env: add check/apply logic to himport_r()

Change hashtable so that a callback function will decide whether a
variable can be overwritten, and possibly apply the changes.

So add a new field to struct hsearch_data:

 o "apply" callback function to check whether a variable can be
    overwritten, and possibly immediately apply the changes;
    when NULL, no check is performed.

And a new argument to himport_r():
 o "do_apply": whether to call the apply callback function

NOTE: This patch does not change the current behavior.

Signed-off-by: Gerlando Falauto <gerlando.falauto@keymile.com>

diff --git a/common/cmd_nvedit.c b/common/cmd_nvedit.c
index 67f78710390e48c9ff7f2da2a63cac3d11e9a2a4..3d7700f4fb11648cbffa1c94cb7bd58a38b26f5b 100644 (file)
--- a/common/cmd_nvedit.c
+++ b/common/cmd_nvedit.c
@@ -202,6 +202,7 @@ static int do_env_grep(cmd_tbl_t *cmdtp, int flag,
  * environment variable, then (if successful) apply the changes to internals so
  * to make them effective.  Code for this function was taken out of
  * _do_env_set(), which now calls it instead.
+ * Also called as a callback function by himport_r().
  * Returns 0 in case of success, 1 in case of failure.
  * When (flag & H_FORCE) is set, do not print out any error message and force
  * overwriting of write-once variables.
@@ -932,7 +933,7 @@ static int do_env_import(cmd_tbl_t *cmdtp, int flag,
        }
 
        if (himport_r(&env_htab, addr, size, sep, del ? 0 : H_NOCLEAR,
-                       0, NULL) == 0) {
+                       0, NULL, 0 /* do_apply */) == 0) {
                error("Environment import failed: errno = %d\n", errno);
                return 1;
        }

diff --git a/common/env_common.c b/common/env_common.c
index 8f142ed9bf1103d54a04e010a2dc2199aa9554e0..c6e7c4ca626e8cd564cac39a4dc7b7386ed7d561 100644 (file)
--- a/common/env_common.c
+++ b/common/env_common.c
@@ -133,7 +133,9 @@ const uchar default_environment[] = {
        "\0"
 };
 
-struct hsearch_data env_htab;
+struct hsearch_data env_htab = {
+       .apply = env_check_apply,
+};
 
 static uchar __env_get_char_spec(int index)
 {
@@ -194,7 +196,7 @@ void set_default_env(const char *s)
 
        if (himport_r(&env_htab, (char *)default_environment,
                        sizeof(default_environment), '\0', 0,
-                       0, NULL) == 0)
+                       0, NULL, 0 /* do_apply */) == 0)
                error("Environment import failed: errno = %d\n", errno);
 
        gd->flags |= GD_FLG_ENV_READY;
@@ -220,7 +222,7 @@ int env_import(const char *buf, int check)
        }
 
        if (himport_r(&env_htab, (char *)ep->data, ENV_SIZE, '\0', 0,
-                       0, NULL)) {
+                       0, NULL, 0 /* do_apply */)) {
                gd->flags |= GD_FLG_ENV_READY;
                return 1;
        }

diff --git a/include/environment.h b/include/environment.h
index ae3f7b6aedf7a74a82f6429ad58b733f4e027347..90fb1302b1e6ffb077f8d1941b4f841804b6df23 100644 (file)
--- a/include/environment.h
+++ b/include/environment.h
@@ -184,6 +184,15 @@ void set_default_env(const char *s);
 /* Import from binary representation into hash table */
 int env_import(const char *buf, int check);
 
+/*
+ * Check if variable "name" can be changed from oldval to newval,
+ * and if so, apply the changes (e.g. baudrate).
+ * When (flag & H_FORCE) is set, it does not print out any error
+ * message and forces overwriting of write-once variables.
+ */
+int env_check_apply(const char *name, const char *oldval,
+                       const char *newval, int flag);
+
 #endif /* DO_DEPS_ONLY */
 
 #endif /* _ENVIRONMENT_H_ */

diff --git a/include/search.h b/include/search.h
index 94d75fc65c26fa4022a87b2631073a2c2cc844b4..721c8acda0675b49ee2c0e405426fda2fc8a07f5 100644 (file)
--- a/include/search.h
+++ b/include/search.h
@@ -57,6 +57,16 @@ struct hsearch_data {
        struct _ENTRY *table;
        unsigned int size;
        unsigned int filled;
+/*
+ * Callback function which will check whether the given change for variable
+ * "name" from "oldval" to "newval" may be applied or not, and possibly apply
+ * such change.
+ * When (flag & H_FORCE) is set, it shall not print out any error message and
+ * shall force overwriting of write-once variables.
+.* Must return 0 for approval, 1 for denial.
+ */
+       int (*apply)(const char *name, const char *oldval,
+                       const char *newval, int flag);
 };
 
 /* Create a new hashing table which will at most contain NEL elements.  */
@@ -97,10 +107,12 @@ extern ssize_t hexport_r(struct hsearch_data *__htab,
 /*
  * nvars: length of vars array
  * vars: array of strings (variable names) to import (nvars == 0 means all)
+ * do_apply: whether to call callback function to check the new argument,
+ * and possibly apply changes (false means accept everything)
  */
 extern int himport_r(struct hsearch_data *__htab,
                     const char *__env, size_t __size, const char __sep,
-                    int __flag, int nvars, char * const vars[]);
+                    int __flag, int nvars, char * const vars[], int do_apply);
 
 /* Flags for himport_r() */
 #define        H_NOCLEAR       (1 << 0) /* do not clear hash table before importing */

diff --git a/lib/hashtable.c b/lib/hashtable.c
index 0610e867d08b5f9f8b55e2352068c2b8ff86c5a0..6cfba5668265e302fc950754f7b7d05fce28c768 100644 (file)
--- a/lib/hashtable.c
+++ b/lib/hashtable.c
@@ -658,7 +658,7 @@ static int is_var_in_set(const char *name, int nvars, char * const vars[])
 
 int himport_r(struct hsearch_data *htab,
                const char *env, size_t size, const char sep, int flag,
-               int nvars, char * const vars[])
+               int nvars, char * const vars[], int do_apply)
 {
        char *data, *sp, *dp, *name, *value;
 
@@ -772,6 +772,24 @@ int himport_r(struct hsearch_data *htab,
                e.key = name;
                e.data = value;
 
+               /* if there is an apply function, check what it has to say */
+               if (do_apply && htab->apply != NULL) {
+                       debug("searching before calling cb function"
+                               " for  %s\n", name);
+                       /*
+                        * Search for variable in existing env, so to pass
+                        * its previous value to the apply callback
+                        */
+                       hsearch_r(e, FIND, &rv, htab);
+                       debug("previous value was %s\n", rv ? rv->data : "");
+                       if (htab->apply(name, rv ? rv->data : NULL,
+                               value, flag)) {
+                               debug("callback function refused to set"
+                                       " variable %s, skipping it!\n", name);
+                               continue;
+                       }
+               }
+
                hsearch_r(e, ENTER, &rv, htab);
                if (rv == NULL) {
                        printf("himport_r: can't insert \"%s=%s\" into hash table\n",