app_mysql.cpp

Linux程序设计（第三版） Neil Matthew, Richard Stones, Alan Cox 著

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include "mysql.h"
#include "app_mysql.h"

static MYSQL my_connection;
static int dbconnected = 0;

static int get_artist_id(char *artist);


int database_start(char *name, char *pwd) {

	if (dbconnected) return 1;

	mysql_init(&my_connection);
	if (!mysql_real_connect(&my_connection, "localhost", name, pwd, "blpcd", 0, NULL, 0)) {
		fprintf(stderr, "Database connection failure: %d, %s\n", mysql_errno(&my_connection), mysql_error(&my_connection));
		return 0;
	}
	dbconnected = 1;
	return 1;
} /* database start */

void database_end() {
	if (dbconnected) mysql_close(&my_connection);
	dbconnected = 0;
} /* database_end */

int add_cd(char *artist, char *title, char *catalogue, int *cd_id) {

  MYSQL_RES *res_ptr;
  MYSQL_ROW mysqlrow;
  
  int res;
  char is[100];
  char es[100];
  int artist_id = -1;
  int new_cd_id = -1;
  
  if (!dbconnected) return 0;
  artist_id = get_artist_id(artist);
  
  mysql_escape_string(es, title, strlen(title));
  sprintf(is, "INSERT INTO cd(title, artist_id, catalogue) VALUES('%s', %d, '%s')", es, artist_id, catalogue);
  res = mysql_query(&my_connection, is);
  if (res) {
    fprintf(stderr, "Insert error %d: %s\n", mysql_errno(&my_connection), mysql_error(&my_connection));
    return 0;
  }
  res = mysql_query(&my_connection, "SELECT LAST_INSERT_ID()");
  if (res) {
    printf("SELECT error: %s\n", mysql_error(&my_connection));
    return 0;
  } else {
    res_ptr = mysql_use_result(&my_connection);
    if (res_ptr) {
      if ((mysqlrow = mysql_fetch_row(res_ptr))) {
	sscanf(mysqlrow[0], "%d", &new_cd_id);
      }
      mysql_free_result(res_ptr);
    }
    *cd_id = new_cd_id;
    
    if (new_cd_id != -1) return 1;
    return 0;
  }
} /* add_cd */


/* Find or create and artist_id for the given string */
static int get_artist_id(char *artist) {
  MYSQL_RES *res_ptr;
  MYSQL_ROW mysqlrow;
  
  int res;
  char qs[100];
  char is[100];
  char es[100];
  int artist_id = -1;
  
  /* Does it already exist? */
  mysql_escape_string(es, artist, strlen(artist));
  sprintf(qs, "SELECT id FROM artist WHERE name = '%s'", es);
  
  res = mysql_query(&my_connection, qs);
  if (res) {
    fprintf(stderr, "SELECT error: %s\n", mysql_error(&my_connection));
  } else {
    res_ptr = mysql_store_result(&my_connection);
    if (res_ptr) {
      if (mysql_num_rows(res_ptr) > 0) {
	if (mysqlrow = mysql_fetch_row(res_ptr)) {
	  sscanf(mysqlrow[0], "%d", &artist_id);
	}
      }
      mysql_free_result(res_ptr);
    }
  }
  if (artist_id != -1) return artist_id;
  
  sprintf(is, "INSERT INTO artist(name) VALUES('%s')", es);
  res = mysql_query(&my_connection, is);
  if (res) {
    fprintf(stderr, "Insert error %d: %s\n", mysql_errno(&my_connection), mysql_error(&my_connection));
    return 0;
  }
  res = mysql_query(&my_connection, "SELECT LAST_INSERT_ID()");
  if (res) {
    printf("SELECT error: %s\n", mysql_error(&my_connection));
    return 0;
  } else {
    res_ptr = mysql_use_result(&my_connection);
    if (res_ptr) {
      if ((mysqlrow = mysql_fetch_row(res_ptr))) {
	sscanf(mysqlrow[0], "%d", &artist_id);
      }
      mysql_free_result(res_ptr);
    }
  }
  return artist_id;
} /* get_artist_id */

int add_tracks(struct current_tracks_st *tracks) {
  
  int res;
  char is[100];
  char es[100];
  int i;
  
  if (!dbconnected) return 0;
  
  i = 0;
  while (tracks->track[i][0]) {
    mysql_escape_string(es, tracks->track[i], strlen(tracks->track[i]));
    sprintf(is, "INSERT INTO track(cd_id, track_id, title) VALUES(%d, %d, '%s')", tracks->cd_id, i + 1, es);
    res = mysql_query(&my_connection, is);
    if (res) {
      fprintf(stderr, "Insert error %d: %s\n", mysql_errno(&my_connection), mysql_error(&my_connection));
      return 0;
    }
    i++;
  }
  return 1;
} /* add_tracks */
		      

int get_cd(int cd_id, struct current_cd_st *dest) {
  MYSQL_RES *res_ptr;
  MYSQL_ROW mysqlrow;
  
  int res;
  char qs[100];

  if (!dbconnected) return 0;
  memset(dest, 0, sizeof(*dest));
  dest->artist_id = -1;

  sprintf(qs, "SELECT artist.id, cd.id, artist.name, cd.title, cd.catalogue FROM artist, cd WHERE artist.id = cd.artist_id and cd.id = %d", cd_id);
  
