#include "../git-compat-util.h"
#include "../strbuf.h"

unsigned int _CRT_fmode = _O_BINARY;

#undef open
int mingw_open (const char *filename, int oflags, ...)
{
        va_list args;
        unsigned mode;
        va_start(args, oflags);
        mode = va_arg(args, int);
        va_end(args);

        if (!strcmp(filename, "/dev/null"))
                filename = "nul";
        int fd = open(filename, oflags, mode);
        if (fd < 0 && (oflags & O_CREAT) && errno == EACCES) {
                DWORD attrs = GetFileAttributes(filename);
                if (attrs != INVALID_FILE_ATTRIBUTES && (attrs & FILE_ATTRIBUTE_DIRECTORY))
                        errno = EISDIR;
        }
        return fd;
}

static inline time_t filetime_to_time_t(const FILETIME *ft)
{
        long long winTime = ((long long)ft->dwHighDateTime << 32) + ft->dwLowDateTime;
        winTime -= 116444736000000000LL; /* Windows to Unix Epoch conversion */
        winTime /= 10000000;             /* Nano to seconds resolution */
        return (time_t)winTime;
}

extern int _getdrive( void );
/* We keep the do_lstat code in a separate function to avoid recursion.
 * When a path ends with a slash, the stat will fail with ENOENT. In
 * this case, we strip the trailing slashes and stat again.
 */
static int do_lstat(const char *file_name, struct stat *buf)
{
        WIN32_FILE_ATTRIBUTE_DATA fdata;

        if (GetFileAttributesExA(file_name, GetFileExInfoStandard, &fdata)) {
                int fMode = S_IREAD;
                if (fdata.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
                        fMode |= S_IFDIR;
                else
                        fMode |= S_IFREG;
                if (!(fdata.dwFileAttributes & FILE_ATTRIBUTE_READONLY))
                        fMode |= S_IWRITE;

                buf->st_ino = 0;
                buf->st_gid = 0;
                buf->st_uid = 0;
                buf->st_nlink = 1;
                buf->st_mode = fMode;
                buf->st_size = fdata.nFileSizeLow; /* Can't use nFileSizeHigh, since it's not a stat64 */
                buf->st_dev = buf->st_rdev = (_getdrive() - 1);
                buf->st_atime = filetime_to_time_t(&(fdata.ftLastAccessTime));
                buf->st_mtime = filetime_to_time_t(&(fdata.ftLastWriteTime));
                buf->st_ctime = filetime_to_time_t(&(fdata.ftCreationTime));
                errno = 0;
                return 0;
        }

        switch (GetLastError()) {
        case ERROR_ACCESS_DENIED:
        case ERROR_SHARING_VIOLATION:
        case ERROR_LOCK_VIOLATION:
        case ERROR_SHARING_BUFFER_EXCEEDED:
                errno = EACCES;
                break;
        case ERROR_BUFFER_OVERFLOW:
                errno = ENAMETOOLONG;
                break;
        case ERROR_NOT_ENOUGH_MEMORY:
                errno = ENOMEM;
                break;
        default:
                errno = ENOENT;
                break;
        }
        return -1;
}

/* We provide our own lstat/fstat functions, since the provided
 * lstat/fstat functions are so slow. These stat functions are
 * tailored for Git's usage (read: fast), and are not meant to be
 * complete. Note that Git stat()s are redirected to mingw_lstat()
 * too, since Windows doesn't really handle symlinks that well.
 */
int mingw_lstat(const char *file_name, struct stat *buf)
{
        int namelen;
        static char alt_name[PATH_MAX];

        if (!do_lstat(file_name, buf))
                return 0;

        /* if file_name ended in a '/', Windows returned ENOENT;
         * try again without trailing slashes
         */
        if (errno != ENOENT)
                return -1;

        namelen = strlen(file_name);
        if (namelen && file_name[namelen-1] != '/')
                return -1;
        while (namelen && file_name[namelen-1] == '/')
                --namelen;
        if (!namelen || namelen >= PATH_MAX)
                return -1;

        memcpy(alt_name, file_name, namelen);
        alt_name[namelen] = 0;
        return do_lstat(alt_name, buf);
}

