安全的使用CreateThread()

/*uses multiple threads to search the files
".c" in the current directory for the string given
on th command line;
this example avoids most C run-time functions,so
that it can use the single-thread Clibraries,
it is necessary to use a critical section to divvy 
up output to the screen or the various threads end up 
with their output intermingled .Normally the multithreaded 
C run-time does this automatically if you use printf*/


#include<Windows.h>
#include "MtVerify.h"


DWORD WINAPI SearchProc(void *arg);
BOOL GetLine(HANDLE hFile, LPSTR buf, DWORD size);
#define MAX_THREADS 3
HANDLE hThreadLimitSemaphore;
HANDLE hConsoleOut;
CRITICAL_SECTION ScreenCritica;
char szSearchFor[1024];
int main(int argc, char *argv[])
{
WIN32_FIND_DATA *lpFindData;
HANDLE hFindFile;
HANDLE hThread;
DWORD dummy;
int i;
hConsoleOut = GetSetHandle(STD_OUTPUT_HANDLE);
if (argc != 2)
{
char errbuf[512];
wsprintf(errbuf, "Usage:%s<search-string>\n", argv[0]);
WriteFile(hConsoleOut, errbuf, strlen(errbuf), &dummy, FALSE);
return EXIT_FAILURE;
}
/*Put search string where everyone can see it */
strcpy(szSearchFor, argv[1]);
/* Allocate a find buffer to be handed to the first thread*/
lpFindData = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, sizeof(WIN32_FIND_DATA));
/*Semaphore prevents too many threads from running*/
MTVERIFY(hThreadLimitSemaphore = CreateSemaphore(NULL, MAX_THREADS, MAX_THREADS, NULL));
InitializeCriticalSection(&ScreenCritical);
hFindFile = FindFirstFile("*.c", lpFindData);
if (hFindFile == INVALID_HANDLE_VALUE)
return EXIT_FAILURE;
do{
WaitForSingleObject(hThreadLimitSemaphore, INFINITE);
MTVERIFY(hThread = CreateThread(NULL, 0, SearchProc, lpFindData, 0, &dummy));
MTVERIFY(CloseHandle(hThread));
lpFindData = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY,
sizeof(WIN32_FIND_DATA));
} while (FindNextFile(hFindFile, lpFindData));
FindClose(hFindFile);
hFindFile = INVALID_HANDLE_VALUE;
for (i = 0; i < MAX_THREADS; i++)
WaitForSingleObject(hThreadLimitSemaphore, INFINITE); 
MTVERIFY(CloseHandle(hThreadLimitSemaphore));
return EXIT_SUCCESS;
}
DWORD WINAPI SearchProc(void *arg)
{
WIN32_FIND_DATA *lpFindData = (WIN32_FIND_DATA*)arg;
char buf[1024];
HANDLE hFile;
DWORD dummy;
hFile = CreateFile(lpFindData->cFileName, GENERIC_READ,
FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_FLAG_SEQUENTIAL_SCAN, NULL);
if (!hFile)
return 1;
while (GetLine(hFile, buf, sizeof(buf)))
{
if (strstr(buf, szSearchFor))
{
EnterCriticalSection(&ScreenCritical);
WriteFile(hConsoleOut, strlen(lpFindData->cFileName), &dummy, FALSE);
WriteFile(hConsoleOut, ":", 2, &dummy, FALSE);
WriteFile(hConsoleOut, buf, strlen(buf), &dummy, FALSE);
WriteFile(hConsoleOut, "\r\n", 2, &dummy, FALSE);
LeaveCriticalSection(&ScreenCritical);
}
}
CloseHandle(hFile); 
HeapFree(GetProcessHeap(), 0, lpFindData);
MTVERIFY(ReleaseSemaphore(hThreadLimitSemaphore, 1, NULL));
}


BOOL GetLine(HANDLE hFile, LPSTR buf, DWORD size)
{
DWORD total = 0;
DWORD numread;
int state = 0;//0 = looking for non-newline 
              // 1 = stop after first newline
for (;;)
{
if (total == size - 1)
{
buf[size - 1] = '\0';
return TRUE;
}
if (!ReadFile(hFile, buf + total, 1, &numread, 0) ||
numread == 0)
{
buf[total] = '\0';
return total != 0;
}
if (buf[total] == 'r' || buf[total] == '\n')
{
if (state == 0)
continue;
buf[total] = '\0';
return TRUE;
}
state = 1;
total++;
}
}