Initial import

libc/calls/hefty/commandv.c

@@ -0,0 +1,170 @@
+/*-*- 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/alg/alg.h"
+#include "libc/bits/progn.h"
+#include "libc/bits/safemacros.h"
+#include "libc/calls/calls.h"
+#include "libc/conv/conv.h"
+#include "libc/dce.h"
+#include "libc/errno.h"
+#include "libc/mem/mem.h"
+#include "libc/nt/ntdll.h"
+#include "libc/runtime/runtime.h"
+#include "libc/str/str.h"
+#include "libc/sysv/consts/ok.h"
+#include "libc/sysv/errfuns.h"
+
+static struct critbit0 g_commandv;
+
+textstartup static void g_commandv_init(void) {
+  __cxa_atexit(critbit0_clear, &g_commandv, NULL);
+}
+
+const void *const g_commandv_ctor[] initarray = {g_commandv_init};
+
+static int accessexe(char pathname[hasatleast PATH_MAX], size_t len,
+                     const char *ext) {
+  len = stpcpy(&pathname[len], ext) - &pathname[0];
+  if (access(pathname, X_OK) != -1) {
+    return len;
+  } else {
+    return -1;
+  }
+}
+
+static int accesscmd(char pathname[hasatleast PATH_MAX], const char *path,
+                     const char *name, size_t namelen) { /* cf. %PATHEXT% */
+  int rc;
+  char *p;
+  bool hasdot;
+  size_t pathlen, len;
+  pathlen = strlen(path);
+  if (pathlen + 1 + namelen + 1 + 4 + 1 > PATH_MAX) return -1;
+  p = mempcpy(pathname, path, pathlen);
+  if (pathlen) *p++ = '/';
+  p = mempcpy(p, name, namelen);
+  len = p - &pathname[0];
+  hasdot = !!memchr(basename(name), '.', namelen);
+  if ((hasdot && (rc = accessexe(pathname, len, "")) != -1) ||
+      (!hasdot &&
+       ((rc = accessexe(pathname, len, ".com")) != -1 ||
+        (IsWindows() && (rc = accessexe(pathname, len, ".exe")) != -1) ||
+        (!IsWindows() && (rc = accessexe(pathname, len, "")) != -1)))) {
+    return rc;
+  } else {
+    return -1;
+  }
+}
+
+static int searchcmdpath(char pathname[hasatleast PATH_MAX], const char *name,
+                         size_t namelen) {
+  int rc;
+  char *ep, *path, *pathtok;
+  struct critbit0 deduplicate;
+  rc = -1;
+  pathtok = ep =
+      strdup(firstnonnull(getenv("PATH"), "/bin:/usr/local/bin:/usr/bin"));
+  memset(&deduplicate, 0, sizeof(deduplicate));
+  while ((path = strsep(&pathtok, IsWindows() ? ";" : ":"))) {
+    if (strchr(path, '=')) continue;
+    if (!critbit0_insert(&deduplicate, path)) continue;
+    if ((rc = accesscmd(pathname, path, name, namelen)) != -1) {
+      break;
+    }
+  }
+  critbit0_clear(&deduplicate);
+  free(ep);
+  return rc;
+}
+
+static char *mkcmdquery(const char *name, size_t namelen,
+                        char scratch[hasatleast PATH_MAX]) {
+  char *p;
+  if (namelen + 1 + 1 > PATH_MAX) return NULL;
+  p = mempcpy(scratch, name, namelen);
+  *p++ = '=';
+  *p++ = '\0';
+  if (IsWindows() || IsXnu()) strntolower(scratch, namelen);
+  return &scratch[0];
+}
+
+static const char *cachecmd(const char *name, size_t namelen,
+                            const char *pathname, size_t pathnamelen) {
+  size_t entrylen;
+  char *res, *entry;
+  if ((entry = malloc((entrylen = namelen + 1 + pathnamelen) + 1))) {
+    mkcmdquery(name, namelen, entry);
+    res = memcpy(&entry[namelen + 1], pathname, pathnamelen + 1);
+    critbit0_emplace(&g_commandv, entry, entrylen);
+  } else {
+    res = NULL;
+  }
+  return res;
+}
+
+static const char *getcmdcache(const char *name, size_t namelen,
+                               char scratch[hasatleast PATH_MAX]) {
+  const char *entry;
+  if ((entry = critbit0_get(&g_commandv, mkcmdquery(name, namelen, scratch)))) {
+    return &entry[namelen + 1];
+  }
+  return NULL;
+}
+
+noinline static const char *findcmdpath(const char *name,
+                                        char pathname[hasatleast PATH_MAX]) {
+  char *p;
+  int rc, olderr;
+  size_t len;
+  olderr = errno;
+  if (!(len = strlen(name))) return PROGN(enoent(), NULL);
+  if (memchr(name, '=', len)) return PROGN(einval(), NULL);
+  if ((p = getcmdcache(name, len, pathname)) ||
+      (((IsWindows() &&
+         ((rc = accesscmd(pathname, kNtSystemDirectory, name, len)) != -1 ||
+          (rc = accesscmd(pathname, kNtWindowsDirectory, name, len)) != -1)) ||
+        (rc = accesscmd(pathname, "", name, len)) != -1 ||
+        (!strpbrk(name, "/\\") &&
+         (rc = searchcmdpath(pathname, name, len)) != -1)) &&
+       (p = cachecmd(name, len, pathname, rc)))) {
+    errno = olderr;
+    return p;
+  } else {
+    return NULL;
+  }
+}
+
+/**
+ * Resolves pathname of executable.
+ *
+ * This does the same thing as `command -v` in bourne shell. Path
+ * lookups are cached for the lifetime of the process. Paths with
+ * multiple components will skip the resolution process. Undotted
+ * basenames get automatic .com and .exe suffix resolution on all
+ * platforms. Windows' system directories will always trump PATH.
+ *
+ * @return execve()'able path, or NULL w/ errno
+ * @errno ENOENT, EACCES, ENOMEM
+ * @see free(), execvpe()
+ */
+const char *commandv(const char *name) {
+  char pathname[PATH_MAX];
+  return findcmdpath(name, pathname);
+}