Really Easy MYSQL C API interface. Features: printf like arguments, auto escape arguments, multiple statement execution and auto reconnection.

easy_sql.c

#ifndef _EASY_SQL_H_
#define _EASY_SQL_H_

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

typedef my_ulonglong MYSQL_COUNT;

MYSQL *sql_open(char *host, int port, char *user, char *pass, char *db);

int sql_execute(
	MYSQL *mysql,
	int (*on_result)(MYSQL_ROW row, MYSQL_COUNT count, void *userdata),
	void *userdata,
	char *format,
	...);

void sql_close(MYSQL *mysql);

#if defined(_WIN32) || defined(_WIN64) || defined(__CYGWIN__)
	#include <winuser.h>
	#define MYSQL_SHOW_ERROR(title, msg) MessageBox(NULL, msg, title, MB_ICONERROR)
	#define MYSQL_INIT_ERROR() MessageBox(NULL, "Could not init mysql library.", "MYSQL ERROR!", MB_ICONERROR);
#else
	#define MYSQL_SHOW_ERROR(title, msg) fprintf(stderr, "%s %s\n", title, msg)
	#define MYSQL_INIT_ERROR() fprintf(stderr, "MYSQL ERROR: Could not init mysql library.\n")
#endif

static void _sql_error(MYSQL *mysql) {
	char title[32];
	
	snprintf(title, sizeof(title)-1, "MYSQL ERROR %u", mysql_errno(mysql));
	
	MYSQL_SHOW_ERROR(title, mysql_error(mysql));
}

MYSQL *sql_open(char *host, int port, char *user, char *pass, char *db) {
	MYSQL *mysql;
	my_bool option = 1;
	
	if (!host || !user || !pass || !db) return NULL;
	
	if ((mysql = mysql_init(NULL)) == NULL) {
		MYSQL_INIT_ERROR();
		return NULL;
	}
	
	if (mysql_options(mysql, MYSQL_OPT_RECONNECT, &option) != 0) goto error;
	
	if (mysql_real_connect(mysql, host, user, pass, db, port, NULL, CLIENT_MULTI_STATEMENTS) == NULL) goto error;
	
	return mysql;

error:
	_sql_error(mysql);
	mysql_close(mysql);
	return NULL;
}

int sql_execute(MYSQL *mysql, int (*on_result)(MYSQL_ROW row, MYSQL_COUNT count, void *userdata), void *userdata, char *format, ...) {
	MYSQL_COUNT i, j, rows_count, columns_count, format_size, args_size;
	MYSQL_RES *res = NULL;
	MYSQL_ROW row;
	char *query, *arg, temp[32];
	va_list args;
	int ret;
	
	if (!mysql || !format) return 1;
	
	va_start(args, format);
	
	format_size = strlen(format);
	args_size = 0;
	
	for (i=0; i<format_size; i++) {
		
		if (format[i] == '%') {
			i++;
			
			if (format[i] == 's') {
				arg = va_arg(args, char*);
				
				while (*arg) {
					if (*arg == '\'' || *arg == '\"') args_size++;
					args_size++;
					arg++;
				}
			}
			else if (format[i] == 'w') {
				arg = va_arg(args, char*);
				
				while (*arg) {
					if (*arg == '\'' || *arg == '\"') args_size++;
					args_size++;
					arg += 2;
				}
			}
			else if (format[i] == 'i' || format[i] == 'd' || format[i] == 'u') {
				snprintf(temp, sizeof(temp)-1, "%i", va_arg(args, int));
				args_size += strlen(temp);
			}
			else if (format[i] == 'c') {
				snprintf(temp, sizeof(temp)-1, "%c", va_arg(args, int));
				args_size += strlen(temp);
			}
			else if (format[i] == 'f') {
				snprintf(temp, sizeof(temp)-1, "%lf", va_arg(args, double));
				args_size += strlen(temp);
			}
			else if (format[i] == 'p') {
				snprintf(temp, sizeof(temp)-1, "%p", va_arg(args, void*));
				args_size += strlen(temp);
			}
			else if (format[i] == 'x') {
				snprintf(temp, sizeof(temp)-1, "%x", va_arg(args, int));
				args_size += strlen(temp);
			}
			else if (format[i] == '%') {
				args_size += 1;
			}
			else return 1;
			
