.idx_nlines] = savestr(buf);
            idx.idx_search[idx.idx_nlines] = 1;
        }

        /*
         * Increment the number of lines.
         */
        idx.idx_nlines++;

        /*
         * Save the length of the longest field name.
         */
        if (len > idx.idx_maxlen)
            idx.idx_maxlen = len;
    }

    /*
     * Close the file.
     */
    fclose(fp);
}

/*
 * read_dbfile - read the database file itself.
 */
read_dbfile(dbname)
char *dbname;
{
    FILE *fp;
    register int i;
    struct dbfile *malloc(), *realloc();
    char buf[BUFSIZ], dbfile[MAXPATHLEN];

    /*
     * Allocate some entries in the array.  16 is just an
     * arbitrary number.
     */
    dbsize = 16;
    dbentries = 0;

    if ((db = malloc(dbsize * sizeof(struct dbfile))) == NULL) {
        error("%s: out of memory.\n", pname, 0, 0);
        exit(1);
    }

    /*
     * Construct the name of the file.
     */
    sprintf(dbfile, "%s/%s%s", dbasedir, dbname, DBFILE_SUFFIX);

    /*
     * Open the file.
     */
    if ((fp = fopen(dbfile, "r")) == NULL)
        return;

    /*
     * Until we hit end of file...
     */
    while (!feof(fp)) {
        /*
         * If we need to, allocate some more entries.
         */
        if (dbentries >= dbsize) {
            dbsize *= 2;
            db = realloc(db, dbsize * sizeof(struct dbfile));

            if (db == NULL) {
                error("%s: out of memory.\n", pname, 0, 0);
                exit(1);
            }
        }

        /*
         * Read in one entry at a time.
         */
        for (i = 0; i < idx.idx_nlines; i++) {
            /*
             * If we hit end of file before getting a
             * complete entry, toss this one.
             */
            if (fgets(buf, sizeof(buf), fp) == NULL)
                goto out;

            /*
             * Save the length of the line, strip the
             * newline, and save the line.
             */
            db[dbentries].db_lens[i] = strlen(buf) - 1;
            buf[db[dbentries].db_lens[i]] = '\0';

            db[dbentries].db_lines[i] = savestr(buf);
        }

        /*
         * Mark this entry as valid and increase the
         * number of entries.
         */
        db[dbentries].db_flag = DB_VALID;
        dbentries++;
    }

out:
    /*
     * Make sure what we've got is sorted.
     */
    qsort(db, dbentries, sizeof(struct dbfile), dbsort);

    fclose(fp);
}

/*
 * save_db - save the database to disk.
 */
save_db(dbname)
char *dbname;
{
    FILE *fp;
    struct stat st;
    register int i, j;
    char realfile[MAXPATHLEN], bakfile[MAXPATHLEN];

    /*
     * If it doesn't need saving, never mind.
     */
    if (!dbmodified)
        return;

    /*
     * Create the name of the file and a backup file.
     */
    sprintf(realfile, "%s/%s%s", dbasedir, dbname, DBFILE_SUFFIX);
    sprintf(bakfile, "%s/#%s%s", dbasedir, dbname, DBFILE_SUFFIX);

    /*
     * Default creation mode.
     */
    st.st_mode = 0400;

    /*
     * If the file already exists, rename it to the
     * backup file name.
     */
    if (stat(realfile, &st) == 0)
        rename(realfile, bakfile);

    /*
     * Open the new file.
     */
    if ((fp = fopen(realfile, "w")) == NULL) {
        error("%s: cannot create \"%s\".\n", pname, realfile);
        exit(1);
    }

    /*
     * Make sure the database is sorted.
     */
    qsort(db, dbentries, sizeof(struct dbfile), dbsort);

    /*
     * Write out the entries.
     */
    for (i=0; i < dbentries; i++) {
        if ((db[i].db_flag & DB_VALID) == 0)
            continue;

        for (j=0; j < idx.idx_nlines; j++)
            fprintf(fp, "%s\n", db[i].db_lines[j]);
    }

    /*
     * Set the file mode to the mode of the original
     * file.  Mark the database as unmodified.
     */
    fchmod(fileno(fp), st.st_mode & 0777);
    dbmodified = 0;

    fclose(fp);
}