#include "../git-compat-util.h"
#include "win32.h"
#include <conio.h>
#include "../strbuf.h"
#include "../run-command.h"

static const int delay[] = { 0, 1, 10, 20, 40 };

int err_win_to_posix(DWORD winerr)
{
        int error = ENOSYS;
        switch(winerr) {
        case ERROR_ACCESS_DENIED: error = EACCES; break;
        case ERROR_ACCOUNT_DISABLED: error = EACCES; break;
        case ERROR_ACCOUNT_RESTRICTION: error = EACCES; break;
        case ERROR_ALREADY_ASSIGNED: error = EBUSY; break;
        case ERROR_ALREADY_EXISTS: error = EEXIST; break;
        case ERROR_ARITHMETIC_OVERFLOW: error = ERANGE; break;
        case ERROR_BAD_COMMAND: error = EIO; break;
        case ERROR_BAD_DEVICE: error = ENODEV; break;
        case ERROR_BAD_DRIVER_LEVEL: error = ENXIO; break;
        case ERROR_BAD_EXE_FORMAT: error = ENOEXEC; break;
        case ERROR_BAD_FORMAT: error = ENOEXEC; break;
        case ERROR_BAD_LENGTH: error = EINVAL; break;
        case ERROR_BAD_PATHNAME: error = ENOENT; break;
        case ERROR_BAD_PIPE: error = EPIPE; break;
        case ERROR_BAD_UNIT: error = ENODEV; break;
        case ERROR_BAD_USERNAME: error = EINVAL; break;
        case ERROR_BROKEN_PIPE: error = EPIPE; break;
        case ERROR_BUFFER_OVERFLOW: error = ENAMETOOLONG; break;
        case ERROR_BUSY: error = EBUSY; break;
        case ERROR_BUSY_DRIVE: error = EBUSY; break;
        case ERROR_CALL_NOT_IMPLEMENTED: error = ENOSYS; break;
        case ERROR_CANNOT_MAKE: error = EACCES; break;
        case ERROR_CANTOPEN: error = EIO; break;
        case ERROR_CANTREAD: error = EIO; break;
        case ERROR_CANTWRITE: error = EIO; break;
        case ERROR_CRC: error = EIO; break;
        case ERROR_CURRENT_DIRECTORY: error = EACCES; break;
        case ERROR_DEVICE_IN_USE: error = EBUSY; break;
        case ERROR_DEV_NOT_EXIST: error = ENODEV; break;
        case ERROR_DIRECTORY: error = EINVAL; break;
        case ERROR_DIR_NOT_EMPTY: error = ENOTEMPTY; break;
        case ERROR_DISK_CHANGE: error = EIO; break;
        case ERROR_DISK_FULL: error = ENOSPC; break;
        case ERROR_DRIVE_LOCKED: error = EBUSY; break;
        case ERROR_ENVVAR_NOT_FOUND: error = EINVAL; break;
        case ERROR_EXE_MARKED_INVALID: error = ENOEXEC; break;
        case ERROR_FILENAME_EXCED_RANGE: error = ENAMETOOLONG; break;
        case ERROR_FILE_EXISTS: error = EEXIST; break;
        case ERROR_FILE_INVALID: error = ENODEV; break;
        case ERROR_FILE_NOT_FOUND: error = ENOENT; break;
        case ERROR_GEN_FAILURE: error = EIO; break;
        case ERROR_HANDLE_DISK_FULL: error = ENOSPC; break;
        case ERROR_INSUFFICIENT_BUFFER: error = ENOMEM; break;
        case ERROR_INVALID_ACCESS: error = EACCES; break;
        case ERROR_INVALID_ADDRESS: error = EFAULT; break;
        case ERROR_INVALID_BLOCK: error = EFAULT; break;
        case ERROR_INVALID_DATA: error = EINVAL; break;
        case ERROR_INVALID_DRIVE: error = ENODEV; break;
        case ERROR_INVALID_EXE_SIGNATURE: error = ENOEXEC; break;
        case ERROR_INVALID_FLAGS: error = EINVAL; break;
        case ERROR_INVALID_FUNCTION: error = ENOSYS; break;
        case ERROR_INVALID_HANDLE: error = EBADF; break;
        case ERROR_INVALID_LOGON_HOURS: error = EACCES; break;
        case ERROR_INVALID_NAME: error = EINVAL; break;
        case ERROR_INVALID_OWNER: error = EINVAL; break;
        case ERROR_INVALID_PARAMETER: error = EINVAL; break;
        case ERROR_INVALID_PASSWORD: error = EPERM; break;
        case ERROR_INVALID_PRIMARY_GROUP: error = EINVAL; break;
        case ERROR_INVALID_SIGNAL_NUMBER: error = EINVAL; break;
        case ERROR_INVALID_TARGET_HANDLE: error = EIO; break;
        case ERROR_INVALID_WORKSTATION: error = EACCES; break;
        case ERROR_IO_DEVICE: error = EIO; break;
        case ERROR_IO_INCOMPLETE: error = EINTR; break;
        case ERROR_LOCKED: error = EBUSY; break;
        case ERROR_LOCK_VIOLATION: error = EACCES; break;
        case ERROR_LOGON_FAILURE: error = EACCES; break;
        case ERROR_MAPPED_ALIGNMENT: error = EINVAL; break;
        case ERROR_META_EXPANSION_TOO_LONG: error = E2BIG; break;
        case ERROR_MORE_DATA: error = EPIPE; break;
        case ERROR_NEGATIVE_SEEK: error = ESPIPE; break;
        case ERROR_NOACCESS: error = EFAULT; break;
        case ERROR_NONE_MAPPED: error = EINVAL; break;
        case ERROR_NOT_ENOUGH_MEMORY: error = ENOMEM; break;
        case ERROR_NOT_READY: error = EAGAIN; break;
        case ERROR_NOT_SAME_DEVICE: error = EXDEV; break;
        case ERROR_NO_DATA: error = EPIPE; break;
        case ERROR_NO_MORE_SEARCH_HANDLES: error = EIO; break;
        case ERROR_NO_PROC_SLOTS: error = EAGAIN; break;
        case ERROR_NO_SUCH_PRIVILEGE: error = EACCES; break;
        case ERROR_OPEN_FAILED: error = EIO; break;
        case ERROR_OPEN_FILES: error = EBUSY; break;
        case ERROR_OPERATION_ABORTED: error = EINTR; break;
        case ERROR_OUTOFMEMORY: error = ENOMEM; break;
        case ERROR_PASSWORD_EXPIRED: error = EACCES; break;
        case ERROR_PATH_BUSY: error = EBUSY; break;
        case ERROR_PATH_NOT_FOUND: error = ENOENT; break;
        case ERROR_PIPE_BUSY: error = EBUSY; break;
        case ERROR_PIPE_CONNECTED: error = EPIPE; break;
        case ERROR_PIPE_LISTENING: error = EPIPE; break;
        case ERROR_PIPE_NOT_CONNECTED: error = EPIPE; break;
        case ERROR_PRIVILEGE_NOT_HELD: error = EACCES; break;
        case ERROR_READ_FAULT: error = EIO; break;
        case ERROR_SEEK: error = EIO; break;
        case ERROR_SEEK_ON_DEVICE: error = ESPIPE; break;
        case ERROR_SHARING_BUFFER_EXCEEDED: error = ENFILE; break;
        case ERROR_SHARING_VIOLATION: error = EACCES; break;
        case ERROR_STACK_OVERFLOW: error = ENOMEM; break;
        case ERROR_SWAPERROR: error = ENOENT; break;
        case ERROR_TOO_MANY_MODULES: error = EMFILE; break;
        case ERROR_TOO_MANY_OPEN_FILES: error = EMFILE; break;
        case ERROR_UNRECOGNIZED_MEDIA: error = ENXIO; break;
        case ERROR_UNRECOGNIZED_VOLUME: error = ENODEV; break;
        case ERROR_WAIT_NO_CHILDREN: error = ECHILD; break;
        case ERROR_WRITE_FAULT: error = EIO; break;
        case ERROR_WRITE_PROTECT: error = EROFS; break;
        }
        return error;
}