			args_size -= 2;
		}
	}
	
	va_end(args);

	if ((query = malloc(format_size + args_size + 1)) == NULL) return 1;
	
	va_start(args, format);
	
	for (i=0,j=0; i<format_size; i++) {
		
		if (format[i] == '%') {
			i++;
			
			if (format[i] == 's') {
				arg = va_arg(args, char*);
				while (*arg) {
					
					if (*arg == '\'' || *arg == '\"') {
						query[j++] = '\\';
						query[j++] = *arg;
					}
					else query[j++] = *arg;
					
					arg++;
				}
			}
			else if (format[i] == 'w') {
				arg = va_arg(args, char*);
				while (*arg) {
					
					if (*arg == '\'' || *arg == '\"') {
						query[j++] = '\\';
						query[j++] = *arg;
					}
					else query[j++] = *arg;
					
					arg += 2;
				}
			}
			else if (format[i] == 'i' || format[i] == 'd' || format[i] == 'u') {
				snprintf(temp, sizeof(temp)-1, "%i", va_arg(args, int));
				strcpy(query + j, temp);
				j += strlen(temp);
			}
			else if (format[i] == 'c') {
				snprintf(temp, sizeof(temp)-1, "%c", va_arg(args, int));
				strcpy(query + j, temp);
				j += strlen(temp);
			}
			else if (format[i] == 'f') {
				snprintf(temp, sizeof(temp)-1, "%lf", va_arg(args, double));
				strcpy(query + j, temp);
				j += strlen(temp);
			}
			else if (format[i] == 'p') {
				snprintf(temp, sizeof(temp)-1, "%p", va_arg(args, void*));
				strcpy(query + j, temp);
				j += strlen(temp);
			}
			else if (format[i] == 'x') {
				snprintf(temp, sizeof(temp)-1, "%x", va_arg(args, int));
				strcpy(query + j, temp);
				j += strlen(temp);
			}
			else if (format[i] == '%') {
				query[j++] = format[i];
			}
			else {
				free(query);
				return 1;
			}
		}
		else query[j++] = format[i];
	}
	query[j] = 0;
	
	va_end(args);
	
	if (mysql_real_query(mysql, query, format_size + args_size) != 0) goto error;
	
	if (!on_result) {
		free(query);
		return 0;
	}
	
	do {
		if ((res = mysql_store_result(mysql)) == NULL) {
			if (mysql_errno(mysql) != 0) goto error;
			
			free(query);
			return on_result(NULL, 0, userdata);
		}
		
		rows_count = mysql_num_rows(res);
		columns_count = mysql_num_fields(res);
		
		if (rows_count == 0) {
			free(query);
			return on_result(NULL, 0, userdata);
		}
		
		for (i=1; i<=rows_count; i++) {
			
			if ((row = mysql_fetch_row(res)) == NULL) {
				mysql_free_result(res);
				goto error;
			}
			
			if ((ret = on_result(row, columns_count, userdata)) != 0) {
				mysql_free_result(res);
				free(query);
				return ret;
			}
			
			mysql_data_seek(res, i);
		}
		
		mysql_free_result(res);
		
	} while(mysql_next_result(mysql) == 0);
	
	free(query);
	return 0;

error:
	_sql_error(mysql);
	free(query);
	return 1;
}

void sql_close(MYSQL *mysql) {
	if (!mysql) return;
	
	mysql_close(mysql);
}

#endif /* _EASY_SQL_H_ */

/*///////////////////////////////////
	
		Testing:
		
///////////////////////////////////*/

int on_result(MYSQL_ROW row, MYSQL_COUNT count, void *userdata) {
	MYSQL_COUNT i;
	(void)userdata;
	
	for (i=0; i<count; i++) {
		printf("%s |", row[i]);
	}
	printf("\n--------------------------------------------------------\n");
	
	return 0;
}

int main(void) {
	MYSQL *mysql;
	
	mysql = sql_open("localhost", 3306, "root", "password", "database");
	
	sql_execute(mysql, on_result, NULL, "select %s from table where id = %i;", "field", 69);
	
	sql_close(mysql);
	
	return 0;
}