Initial import

libc/str/memccpy.c

@@ -0,0 +1,55 @@
+/*-*- 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/str/str.h"
+
+/**
+ * Copies at most 𝑛 bytes from 𝑠 to 𝑑 until 𝑐 is encountered.
+ *
+ * This is little-known C Standard Library approach, dating back to the
+ * Fourth Edition of System Five, for copying a C strings to fixed-width
+ * buffers, with added generality.
+ *
+ * For example, strictly:
+ *
+ *   char buf[16];
+ *   CHECK_NOTNULL(memccpy(buf, s, '\0', sizeof(buf)));
+ *
+ * Or unstrictly:
+ *
+ *   if (!memccpy(buf, s, '\0', sizeof(buf))) strcpy(buf, "?");
+ *
+ * Are usually more sensible than the following:
+ *
+ *   char cstrbuf[16];
+ *   snprintf(cstrbuf, sizeof(cstrbuf), "%s", CSTR);
+ *
+ * @return 𝑑 + idx(𝑐) + 1, or NULL if 𝑐 ∉ 𝑠₀․․ₙ₋₁
+ * @note 𝑑 and 𝑠 can't overlap
+ * @asyncsignalsafe
+ */
+void *memccpy(void *d, const void *s, int c, size_t n) {
+  const char *p, *pe;
+  if ((pe = memchr((p = s), c, n))) {
+    return mempcpy(d, s, pe - p + 1);
+  } else {
+    memcpy(d, s, n);
+    return NULL;
+  }
+}