env: add env_delete()

Change-Id: I3a94942b1670e641c8558c64dabca0155e53e2ea
Signed-off-by: Joseph Chen <chenjh@rock-chips.com>

cmd/nvedit.c

@@ -533,6 +533,37 @@ int env_exist(const char *varname, const char *varvalue)
 	return ret;
 }
 
+int env_delete(const char *varname, const char *varvalue)
+{
+	const char *str;
+	char *value, *start;
+
+	/* before import into hashtable */
+	if (!(gd->flags & GD_FLG_ENV_READY) || !varname)
+		return 1;
+
+	value = env_get(varname);
+	if (value) {
+		start = strstr(value, varvalue);
+		if (start) {
+			/* varvalue is not the last property */
+			str = strstr(start, " ");
+			if (str) {
+				/* Terminate, so cmdline can be dest for strcat() */
+				*start = '\0';
+				/* +1 to skip white space */
+				strcat((char *)value, (str + 1));
+			/* varvalue is the last property */
+			} else {
+				/* skip white space */
+				*(start - 1) = '\0';
+			}
+		}
+	}
+
+	return 0;
+}
+
 /**
  * Set an environment variable to an integer value
  *

include/common.h

@@ -349,6 +349,15 @@ int env_update(const char *varname, const char *varvalue);
  */
 int env_exist(const char *varname, const char *varvalue);
 
+/**
+ * env_delete() - delete sub value of an environment variable
+ *
+ * @varname: Variable to look up
+ * @value: Item head of value to delete
+ * @return 0 if ok, 1 on error
+ */
+int env_delete(const char *varname, const char *varvalue);
+
 /**
  * env_set_ulong() - set an environment variable to an integer
  *