Make unset strings in kim_options and kim_selection_hints

be empty strings rather than NULL.  This simplifies the
stream code (and makes it easier to read and debug).
In order to prevent copying tons of NUL bytes around,
special case kim_string functions to use a special 
constant kim_empty_string.

ticket: 6055

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@20804 dc483132-0cff-0310-8789-dd5450dbe970

5 files changed, 90 insertions, 113 deletions

diff --git a/src/kim/lib/kim_library_private.h b/src/kim/lib/kim_library_private.h
index 83c06d791..160fba3a5 100644
--- a/src/kim/lib/kim_library_private.h
+++ b/src/kim/lib/kim_library_private.h
@@ -28,6 +28,7 @@
 #define KIM_LIBRARY_PRIVATE_H
 
 #include <kim/kim.h>
+#include <kim/kim_library.h>
 
 kim_error kim_library_init (void);
 
diff --git a/src/kim/lib/kim_options.c b/src/kim/lib/kim_options.c
index 8cefa2ecf..06c25ae88 100644
--- a/src/kim/lib/kim_options.c
+++ b/src/kim/lib/kim_options.c
@@ -49,7 +49,7 @@ kim_default_renewal_lifetime,
 kim_default_forwardable,
 kim_default_proxiable,
 kim_default_addressless,
-NULL,
+kim_empty_string,
 NULL,
 NULL };
 
@@ -384,17 +384,16 @@ kim_error kim_options_set_service_name (kim_options  io_options,
                                         kim_string   in_service_name)
 {
     kim_error err = KIM_NO_ERROR;
-    kim_string service_name = NULL;
     
     if (!err && !io_options) { err = check_error (KIM_NULL_PARAMETER_ERR); }
     
-    if (!err && in_service_name) {
-        err = kim_string_copy (&service_name, in_service_name);
-    }
-    
     if (!err) {
 	kim_string_free (&io_options->service_name);
-	io_options->service_name = service_name;
+        if (in_service_name) {
+            err = kim_string_copy (&io_options->service_name, in_service_name);
+        } else {
+            io_options->service_name = kim_empty_string;
+        }
     }
     
     return check_error (err);
@@ -411,7 +410,8 @@ kim_error kim_options_get_service_name (kim_options  in_options,
     if (!err && !out_service_name) { err = check_error (KIM_NULL_PARAMETER_ERR); }
     
     if (!err) {
-        if (in_options->service_name) {
+        if (in_options->service_name && 
+            in_options->service_name != kim_empty_string) {
             err = kim_string_copy (out_service_name, in_options->service_name);
         } else {
             *out_service_name = NULL;
@@ -428,7 +428,11 @@ kim_error kim_options_get_service_name (kim_options  in_options,
 char *kim_options_service_name (kim_options in_options)
 {
     if (in_options) {
-        return (char *) in_options->service_name;
+        if (in_options->service_name == kim_empty_string) {
+            return NULL;
+        } else {
+            return (char *) in_options->service_name;
+        }
     }
     check_error (KIM_NULL_PARAMETER_ERR);  /* log bad options input */
     return NULL;
@@ -560,9 +564,7 @@ kim_error kim_options_write_to_stream (kim_options   in_options,
     }
     
     if (!err) {
-        kim_string service_name = (options->service_name ?
-                                   options->service_name : "");
-        err = k5_ipc_stream_write_string (io_stream, service_name);
+        err = k5_ipc_stream_write_string (io_stream,  options->service_name);
     }
     
     if (options != in_options) { kim_options_free (&options); }
@@ -618,7 +620,7 @@ kim_error kim_options_read_from_stream (kim_options    io_options,
             if (service_name[0]) {
                 err = kim_string_copy (&io_options->service_name, service_name);
             } else {
-                io_options->service_name = NULL;
+                io_options->service_name = kim_empty_string;
             }
         }
         
diff --git a/src/kim/lib/kim_selection_hints.c b/src/kim/lib/kim_selection_hints.c
index 795435359..c9d5df16d 100644
--- a/src/kim/lib/kim_selection_hints.c
+++ b/src/kim/lib/kim_selection_hints.c
@@ -42,16 +42,16 @@ struct kim_selection_hints_opaque {
 
 struct kim_selection_hints_opaque kim_selection_hints_initializer = { 
     NULL,
-    NULL,
+    kim_empty_string,
     KIM_OPTIONS_DEFAULT,
     TRUE,
     TRUE,
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    NULL
+    kim_empty_string,
+    kim_empty_string,
+    kim_empty_string,
+    kim_empty_string,
+    kim_empty_string,
+    kim_empty_string
 };
 