static inline int is_file_in_use_error(DWORD errcode)
{
        switch (errcode) {
        case ERROR_SHARING_VIOLATION:
        case ERROR_ACCESS_DENIED:
                return 1;
        }

        return 0;
}

static int read_yes_no_answer(void)
{
        char answer[1024];

        if (fgets(answer, sizeof(answer), stdin)) {
                size_t answer_len = strlen(answer);
                int got_full_line = 0, c;

                /* remove the newline */
                if (answer_len >= 2 && answer[answer_len-2] == '\r') {
                        answer[answer_len-2] = '\0';
                        got_full_line = 1;
                } else if (answer_len >= 1 && answer[answer_len-1] == '\n') {
                        answer[answer_len-1] = '\0';
                        got_full_line = 1;
                }
                /* flush the buffer in case we did not get the full line */
                if (!got_full_line)
                        while ((c = getchar()) != EOF && c != '\n')
                                ;
        } else
                /* we could not read, return the
                 * default answer which is no */
                return 0;

        if (tolower(answer[0]) == 'y' && !answer[1])
                return 1;
        if (!strncasecmp(answer, "yes", sizeof(answer)))
                return 1;
        if (tolower(answer[0]) == 'n' && !answer[1])
                return 0;
        if (!strncasecmp(answer, "no", sizeof(answer)))
                return 0;

