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当我使用CreateProcess创建进程adb.exe时，它将在ReadFile中阻塞。Android的adb启动服务器的CreateProcess？
void KillAdbProcess()
{
DWORD aProcesses[1024], cbNeeded, cProcesses;
unsigned int i;
if (!EnumProcesses(aProcesses, sizeof(aProcesses), &cbNeeded))
return;
cProcesses = cbNeeded/sizeof(DWORD);
for (i = 0; i < cProcesses; i++)
if(aProcesses[i] != 0){
bool shouldKill =false;
wchar_t szProcessName[MAX_PATH] = L"<unknown>";
//Get a handle to the process.
HANDLE hProcess = OpenProcess(PROCESS_QUERY_INFORMATION |
PROCESS_VM_READ | PROCESS_TERMINATE,
FALSE, aProcesses[i]);
if (NULL != hProcess)
{
HMODULE hMod;
DWORD cbNeeded;
if (EnumProcessModules(hProcess, &hMod, sizeof(hMod),
&cbNeeded))
{
GetModuleFileNameExW(hProcess, hMod, szProcessName,
sizeof(szProcessName)/sizeof(TCHAR));
int len = wcslen(szProcessName);
if(!wcscmp(L"\\adb.exe",szProcessName+len-8)){
shouldKill = true;
}
}
}
if(shouldKill) TerminateProcess(hProcess,0);
CloseHandle(hProcess);
}
}
int testadb(){
KillAdbProcess();
char buff[4096] = {0};
int len = sizeof(buff);
DWORD exitCode = 0;
SECURITY_ATTRIBUTES sa;
ZeroMemory(&sa, sizeof(sa));
sa.bInheritHandle = TRUE;
sa.lpSecurityDescriptor = NULL;
sa.nLength = sizeof(sa);
HANDLE hOutputReadTmp,hOutputRead,hOutputWrite;
// Create the child output pipe.
if (!CreatePipe(&hOutputReadTmp,&hOutputWrite,&sa,0))
return false;
// Create new output read handle and the input write handles. Set
// the Properties to FALSE. Otherwise, the child inherits the
// properties and, as a result, non-closeable handles to the pipes
// are created.
if (!DuplicateHandle(GetCurrentProcess(),hOutputReadTmp,
GetCurrentProcess(),
&hOutputRead, // Address of new handle.
0,FALSE, // Make it uninheritable.
DUPLICATE_SAME_ACCESS))
return false;
// Close inheritable copies of the handles you do not want to be
// inherited.
if (!CloseHandle(hOutputReadTmp)) return false;
PROCESS_INFORMATION pi;
ZeroMemory(&pi, sizeof(pi));
STARTUPINFOW si;
GetStartupInfoW(&si);
si.cb = sizeof(STARTUPINFO);
si.dwFlags = STARTF_USESTDHANDLES;
si.wShowWindow = SW_HIDE;
si.hStdInput = NULL;
if(buff) {
si.hStdOutput = hOutputWrite;
si.hStdError = hOutputWrite;
} else {
si.hStdOutput = NULL;
si.hStdError = NULL;
}
wchar_t cmdBuf[512] = L"adb.exe start-server";
if(!::CreateProcessW(NULL, cmdBuf, NULL, NULL, TRUE, DETACHED_PROCESS, NULL, NULL, &si, &pi))
{
exitCode = -1;
goto exit;
}
::CloseHandle(hOutputWrite);
hOutputWrite = NULL;
len--; //keep it for string end char.
