machinemode: fix bugs and increase readability

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

1 files changed, 171 insertions, 68 deletions

diff --git a/src/slibc-human/machinemode.c b/src/slibc-human/machinemode.c
index 06029d3..f454613 100644
--- a/src/slibc-human/machinemode.c
+++ b/src/slibc-human/machinemode.c
@@ -24,6 +24,173 @@
 
 
 /**
+ * Owner can execute/list or/and set UID.
+ */
+#define S_ISUSR  (S_ISUID | S_IXUSR)
+
+/**
+ * Group can execute/list or/and set GID.
+ */
+#define S_ISGRP  (S_ISGID | S_IXGRO)
+
+/**
+ * Others (not in group) can execute/list or/and sticky bit.
+ */
+#define S_ISOTH  (S_ISVTX | S_IXOTH)
+
+
+/**
+ * Store permission bits.
+ * 
+ * @param  V:mode_t    The variables for the permissions.
+ * @param  U:int type  First-level index in `bits` for the user.
+ * @param  T:int type  Second-level index in `bits` for bits to verify are unset.
+ * @param  S:int type  Second-level index in `bits` for bits to set.
+ */
+#define  BITS_(V, U, T, S)  if ((V) & bits[U][T])  goto invalid;  else  V |= bits[U][S]
+
+/**
+ * Store permission bits.
+ * 
+ * @parma  S:char      Character representing the bits to set.
+ * @param  V:mode_t    The variables for the permissions.
+ * @param  U:int type  First-level index in `bits` for the user.
+ */
+#define  BITS(S, V, U)  \
+  if      ((S) == 'r')  { BITS_(V, U, 0, 0); }  \
+  else if ((S) == 'w')  { BITS_(V, U, 1, 1); }  \
+  else if ((S) == 'x')  { BITS_(V, U, 3, 2); }  \
+  else if ((S) == 's')  { BITS_(V, U, 3, 3); }  \
+  else if ((S) == 't')  { BITS_(V, U, 3, 3); }  \
+  else if ((S) == 'S')  { BITS_(V, U, 3, 4); }  \
+  else if ((S) == 'T')  { BITS_(V, U, 3, 4); }  \
+  else if ((S) != '-')  goto invalid
+
+
+
+/**
+ * User {0=owner. 1=group, 2=others} to permissions {0=can read,
+ * 1=can write, 2=can execute/list, 3=can execute/list or/and
+ * special, 4=special} to permissions bits map.
+ */
+static 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},
+};
+
+
+/**
+ * Parse a symbolic file permission string with partial update.
+ * 
+ * @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.
+ */
+static inline int partial_symbolic(mode_t* restrict mode, mode_t* restrict mask, const char* restrict str)
+{
+#define  TEST_(S, T, V)  (strstarts(str, S) && !(T & (symbols = V)))
+#define  TEST(S, T)      (TEST_(S"+", T, 1) || TEST_(S"-", T, 2) || TEST_(S"=", T, 3))
+#define  TESTV(T)        (TEST(#T, T) ? (T |= symbols) : 0)
+  
+  int u = 0, g = 0, o = 0, symbols, first, user, last;
+  mode_t or = 0, andn = 0, partial_or;
+  char symbol;
+  
+  for (; *str; str++)
+    {
+      /* Check a/u/g/o and =/+/-. */
+      if (TEST("a", u|g|o))  first = 3, u |= symbols, g |= symbols, o |= symbols;
+      else if (TESTV(u))     first = 0;
+      else if (TESTV(g))     first = 1;
+      else if (TESTV(o))     first = 2;
+      else
+	goto invalid;
+      
+      /* Get range of effected users. */
+      if (first < 3)  last = first + 1;
+      else            last = first, first = 0;
+      
+      /* Get =/+/- and jump to permissions. */
+      symbol = str[1], str += 2;
+      
+      /* Get permissions. */
+      for (partial_or = 0; *str && (*str != ','); str++)
+	for (user = first; user < last; user++)
+	  BITS(*str, partial_or, j);
+      
+      /* Apply permissions. */
+      if (symbol != '-')  or   |= partial_or;
+      if (symbol != '=')  andn |= partial_or;
+      else
+	for (user = first; user < last; user++)
+	  andn |= bits[user][0] | bits[user][1] | bits[user][3];
+    }
+  
+  if (mode)  *mode = or;
+  if (mask)  *mask = andn;
+  return 0;
+ invalid:
+  return errno = EINVAL, -1;
+}
+
+
+/**
+ * Parse a full symbolic file permission string.
+ * 
+ * @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.
+ */
+static inline int exact_symbolic(mode_t* restrict mode, mode_t* restrict mask, const char* restrict str)
+{
+  mode_t or = 0;
+  long int user, perm;
+  
+  for (user = 0; user < 3; user++)
+    for (perm = 0; perm < 3; perm++, str++)
+      BITS(*str, or, user);
+  
+  if (mode)  *mode = or;
+  if (mask)  *mask = 07777;
+  return 0;
+ invalid:
+  return errno = EINVAL, -1;
+}
+
+
+/**
+ * Parse a numeric file permission string.
+ * 
+ * @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.
+ */
+static inline int exact_numeric(mode_t* restrict mode, mode_t* restrict mask, const char* restrict str)
+{
+  mode_t or = 0;
+  char s;
+  
+  for (; (s = *str); str++)
+    if (('0' > s) || (s > '7') || (or = (or << 3) | (s & 15), or > 07777))
+      return errno = EINVAL, -1;
+  
+  if (mode)  *mode = or;
+  if (mask)  *mask = 07777;
+  return 0;
+}
+
+
+/**
  * Parses a human representation of file permissions, and updates to file permissions.
  * 
  * Assuming the current file permissions is `value`, and neither
@@ -40,84 +207,20 @@
  */
 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)
-
-#define  TEST_(S, T, V)  (strstarts(str, S) && !(T & (v = V)))
-#define  TEST(S, T)      (TEST_(S"+", T, 1) || TEST_(S"-", T, 2) || TEST_(S"=", T, 3))
-#define  TESTV(T)        (TEST(#T, T) ? (T = v) : 0)
-
-#define  BITS_(V, T, S)  if (V & bits[i][T])  goto invalid;  else  V |= bits[i][S]
-#define  BITS(V)  \
-  if      (*str == 'r')  { BITS_(V, 0, 0); }  \
-  else if (*str == 'w')  { BITS_(V, 1, 1); }  \
-  else if (*str == 'x')  { BITS_(V, 3, 2); }  \
-  else if (*str == 's')  { BITS_(V, 3, 3); }  \
-  else if (*str == 't')  { BITS_(V, 3, 3); }  \
-  else if (*str == 'S')  { BITS_(V, 3, 4); }  \
-  else if (*str == 'T')  { BITS_(V, 3, 4); }  \
-  else if (*str != '-')  goto invalid
-  
-  int i, j, n, u = 0, g = 0, o = 0, v;
-  char s;
-  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 '\0':
-      goto invalid;
+      return errno = EINVAL, -1;
       