        /* did not find an answer we understand */
        return -1;
}

static int ask_yes_no_if_possible(const char *format, ...)
{
        char question[4096];
        const char *retry_hook[] = { NULL, NULL, NULL };
        va_list args;

        va_start(args, format);
        vsnprintf(question, sizeof(question), format, args);
        va_end(args);

        if ((retry_hook[0] = mingw_getenv("GIT_ASK_YESNO"))) {
                retry_hook[1] = question;
                return !run_command_v_opt(retry_hook, 0);
        }

        if (!isatty(_fileno(stdin)) || !isatty(_fileno(stderr)))
                return 0;

        while (1) {
                int answer;
                fprintf(stderr, "%s (y/n) ", question);

                if ((answer = read_yes_no_answer()) >= 0)
                        return answer;

                fprintf(stderr, "Sorry, I did not understand your answer. "
                                "Please type 'y' or 'n'\n");
        }
}

#undef unlink
int mingw_unlink(const char *pathname)
{
        int ret, tries = 0;

        /* read-only files cannot be removed */
        chmod(pathname, 0666);
        while ((ret = unlink(pathname)) == -1 && tries < ARRAY_SIZE(delay)) {
                if (!is_file_in_use_error(GetLastError()))
                        break;
                /*
                 * We assume that some other process had the source or
                 * destination file open at the wrong moment and retry.
                 * In order to give the other process a higher chance to
                 * complete its operation, we give up our time slice now.
                 * If we have to retry again, we do sleep a bit.
                 */
                Sleep(delay[tries]);
                tries++;
        }
        while (ret == -1 && is_file_in_use_error(GetLastError()) &&
               ask_yes_no_if_possible("Unlink of file '%s' failed. "
                        "Should I try again?", pathname))
               ret = unlink(pathname);
        return ret;
}

static int is_dir_empty(const char *path)
{
        struct strbuf buf = STRBUF_INIT;
        WIN32_FIND_DATAA findbuf;
        HANDLE handle;

        strbuf_addf(&buf, "%s\\*", path);
        handle = FindFirstFileA(buf.buf, &findbuf);
        if (handle == INVALID_HANDLE_VALUE) {
                strbuf_release(&buf);
                return GetLastError() == ERROR_NO_MORE_FILES;
        }

        while (!strcmp(findbuf.cFileName, ".") ||
                        !strcmp(findbuf.cFileName, ".."))
                if (!FindNextFile(handle, &findbuf)) {
                        strbuf_release(&buf);
                        return GetLastError() == ERROR_NO_MORE_FILES;
                }
        FindClose(handle);
        strbuf_release(&buf);
        return 0;
}

#undef rmdir
int mingw_rmdir(const char *pathname)
{
        int ret, tries = 0;

        while ((ret = rmdir(pathname)) == -1 && tries < ARRAY_SIZE(delay)) {
                if (!is_file_in_use_error(GetLastError()))
                        break;
                if (!is_dir_empty(pathname)) {
                        errno = ENOTEMPTY;
                        break;
                }
                /*
                 * We assume that some other process had the source or
                 * destination file open at the wrong moment and retry.
                 * In order to give the other process a higher chance to
                 * complete its operation, we give up our time slice now.
                 * If we have to retry again, we do sleep a bit.
                 */
                Sleep(delay[tries]);
                tries++;
        }
        while (ret == -1 && is_file_in_use_error(GetLastError()) &&
               ask_yes_no_if_possible("Deletion of directory '%s' failed. "
                        "Should I try again?", pathname))
               ret = rmdir(pathname);
        return ret;
}

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

        va_start(args, oflags);
        mode = va_arg(args, int);
        va_end(args);

        if (filename && !strcmp(filename, "/dev/null"))
                filename = "nul";

        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;
}

#undef write
ssize_t mingw_write(int fd, const void *buf, size_t count)
{
        /*
         * While write() calls to a file on a local disk are translated
         * into WriteFile() calls with a maximum size of 64KB on Windows
         * XP and 256KB on Vista, no such cap is placed on writes to
         * files over the network on Windows XP.  Unfortunately, there
         * seems to be a limit of 32MB-28KB on X64 and 64MB-32KB on x86;
         * bigger writes fail on Windows XP.
         * So we cap to a nice 31MB here to avoid write failures over
         * the net without changing the number of WriteFile() calls in
         * the local case.
         */
        return write(fd, buf, min(count, 31 * 1024 * 1024));
}

#undef fopen
FILE *mingw_fopen (const char *filename, const char *otype)
{
        if (filename && !strcmp(filename, "/dev/null"))
                filename = "nul";
        return fopen(filename, otype);
}

#undef freopen
FILE *mingw_freopen (const char *filename, const char *otype, FILE *stream)
{
        if (filename && !strcmp(filename, "/dev/null"))
                filename = "nul";
        return freopen(filename, otype, stream);
}

/*
 * The unit of FILETIME is 100-nanoseconds since January 1, 1601, UTC.
 * Returns the 100-nanoseconds ("hekto nanoseconds") since the epoch.
 */
static inline long long filetime_to_hnsec(const FILETIME *ft)
{
        long long winTime = ((long long)ft->dwHighDateTime << 32) + ft->dwLowDateTime;
        /* Windows to Unix Epoch conversion */
        return winTime - 116444736000000000LL;
}

static inline time_t filetime_to_time_t(const FILETIME *ft)
{
        return (time_t)(filetime_to_hnsec(ft) / 10000000);
}

