Improve system call support on NT

- Improve i/o perf on New Technology
- Code cleanup on read() for New Technology
- Fix bad bug with dup() of socket on New Technology
- Clean up some more strace errors on New Technology

libc/mem/copyfd.c

@@ -0,0 +1,86 @@
+/*-*- 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 2022 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/errno.h"
+#include "libc/mem/mem.h"
+
+#define CHUNK 32768
+
+/**
+ * Copies data between fds the old fashioned way.
+ *
+ * Even though Cosmopolitan polyfills copy_file_range() to fallback to
+ * doing this, it's useful to call this function in cases where you know
+ * it'd be more helpful to get the larger buffer size with read/write.
+ *
+ * Reads are allowed to be interrupted. Writes are uninterruptible. If
+ * we get an interrupt when partial data was written, we return the
+ * partial amount. Therefore the file descriptors are guaranteed to
+ * remain in a consistent state, provided EINTR is the only error.
+ *
+ * If n is 0 then 0 is returned and no i/o operations are performed.
+ *
+ * @return bytes successfully exchanged
+ */
+ssize_t _copyfd(int infd, int outfd, size_t n) {
+  int e;
+  char *buf;
+  ssize_t rc;
+  size_t i, j, got, sent;
+  rc = 0;
+  if (n) {
+    if ((buf = malloc(CHUNK))) {
+      for (e = errno, i = 0; i < n; i += j) {
+        rc = read(infd, buf, CHUNK);
+        if (rc == -1) {
+          // eintr may interrupt the read operation
+          if (i && errno == EINTR) {
+            // suppress error if partially completed
+            errno = e;
+            rc = i;
+          }
+          break;
+        }
+        got = rc;
+        if (!got) {
+          rc = i;
+          break;
+        }
+        // write operation must complete
+        for (j = 0; j < got; j += sent) {
+          rc = write(outfd, buf + j, got - j);
+          if (rc != -1) {
+            sent = rc;
+          } else if (errno == EINTR) {
+            // write operation must be uninterruptible
+            errno = e;
+            sent = 0;
+          } else {
+            break;
+          }
+        }
+        if (rc == -1) break;
+      }
+      free(buf);
+    } else {
+      rc = -1;
+    }
+  }
+  return rc;
+}