gtpc2mfq | C/C++ Language Support User's Guide |
This function returns the previous element in the collection and points the cursor at the element. The definition of the previous element depends on the collection implementation.
Format
#include <c$to2.h> TO2_BUF_PTR TO2_previous (const TO2_PID_PTR pid_ptr, TO2_ENV_PTR env_ptr);
Normal Return
For a normal return, this buffer contains a C header file followed by a copy of the data requested. The normal return is a pointer (TO2_BUF_PTR) to a structure (buffer) of type TO2_BUF_HDR (see Type Definitions).
Error Return
An error return is indicated by a zero. When zero is returned, use the TO2_getErrorCode function to determine the specific error code. For more information, see Error Handling.
The following error codes are common for this function:
TO2_ERROR_CURSOR
TO2_ERROR_EMPTY
TO2_ERROR_ENV
TO2_ERROR_EODAD
TO2_ERROR_METHOD
TO2_ERROR_PID
TO2_ERROR_ZERO_PID
Programming Considerations
Examples
The following example returns the previous element in the collection that the cursor points to and repositions the cursor to point to it.
#include <c$to2.h> /* Needed for TO2 API Functions */ #include <stdio.h> /* APIs for standard I/O functions */ TO2_ERR_CODE err_code; /* TO2 error code value */ TO2_ERR_TEXT_PTR err_text_ptr; /* TO2 error code text pointer */ TO2_BUF_PTR buffer_ptr; TO2_PID cursor; TO2_ENV_PTR env_ptr;
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/*********************************************************************/ /* Read the previous item that the cursor points to. */ /*********************************************************************/ if ((buffer_ptr = TO2_previous(&cursor, env_ptr)) == NULL) { err_code = TO2_getErrorCode(env_ptr); if (err_code != TO2_ERROR_EODAD) { printf("TO2_previous failed!\n"); process_error(env_ptr); } else { printf("TO2_previous successful!\n"); } }
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