/* 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.
 *
 * If follow is true then act like stat() and report on the link
 * target. Otherwise report on the link itself.
 */
static int do_lstat(int follow, const char *file_name, struct stat *buf)
{
        int err;
        WIN32_FILE_ATTRIBUTE_DATA fdata;

        if (!(err = get_file_attr(file_name, &fdata))) {
                buf->st_ino = 0;
                buf->st_gid = 0;
                buf->st_uid = 0;
                buf->st_nlink = 1;
                buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes);
                buf->st_size = fdata.nFileSizeLow |
                        (((off_t)fdata.nFileSizeHigh)<<32);
                buf->st_dev = buf->st_rdev = 0; /* not used by Git */
                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));
                if (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {
                        WIN32_FIND_DATAA findbuf;
                        HANDLE handle = FindFirstFileA(file_name, &findbuf);
                        if (handle != INVALID_HANDLE_VALUE) {
                                if ((findbuf.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) &&
                                                (findbuf.dwReserved0 == IO_REPARSE_TAG_SYMLINK)) {
                                        if (follow) {
                                                char buffer[MAXIMUM_REPARSE_DATA_BUFFER_SIZE];
                                                buf->st_size = readlink(file_name, buffer, MAXIMUM_REPARSE_DATA_BUFFER_SIZE);
                                        } else {
                                                buf->st_mode = S_IFLNK;
                                        }
                                        buf->st_mode |= S_IREAD;
                                        if (!(findbuf.dwFileAttributes & FILE_ATTRIBUTE_READONLY))
                                                buf->st_mode |= S_IWRITE;
                                }
                                FindClose(handle);
                        }
                }
                return 0;
        }
        errno = err;
        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.
 */
static int do_stat_internal(int follow, const char *file_name, struct stat *buf)
{
        int namelen;
        static char alt_name[PATH_MAX];

        if (!do_lstat(follow, 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(follow, alt_name, buf);
}

int mingw_lstat(const char *file_name, struct stat *buf)
{
        return do_stat_internal(0, file_name, buf);
}
int mingw_stat(const char *file_name, struct stat *buf)
{
        return do_stat_internal(1, file_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 _fstati64(fd, buf);

        if (GetFileInformationByHandle(fh, &fdata)) {
                buf->st_ino = 0;
                buf->st_gid = 0;
                buf->st_uid = 0;
                buf->st_nlink = 1;
                buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes);
                buf->st_size = fdata.nFileSizeLow |
                        (((off_t)fdata.nFileSizeHigh)<<32);
                buf->st_dev = buf->st_rdev = 0; /* not used by Git */
                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;
}

static inline void time_t_to_filetime(time_t t, FILETIME *ft)
{
        long long winTime = t * 10000000LL + 116444736000000000LL;
        ft->dwLowDateTime = winTime;
        ft->dwHighDateTime = winTime >> 32;
}

int mingw_utime (const char *file_name, const struct utimbuf *times)
{
        FILETIME mft, aft;
        int fh, rc;

        /* must have write permission */
        DWORD attrs = GetFileAttributes(file_name);
        if (attrs != INVALID_FILE_ATTRIBUTES &&
            (attrs & FILE_ATTRIBUTE_READONLY)) {
                /* ignore errors here; open() will report them */
                SetFileAttributes(file_name, attrs & ~FILE_ATTRIBUTE_READONLY);
        }

        if ((fh = open(file_name, O_RDWR | O_BINARY)) < 0) {
                rc = -1;
                goto revert_attrs;
        }

        if (times) {
                time_t_to_filetime(times->modtime, &mft);
                time_t_to_filetime(times->actime, &aft);
        } else {
                GetSystemTimeAsFileTime(&mft);
                aft = mft;
        }
        if (!SetFileTime((HANDLE)_get_osfhandle(fh), NULL, &aft, &mft)) {
                errno = EINVAL;
                rc = -1;
        } else
                rc = 0;
        close(fh);

revert_attrs:
        if (attrs != INVALID_FILE_ATTRIBUTES &&
            (attrs & FILE_ATTRIBUTE_READONLY)) {
                /* ignore errors again */
                SetFileAttributes(file_name, attrs);
        }
        return rc;
}

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)
{
        FILETIME ft;
        long long hnsec;

        GetSystemTimeAsFileTime(&ft);
        hnsec = filetime_to_hnsec(&ft);
        tv->tv_sec = hnsec / 10000000;
        tv->tv_usec = (hnsec % 10000000) / 10;
        return 0;
}