 /* ------------------------------------------------------------------------ */
@@ -196,26 +196,32 @@ kim_error kim_selection_hints_set_hint (kim_selection_hints io_selection_hints,
     
     if (!err) {
         if (!strcmp (in_hint_key, kim_hint_key_client_realm)) {
+            kim_string_free (&io_selection_hints->client_realm);
             err = kim_string_copy (&io_selection_hints->client_realm, 
                                    in_hint_string);
             
         } else if (!strcmp (in_hint_key, kim_hint_key_user)) {
+            kim_string_free (&io_selection_hints->user);
             err = kim_string_copy (&io_selection_hints->user, 
                                    in_hint_string);
             
         } else if (!strcmp (in_hint_key, kim_hint_key_service_realm)) {
+            kim_string_free (&io_selection_hints->service_realm);
             err = kim_string_copy (&io_selection_hints->service_realm, 
                                    in_hint_string);
             
         } else if (!strcmp (in_hint_key, kim_hint_key_service)) {
+            kim_string_free (&io_selection_hints->service);
             err = kim_string_copy (&io_selection_hints->service, 
                                    in_hint_string);
             
         } else if (!strcmp (in_hint_key, kim_hint_key_server)) {
+            kim_string_free (&io_selection_hints->server);
             err = kim_string_copy (&io_selection_hints->server, 
                                    in_hint_string);
             
         } else if (!strcmp (in_hint_key, kim_hint_key_service_identity)) {
+            kim_string_free (&io_selection_hints->service_identity);
             err = kim_string_copy (&io_selection_hints->service_identity, 
                                    in_hint_string);
             
@@ -235,6 +241,7 @@ kim_error kim_selection_hints_get_hint (kim_selection_hints  in_selection_hints,
                                         kim_string          *out_hint_string)
 {
     kim_error err = KIM_NO_ERROR;
+    kim_string hint = NULL;
     
     if (!err && !in_selection_hints) { err = check_error (KIM_NULL_PARAMETER_ERR); }
     if (!err && !in_hint_key       ) { err = check_error (KIM_NULL_PARAMETER_ERR); }
@@ -242,28 +249,22 @@ kim_error kim_selection_hints_get_hint (kim_selection_hints  in_selection_hints,
     
     if (!err) {
         if (!strcmp (in_hint_key, kim_hint_key_client_realm)) {
-            err = kim_string_copy (out_hint_string, 
-                                   in_selection_hints->client_realm);
+            hint = in_selection_hints->client_realm;
             
         } else if (!strcmp (in_hint_key, kim_hint_key_user)) {
-            err = kim_string_copy (out_hint_string, 
-                                   in_selection_hints->user);
+            hint = in_selection_hints->user;
             
         } else if (!strcmp (in_hint_key, kim_hint_key_service_realm)) {
-            err = kim_string_copy (out_hint_string, 
-                                   in_selection_hints->service_realm);
+            hint = in_selection_hints->service_realm;
             
         } else if (!strcmp (in_hint_key, kim_hint_key_service)) {
-            err = kim_string_copy (out_hint_string, 
-                                   in_selection_hints->service);
-            
+            hint = in_selection_hints->service;
+           
         } else if (!strcmp (in_hint_key, kim_hint_key_server)) {
-            err = kim_string_copy (out_hint_string, 
-                                   in_selection_hints->server);
+            hint = in_selection_hints->server;
             
         } else if (!strcmp (in_hint_key, kim_hint_key_service_identity)) {
-            err = kim_string_copy (out_hint_string, 
-                                   in_selection_hints->service_identity);
+            hint = in_selection_hints->service_identity;
             
