Make improvements

libc/calls/mkntpath.c

@@ -0,0 +1,84 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ This program is free software; you can redistribute it and/or modify         │
+│ it under the terms of the GNU General Public License as published by         │
+│ the Free Software Foundation; version 2 of the License.                      │
+│                                                                              │
+│ This program is distributed in the hope that it will be useful, but          │
+│ WITHOUT ANY WARRANTY; without even the implied warranty of                   │
+│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU             │
+│ General Public License for more details.                                     │
+│                                                                              │
+│ You should have received a copy of the GNU General Public License            │
+│ along with this program; if not, write to the Free Software                  │
+│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA                │
+│ 02110-1301 USA                                                               │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/internal.h"
+#include "libc/calls/ntmagicpaths.internal.h"
+#include "libc/str/oldutf16.internal.h"
+#include "libc/str/str.h"
+#include "libc/str/tpdecode.internal.h"
+#include "libc/sysv/consts/o.h"
+#include "libc/sysv/errfuns.h"
+
+textwindows static const char *FixNtMagicPath(const char *path,
+                                              unsigned flags) {
+  const struct NtMagicPaths *mp = &kNtMagicPaths;
+  asm("" : "+r"(mp));
+  if (path[0] != '/') return path;
+  if (strcmp(path, mp->devtty) == 0) {
+    if ((flags & O_ACCMODE) == O_RDONLY) {
+      return mp->conin;
+    } else if ((flags & O_ACCMODE) == O_WRONLY) {
+      return mp->conout;
+    }
+  }
+  if (strcmp(path, mp->devnull) == 0) return mp->nul;
+  if (strcmp(path, mp->devstdin) == 0) return mp->conin;
+  if (strcmp(path, mp->devstdout) == 0) return mp->conout;
+  return path;
+}
+
+textwindows int __mkntpath(const char *path,
+                           char16_t path16[hasatleast PATH_MAX - 16]) {
+  return __mkntpath2(path, path16, -1);
+}
+
+/**
+ * Copies path for Windows NT.
+ *
+ * This entails (1) UTF-8 to UTF-16 conversion; (2) replacing
+ * forward-slashes with backslashes; and (3) remapping several
+ * well-known paths (e.g. /dev/null → NUL) for convenience.
+ *
+ * @param flags is used by open()
+ * @param path16 is shortened so caller can prefix, e.g. \\.\pipe\, and
+ *     due to a plethora of special-cases throughout the Win32 API
+ * @return short count excluding NUL on success, or -1 w/ errno
+ * @error ENAMETOOLONG
+ */
+textwindows int __mkntpath2(const char *path,
+                            char16_t path16[hasatleast PATH_MAX - 16],
+                            int flags) {
+  /*
+   * 1. Reserve +1 for NUL-terminator
+   * 2. Reserve +1 for UTF-16 overflow
+   * 3. Reserve ≥2 for SetCurrentDirectory trailing slash requirement
+   * 4. Reserve ≥10 for CreateNamedPipe "\\.\pipe\" prefix requirement
+   * 5. Reserve ≥13 for mkdir() i.e. 1+8+3+1, e.g. "\\ffffffff.xxx\0"
+   */
+  size_t i, n;
+  path = FixNtMagicPath(path, flags);
+  n = tprecode8to16(path16, PATH_MAX - 16, path).ax;
+  if (n == PATH_MAX - 16 - 1) return enametoolong();
+  for (i = 0; i < n; ++i) {
+    if (path16[i] == '/') {
+      path16[i] = '\\';
+    }
+  }
+  return n;
+}