lrs_length_receive

Receives data of a specified length.

int lrs_length_receive( char *socket_descriptor, char *buffer, int location_option, [char* locators], [char* additional_params], LrsLastArg );

The lrs_length_receive function reads data of a specified length from sock_descriptor into buffer . The length is located within the received buffer itself. The user must be aware where the length value is placed within the buffer (unless the RecieveOption_None option is chosen) and its location is specified by the parameters location_option and locators. lrs_length_receive first obtains the value of length (hereafter called length) and afterwards reads length number of bytes from the socket_descriptor into buffer.

The socket_descriptor and buffer parameters are identical to the first two parameters of lrs_receive.

location_option argument

The following table lists the values for the location_option argument:

locator argument

The following table lists the values for the locator argument:

Mulitple Locator argument values can be used by passing them as separate string parameters to lrs_length_receive e.g., "LB=LeftLeft ", "Size=1", "Offset=18".

Return Values

If this function fails, it returns NULL. If it succeeds, it returns a pointer to the converted buffer. You can also retrieve the converted buffer using lrs_get_user_buffer.

Parameterization

You cannot use standard parameterization for any arguments in this function.

Examples

Example 1

In the following example, data (buffer1) is sent on a socket (socket0). Then the same data is received on the same socket with lrs_length_receive using the OffsetSize location_option. buffer1 consists of a length value of 2 bytes (in bold) and data. After obtaining the length value of 51, lrs_length_receive goes on to read 51 bytes of data from socket0 into buffer2. There is no need to pass the locator parameter"Offset=0" as this is the default setting.

lrs_create_socket("socket0", "TCP", "RemoteHost=bona.abc.com:7", LrsLastArg);
lrs_send("socket0", "buffer1", LrsLastArg);
lrs_length_receive("socket0", "buffer2", OffsetSize, "Size=2", LrsLastArg);

Example 2

In this example, the contents of buffer3 are sent on a socket (socket0). The same data is received on the socket with lrs_length_receive. The LeftRightBoundaries location_option is used with the left boundary being the string "LLLL" and the right boundary "RRRR". The lrs_length_receive first locates the second instance of the left boundary string (in bold) because the Ordinal locator is set to 2. The function is then told to jump a further 27 bytes (Offset=27) to finally locate the length value. This value is 9 (in bold) and is bounded by the right boundary of "RRRR". The 9 bytes after the right boundary are the characters "Requested" which lrs_length_receive reads from socket0 and writes to buffer4.
The subsequent call to lrs_receive reads the rest of the data into another buffer.

lrs_create_socket("socket0", "TCP", "RemoteHost=bona.abc.com:7", LrsLastArg);
lrs_send("socket0", "buffer3", LrsLastArg);
lrs_length_receive("socket0", "buffer4", 2, "LB=LLLL", "RB=RRRR", "Offset=27", "Ordinal=1", LrsLastArg);
// Now receive the rest of received data
lrs_receive("socket0", "buffer5", LrsLastArg);

Example 3

In this example, the contents of buffer6 are sent on a socket (socket0). The same data is received on the socket with lrs_length_receive using the LeftBoundarySize location_option, the left boundary being the binary values \\x00\\x00\\x00\\x07. lrs_length_receive first locates these values (in bold) and then is told to jump a further 7 bytes (Offset=7) to finally locate the length value which takes up 2 bytes (Size=2). This value is 16 (also in bold). However, because the additional_param SubtractSize is set to zero, the size of the length field itself, 2, is subtracted from the total, making 14. The 14 byte string following the length field, "Requested Data", is read from socket0 and written to buffer7.
The subsequent call to lrs_receive reads the rest of the data into another buffer.

lrs_create_socket("socket0", "TCP", "RemoteHost=bona.abc.com:7",
lrs_send("socket0", "buffer6", LrsLastArg);
lrs_length_receive("socket0", "buffer7", 3, "LB/BIN=\\x00\\x00\\x00\\x07", "size=2", "Offset=7", "SubtractSize=0", LrsLastArg);
// Now receive the rest of received data
lrs_receive("socket0", "buffer8", LrsLastArg);