         } else {
             err = kim_error_set_message_for_code (KIM_UNSUPPORTED_HINT_ERR,
@@ -271,6 +272,14 @@ kim_error kim_selection_hints_get_hint (kim_selection_hints  in_selection_hints,
         }
     }
     
+    if (!err) {
+        if (hint && hint != kim_empty_string) {
+            err = kim_string_copy (out_hint_string, hint);
+        } else {
+            *out_hint_string = NULL;
+        }
+    }
+    
     return check_error (err);
 }
 
@@ -302,7 +311,8 @@ kim_error kim_selection_hints_get_explanation (kim_selection_hints  in_selection
     if (!err && !out_explanation   ) { err = check_error (KIM_NULL_PARAMETER_ERR); }
     
     if (!err) {
-        if (in_selection_hints->explanation) {
+        if (in_selection_hints->explanation && 
+            in_selection_hints->explanation != kim_empty_string) {
             err = kim_string_copy (out_explanation, in_selection_hints->explanation);
         } else {
             *out_explanation = NULL;
@@ -576,49 +586,43 @@ kim_error kim_selection_hints_write_to_stream (kim_selection_hints in_selection_
     }
     
     if (!err) {
-        kim_string explanation = (in_selection_hints->explanation ?
-                                  in_selection_hints->explanation : "");
-        err = k5_ipc_stream_write_string (io_stream, explanation);
+        err = k5_ipc_stream_write_string (io_stream, 
+                                          in_selection_hints->explanation);
     }
     
     if (!err) {
-        err = kim_options_write_to_stream (in_selection_hints->options, io_stream);
+        err = kim_options_write_to_stream (in_selection_hints->options, 
+                                           io_stream);
     }
     
     if (!err) {
-        kim_string service_identity = (in_selection_hints->service_identity ?
-                                       in_selection_hints->service_identity : "");
-        err = k5_ipc_stream_write_string (io_stream, service_identity);
+        err = k5_ipc_stream_write_string (io_stream, 
+                                          in_selection_hints->service_identity);
     }
     
     if (!err) {
-        kim_string client_realm = (in_selection_hints->client_realm ?
-                                   in_selection_hints->client_realm : "");
-        err = k5_ipc_stream_write_string (io_stream, client_realm);
+        err = k5_ipc_stream_write_string (io_stream, 
+                                          in_selection_hints->client_realm);
     }
     
     if (!err) {
-        kim_string user = (in_selection_hints->user ?
-                           in_selection_hints->user : "");
-        err = k5_ipc_stream_write_string (io_stream, user);
+        err = k5_ipc_stream_write_string (io_stream, 
+                                          in_selection_hints->user);
     }
     
     if (!err) {
-        kim_string service_realm = (in_selection_hints->service_realm ?
-                                    in_selection_hints->service_realm : "");
-        err = k5_ipc_stream_write_string (io_stream, service_realm);
+        err = k5_ipc_stream_write_string (io_stream, 
+                                          in_selection_hints->service_realm);
     }
     
     if (!err) {
-        kim_string service = (in_selection_hints->service ?
-                              in_selection_hints->service : "");
-        err = k5_ipc_stream_write_string (io_stream, service);
+       err = k5_ipc_stream_write_string (io_stream, 
+                                         in_selection_hints->service);
     }
     
     if (!err) {
-        kim_string server = (in_selection_hints->server ?
-                             in_selection_hints->server : "");
-        err = k5_ipc_stream_write_string (io_stream, server);
+        err = k5_ipc_stream_write_string (io_stream, 
+                                          in_selection_hints->server);
     }
     
     return check_error (err);    
@@ -651,13 +655,8 @@ kim_error kim_selection_hints_read_from_stream (kim_selection_hints io_selection
         err = k5_ipc_stream_read_string (io_stream, &explanation);
         
         if (!err) {
-            if (!explanation[0]) {
-                err = kim_string_copy (&io_selection_hints->explanation, 
-                                       explanation);
-            } else {
-                err = kim_selection_hints_set_explanation (io_selection_hints, 
-                                                           NULL);
-            }
+            err = kim_string_copy (&io_selection_hints->explanation, 
+                                   explanation);
         }
         
