network-mysqld-proto.c

Mysql Proxy本身是个很好的mysql负载均衡工具,但是其本身有bug:当多个mysql 做slave的时候,如果一个slave死掉,会影响别的slave也死掉!这个文件修复了这个bug!

	g_assert(*(packet->str + *_off + len) == '\0'); /* this has to be a \0 */

	if (len > 0) {
		g_assert(*_off < packet->len);
		g_assert(*_off + len <= packet->len);

		/**
		 * copy the string w/o the NUL byte 
		 */
		r = network_mysqld_proto_get_string_len(packet, _off, len);
	}

	*_off += 1;

	return r;
}


/**
 * get a GString from the network packet
 *
 * @param packet the MySQL network packet
 * @param _off   offset into the packet
 * @param len    bytes to copy
 * @param out    a GString which carries the string
 * @return       a pointer to the string in out
 */
gchar *network_mysqld_proto_get_gstring_len(GString *packet, guint *_off, gsize len, GString *out) {
	g_string_truncate(out, 0);

	if (len) {
		g_assert(*_off < packet->len);
		if (*_off + len > packet->len) {
			g_error("packet-offset out of range: %u + "F_SIZE_T" > "F_SIZE_T, *_off, len, packet->len);
		}

		g_string_append_len(out, packet->str + *_off, len);
		*_off += len;
	}

	return out->str;
}

/**
 * get a NUL-terminated GString from the network packet
 *
 * @param packet the MySQL network packet
 * @param _off   offset into the packet
 * @param out    a GString which carries the string
 * @return       a pointer to the string in out
 *
 * @see network_mysqld_proto_get_gstring_len()
 */
gchar *network_mysqld_proto_get_gstring(GString *packet, guint *_off, GString *out) {
	guint len;
	gchar *r = NULL;

	for (len = 0; *_off + len < packet->len && *(packet->str + *_off + len); len++);

	g_assert(*(packet->str + *_off + len) == '\0'); /* this has to be a \0 */

	if (len > 0) {
		g_assert(*_off < packet->len);
		g_assert(*_off + len <= packet->len);

		r = network_mysqld_proto_get_gstring_len(packet, _off, len, out);
	}

	/* skip the \0 */
	*_off += 1;

	return r;
}

/**
 * get a variable-length GString from the network packet
 *
 * @param packet the MySQL network packet
 * @param _off   offset into the packet
 * @param out    a GString which carries the string
 * @return       a pointer to the string in out
 *
 * @see network_mysqld_proto_get_gstring_len(), network_mysqld_proto_get_lenenc_int()
 */
gchar *network_mysqld_proto_get_lenenc_gstring(GString *packet, guint *_off, GString *out) {
	guint64 len;

	len = network_mysqld_proto_get_lenenc_int(packet, _off);

	return network_mysqld_proto_get_gstring_len(packet, _off, len, out);
}

/**
 * create a empty field for a result-set definition
 *
 * @return a empty MYSQL_FIELD
 */
MYSQL_FIELD *network_mysqld_proto_field_init() {
	MYSQL_FIELD *field;
	
	field = g_new0(MYSQL_FIELD, 1);

	return field;
}

/**
 * free a MYSQL_FIELD and its components
 *
 * @param field  the MYSQL_FIELD to free
 */
void network_mysqld_proto_field_free(MYSQL_FIELD *field) {
	if (field->catalog) g_free(field->catalog);
	if (field->db) g_free(field->db);
	if (field->name) g_free(field->name);
	if (field->org_name) g_free(field->org_name);
	if (field->table) g_free(field->table);
	if (field->org_table) g_free(field->org_table);

	g_free(field);
}

/**
 * create a array of MYSQL_FIELD 
 *
 * @return a empty array of MYSQL_FIELD
 */
GPtrArray *network_mysqld_proto_fields_init(void) {
	GPtrArray *fields;
	
	fields = g_ptr_array_new();

	return fields;
}

/**
 * free a array of MYSQL_FIELD 
 *
 * @param fields  array of MYSQL_FIELD to free
 * @see network_mysqld_proto_field_free()
 */
void network_mysqld_proto_fields_free(GPtrArray *fields) {
	guint i;

	for (i = 0; i < fields->len; i++) {
		MYSQL_FIELD *field = fields->pdata[i];

		if (field) network_mysqld_proto_field_free(field);
	}

	g_ptr_array_free(fields, TRUE);
}

/**
 * set length of the packet in the packet header
 *
 * each MySQL packet is 
 *  - is prefixed by a 4 byte packet header
 *  - length is max 16Mbyte (3 Byte)
 *  - sequence-id (1 Byte) 
 *
 * To encode a packet of more then 16M clients have to send multiple 16M frames
 *
 * the sequence-id is incremented for each related packet and wrapping from 255 to 0
 *
 * @param header  string of at least 4 byte to write the packet header to
 * @param length  length of the packet
 * @param id      sequence-id of the packet
 * @return 0
 */
int network_mysqld_proto_set_header(unsigned char *header, size_t length, unsigned char id) {
	g_assert(length <= PACKET_LEN_MAX);

