Make improvements

libc/runtime/getdosenviron.c

@@ -0,0 +1,51 @@
+/*-*- 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/runtime/runtime.h"
+#include "libc/str/str.h"
+
+/**
+ * Transcodes NT environment variable block from UTF-16 to UTF-8.
+ *
+ * @param env is a double NUL-terminated block of key=values
+ * @param buf is the new environment which gets double-nul'd
+ * @param size is the byte capacity of buf
+ * @param envp stores NULL-terminated string pointer list (optional)
+ * @param max is the pointer count capacity of envp
+ * @return number of variables decoded, excluding NULL-terminator
+ */
+textwindows int GetDosEnviron(const char16_t *env, char *buf, size_t size,
+                              char **envp, size_t max) {
+  int i;
+  axdx_t r;
+  i = 0;
+  if (size) {
+    --size;
+    while (*env) {
+      if (i + 1 < max) envp[i++] = buf;
+      r = tprecode16to8(buf, size, env);
+      size -= r.ax + 1;
+      buf += r.ax + 1;
+      env += r.dx;
+    }
+    *buf = '\0';
+  }
+  if (i < max) envp[i] = NULL;
+  return i;
+}