Make improvements for Actually Portable Emacs

- Get SIGWINCH working again on the New Technology
- Correctly handle O_NOFOLLOW in open() on Windows
- Implement synthetic umask() functionality on Windows
- Do a better job managing file execute access on Windows
- Fill in `st_uid` and `st_gid` with username hash on Windows
- Munge UNICODE control pictures into control codes on Windows
- Do a better job ensuring Windows console settings are restored
- Introduce KPRINTF_LOG environment variable to log kprintf to a file

libc/runtime/zipos-seek.c

@@ -0,0 +1,81 @@
+/*-*- 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 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
+#include "libc/runtime/zipos.internal.h"
+#include "libc/stdckdint.h"
+#include "libc/sysv/consts/s.h"
+#include "libc/sysv/errfuns.h"
+#include "libc/thread/thread.h"
+#include "libc/thread/tls.h"
+#include "libc/zip.internal.h"
+
+static int64_t __zipos_seek_impl(struct ZiposHandle *h, int64_t offset,
+                                 unsigned whence) {
+  int64_t pos;
+  if (h->cfile == ZIPOS_SYNTHETIC_DIRECTORY ||
+      S_ISDIR(GetZipCfileMode(h->zipos->map + h->cfile))) {
+    return eisdir();
+  }
+  switch (whence) {
+    case SEEK_SET:
+      if (offset >= 0) {
+        return offset;
+      } else {
+        return einval();
+      }
+    case SEEK_CUR:
+      if (!ckd_add(&pos, h->pos, offset)) {
+        if (pos >= 0) {
+          return pos;
+        } else {
+          return einval();
+        }
+      } else {
+        return eoverflow();
+      }
+    case SEEK_END:
+      if (!ckd_sub(&pos, h->size, offset)) {
+        if (pos >= 0) {
+          return pos;
+        } else {
+          return einval();
+        }
+      } else {
+        return eoverflow();
+      }
+    default:
+      return einval();
+  }
+}
+
+/**
+ * Changes current position of zip file handle.
+ *
+ * @param offset is the relative byte count
+ * @param whence can be SEEK_SET, SEEK_CUR, or SEEK_END
+ * @return new position relative to beginning, or -1 on error
+ * @asyncsignalsafe
+ */
+int64_t __zipos_seek(struct ZiposHandle *h, int64_t offset, unsigned whence) {
+  int64_t pos;
+  if ((pos = __zipos_seek_impl(h, offset, whence)) != -1) {
+    h->pos = pos;
+  }
+  return pos;
+}