	header[0] = (length >>  0) & 0xFF;
	header[1] = (length >>  8) & 0xFF;
	header[2] = (length >> 16) & 0xFF;
	header[3] = id;

	return 0;
}

/**
 * decode the packet length from a packet header
 *
 * @param header the first 3 bytes of the network packet
 * @return the packet length
 * @see network_mysqld_proto_set_header()
 */
size_t network_mysqld_proto_get_header(unsigned char *header) {
	return header[0] | header[1] << 8 | header[2] << 16;
}

/**
 * append the variable-length integer to the packet
 *
 * @param packet  the MySQL network packet
 * @param length  integer to encode
 * @return        0
 */
int network_mysqld_proto_append_lenenc_int(GString *packet, guint64 length) {
	if (length < 251) {
		g_string_append_c(packet, length);
	} else if (length < 65536) {
		g_string_append_c(packet, (gchar)252);
		g_string_append_c(packet, (length >> 0) & 0xff);
		g_string_append_c(packet, (length >> 8) & 0xff);
	} else if (length < 16777216) {
		g_string_append_c(packet, (gchar)253);
		g_string_append_c(packet, (length >> 0) & 0xff);
		g_string_append_c(packet, (length >> 8) & 0xff);
		g_string_append_c(packet, (length >> 16) & 0xff);
	} else {
		g_string_append_c(packet, (gchar)254);

		g_string_append_c(packet, (length >> 0) & 0xff);
		g_string_append_c(packet, (length >> 8) & 0xff);
		g_string_append_c(packet, (length >> 16) & 0xff);
		g_string_append_c(packet, (length >> 24) & 0xff);

		g_string_append_c(packet, (length >> 32) & 0xff);
		g_string_append_c(packet, (length >> 40) & 0xff);
		g_string_append_c(packet, (length >> 48) & 0xff);
		g_string_append_c(packet, (length >> 56) & 0xff);
	}

	return 0;
}

/**
 * encode a GString in to a MySQL len-encoded string 
 *
 * @param packet  the MySQL network packet
 * @param s       string to encode
 * @param length  length of the string to encode
 * @return 0
 */
int network_mysqld_proto_append_lenenc_string_len(GString *packet, const char *s, guint64 length) {
	if (!s) {
		g_string_append_c(packet, (gchar)251); /** this is NULL */
	} else {
		network_mysqld_proto_append_lenenc_int(packet, length);
		g_string_append_len(packet, s, length);
	}

	return 0;
}

/**
 * encode a GString in to a MySQL len-encoded string 
 *
 * @param packet  the MySQL network packet
 * @param s       string to encode
 *
 * @see network_mysqld_proto_append_lenenc_string_len()
 */
int network_mysqld_proto_append_lenenc_string(GString *packet, const char *s) {
	return network_mysqld_proto_append_lenenc_string_len(packet, s, s ? strlen(s) : 0);
}

/**
 * encode fixed length integer in to a network packet
 *
 * @param packet  the MySQL network packet
 * @param num     integer to encode
 * @param size    byte size of the integer
 * @return        0
 */
static int network_mysqld_proto_append_int_len(GString *packet, guint64 num, gsize size) {
	gsize i;

	for (i = 0; i < size; i++) {
		g_string_append_c(packet, num & 0xff);
		num >>= 8;
	}

	return 0;
}

/**
 * encode 8-bit integer in to a network packet
 *
 * @param packet  the MySQL network packet
 * @param num     integer to encode
 *
 * @see network_mysqld_proto_append_int_len()
 */
int network_mysqld_proto_append_int8(GString *packet, guint8 num) {
	return network_mysqld_proto_append_int_len(packet, num, sizeof(num));
}

/**
 * encode 16-bit integer in to a network packet
 *
 * @param packet  the MySQL network packet
 * @param num     integer to encode
 *
 * @see network_mysqld_proto_append_int_len()
 */
int network_mysqld_proto_append_int16(GString *packet, guint16 num) {
	return network_mysqld_proto_append_int_len(packet, num, sizeof(num));
}

/**
 * encode 32-bit integer in to a network packet
 *
 * @param packet  the MySQL network packet
 * @param num     integer to encode
 *
 * @see network_mysqld_proto_append_int_len()
 */
int network_mysqld_proto_append_int32(GString *packet, guint32 num) {
	return network_mysqld_proto_append_int_len(packet, num, sizeof(num));
}

/*@}*/