#undef fstat
int mingw_fstat(int fd, struct stat *buf)
{
        HANDLE fh = (HANDLE)_get_osfhandle(fd);
        BY_HANDLE_FILE_INFORMATION fdata;

        if (fh == INVALID_HANDLE_VALUE) {
                errno = EBADF;
                return -1;
        }
        /* direct non-file handles to MS's fstat() */
        if (GetFileType(fh) != FILE_TYPE_DISK)
                return fstat(fd, buf);

        if (GetFileInformationByHandle(fh, &fdata)) {
                int fMode = S_IREAD;
                if (fdata.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
                        fMode |= S_IFDIR;
                else
                        fMode |= S_IFREG;
                if (!(fdata.dwFileAttributes & FILE_ATTRIBUTE_READONLY))
                        fMode |= S_IWRITE;

                buf->st_ino = 0;
                buf->st_gid = 0;
                buf->st_uid = 0;
                buf->st_nlink = 1;
                buf->st_mode = fMode;
                buf->st_size = fdata.nFileSizeLow; /* Can't use nFileSizeHigh, since it's not a stat64 */
                buf->st_dev = buf->st_rdev = (_getdrive() - 1);
                buf->st_atime = filetime_to_time_t(&(fdata.ftLastAccessTime));
                buf->st_mtime = filetime_to_time_t(&(fdata.ftLastWriteTime));
                buf->st_ctime = filetime_to_time_t(&(fdata.ftCreationTime));
                return 0;
        }
        errno = EBADF;
        return -1;
}

unsigned int sleep (unsigned int seconds)
{
        Sleep(seconds*1000);
        return 0;
}

int mkstemp(char *template)
{
        char *filename = mktemp(template);
        if (filename == NULL)
                return -1;
        return open(filename, O_RDWR | O_CREAT, 0600);
}

int gettimeofday(struct timeval *tv, void *tz)
{
        SYSTEMTIME st;
        struct tm tm;
        GetSystemTime(&st);
        tm.tm_year = st.wYear-1900;
        tm.tm_mon = st.wMonth-1;
        tm.tm_mday = st.wDay;
        tm.tm_hour = st.wHour;
        tm.tm_min = st.wMinute;
        tm.tm_sec = st.wSecond;
        tv->tv_sec = tm_to_time_t(&tm);
        if (tv->tv_sec < 0)
                return -1;
        tv->tv_usec = st.wMilliseconds*1000;
        return 0;
}

int pipe(int filedes[2])
{
        int fd;
        HANDLE h[2], parent;

        if (_pipe(filedes, 8192, 0) < 0)
                return -1;

        parent = GetCurrentProcess();

        if (!DuplicateHandle (parent, (HANDLE)_get_osfhandle(filedes[0]),
                        parent, &h[0], 0, FALSE, DUPLICATE_SAME_ACCESS)) {
                close(filedes[0]);
                close(filedes[1]);
                return -1;
        }
        if (!DuplicateHandle (parent, (HANDLE)_get_osfhandle(filedes[1]),
                        parent, &h[1], 0, FALSE, DUPLICATE_SAME_ACCESS)) {
                close(filedes[0]);
                close(filedes[1]);
                CloseHandle(h[0]);
                return -1;
        }
        fd = _open_osfhandle((int)h[0], O_NOINHERIT);
        if (fd < 0) {
                close(filedes[0]);
                close(filedes[1]);
                CloseHandle(h[0]);
                CloseHandle(h[1]);
                return -1;
        }
        close(filedes[0]);
        filedes[0] = fd;
        fd = _open_osfhandle((int)h[1], O_NOINHERIT);
        if (fd < 0) {
                close(filedes[0]);
                close(filedes[1]);
                CloseHandle(h[1]);
                return -1;
        }
        close(filedes[1]);
        filedes[1] = fd;
        return 0;
}

int poll(struct pollfd *ufds, unsigned int nfds, int timeout)
{
        int i, pending;

        if (timeout != -1)
                return errno = EINVAL, error("poll timeout not supported");

