/*   This file provides the functions for accessing the CD database. */#include <unistd.h>#include <stdlib.h>#include <stdio.h>#include <fcntl.h>#include <string.h>#include <ndbm.h>#include "cd_data.h"#define CDC_FILE_BASE "cdc_data"#define CDT_FILE_BASE "cdt_data"#define CDC_FILE_DIR  "cdc_data.dir"#define CDC_FILE_PAG  "cdc_data.pag"#define CDT_FILE_DIR "cdt_data.dir"#define CDT_FILE_PAG "cdt_data.pag"/* Some file scope variables for accessing the database */static DBM *cdc_dbm_ptr = NULL;static DBM *cdt_dbm_ptr = NULL;/* This function initializes access to the database. If the parameter   new_database is true, then a new database is started. */int database_initialise(const int new_database){    int open_mode = O_RDWR;    /* If any existing database is open then close it */    if (cdc_dbm_ptr) dbm_close(cdc_dbm_ptr);    if (cdt_dbm_ptr) dbm_close(cdt_dbm_ptr);    if (new_database) {	/* delete the old files */	(void) unlink(CDC_FILE_PAG);	(void) unlink(CDC_FILE_DIR);	(void) unlink(CDT_FILE_PAG);	(void) unlink(CDT_FILE_DIR);	open_mode = O_CREAT | O_RDWR;    }    /* Open some new files, creating them if required */    cdc_dbm_ptr = dbm_open(CDC_FILE_BASE, open_mode, 0644);    cdt_dbm_ptr = dbm_open(CDT_FILE_BASE, open_mode, 0644);    if (!cdc_dbm_ptr || !cdt_dbm_ptr) {	fprintf(stderr, "Unable to create database\n");	cdc_dbm_ptr = cdt_dbm_ptr = NULL;	return (0);    }    return (1);} /* database_initialize */void database_close(void){    if (cdc_dbm_ptr) dbm_close(cdc_dbm_ptr);    if (cdt_dbm_ptr) dbm_close(cdt_dbm_ptr);    cdc_dbm_ptr = cdt_dbm_ptr = NULL;} /* database_close *//*   This function retrieves a single catalogue entry, when passed a pointer   pointing to catalogue text string. If the entry is not found then the   returned data has an empty catalogue field. */cdc_entry get_cdc_entry(const char *cd_catalogue_ptr){    cdc_entry entry_to_return;    char entry_to_find[CAT_CAT_LEN + 1];    datum local_data_datum;    datum local_key_datum;    memset(&entry_to_return, '\0', sizeof(entry_to_return));    /* check database initialized and parameters valid */    if (!cdc_dbm_ptr || !cdt_dbm_ptr) return (entry_to_return);    if (!cd_catalogue_ptr) return (entry_to_return);    if (strlen(cd_catalogue_ptr) >= CAT_CAT_LEN) return (entry_to_return);    /* ensure the search key contains only the valid string and nulls */    memset(&entry_to_find, '\0', sizeof(entry_to_find));    strcpy(entry_to_find, cd_catalogue_ptr);    local_key_datum.dptr = (void *) entry_to_find;    local_key_datum.dsize = sizeof(entry_to_find);    memset(&local_data_datum, '\0', sizeof(local_data_datum));    local_data_datum = dbm_fetch(cdc_dbm_ptr, local_key_datum);    if (local_data_datum.dptr) {	memcpy(&entry_to_return, (char *)local_data_datum.dptr, local_data_datum.dsize);    }    return (entry_to_return);} /* get_cdc_entry *//*   This function retrieves a single track entry, when passed a pointer   pointing to a catalogue string and a track number. If the entry is not   found then the returned data has an empty catalogue field. */cdt_entry get_cdt_entry(const char *cd_catalogue_ptr, const int track_no){    cdt_entry entry_to_return;    char entry_to_find[CAT_CAT_LEN + 10];    datum local_data_datum;    datum local_key_datum;    memset(&entry_to_return, '\0', sizeof(entry_to_return));    /* check database initialized and parameters valid */    if (!cdc_dbm_ptr || !cdt_dbm_ptr) return (entry_to_return);    if (!cd_catalogue_ptr) return (entry_to_return);    if (strlen(cd_catalogue_ptr) >= CAT_CAT_LEN) return (entry_to_return);    /* setup the search key, which is a composite key of catalogue entry       and track number */    memset(&entry_to_find, '\0', sizeof(entry_to_find));    sprintf(entry_to_find, "%s %d", cd_catalogue_ptr, track_no);    local_key_datum.dptr = (void *) entry_to_find;    local_key_datum.dsize = sizeof(entry_to_find);    memset(&local_data_datum, '\0', sizeof(local_data_datum));    local_data_datum = dbm_fetch(cdt_dbm_ptr, local_key_datum);    if (local_data_datum.dptr) {	memcpy(&entry_to_return, (char *) local_data_datum.dptr, local_data_datum.dsize);    }    return (entry_to_return);} /* get_cdt_entry *//* This function adds a new catalogue entry. */int add_cdc_entry(const cdc_entry entry_to_add){    char key_to_add[CAT_CAT_LEN + 1];    datum local_data_datum;    datum local_key_datum;    int result;    /* check database initialized and parameters valid */    if (!cdc_dbm_ptr || !cdt_dbm_ptr) return (0);    if (strlen(entry_to_add.catalogue) >= CAT_CAT_LEN) return (0);    /* ensure the search key contains only the valid string and nulls */    memset(&key_to_add, '\0', sizeof(key_to_add));    strcpy(key_to_add, entry_to_add.catalogue);    