The WinCPICIsBlocking function determines if a task is executing while waiting for a previous blocking call to finish.
BOOL WINAPI WinCPICIsBlocking(void);
The return value specifies the outcome of the function. If the value is not zero, there is an outstanding blocking call awaiting completion. A value of zero indicates the absence of an outstanding blocking call.
This call does not infer any information about a particular conversation; it is only intended to provide help to an application written to use the CM_BLOCKING characteristic of Set_Processing_Mode. WinCPICIsBlocking serves the same purpose as InSendMessage in the Microsoft® Windows® API. Applications targeted at Windows version 3.x that support multiple conversations must specify CM_NONBLOCKING in Set_Processing_Mode so they can support multiple outstanding operations simultaneously. Applications are still limited to one outstanding operation per conversation in all environments.
Although a call issued on a blocking function appears to an application as though it blocks, the Windows CPI-C DLL has to relinquish the processor to allow other applications to run. This means that it is possible for the application that issued the blocking call to be re-entered, depending on the message(s) it receives. In this instance, WinCPICIsBlocking can be used to determine whether the application task currently has been re-entered while waiting for an outstanding blocking call to finish. Note that Windows CPI-C prohibits more than one outstanding blocking call per thread.
Specify_Windows_Handle, WinCPICSetBlockingHook, WinCPICUnhookBlockingHook