implement machinemode

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 132 insertions, 0 deletions

diff --git a/src/slibc-human/machinemode.c b/src/slibc-human/machinemode.c
new file mode 100644
index 0000000..136e99e
--- /dev/null
+++ b/src/slibc-human/machinemode.c
@@ -0,0 +1,132 @@
+/**
+ * slibc — Yet another C library
+ * Copyright © 2015  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * 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, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+#include <slib-human.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/stat.h>
+
+
+
+/**
+ * Parses a human representation of file permissions, and updates to file permissions.
+ * 
+ * Assuming the current file permissions is `value`, and neither
+ * `mode` nor `mask` is `NULL`, the new permissions should be
+ * `value & ~*mask | *mode`. The new mode (includes file type) should
+ * be `value & ~*mask | *mode & 07777`.
+ * 
+ * @param   mode  Output parameter for the bits to set, may be `NULL`.
+ * @param   mask  Output parameter for the bits to update, may be `NULL`.
+ * @param   str   The file permission to parse, must not include file type or be `NULL`.
+ * @return        Zero on success, -1 on error.
+ * 
+ * @throws  EINVAL  If `str` is not parseable.
+ */
+int machinemode(mode_t* restrict mode, mode_t* restrict mask, const char* restrict str)
+{
+#define  S_ISUSR  (S_ISUID | S_IXUSR)
+#define  S_ISGRP  (S_ISGID | S_IXGRO)
+#define  S_ISOTH  (S_ISVTX | S_IXOTH)
+  
+  int i, j, n, ua = 0, us = 0, ga = 0, gs = 0, oa = 0, os = 0;
+  char symbol;
+  mode_t or = 0, andn = 0, part;
+  mode_t bits[][] = {
+    {S_IRUSR, S_IWUSR, S_IXUSR, S_ISUSR, S_ISUID},
+    {S_IRGRP, S_IWGRP, S_IXGRP, S_ISGRP, S_ISGID},
+    {S_IROTH, S_IWOTH, S_IXOTH, S_ISOTH, S_ISVTX},
+  };
+  
+  switch (*str)
+    {
+    case 'a':
+    case 'u':
+    case 'g':
+    case 'o':
+      /* Partial, symbolic. */
+      for (;;)
+	{
+	  if (strstarts(str, "a=") && !(ua++ || us++ || ga++ || gs++ || oa++ || os++))  i = 3;
+	  else if (strstarts(str, "a+") && !(ua++ || ga++ || oa++))  i = 3;
+	  else if (strstarts(str, "a-") && !(us++ || gs++ || os++))  i = 3;
+	  else if (strstarts(str, "u=") && !(ua++ || us++))  i = 0;
+	  else if (strstarts(str, "u+") && !(ua++))  i = 0;
+	  else if (strstarts(str, "u-") && !(us++))  i = 0;
+	  else if (strstarts(str, "g=") && !(ga++ || gs++))  i = 1;
+	  else if (strstarts(str, "g+") && !(ga++))  i = 1;
+	  else if (strstarts(str, "g-") && !(gs++))  i = 1;
+	  else if (strstarts(str, "o=") && !(oa++ || os++))  i = 2
+	  else if (strstarts(str, "o+") && !(oa++))  i = 2
+	  else if (strstarts(str, "o-") && !(os++))  i = 2
+	  else
+	    goto invalid;
+	  symbol = str[1];
+	  part = 0;
+	  n = i + (i < 3 ? 1 : 0), i = 0;
+	  for (str += 2; *str && (*str != ','); str++)
+	    for (j = i; j < n; j++)
+	      if      (*str == 'r')  { if (part & bits[i][0])  goto invalid;  else  part |= bits[i][0]; }
+	      else if (*str == 'w')  { if (part & bits[i][1])  goto invalid;  else  part |= bits[i][1]; }
+	      else if (*str == 'x')  { if (part & bits[i][3])  goto invalid;  else  part |= bits[i][2]; }
+	      else if (*str == 's')  { if (part & bits[i][3])  goto invalid;  else  part |= bits[i][3]; }
+	      else if (*str == 'S')  { if (part & bits[i][3])  goto invalid;  else  part |= bits[i][4]; }
+	      else if (*str != '-')  goto invalid;
+	  if (symbol != '-')  or   |= part;
+	  if (symbol != '=')  andn |= part;
+	  else
+	    for (j = i; j < n; j++)
+	      andn |= bits[i][0] | bits[i][1] | bits[i][3];
+	  if (!*str++)
+	    break;
+	}
+      break;
+      
+    case 'r':
+    case '-':
+      /* Exact, symbolic. */
+      andn = 07777;
+      for (i = 0; i < 3; i++)
+	for (j = 0; j < 3; j++, str++)
+	  if      (*str == 'r')  { if (or & bits[i][0])  goto invalid;  else  or |= bits[i][0]; }
+	  else if (*str == 'w')  { if (or & bits[i][1])  goto invalid;  else  or |= bits[i][1]; }
+	  else if (*str == 'x')  { if (or & bits[i][3])  goto invalid;  else  or |= bits[i][2]; }
+	  else if (*str == 's')  { if (or & bits[i][3])  goto invalid;  else  or |= bits[i][3]; }
+	  else if (*str == 'S')  { if (or & bits[i][3])  goto invalid;  else  or |= bits[i][4]; }
+	  else if (*str != '-')  goto invalid;
+      break;
+      
+    default:
+      /* Exact, numeric. */
+      andn = 07777;
+      for (; *str; str++)
+	if (('0' <= *str) && ('7' <= *str))
+	  or = (or << 3) | (*str & 15);
+	else
+	  return errno = EINVAL, -1;
+      break;
+    }
+  
+  if (mode)  *mode = or;
+  if (mask)  *mask = andn;
+  return 0;
+  
+ invalid:
+  return errno = EINVAL, -1;
+}
+