local_key_datum.dptr = (void *) key_to_add;    local_key_datum.dsize = sizeof(key_to_add);    local_data_datum.dptr = (void *) &entry_to_add;    local_data_datum.dsize = sizeof(entry_to_add);    result = dbm_store(cdc_dbm_ptr, local_key_datum, local_data_datum, DBM_REPLACE);    /* dbm_store() uses 0 for success */    if (result == 0) return (1);    return (0);} /* add_cdc_entry *//* This function adds a new catalogue entry. The access key is the   catalogue string and track number acting as a composite key */int add_cdt_entry(const cdt_entry entry_to_add){    char key_to_add[CAT_CAT_LEN + 10];    datum local_data_datum;    datum local_key_datum;    int result;    /* check database initialized and parameters valid */    if (!cdc_dbm_ptr || !cdt_dbm_ptr) return (0);    if (strlen(entry_to_add.catalogue) >= CAT_CAT_LEN) return (0);    /* ensure the search key contains only the valid string and nulls */    memset(&key_to_add, '\0', sizeof(key_to_add));    sprintf(key_to_add, "%s %d", entry_to_add.catalogue, entry_to_add.track_no);    local_key_datum.dptr = (void *) key_to_add;    local_key_datum.dsize = sizeof(key_to_add);    local_data_datum.dptr = (void *) &entry_to_add;    local_data_datum.dsize = sizeof(entry_to_add);    result = dbm_store(cdt_dbm_ptr, local_key_datum, local_data_datum, DBM_REPLACE);    /* dbm_store() uses 0 for success and -ve numbers for errors */    if (result == 0)	return (1);    return (0);} /* add_cdt_entry */int del_cdc_entry(const char *cd_catalogue_ptr) {    char key_to_del[CAT_CAT_LEN + 1];    datum local_key_datum;    int result;    /* check database initialized and parameters valid */    if (!cdc_dbm_ptr || !cdt_dbm_ptr) return (0);    if (strlen(cd_catalogue_ptr) >= CAT_CAT_LEN) return (0);    /* ensure the search key contains only the valid string and nulls */    memset(&key_to_del, '\0', sizeof(key_to_del));    strcpy(key_to_del, cd_catalogue_ptr);    local_key_datum.dptr = (void *) key_to_del;    local_key_datum.dsize = sizeof(key_to_del);    result = dbm_delete(cdc_dbm_ptr, local_key_datum);    /* dbm_delete() uses 0 for success */    if (result == 0) return (1);    return (0);} /* del_cdc_entry */int del_cdt_entry(const char *cd_catalogue_ptr, const int track_no) {    char key_to_del[CAT_CAT_LEN + 10];    datum local_key_datum;    int result;    /* check database initialized and parameters valid */    if (!cdc_dbm_ptr || !cdt_dbm_ptr) return (0);    if (strlen(cd_catalogue_ptr) >= CAT_CAT_LEN) return (0);    /* ensure the search key contains only the valid string and nulls */    memset(&key_to_del, '\0', sizeof(key_to_del));    sprintf(key_to_del, "%s %d", cd_catalogue_ptr, track_no);    local_key_datum.dptr = (void *) key_to_del;    local_key_datum.dsize = sizeof(key_to_del);    result = dbm_delete(cdt_dbm_ptr, local_key_datum);    /* dbm_delete() uses 0 for success */    if (result == 0) return (1);    return (0);} /* del_cdt_entry *//* This function searches for a catalogue entry, where the catalogue   text contains the provided search text. If the search text points   to a null character then all entries are considered to match */cdc_entry search_cdc_entry(const char *cd_catalogue_ptr, int *first_call_ptr){    static int local_first_call = 1;    cdc_entry entry_to_return;    datum local_data_datum;    static datum local_key_datum;	/* notice this must be static */    memset(&entry_to_return, '\0', sizeof(entry_to_return));    /* check database initialized and parameters valid */    if (!cdc_dbm_ptr || !cdt_dbm_ptr) return (entry_to_return);    if (!cd_catalogue_ptr || !first_call_ptr) return (entry_to_return);    if (strlen(cd_catalogue_ptr) >= CAT_CAT_LEN) return (entry_to_return);    /* protect against never passing *first_call_ptr true */    if (local_first_call) {	local_first_call = 0;	*first_call_ptr = 1;    }    if (*first_call_ptr) {	*first_call_ptr = 0;	local_key_datum = dbm_firstkey(cdc_dbm_ptr);    } else {	local_key_datum = dbm_nextkey(cdc_dbm_ptr);    }    do {	if (local_key_datum.dptr != NULL) {	    /* an entry was found */	    local_data_datum = dbm_fetch(cdc_dbm_ptr, local_key_datum);	    if (local_data_datum.dptr) {		memcpy(&entry_to_return, (char *) local_data_datum.dptr, local_data_datum.dsize);		/* check if search string occures in the entry */		if (!strstr(entry_to_return.catalogue, cd_catalogue_ptr)) {		    memset(&entry_to_return, '\0', sizeof(entry_to_return));		    local_key_datum = dbm_nextkey(cdc_dbm_ptr);		}	    }	}    } while (local_key_datum.dptr &&	     local_data_datum.dptr &&	     (entry_to_return.catalogue[0] == '\0'));    /* Finished finding entries, either there are no more or one matched */    return (entry_to_return);} /* search_cdc_entry */