DWORD dwBytes = 0;
DWORD dwHasRead = 0;
while(::ReadFile(hOutputRead, buff+dwHasRead, len-dwHasRead, &dwBytes, NULL))
{
printf("read byte=%d\n",dwBytes);
if(0 == dwBytes) break;
dwHasRead += dwBytes;
//GetExitCodeProcess(pi.hProcess, &exitCode);
//if(STILL_ACTIVE != exitCode) break;
if(dwHasRead >= len) break;
}
buff[dwHasRead] = 0;
::GetExitCodeProcess(pi.hProcess, &exitCode);
exit:
if(hOutputRead) ::CloseHandle(hOutputRead);
if(hOutputWrite) ::CloseHandle(hOutputWrite);
::CloseHandle(pi.hProcess);
::CloseHandle(pi.hThread);
return 0;
}
如果我改变代码
while(::ReadFile(hOutputRead, buff+dwHasRead, len-dwHasRead, &dwBytes, NULL))
{
printf("read byte=%d\n",dwBytes);
if(0 == dwBytes) break;
dwHasRead += dwBytes;
GetExitCodeProcess(pi.hProcess, &exitCode);
if(STILL_ACTIVE != exitCode) break;
if(dwHasRead >= len) break;
}
它的工作原理，但是当我删除printf的代码，它将再次阻止。
while(::ReadFile(hOutputRead, buff+dwHasRead, len-dwHasRead, &dwBytes, NULL))
{
if(0 == dwBytes) break;
dwHasRead += dwBytes;
GetExitCodeProcess(pi.hProcess, &exitCode);
if(STILL_ACTIVE != exitCode) break;
if(dwHasRead >= len) break;
}
在adb.exe的代码，我看到像初级讲座一些代码：
#if ADB_HOST
int launch_server()
{
#ifdef HAVE_WIN32_PROC
/* we need to start the server in the background */
/* we create a PIPE that will be used to wait for the server's "OK" */
/* message since the pipe handles must be inheritable, we use a */
/* security attribute */
HANDLE pipe_read, pipe_write;
SECURITY_ATTRIBUTES sa;
STARTUPINFO startup;
PROCESS_INFORMATION pinfo;
char program_path[ MAX_PATH ];
int ret;
sa.nLength = sizeof(sa);
sa.lpSecurityDescriptor = NULL;
sa.bInheritHandle = TRUE;
/* create pipe, and ensure its read handle isn't inheritable */
ret = CreatePipe(&pipe_read, &pipe_write, &sa, 0);
if (!ret) {
fprintf(stderr, "CreatePipe() failure, error %ld\n", GetLastError());
return -1;
}
SetHandleInformation(pipe_read, HANDLE_FLAG_INHERIT, 0);
ZeroMemory(&startup, sizeof(startup));
startup.cb = sizeof(startup);
startup.hStdInput = GetStdHandle(STD_INPUT_HANDLE);
startup.hStdOutput = pipe_write;
startup.hStdError = GetStdHandle(STD_ERROR_HANDLE);
startup.dwFlags = STARTF_USESTDHANDLES;
ZeroMemory(&pinfo, sizeof(pinfo));
/* get path of current program */
GetModuleFileName(NULL, program_path, sizeof(program_path));
ret = CreateProcess(
program_path, /* program path */
"adb fork-server server",
/* the fork-server argument will set the
debug = 2 in the child */
NULL, /* process handle is not inheritable */
NULL, /* thread handle is not inheritable */
TRUE, /* yes, inherit some handles */
DETACHED_PROCESS, /* the new process doesn't have a console */
NULL, /* use parent's environment block */
NULL, /* use parent's starting directory */
&startup, /* startup info, i.e. std handles */
&pinfo);
CloseHandle(pipe_write);
if (!ret) {
fprintf(stderr, "CreateProcess failure, error %ld\n", GetLastError());
CloseHandle(pipe_read);
return -1;
}
CloseHandle(pinfo.hProcess);
CloseHandle(pinfo.hThread);
/* wait for the "OK\n" message */
{
char temp[3];
DWORD count;
ret = ReadFile(pipe_read, temp, 3, &count, NULL);
CloseHandle(pipe_read);
if (!ret) {
fprintf(stderr, "could not read ok from ADB Server, error = %ld\n", GetLastError());
return -1;
}
if (count != 3 || temp[0] != 'O' || temp[1] != 'K' || temp[2] != '\n') {
fprintf(stderr, "ADB server didn't ACK\n");
return -1;
}
}
#elif defined(HAVE_FORKEXEC)
char path[PATH_MAX];
int fd[2];
// set up a pipe so the child can tell us when it is ready.
// fd[0] will be parent's end, and fd[1] will get mapped to stderr in the child.
if (pipe(fd)) {
fprintf(stderr, "pipe failed in launch_server, errno: %d\n", errno);
return -1;
}
get_my_path(path);
pid_t pid = fork();
if(pid < 0) return -1;
if (pid == 0) {
// child side of the fork
// redirect stderr to the pipe
// we use stderr instead of stdout due to stdout's buffering behavior.
adb_close(fd[0]);
dup2(fd[1], STDERR_FILENO);
adb_close(fd[1]);
// child process
int result = execl(path, "adb", "fork-server", "server", NULL);
// this should not return
fprintf(stderr, "OOPS! execl returned %d, errno: %d\n", result, errno);
} else {
// parent side of the fork
char temp[3];
temp[0] = 'A'; temp[1] = 'B'; temp[2] = 'C';
// wait for the "OK\n" message
adb_close(fd[1]);
int ret = adb_read(fd[0], temp, 3);
adb_close(fd[0]);
if (ret < 0) {
fprintf(stderr, "could not read ok from ADB Server, errno = %d\n", errno);
return -1;
}
if (ret != 3 || temp[0] != 'O' || temp[1] != 'K' || temp[2] != '\n') {
fprintf(stderr, "ADB server didn't ACK\n");
return -1;
}
setsid();
}
#else
#error "cannot implement background server start on this platform"
#endif
return 0;
}
#endif
我认为adb.exe子进程继承adb.exe的手柄，如果子进程的adb.exe不会退出，ReadFile将永远阻止。但是当我执行命令“adb.exe start-server”时，一切正常。那么windows如何调用CreateProcess和ReadFile呢？