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

        /* this creates non-inheritable handles */
        if (!CreatePipe(&h[0], &h[1], NULL, 8192)) {
                errno = err_win_to_posix(GetLastError());
                return -1;
        }
        filedes[0] = _open_osfhandle((int)h[0], O_NOINHERIT);
        if (filedes[0] < 0) {
                CloseHandle(h[0]);
                CloseHandle(h[1]);
                return -1;
        }
        filedes[1] = _open_osfhandle((int)h[1], O_NOINHERIT);
        if (filedes[0] < 0) {
                close(filedes[0]);
                CloseHandle(h[1]);
                return -1;
        }
        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 == '{' || *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 = buf + strcspn(buf, "\r\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 = mingw_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)
{
        char **p = path;

        if (!path)
                return;

        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)
                if (!(GetFileAttributes(path) & FILE_ATTRIBUTE_DIRECTORY))
                        return xstrdup(path);
        return NULL;
}

/*
 * Determines the absolute path of cmd using 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);
}

struct pinfo_t {
        struct pinfo_t *next;
        pid_t pid;
        HANDLE proc;
} pinfo_t;
struct pinfo_t *pinfo = NULL;
CRITICAL_SECTION pinfo_cs;

static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **env,
                              const char *dir,
                              int prepend_cmd, int fhin, int fhout, int fherr)
{
        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.
                 * It is necessary to use DETACHED_PROCESS
                 * instead of CREATE_NO_WINDOW to make ssh
                 * recognize that it has no console.
                 */
                flags = DETACHED_PROCESS;
        } else {
                /* There is already a console. If we specified
                 * DETACHED_PROCESS here, too, Windows would
                 * disassociate the child from the console.
                 * The same is true for CREATE_NO_WINDOW.
                 * Go figure!
                 */
                flags = 0;
                CloseHandle(cons);
        }
        memset(&si, 0, sizeof(si));
        si.cb = sizeof(si);
        si.dwFlags = STARTF_USESTDHANDLES;
        si.hStdInput = (HANDLE) _get_osfhandle(fhin);
        si.hStdOutput = (HANDLE) _get_osfhandle(fhout);
        si.hStdError = (HANDLE) _get_osfhandle(fherr);

        /* 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, dir, &si, &pi);

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

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

        /*
         * The process ID is the human-readable identifier of the process
         * that we want to present in log and error messages. The handle
         * is not useful for this purpose. But we cannot close it, either,
         * because it is not possible to turn a process ID into a process
         * handle after the process terminated.
         * Keep the handle in a list for waitpid.
         */
        EnterCriticalSection(&pinfo_cs);
        {
                struct pinfo_t *info = xmalloc(sizeof(struct pinfo_t));
                info->pid = pi.dwProcessId;
                info->proc = pi.hProcess;
                info->next = pinfo;
                pinfo = info;
        }
        LeaveCriticalSection(&pinfo_cs);

        return (pid_t)pi.dwProcessId;
}

static pid_t mingw_spawnve(const char *cmd, const char **argv, char **env,
                           int prepend_cmd)
{
        return mingw_spawnve_fd(cmd, argv, env, NULL, prepend_cmd, 0, 1, 2);
}

pid_t mingw_spawnvpe(const char *cmd, const char **argv, char **env,
                     const char *dir,
                     int fhin, int fhout, int fherr)
{
        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_fd(iprog, argv, env, dir, 1,
                                                       fhin, fhout, fherr);
                                free(iprog);
                        }
                        argv[0] = argv0;
                }
                else
                        pid = mingw_spawnve_fd(prog, argv, env, dir, 0,
                                               fhin, fhout, fherr);
                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);
}

void mingw_execv(const char *cmd, char *const *argv)
{
        mingw_execve(cmd, argv, environ);
}

int mingw_kill(pid_t pid, int sig)
{
        if (pid > 0 && sig == SIGTERM) {
                HANDLE h = OpenProcess(PROCESS_TERMINATE, FALSE, pid);

                if (TerminateProcess(h, -1)) {
                        CloseHandle(h);
                        return 0;
                }

                errno = err_win_to_posix(GetLastError());
                CloseHandle(h);
                return -1;
        }

        errno = EINVAL;
        return -1;
}

static char **copy_environ(void)
{
        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
 */
static 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;
}

/*
 * Copies global environ and adjusts variables as specified by vars.
 */
char **make_augmented_environ(const char *const *vars)
{
        char **env = copy_environ();

        while (*vars)
                env = env_setenv(env, *vars++);
        return env;
}

#undef getenv

/*
 * The system's getenv looks up the name in a case-insensitive manner.
 * This version tries a case-sensitive lookup and falls back to
 * case-insensitive if nothing was found.  This is necessary because,
 * as a prominent example, CMD sets 'Path', but not 'PATH'.
 * Warning: not thread-safe.
 */
static char *getenv_cs(const char *name)
{
        size_t len = strlen(name);
        int i = lookup_env(environ, name, len);
        if (i >= 0)
                return environ[i] + len + 1;    /* skip past name and '=' */
        return getenv(name);
}

char *mingw_getenv(const char *name)
{
        char *result = getenv_cs(name);
        if (!result && !strcmp(name, "TMPDIR")) {
                /* on Windows it is TMP and TEMP */
                result = getenv_cs("TMP");
                if (!result)
                        result = getenv_cs("TEMP");
        }
        return result;
}