     case 'a': case 'u': case 'g': case 'o':
-      /* Partial, symbolic. */
-      for (; *str; str++)
-	{
-	  if (TEST("a", u|g|o))  i = 3, u |= v, g |= v, o |= v;
-	  else if (TESTV(u))     i = 0;
-	  else if (TESTV(g))     i = 1;
-	  else if (TESTV(o))     i = 2;
-	  else
-	    goto invalid;
-	  if (n < 3)  n = i + 1;
-	  else        n = i, i = 0;
-	  s = str[1], str += 2;
-	  for (part = 0; *str && (*str != ','); str++)
-	    for (j = i; j < n; j++)
-	      BITS(part);
-	  if (s != '-')  or   |= part;
-	  if (s != '=')  andn |= part;
-	  else
-	    for (j = i; j < n; j++)
-	      andn |= bits[i][0] | bits[i][1] | bits[i][3];
-	}
-      break;
+      return partial_symbolic(mode, mask, str);
       
     case 'r': case 'w': case 'x': case '-':
     case 's': case 'S': case 't': case 'T':
-      /* Exact, symbolic. */
-      for (andn = 07777, i = 0; i < 3; i++)
-	for (j = 0; j < 3; j++, str++)
-	  BITS(or);
-      break;
+      return exact_symbolic(mode, mask, str);
       
     default:
-      /* Exact, numeric. */
-      for (andn = 07777; (s = *str); str++)
-	if (('0' > s) || (s > '7') || (or = (or << 3) | (s & 15), or > 07777))
-	  goto invalid;
-      break;
+      return exact_numeric(mode, mask, str);
     }
-  
-  if (mode)  *mode = or;
-  if (mask)  *mask = andn;
-  return 0;
-  
- invalid:
-  return errno = EINVAL, -1;
 }