        /* When there is only one fd to wait for, then we pretend that
         * input is available and let the actual wait happen when the
         * caller invokes read().
         */
        if (nfds == 1) {
                if (!(ufds[0].events & POLLIN))
                        return errno = EINVAL, error("POLLIN not set");
                ufds[0].revents = POLLIN;
                return 0;
        }

repeat:
        pending = 0;
        for (i = 0; i < nfds; i++) {
                DWORD avail = 0;
                HANDLE h = (HANDLE) _get_osfhandle(ufds[i].fd);
                if (h == INVALID_HANDLE_VALUE)
                        return -1;      /* errno was set */

                if (!(ufds[i].events & POLLIN))
                        return errno = EINVAL, error("POLLIN not set");

                /* this emulation works only for pipes */
                if (!PeekNamedPipe(h, NULL, 0, NULL, &avail, NULL)) {
                        int err = GetLastError();
                        if (err == ERROR_BROKEN_PIPE) {
                                ufds[i].revents = POLLHUP;
                                pending++;
                        } else {
                                errno = EINVAL;
                                return error("PeekNamedPipe failed,"
                                        " GetLastError: %u", err);
                        }
                } else if (avail) {
                        ufds[i].revents = POLLIN;
                        pending++;
                } else
                        ufds[i].revents = 0;
        }
        if (!pending) {
                /* The only times that we spin here is when the process
                 * that is connected through the pipes is waiting for
                 * its own input data to become available. But since
                 * the process (pack-objects) is itself CPU intensive,
                 * it will happily pick up the time slice that we are
                 * relinguishing here.
                 */
                Sleep(0);
                goto repeat;
        }
        return 0;
}

struct tm *gmtime_r(const time_t *timep, struct tm *result)
{
        /* gmtime() in MSVCRT.DLL is thread-safe, but not reentrant */
        memcpy(result, gmtime(timep), sizeof(struct tm));
        return result;
}

struct tm *localtime_r(const time_t *timep, struct tm *result)
{
        /* localtime() in MSVCRT.DLL is thread-safe, but not reentrant */
        memcpy(result, localtime(timep), sizeof(struct tm));
        return result;
}

#undef getcwd
char *mingw_getcwd(char *pointer, int len)
{
        int i;
        char *ret = getcwd(pointer, len);
        if (!ret)
                return ret;
        for (i = 0; pointer[i]; i++)
                if (pointer[i] == '\\')
                        pointer[i] = '/';
        return ret;
}

/*
 * See http://msdn2.microsoft.com/en-us/library/17w5ykft(vs.71).aspx
 * (Parsing C++ Command-Line Arguments)
 */
static const char *quote_arg(const char *arg)
{
        /* count chars to quote */
        int len = 0, n = 0;
        int force_quotes = 0;
        char *q, *d;
        const char *p = arg;
        if (!*p) force_quotes = 1;
        while (*p) {
                if (isspace(*p) || *p == '*' || *p == '?' || *p == '{')
                        force_quotes = 1;
                else if (*p == '"')
                        n++;
                else if (*p == '\\') {
                        int count = 0;
                        while (*p == '\\') {
                                count++;
                                p++;
                                len++;
                        }
                        if (*p == '"')
                                n += count*2 + 1;
                        continue;
                }
                len++;
                p++;
        }
        if (!force_quotes && n == 0)
                return arg;

        /* insert \ where necessary */
        d = q = xmalloc(len+n+3);
        *d++ = '"';
        while (*arg) {
                if (*arg == '"')
                        *d++ = '\\';
                else if (*arg == '\\') {
                        int count = 0;
                        while (*arg == '\\') {
                                count++;
                                *d++ = *arg++;
                        }
                        if (*arg == '"') {
                                while (count-- > 0)
                                        *d++ = '\\';
                                *d++ = '\\';
                        }
                }
                *d++ = *arg++;
        }
        *d++ = '"';
        *d++ = 0;
        return q;
}

static const char *parse_interpreter(const char *cmd)
{
        static char buf[100];
        char *p, *opt;
        int n, fd;