/*
 * Note, this isn't a complete replacement for getaddrinfo. It assumes
 * that service contains a numerical port, or that it is null. It
 * does a simple search using gethostbyname, and returns one IPv4 host
 * if one was found.
 */
static int WSAAPI getaddrinfo_stub(const char *node, const char *service,
                                   const struct addrinfo *hints,
                                   struct addrinfo **res)
{
        struct hostent *h = NULL;
        struct addrinfo *ai;
        struct sockaddr_in *sin;

        if (node) {
                h = gethostbyname(node);
                if (!h)
                        return WSAGetLastError();
        }

        ai = xmalloc(sizeof(struct addrinfo));
        *res = ai;
        ai->ai_flags = 0;
        ai->ai_family = AF_INET;
        ai->ai_socktype = hints ? hints->ai_socktype : 0;
        switch (ai->ai_socktype) {
        case SOCK_STREAM:
                ai->ai_protocol = IPPROTO_TCP;
                break;
        case SOCK_DGRAM:
                ai->ai_protocol = IPPROTO_UDP;
                break;
        default:
                ai->ai_protocol = 0;
                break;
        }
        ai->ai_addrlen = sizeof(struct sockaddr_in);
        if (hints && (hints->ai_flags & AI_CANONNAME))
                ai->ai_canonname = h ? strdup(h->h_name) : NULL;
        else
                ai->ai_canonname = NULL;

        sin = xmalloc(ai->ai_addrlen);
        memset(sin, 0, ai->ai_addrlen);
        sin->sin_family = AF_INET;
        /* Note: getaddrinfo is supposed to allow service to be a string,
         * which should be looked up using getservbyname. This is
         * currently not implemented */
        if (service)
                sin->sin_port = htons(atoi(service));
        if (h)
                sin->sin_addr = *(struct in_addr *)h->h_addr;
        else if (hints && (hints->ai_flags & AI_PASSIVE))
                sin->sin_addr.s_addr = INADDR_ANY;
        else
                sin->sin_addr.s_addr = INADDR_LOOPBACK;
        ai->ai_addr = (struct sockaddr *)sin;
        ai->ai_next = 0;
        return 0;
}

static void WSAAPI freeaddrinfo_stub(struct addrinfo *res)
{
        free(res->ai_canonname);
        free(res->ai_addr);
        free(res);
}

static int WSAAPI getnameinfo_stub(const struct sockaddr *sa, socklen_t salen,
                                   char *host, DWORD hostlen,
                                   char *serv, DWORD servlen, int flags)
{
        const struct sockaddr_in *sin = (const struct sockaddr_in *)sa;
        if (sa->sa_family != AF_INET)
                return EAI_FAMILY;
        if (!host && !serv)
                return EAI_NONAME;

        if (host && hostlen > 0) {
                struct hostent *ent = NULL;
                if (!(flags & NI_NUMERICHOST))
                        ent = gethostbyaddr((const char *)&sin->sin_addr,
                                            sizeof(sin->sin_addr), AF_INET);

                if (ent)
                        snprintf(host, hostlen, "%s", ent->h_name);
                else if (flags & NI_NAMEREQD)
                        return EAI_NONAME;
                else
                        snprintf(host, hostlen, "%s", inet_ntoa(sin->sin_addr));
        }

        if (serv && servlen > 0) {
                struct servent *ent = NULL;
                if (!(flags & NI_NUMERICSERV))
                        ent = getservbyport(sin->sin_port,
                                            flags & NI_DGRAM ? "udp" : "tcp");

                if (ent)
                        snprintf(serv, servlen, "%s", ent->s_name);
                else
                        snprintf(serv, servlen, "%d", ntohs(sin->sin_port));
        }

        return 0;
}

static HMODULE ipv6_dll = NULL;
static void (WSAAPI *ipv6_freeaddrinfo)(struct addrinfo *res);
static int (WSAAPI *ipv6_getaddrinfo)(const char *node, const char *service,
                                      const struct addrinfo *hints,
                                      struct addrinfo **res);
static int (WSAAPI *ipv6_getnameinfo)(const struct sockaddr *sa, socklen_t salen,
                                      char *host, DWORD hostlen,
                                      char *serv, DWORD servlen, int flags);
/*
 * gai_strerror is an inline function in the ws2tcpip.h header, so we
 * don't need to try to load that one dynamically.
 */

static void socket_cleanup(void)
{
        WSACleanup();
        if (ipv6_dll)
                FreeLibrary(ipv6_dll);
        ipv6_dll = NULL;
        ipv6_freeaddrinfo = freeaddrinfo_stub;
        ipv6_getaddrinfo = getaddrinfo_stub;
        ipv6_getnameinfo = getnameinfo_stub;
}

static void ensure_socket_initialization(void)
{
        WSADATA wsa;
        static int initialized = 0;
        const char *libraries[] = { "ws2_32.dll", "wship6.dll", NULL };
        const char **name;

        if (initialized)
                return;

