6-2

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/* * IoByEvnt.c * * Sample code for Multithreading Applications in Win32 * This is from Chapter 6, Listing 6-2 * * Demonstrates how to use event objects instead of * file handles to signal multiple outstanding * overlapped operation on a file. */

#define WIN32_LEAN_AND_MEAN#include <stdio.h>#include <stdlib.h>#include <windows.h>#include "MtVerify.h"

//// Constants//#define MAX_REQUESTS 5#define READ_SIZE 512#define MAX_TRY_COUNT 5

//// Function prototypes//int QueueRequest(int nIndex, DWORD dwLocation, DWORD dwAmount);void CheckOsVersion();

//// Global variables//

// Need to keep the events in their own array// so we can wait on them.HANDLE ghEvents[MAX_REQUESTS];// Keep track of each individual I/O operationOVERLAPPED gOverlapped[MAX_REQUESTS];// Handle to the file of interest.HANDLE ghFile;// Need a place to put all this datachar gBuffers[MAX_REQUESTS][READ_SIZE];

int main(){ int i; BOOL rc; char szPath[MAX_PATH];

CheckOsVersion();

GetWindowsDirectory(szPath, sizeof(szPath)); strcat(szPath, "http://www.cnblogs.com/nanshouyong326/admin/file://WINHLP32.EXE/"); // Open the file for overlapped reads ghFile = CreateFile( szPath, GENERIC_READ, FILE_SHARE_READ|FILE_SHARE_WRITE, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL ); if (ghFile == INVALID_HANDLE_VALUE) { printf("Could not open %s\n", szPath); return -1; }

for (i=0; i<MAX_REQUESTS; i++) { // Read some bytes every few K QueueRequest(i, i*16384, READ_SIZE); }

printf("QUEUED!!\n");

// Wait for all the operations to complete. MTVERIFY( WaitForMultipleObjects( MAX_REQUESTS, ghEvents, TRUE, INFINITE ) != WAIT_FAILED );

// Describe what just happened. for (i=0; i<MAX_REQUESTS; i++) { DWORD dwNumread;

rc = GetOverlappedResult( ghFile, &gOverlapped[i], &dwNumread, FALSE ); printf("Read #%d returned %d. %d bytes were read.\n", i, rc, dwNumread); CloseHandle(gOverlapped[i].hEvent); }

CloseHandle(ghFile);

return EXIT_SUCCESS;}

/* * Call ReadFile to start an overlapped request. * Make sure we handle errors that are recoverable. * Properly set up the event object for this operation. */int QueueRequest(int nIndex, DWORD dwLocation, DWORD dwAmount){ int i; BOOL rc; DWORD dwNumread; DWORD err;

MTVERIFY( ghEvents[nIndex] = CreateEvent( NULL, // No security TRUE, // Manual reset - extremely important! FALSE, // Initially set Event to non-signaled state NULL // No name ) ); gOverlapped[nIndex].hEvent = ghEvents[nIndex]; gOverlapped[nIndex].Offset = dwLocation;

for (i=0; i<MAX_TRY_COUNT; i++) { rc = ReadFile( ghFile, gBuffers[nIndex], dwAmount, &dwNumread, &gOverlapped[nIndex] );

// Handle success if (rc) { printf("Read #%d completed immediately.\n", nIndex); return TRUE; }

err = GetLastError();

// Handle the error that isn't an error. rc is zero here. if (err == ERROR_IO_PENDING) { // asynchronous i/o is still in progress printf("Read #%d queued for overlapped I/O.\n", nIndex); return TRUE; }

// Handle recoverable error if ( err == ERROR_INVALID_USER_BUFFER || err == ERROR_NOT_ENOUGH_QUOTA || err == ERROR_NOT_ENOUGH_MEMORY ) { Sleep(50); // Wait around and try later continue; }

// Give up on fatal error. break; }

printf("ReadFile failed.\n"); return -1;}

//// Make sure we are running under an operating// system that supports overlapped I/O to files.//void CheckOsVersion(){ OSVERSIONINFO ver; BOOL bResult;

ver.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);

bResult = GetVersionEx((LPOSVERSIONINFO) &ver);

if ( (!bResult) || (ver.dwPlatformId != VER_PLATFORM_WIN32_NT) ) { fprintf(stderr, "IoByEvnt must be run under Windows NT.\n"); exit(EXIT_FAILURE); }

}

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转载于:https://www.cnblogs.com/nanshouyong326/archive/2010/07/08/1773820.html

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