        /* don't even try a .exe */
        n = strlen(cmd);
        if (n >= 4 && !strcasecmp(cmd+n-4, ".exe"))
                return NULL;

        fd = open(cmd, O_RDONLY);
        if (fd < 0)
                return NULL;
        n = read(fd, buf, sizeof(buf)-1);
        close(fd);
        if (n < 4)      /* at least '#!/x' and not error */
                return NULL;

        if (buf[0] != '#' || buf[1] != '!')
                return NULL;
        buf[n] = '\0';
        p = strchr(buf, '\n');
        if (!p)
                return NULL;

        *p = '\0';
        if (!(p = strrchr(buf+2, '/')) && !(p = strrchr(buf+2, '\\')))
                return NULL;
        /* strip options */
        if ((opt = strchr(p+1, ' ')))
                *opt = '\0';
        return p+1;
}

/*
 * Splits the PATH into parts.
 */
static char **get_path_split(void)
{
        char *p, **path, *envpath = getenv("PATH");
        int i, n = 0;

        if (!envpath || !*envpath)
                return NULL;

        envpath = xstrdup(envpath);
        p = envpath;
        while (p) {
                char *dir = p;
                p = strchr(p, ';');
                if (p) *p++ = '\0';
                if (*dir) {     /* not earlier, catches series of ; */
                        ++n;
                }
        }
        if (!n)
                return NULL;

        path = xmalloc((n+1)*sizeof(char*));
        p = envpath;
        i = 0;
        do {
                if (*p)
                        path[i++] = xstrdup(p);
                p = p+strlen(p)+1;
        } while (i < n);
        path[i] = NULL;

        free(envpath);

        return path;
}

static void free_path_split(char **path)
{
        if (!path)
                return;

        char **p = path;
        while (*p)
                free(*p++);
        free(path);
}

/*
 * exe_only means that we only want to detect .exe files, but not scripts
 * (which do not have an extension)
 */
static char *lookup_prog(const char *dir, const char *cmd, int isexe, int exe_only)
{
        char path[MAX_PATH];
        snprintf(path, sizeof(path), "%s/%s.exe", dir, cmd);

        if (!isexe && access(path, F_OK) == 0)
                return xstrdup(path);
        path[strlen(path)-4] = '\0';
        if ((!exe_only || isexe) && access(path, F_OK) == 0)
                return xstrdup(path);
        return NULL;
}

/*
 * Determines the absolute path of cmd using the the split path in path.
 * If cmd contains a slash or backslash, no lookup is performed.
 */
static char *path_lookup(const char *cmd, char **path, int exe_only)
{
        char *prog = NULL;
        int len = strlen(cmd);
        int isexe = len >= 4 && !strcasecmp(cmd+len-4, ".exe");

        if (strchr(cmd, '/') || strchr(cmd, '\\'))
                prog = xstrdup(cmd);

        while (!prog && *path)
                prog = lookup_prog(*path++, cmd, isexe, exe_only);

        return prog;
}

static int env_compare(const void *a, const void *b)
{
        char *const *ea = a;
        char *const *eb = b;
        return strcasecmp(*ea, *eb);
}

static pid_t mingw_spawnve(const char *cmd, const char **argv, char **env,
                           int prepend_cmd)
{
        STARTUPINFO si;
        PROCESS_INFORMATION pi;
        struct strbuf envblk, args;
        unsigned flags;
        BOOL ret;

        /* Determine whether or not we are associated to a console */
        HANDLE cons = CreateFile("CONOUT$", GENERIC_WRITE,
                        FILE_SHARE_WRITE, NULL, OPEN_EXISTING,
                        FILE_ATTRIBUTE_NORMAL, NULL);
        if (cons == INVALID_HANDLE_VALUE) {
                /* There is no console associated with this process.
                 * Since the child is a console process, Windows
                 * would normally create a console window. But
                 * since we'll be redirecting std streams, we do
                 * not need the console.
                 */
                flags = CREATE_NO_WINDOW;
        } else {
                /* There is already a console. If we specified
                 * CREATE_NO_WINDOW here, too, Windows would
                 * disassociate the child from the console.
                 * Go figure!
                 */
                flags = 0;
                CloseHandle(cons);
        }
        memset(&si, 0, sizeof(si));
        si.cb = sizeof(si);
        si.dwFlags = STARTF_USESTDHANDLES;
        si.hStdInput = (HANDLE) _get_osfhandle(0);
        si.hStdOutput = (HANDLE) _get_osfhandle(1);
        si.hStdError = (HANDLE) _get_osfhandle(2);