        if (WSAStartup(MAKEWORD(2,2), &wsa))
                die("unable to initialize winsock subsystem, error %d",
                        WSAGetLastError());

        for (name = libraries; *name; name++) {
                ipv6_dll = LoadLibrary(*name);
                if (!ipv6_dll)
                        continue;

                ipv6_freeaddrinfo = (void (WSAAPI *)(struct addrinfo *))
                        GetProcAddress(ipv6_dll, "freeaddrinfo");
                ipv6_getaddrinfo = (int (WSAAPI *)(const char *, const char *,
                                                   const struct addrinfo *,
                                                   struct addrinfo **))
                        GetProcAddress(ipv6_dll, "getaddrinfo");
                ipv6_getnameinfo = (int (WSAAPI *)(const struct sockaddr *,
                                                   socklen_t, char *, DWORD,
                                                   char *, DWORD, int))
                        GetProcAddress(ipv6_dll, "getnameinfo");
                if (!ipv6_freeaddrinfo || !ipv6_getaddrinfo || !ipv6_getnameinfo) {
                        FreeLibrary(ipv6_dll);
                        ipv6_dll = NULL;
                } else
                        break;
        }
        if (!ipv6_freeaddrinfo || !ipv6_getaddrinfo || !ipv6_getnameinfo) {
                ipv6_freeaddrinfo = freeaddrinfo_stub;
                ipv6_getaddrinfo = getaddrinfo_stub;
                ipv6_getnameinfo = getnameinfo_stub;
        }

        atexit(socket_cleanup);
        initialized = 1;
}

#undef gethostbyname
struct hostent *mingw_gethostbyname(const char *host)
{
        ensure_socket_initialization();
        return gethostbyname(host);
}

void mingw_freeaddrinfo(struct addrinfo *res)
{
        ipv6_freeaddrinfo(res);
}

int mingw_getaddrinfo(const char *node, const char *service,
                      const struct addrinfo *hints, struct addrinfo **res)
{
        ensure_socket_initialization();
        return ipv6_getaddrinfo(node, service, hints, res);
}

int mingw_getnameinfo(const struct sockaddr *sa, socklen_t salen,
                      char *host, DWORD hostlen, char *serv, DWORD servlen,
                      int flags)
{
        ensure_socket_initialization();
        return ipv6_getnameinfo(sa, salen, host, hostlen, serv, servlen, flags);
}

int mingw_socket(int domain, int type, int protocol)
{
        int sockfd;
        SOCKET s;

        ensure_socket_initialization();
        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 bind
int mingw_bind(int sockfd, struct sockaddr *sa, size_t sz)
{
        SOCKET s = (SOCKET)_get_osfhandle(sockfd);
        return bind(s, sa, sz);
}

#undef setsockopt
int mingw_setsockopt(int sockfd, int lvl, int optname, void *optval, int optlen)
{
        SOCKET s = (SOCKET)_get_osfhandle(sockfd);
        return setsockopt(s, lvl, optname, (const char*)optval, optlen);
}

#undef shutdown
int mingw_shutdown(int sockfd, int how)
{
        SOCKET s = (SOCKET)_get_osfhandle(sockfd);
        return shutdown(s, how);
}

#undef listen
int mingw_listen(int sockfd, int backlog)
{
        SOCKET s = (SOCKET)_get_osfhandle(sockfd);
        return listen(s, backlog);
}

#undef accept
int mingw_accept(int sockfd1, struct sockaddr *sa, socklen_t *sz)
{
        int sockfd2;

        SOCKET s1 = (SOCKET)_get_osfhandle(sockfd1);
        SOCKET s2 = accept(s1, sa, sz);

        /* convert into a file descriptor */
        if ((sockfd2 = _open_osfhandle(s2, O_RDWR|O_BINARY)) < 0) {
                int err = errno;
                closesocket(s2);
                return error("unable to make a socket file descriptor: %s",
                        strerror(err));
        }
        return sockfd2;
}

#undef rename
int mingw_rename(const char *pold, const char *pnew)
{
        DWORD attrs, gle;
        int tries = 0;

        /*
         * 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;
repeat:
        if (MoveFileEx(pold, pnew, MOVEFILE_REPLACE_EXISTING))
                return 0;
        /* TODO: translate more errors */
        gle = GetLastError();
        if (gle == ERROR_ACCESS_DENIED &&
            (attrs = GetFileAttributes(pnew)) != INVALID_FILE_ATTRIBUTES) {
                if (attrs & FILE_ATTRIBUTE_DIRECTORY) {
                        errno = EISDIR;
                        return -1;
                }
                if ((attrs & FILE_ATTRIBUTE_READONLY) &&
                    SetFileAttributes(pnew, attrs & ~FILE_ATTRIBUTE_READONLY)) {
                        if (MoveFileEx(pold, pnew, MOVEFILE_REPLACE_EXISTING))
                                return 0;
                        gle = GetLastError();
                        /* revert file attributes on failure */
                        SetFileAttributes(pnew, attrs);
                }
        }
        if (tries < ARRAY_SIZE(delay) && gle == ERROR_ACCESS_DENIED) {
                /*
                 * We assume that some other process had the source or
                 * destination file open at the wrong moment and retry.
                 * In order to give the other process a higher chance to
                 * complete its operation, we give up our time slice now.
                 * If we have to retry again, we do sleep a bit.
                 */
                Sleep(delay[tries]);
                tries++;
                goto repeat;
        }
        if (gle == ERROR_ACCESS_DENIED &&
               ask_yes_no_if_possible("Rename from '%s' to '%s' failed. "
                       "Should I try again?", pold, pnew))
                goto repeat;