  res = mysql_query(&my_connection, qs);
  if (res) {
    fprintf(stderr, "SELECT error: %s\n", mysql_error(&my_connection));
  } else {
    res_ptr = mysql_store_result(&my_connection);
    if (res_ptr) {
      if (mysql_num_rows(res_ptr) > 0) {
	if (mysqlrow = mysql_fetch_row(res_ptr)) {
	  sscanf(mysqlrow[0], "%d", &dest->artist_id);
	  sscanf(mysqlrow[1], "%d", &dest->cd_id);
	  strcpy(dest->artist_name, mysqlrow[2]);
	  strcpy(dest->title, mysqlrow[3]);
	  strcpy(dest->catalogue, mysqlrow[4]);
	}
      }
      mysql_free_result(res_ptr);
    }
  }
  if (dest->artist_id != -1) return 1;
  return 0;
} /* get_cd */
	 
int get_cd_tracks(int cd_id, struct current_tracks_st *dest) {
  MYSQL_RES *res_ptr;
  MYSQL_ROW mysqlrow;
  
  int res;
  char qs[100];
  int i = 0, num_tracks = 0;

  if (!dbconnected) return 0;
  memset(dest, 0, sizeof(*dest));
  dest->cd_id = -1;

  sprintf(qs, "SELECT track_id, title FROM track WHERE track.cd_id = %d ORDER BY track_id", cd_id);
  
  res = mysql_query(&my_connection, qs);
  if (res) {
    fprintf(stderr, "SELECT error: %s\n", mysql_error(&my_connection));
  } else {
    res_ptr = mysql_store_result(&my_connection);
    if (res_ptr) {
      if ((num_tracks = mysql_num_rows(res_ptr)) > 0) {
	while (mysqlrow = mysql_fetch_row(res_ptr)) {
	  strcpy(dest->track[i], mysqlrow[1]);
	  i++;
	}
	dest->cd_id = cd_id;
      }
      mysql_free_result(res_ptr);
    }
  }
  return num_tracks;
} /* get_cd_tracks */


int find_cds(char *search_str, struct cd_search_st *dest) {
  MYSQL_RES *res_ptr;
  MYSQL_ROW mysqlrow;
  
  int res;
  char qs[500];
  int i = 0;
  char ss[100];
  int num_rows;

  if (!dbconnected) return 0;
  memset(dest, -1, sizeof(*dest));
  mysql_escape_string(ss, search_str, strlen(search_str));

  sprintf(qs, "SELECT DISTINCT artist.id, cd.id FROM artist, cd WHERE artist.id = cd.artist_id and (artist.name LIKE '%%%s%%' OR cd.title LIKE '%%%s%%' OR cd.catalogue LIKE '%%%s%%')", ss, ss, ss);

  res = mysql_query(&my_connection, qs);
  if (res) {
    fprintf(stderr, "SELECT error: %s\n", mysql_error(&my_connection));
  } else {
    res_ptr = mysql_store_result(&my_connection);
    if (res_ptr) {
      num_rows = mysql_num_rows(res_ptr);
      if ( num_rows > 0) {
	while ((mysqlrow = mysql_fetch_row(res_ptr)) && i < MAX_CD_RESULT) {
	  sscanf(mysqlrow[1], "%d", &dest->cd_id[i]);
	  i++;
	}
      }
      mysql_free_result(res_ptr);
    }
  }
  return num_rows;
} /* find_cds */

int delete_cd(int cd_id) {

  int res;
  char qs[100];
  int artist_id, num_rows;
  MYSQL_RES *res_ptr;
  MYSQL_ROW mysqlrow;

  if (!dbconnected) return 0;

  artist_id = -1;
  sprintf(qs, "SELECT artist_id FROM cd WHERE id = '%d'", cd_id);
  res = mysql_query(&my_connection, qs);
  if (res) {
    fprintf(stderr, "SELECT error: %s\n", mysql_error(&my_connection));
  } else {
    res_ptr = mysql_store_result(&my_connection);
    if (res_ptr) {
      num_rows = mysql_num_rows(res_ptr);
      if (num_rows == 1) {
	/* Artist not used by any other CDs */
	mysqlrow = mysql_fetch_row(res_ptr);
	sscanf(mysqlrow[0], "%d", &artist_id);
      }
    }
  }


  sprintf(qs, "DELETE FROM track WHERE cd_id = '%d'", cd_id);
  res = mysql_query(&my_connection, qs);
  if (res) {
    fprintf(stderr, "Delete error (track) %d: %s\n", mysql_errno(&my_connection), mysql_error(&my_connection));
    return 0;
  }

  sprintf(qs, "DELETE FROM cd WHERE id = '%d'", cd_id);
  res = mysql_query(&my_connection, qs);
  if (res) {
    fprintf(stderr, "Delete error (cd) %d: %s\n", mysql_errno(&my_connection), mysql_error(&my_connection));
    return 0;
  }

  if (artist_id != -1) {
    /* artist entry is now unrelated to any CDs, delete it */
    sprintf(qs, "DELETE FROM artist WHERE id = '%d'", artist_id);
    res = mysql_query(&my_connection, qs);
    if (res) {
      fprintf(stderr, "Delete error (artist) %d: %s\n", mysql_errno(&my_connection), mysql_error(&my_connection));
    }
  }

  return 1;

} /* delete_cd */