        /* concatenate argv, quoting args as we go */
        strbuf_init(&args, 0);
        if (prepend_cmd) {
                char *quoted = (char *)quote_arg(cmd);
                strbuf_addstr(&args, quoted);
                if (quoted != cmd)
                        free(quoted);
        }
        for (; *argv; argv++) {
                char *quoted = (char *)quote_arg(*argv);
                if (*args.buf)
                        strbuf_addch(&args, ' ');
                strbuf_addstr(&args, quoted);
                if (quoted != *argv)
                        free(quoted);
        }

        if (env) {
                int count = 0;
                char **e, **sorted_env;

                for (e = env; *e; e++)
                        count++;

                /* environment must be sorted */
                sorted_env = xmalloc(sizeof(*sorted_env) * (count + 1));
                memcpy(sorted_env, env, sizeof(*sorted_env) * (count + 1));
                qsort(sorted_env, count, sizeof(*sorted_env), env_compare);

                strbuf_init(&envblk, 0);
                for (e = sorted_env; *e; e++) {
                        strbuf_addstr(&envblk, *e);
                        strbuf_addch(&envblk, '\0');
                }
                free(sorted_env);
        }

        memset(&pi, 0, sizeof(pi));
        ret = CreateProcess(cmd, args.buf, NULL, NULL, TRUE, flags,
                env ? envblk.buf : NULL, NULL, &si, &pi);

        if (env)
                strbuf_release(&envblk);
        strbuf_release(&args);

        if (!ret) {
                errno = ENOENT;
                return -1;
        }
        CloseHandle(pi.hThread);
        return (pid_t)pi.hProcess;
}

pid_t mingw_spawnvpe(const char *cmd, const char **argv, char **env)
{
        pid_t pid;
        char **path = get_path_split();
        char *prog = path_lookup(cmd, path, 0);

        if (!prog) {
                errno = ENOENT;
                pid = -1;
        }
        else {
                const char *interpr = parse_interpreter(prog);

                if (interpr) {
                        const char *argv0 = argv[0];
                        char *iprog = path_lookup(interpr, path, 1);
                        argv[0] = prog;
                        if (!iprog) {
                                errno = ENOENT;
                                pid = -1;
                        }
                        else {
                                pid = mingw_spawnve(iprog, argv, env, 1);
                                free(iprog);
                        }
                        argv[0] = argv0;
                }
                else
                        pid = mingw_spawnve(prog, argv, env, 0);
                free(prog);
        }
        free_path_split(path);
        return pid;
}

static int try_shell_exec(const char *cmd, char *const *argv, char **env)
{
        const char *interpr = parse_interpreter(cmd);
        char **path;
        char *prog;
        int pid = 0;

        if (!interpr)
                return 0;
        path = get_path_split();
        prog = path_lookup(interpr, path, 1);
        if (prog) {
                int argc = 0;
                const char **argv2;
                while (argv[argc]) argc++;
                argv2 = xmalloc(sizeof(*argv) * (argc+1));
                argv2[0] = (char *)cmd; /* full path to the script file */
                memcpy(&argv2[1], &argv[1], sizeof(*argv) * argc);
                pid = mingw_spawnve(prog, argv2, env, 1);
                if (pid >= 0) {
                        int status;
                        if (waitpid(pid, &status, 0) < 0)
                                status = 255;
                        exit(status);
                }
                pid = 1;        /* indicate that we tried but failed */
                free(prog);
                free(argv2);
        }
        free_path_split(path);
        return pid;
}

static void mingw_execve(const char *cmd, char *const *argv, char *const *env)
{
        /* check if git_command is a shell script */
        if (!try_shell_exec(cmd, argv, (char **)env)) {
                int pid, status;