        errno = EACCES;
        return -1;
}

/*
 * Note that this doesn't return the actual pagesize, but
 * the allocation granularity. If future Windows specific git code
 * needs the real getpagesize function, we need to find another solution.
 */
int mingw_getpagesize(void)
{
        SYSTEM_INFO si;
        GetSystemInfo(&si);
        return si.dwAllocationGranularity;
}

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 unsigned __stdcall 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)
{
        sig_handler_t old = timer_fn;
        if (sig != SIGALRM)
                return signal(sig, handler);
        timer_fn = handler;
        return old;
}

static const char *make_backslash_path(const char *path)
{
        static char buf[PATH_MAX + 1];
        char *c;

        if (strlcpy(buf, path, PATH_MAX) >= PATH_MAX)
                die("Too long path: %.*s", 60, path);

        for (c = buf; *c; c++) {
                if (*c == '/')
                        *c = '\\';
        }
        return buf;
}

void mingw_open_html(const char *unixpath)
{
        const char *htmlpath = make_backslash_path(unixpath);
        typedef HINSTANCE (WINAPI *T)(HWND, const char *,
                        const char *, const char *, const char *, INT);
        T ShellExecute;
        HMODULE shell32;
        int r;

        shell32 = LoadLibrary("shell32.dll");
        if (!shell32)
                die("cannot load shell32.dll");
        ShellExecute = (T)GetProcAddress(shell32, "ShellExecuteA");
        if (!ShellExecute)
                die("cannot run browser");

        printf("Launching default browser to display HTML ...\n");
        r = (int)ShellExecute(NULL, "open", htmlpath, NULL, "\\", SW_SHOWNORMAL);
        FreeLibrary(shell32);
        /* see the MSDN documentation referring to the result codes here */
        if (r <= 32) {
                die("failed to launch browser for %.*s", MAX_PATH, unixpath);
        }
}

int link(const char *oldpath, const char *newpath)
{
        typedef BOOL (WINAPI *T)(const char*, const char*, LPSECURITY_ATTRIBUTES);
        static T create_hard_link = NULL;
        if (!create_hard_link) {
                create_hard_link = (T) GetProcAddress(
                        GetModuleHandle("kernel32.dll"), "CreateHardLinkA");
                if (!create_hard_link)
                        create_hard_link = (T)-1;
        }
        if (create_hard_link == (T)-1) {
                errno = ENOSYS;
                return -1;
        }
        if (!create_hard_link(newpath, oldpath, NULL)) {
                errno = err_win_to_posix(GetLastError());
                return -1;
        }
        return 0;
}

char *getpass(const char *prompt)
{
        struct strbuf buf = STRBUF_INIT;

        fputs(prompt, stderr);
        for (;;) {
                char c = _getch();
                if (c == '\r' || c == '\n')
                        break;
                strbuf_addch(&buf, c);
        }
        fputs("\n", stderr);
        return strbuf_detach(&buf, NULL);
}

pid_t waitpid(pid_t pid, int *status, unsigned options)
{
        HANDLE h = OpenProcess(SYNCHRONIZE | PROCESS_QUERY_INFORMATION,
            FALSE, pid);
        if (!h) {
                errno = ECHILD;
                return -1;
        }

        if (pid > 0 && options & WNOHANG) {
                if (WAIT_OBJECT_0 != WaitForSingleObject(h, 0)) {
                        CloseHandle(h);
                        return 0;
                }
                options &= ~WNOHANG;
        }

        if (options == 0) {
                struct pinfo_t **ppinfo;
                if (WaitForSingleObject(h, INFINITE) != WAIT_OBJECT_0) {
                        CloseHandle(h);
                        return 0;
                }

                if (status)
                        GetExitCodeProcess(h, (LPDWORD)status);

                EnterCriticalSection(&pinfo_cs);

                ppinfo = &pinfo;
                while (*ppinfo) {
                        struct pinfo_t *info = *ppinfo;
                        if (info->pid == pid) {
                                CloseHandle(info->proc);
                                *ppinfo = info->next;
                                free(info);
                                break;
                        }
                        ppinfo = &info->next;
                }

                LeaveCriticalSection(&pinfo_cs);

                CloseHandle(h);
                return pid;
        }
        CloseHandle(h);

        errno = EINVAL;
        return -1;
}