cursor.c

eXtremeDB数据库在Linux平台下的使用源码。内含多个示例程序

/***************************************************************
 *                                                             *
 * Copyright (c) 2001-2007 McObject LLC. All Right Reserved.   *
 *                                                             *
 ***************************************************************/

/* This samples demonstartes basic cursor methods */

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

#include "samples.h"

static const char   *   dbname = "SimpleDb";
static const int        FIRST_SEGSZ = 1024 * 8000UL;
#ifndef MCO_PLATFORM_X64
static const int        PAGESIZE = 96;
#else
static const int        PAGESIZE = 192;
#endif

const int MAP_ADDRESS =  0x20000000;

void _SH_(void) {

	char text[] = {
		"\nThis samples demonstartes basic eXtremeDB cursor methods.\n"
	};
	char text1[] = {
		"Copyright (c) 2001-2007 McObject LLC. All Right Reserved.\n\n"
	};

	printf("%s\neXtremeDB runtime version %d.%d, build %d\n%s\n\nPress Enter to start",
		text, MCO_COMP_VER_MAJOR, MCO_COMP_VER_MINOR, MCO_COMP_BUILD_NUM,text1);

	getchar();

}


void cursor( mco_db_h db ) {
	MCO_RET                 rc = 0;
	mco_cursor_t            csr;
	mco_trans_h             trn;
	SimpleClass             simple;
	uint2                   a, b, size;
	uint4                   h;
	char                    src[64];
	simple_oid    			oid;
	MCO_CURSOR_TYPE         ctype;

	printf( "\n\nReading using \"UniqueIndex\"\n" );

	/* start read-only transaction and initialize	a cursor.
	 */
	mco_trans_start( db, MCO_READ_ONLY, MCO_TRANS_FOREGROUND, &trn );

	/* initialize cursor */
	rc = SimpleClass_Iabc_index_cursor( trn, &csr );

	if ( rc != MCO_S_OK ) {
		/* if not found for whatever reason - close the transaction and
		 * bail out
		 */
		mco_trans_commit( trn );
		return;
	}

	/* commit the transaction. This is only done to illuatrate the fact that
	 * cursors could be used across the transaction boundaries. In
	 * real-life application the "commit" is not needed and shouldn't be
	 * issued.
	 */
	rc = mco_trans_commit( trn );

	/* re-open a transaction */
	mco_trans_start( db, MCO_READ_ONLY, MCO_TRANS_FOREGROUND, &trn );

	/* check whether the cursor is still valid */
	if ( MCO_S_OK != mco_cursor_type(&csr, &ctype) ) {
		/* cursor invalid... */
		printf( "\n\tcursor invalid" );

		/* ..reinitialize it. */
		rc = SimpleClass_Iabc_index_cursor( trn, &csr );
	}

	for	(
		rc = mco_cursor_first(trn, &csr);		  /* position the cursor at the first object */
		rc == MCO_S_OK;
		rc = mco_cursor_next(trn, &csr)			  /* advance the cursor (fetch)*/
	) {
		/* obtain object handle through the current cursor
		 */
		rc = SimpleClass_from_cursor( trn, &csr, &simple );
		if ( rc != MCO_S_OK ) {
			printf( "\n\terror:%d", rc );
			break;
		}

		/* read data out from handle
		 */
		SimpleClass_a_get( &simple, &a );
		SimpleClass_b_get( &simple, &b );
		SimpleClass_h_get( &simple, &h );
		SimpleClass_c_get( &simple, src, (uint2) sizeof(src), &size );

		/* obtain OID for the object */
		rc = SimpleClass_oid_get( &simple, &oid );

		if ( rc == MCO_S_OK )
			printf( "\n\tobject with OID=%d\n\ta=%d,b=%d,c=%s(%d)\n\n", oid.seq, a, b, src, size );
		else
			printf( "\n\terror:%d", rc );
	}

	/* commit */
	mco_trans_commit( trn );
	return;
}


/* fatal error handler */
static void errhandler( int n ) {
	printf( "\neXtremeDB runtime fatal error: %d", n );
	getchar();
	exit( -1 );
}


int main( void ) {
	MCO_RET     rc;
	mco_db_h    db = 0;
	int         num = NUMOBJECTS, one_id[NUMOBJECTS], vhash[NUMOBJECTS];
	char    *  start_mem;
	mco_runtime_info_t info;

	_SH_();
	mco_get_runtime_info( &info);
	if ( info.mco_shm_supported ) {
		start_mem = (char*)MAP_ADDRESS;
	}
	else {
		start_mem = (char*)malloc(FIRST_SEGSZ);
		if (!start_mem) {
			printf("Couldn't allocated memory\n");
			exit (1);
		}
	};

	/* set fatal error handler */
	mco_error_set_handler( &errhandler );

	mco_runtime_start();
	/* Create a database - allocate 2M starting from mem. */
	rc = mco_db_open( dbname, simple_get_dictionary(), start_mem, FIRST_SEGSZ, (uint2) PAGESIZE );

	if ( rc ) {
		printf( "\nerror creating database" );
		if ( !info.mco_shm_supported )
			free( start_mem );
		exit( 1 );
	}

	/* connect to the database, obtain a database handle */
	mco_db_connect( dbname, &db );
	printf( "\ndb handle = %d\n", db );

	srand( (unsigned) time(NULL) );
	while ( 0 < num-- ) {
		/* get some random values */
		one_id[num] = rand();
		vhash[num] = ( uint4 ) rand();

		/* create a new object */
		newobj( db, one_id[num], vhash[num] );
	}

	cursor( db );

	/* disconnect from the database, db is no longer valid */
	mco_db_disconnect( db );

	/* destroy the db */
	mco_db_close( dbname );

	mco_runtime_stop();

	if ( !info.mco_shm_supported )
		free( start_mem );

	printf( "Press Enter key to exit" );
	getchar();
  PROG_EXIT(0);
}