                pid = mingw_spawnve(cmd, (const char **)argv, (char **)env, 0);
                if (pid < 0)
                        return;
                if (waitpid(pid, &status, 0) < 0)
                        status = 255;
                exit(status);
        }
}

void mingw_execvp(const char *cmd, char *const *argv)
{
        char **path = get_path_split();
        char *prog = path_lookup(cmd, path, 0);

        if (prog) {
                mingw_execve(prog, argv, environ);
                free(prog);
        } else
                errno = ENOENT;

        free_path_split(path);
}

char **copy_environ()
{
        char **env;
        int i = 0;
        while (environ[i])
                i++;
        env = xmalloc((i+1)*sizeof(*env));
        for (i = 0; environ[i]; i++)
                env[i] = xstrdup(environ[i]);
        env[i] = NULL;
        return env;
}

void free_environ(char **env)
{
        int i;
        for (i = 0; env[i]; i++)
                free(env[i]);
        free(env);
}

static int lookup_env(char **env, const char *name, size_t nmln)
{
        int i;

        for (i = 0; env[i]; i++) {
                if (0 == strncmp(env[i], name, nmln)
                    && '=' == env[i][nmln])
                        /* matches */
                        return i;
        }
        return -1;
}

/*
 * If name contains '=', then sets the variable, otherwise it unsets it
 */
char **env_setenv(char **env, const char *name)
{
        char *eq = strchrnul(name, '=');
        int i = lookup_env(env, name, eq-name);

        if (i < 0) {
                if (*eq) {
                        for (i = 0; env[i]; i++)
                                ;
                        env = xrealloc(env, (i+2)*sizeof(*env));
                        env[i] = xstrdup(name);
                        env[i+1] = NULL;
                }
        }
        else {
                free(env[i]);
                if (*eq)
                        env[i] = xstrdup(name);
                else
                        for (; env[i]; i++)
                                env[i] = env[i+1];
        }
        return env;
}

/* this is the first function to call into WS_32; initialize it */
#undef gethostbyname
struct hostent *mingw_gethostbyname(const char *host)
{
        WSADATA wsa;

        if (WSAStartup(MAKEWORD(2,2), &wsa))
                die("unable to initialize winsock subsystem, error %d",
                        WSAGetLastError());
        atexit((void(*)(void)) WSACleanup);
        return gethostbyname(host);
}

int mingw_socket(int domain, int type, int protocol)
{
        int sockfd;
        SOCKET s = WSASocket(domain, type, protocol, NULL, 0, 0);
        if (s == INVALID_SOCKET) {
                /*
                 * WSAGetLastError() values are regular BSD error codes
                 * biased by WSABASEERR.
                 * However, strerror() does not know about networking
                 * specific errors, which are values beginning at 38 or so.
                 * Therefore, we choose to leave the biased error code
                 * in errno so that _if_ someone looks up the code somewhere,
                 * then it is at least the number that are usually listed.
                 */
                errno = WSAGetLastError();
                return -1;
        }
        /* convert into a file descriptor */
        if ((sockfd = _open_osfhandle(s, O_RDWR|O_BINARY)) < 0) {
                closesocket(s);
                return error("unable to make a socket file descriptor: %s",
                        strerror(errno));
        }
        return sockfd;
}

#undef connect
int mingw_connect(int sockfd, struct sockaddr *sa, size_t sz)
{
        SOCKET s = (SOCKET)_get_osfhandle(sockfd);
        return connect(s, sa, sz);
}

#undef rename
int mingw_rename(const char *pold, const char *pnew)
{
        /*
         * Try native rename() first to get errno right.
         * It is based on MoveFile(), which cannot overwrite existing files.
         */
        if (!rename(pold, pnew))
                return 0;
        if (errno != EEXIST)
                return -1;
        if (MoveFileEx(pold, pnew, MOVEFILE_REPLACE_EXISTING))
                return 0;
        /* TODO: translate more errors */
        if (GetLastError() == ERROR_ACCESS_DENIED) {
                DWORD attrs = GetFileAttributes(pnew);
                if (attrs != INVALID_FILE_ATTRIBUTES && (attrs & FILE_ATTRIBUTE_DIRECTORY)) {
                        errno = EISDIR;
                        return -1;
                }
        }
        errno = EACCES;
        return -1;
}

struct passwd *getpwuid(int uid)
{
        static char user_name[100];
        static struct passwd p;

