DataBlade API Programmer's Manual

DataBlade API Programmer's Manual
Chapter 12: DataBlade API Function Descriptions

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mi_lo_readwithseek()

The mi_lo_readwithseek() function performs a seek operation and then reads a specified number of bytes of data from an open smart large object.

Syntax

#include "milo.h"

...
mi_integer mi_lo_readwithseek(conn, LO_fd, buf, nbytes, offset, whence)

		MI_CONNECTION *conn;

		MI_LO_FD LO_fd;

		char *buf;

		mi_integer nbytes;

		mi_int8 *offset;

		mi_integer whence; 


conn
is a pointer to the connection descriptor that a previous call to mi_open() or mi_server_connect() established.

LO_fd
is an LO file descriptor for the smart large object from which to read. 

buf
is a pointer to a user-allocated character buffer that contains the data that mi_lo_readwithseek() reads from the smart large object.

nbytes
is the maximum number of bytes to read from the buf character buffer. This value cannot exceed 2 gigabytes.

offset
is a pointer to the 8-byte integer (mi_int8) offset from the starting LO seek position.

whence
is an integer value that identifies the starting LO seek position.







 



Valid in Client Application?

Valid in Server Routine?

Yes
Yes

Usage

The mi_lo_readwithseek() function reads nbytes of data from the open smart large object that the LO_fd file descriptor identifies. The read begins at the LO seek position of LO_fd that the offset and whence arguments indicate, as follows:

The whence argument identifies the position from which to start the seek operation.


Whence Constant	Starting LO Seek Position
`MI_LO_SEEK_SET`	The start of the smart large object
`MI_LO_SEEK_CUR`	The current `LO` seek position in the smart large object
`MI_LO_SEEK_END`	The end of the smart large object

The offset argument identifies the offset, in bytes, relative to the starting seek position (which the whence argument specifies) at which to begin the read operation.

This offset value can be negative for all values of whence. The function reads this data into the user-allocated buffer that buf references. The buf buffer must be less than 2 gigabytes in size. To read smart large objects that are larger than 2 gigabytes, read them in 2-gigabyte chunks.

Tip: The mi_lo_readwithseek() function replaces the function mi_large_object_readwithseek(), which Informix supports for backward compatibility only. Use mi_lo_readwithseek() for all new DataBlade routines.

Return Values

>=0
The number of bytes that the function has read from the open smart large object to the buf character buffer.

MI_ERROR
The function was not successful.

DataBlade API Programmer's ManualChapter 12: DataBlade API Function Descriptions Home Contents Index Master Index New Book

mi_lo_readwithseek()

Syntax

Usage

Return Values >=0 The number of bytes that the function has read from the open smart large object to the buf character buffer. MI_ERROR The function was not successful.

Related Topics

DataBlade API Programmer's Manual
Chapter 12: DataBlade API Function Descriptions

Home Contents Index Master Index New Book

Return Values

>=0
The number of bytes that the function has read from the open smart large object to the buf character buffer.

MI_ERROR
The function was not successful.