        DWORD len = sizeof(user_name);
        if (!GetUserName(user_name, &len))
                return NULL;
        p.pw_name = user_name;
        p.pw_gecos = "unknown";
        p.pw_dir = NULL;
        return &p;
}

static HANDLE timer_event;
static HANDLE timer_thread;
static int timer_interval;
static int one_shot;
static sig_handler_t timer_fn = SIG_DFL;

/* The timer works like this:
 * The thread, ticktack(), is a trivial routine that most of the time
 * only waits to receive the signal to terminate. The main thread tells
 * the thread to terminate by setting the timer_event to the signalled
 * state.
 * But ticktack() interrupts the wait state after the timer's interval
 * length to call the signal handler.
 */

static __stdcall unsigned ticktack(void *dummy)
{
        while (WaitForSingleObject(timer_event, timer_interval) == WAIT_TIMEOUT) {
                if (timer_fn == SIG_DFL)
                        die("Alarm");
                if (timer_fn != SIG_IGN)
                        timer_fn(SIGALRM);
                if (one_shot)
                        break;
        }
        return 0;
}

static int start_timer_thread(void)
{
        timer_event = CreateEvent(NULL, FALSE, FALSE, NULL);
        if (timer_event) {
                timer_thread = (HANDLE) _beginthreadex(NULL, 0, ticktack, NULL, 0, NULL);
                if (!timer_thread )
                        return errno = ENOMEM,
                                error("cannot start timer thread");
        } else
                return errno = ENOMEM,
                        error("cannot allocate resources for timer");
        return 0;
}

static void stop_timer_thread(void)
{
        if (timer_event)
                SetEvent(timer_event);  /* tell thread to terminate */
        if (timer_thread) {
                int rc = WaitForSingleObject(timer_thread, 1000);
                if (rc == WAIT_TIMEOUT)
                        error("timer thread did not terminate timely");
                else if (rc != WAIT_OBJECT_0)
                        error("waiting for timer thread failed: %lu",
                              GetLastError());
                CloseHandle(timer_thread);
        }
        if (timer_event)
                CloseHandle(timer_event);
        timer_event = NULL;
        timer_thread = NULL;
}

static inline int is_timeval_eq(const struct timeval *i1, const struct timeval *i2)
{
        return i1->tv_sec == i2->tv_sec && i1->tv_usec == i2->tv_usec;
}

int setitimer(int type, struct itimerval *in, struct itimerval *out)
{
        static const struct timeval zero;
        static int atexit_done;

        if (out != NULL)
                return errno = EINVAL,
                        error("setitimer param 3 != NULL not implemented");
        if (!is_timeval_eq(&in->it_interval, &zero) &&
            !is_timeval_eq(&in->it_interval, &in->it_value))
                return errno = EINVAL,
                        error("setitimer: it_interval must be zero or eq it_value");

        if (timer_thread)
                stop_timer_thread();

        if (is_timeval_eq(&in->it_value, &zero) &&
            is_timeval_eq(&in->it_interval, &zero))
                return 0;

        timer_interval = in->it_value.tv_sec * 1000 + in->it_value.tv_usec / 1000;
        one_shot = is_timeval_eq(&in->it_interval, &zero);
        if (!atexit_done) {
                atexit(stop_timer_thread);
                atexit_done = 1;
        }
        return start_timer_thread();
}

int sigaction(int sig, struct sigaction *in, struct sigaction *out)
{
        if (sig != SIGALRM)
                return errno = EINVAL,
                        error("sigaction only implemented for SIGALRM");
        if (out != NULL)
                return errno = EINVAL,
                        error("sigaction: param 3 != NULL not implemented");

        timer_fn = in->sa_handler;
        return 0;
}

#undef signal
sig_handler_t mingw_signal(int sig, sig_handler_t handler)
{
        if (sig != SIGALRM)
                return signal(sig, handler);
        sig_handler_t old = timer_fn;
        timer_fn = handler;
        return old;
}