         k5_ipc_stream_free_string (explanation);
@@ -678,14 +677,8 @@ kim_error kim_selection_hints_read_from_stream (kim_selection_hints io_selection
         err = k5_ipc_stream_read_string (io_stream, &service_identity);
         
         if (!err) {
-            if (!service_identity[0]) {
-                err = kim_string_copy (&io_selection_hints->service_identity, 
-                                       service_identity);
-            } else {
-                err = kim_selection_hints_set_hint (io_selection_hints, 
-                                                    kim_hint_key_service_identity,
-                                                    NULL);
-            }
+            err = kim_string_copy (&io_selection_hints->service_identity, 
+                                   service_identity);
         }
         
         k5_ipc_stream_free_string (service_identity);
@@ -696,14 +689,8 @@ kim_error kim_selection_hints_read_from_stream (kim_selection_hints io_selection
         err = k5_ipc_stream_read_string (io_stream, &client_realm);
         
         if (!err) {
-            if (!client_realm[0]) {
-                err = kim_string_copy (&io_selection_hints->client_realm, 
-                                       client_realm);
-            } else {
-                err = kim_selection_hints_set_hint (io_selection_hints, 
-                                                    kim_hint_key_client_realm,
-                                                    NULL);
-            }
+            err = kim_string_copy (&io_selection_hints->client_realm, 
+                                   client_realm);
         }
         
         k5_ipc_stream_free_string (client_realm);
@@ -714,13 +701,7 @@ kim_error kim_selection_hints_read_from_stream (kim_selection_hints io_selection
         err = k5_ipc_stream_read_string (io_stream, &user);
         
         if (!err) {
-            if (!user[0]) {
-                err = kim_string_copy (&io_selection_hints->user, user);
-            } else {
-                err = kim_selection_hints_set_hint (io_selection_hints,
-                                                    kim_hint_key_user,
-                                                    NULL);
-            }
+            err = kim_string_copy (&io_selection_hints->user, user);
         }
         
         k5_ipc_stream_free_string (user);
@@ -731,14 +712,8 @@ kim_error kim_selection_hints_read_from_stream (kim_selection_hints io_selection
         err = k5_ipc_stream_read_string (io_stream, &service_realm);
         
         if (!err) {
-            if (!service_realm[0]) {
-                err = kim_string_copy (&io_selection_hints->service_realm, 
-                                       service_realm);
-            } else {
-                err = kim_selection_hints_set_hint (io_selection_hints,
-                                                    kim_hint_key_service_realm,
-                                                    NULL);
-            }
+            err = kim_string_copy (&io_selection_hints->service_realm, 
+                                   service_realm);
         }
         
         k5_ipc_stream_free_string (service_realm);
@@ -749,13 +724,7 @@ kim_error kim_selection_hints_read_from_stream (kim_selection_hints io_selection
         err = k5_ipc_stream_read_string (io_stream, &service);
         
         if (!err) {
-            if (!service[0]) {
-                err = kim_string_copy (&io_selection_hints->service, service);
-            } else {
-                err = kim_selection_hints_set_hint (io_selection_hints,
-                                                    kim_hint_key_service,
-                                                    NULL);
-            }
+            err = kim_string_copy (&io_selection_hints->service, service);
         }
         
         k5_ipc_stream_free_string (service);
@@ -766,16 +735,10 @@ kim_error kim_selection_hints_read_from_stream (kim_selection_hints io_selection
         err = k5_ipc_stream_read_string (io_stream, &server);
         
         if (!err) {
-            if (!server[0]) {
-                err = kim_string_copy (&io_selection_hints->server, server);
-            } else {
-                err = kim_selection_hints_set_hint (io_selection_hints,
-                                                    kim_hint_key_server,
-                                                    NULL);
-            }
+            err = kim_string_copy (&io_selection_hints->server, server);
         }
         
-         k5_ipc_stream_free_string (server);
+        k5_ipc_stream_free_string (server);
     }
     
     return check_error (err);    
diff --git a/src/kim/lib/kim_string.c b/src/kim/lib/kim_string.c
index b84a12c8e..8b9af7010 100644
--- a/src/kim/lib/kim_string.c
+++ b/src/kim/lib/kim_string.c
@@ -26,6 +26,8 @@
 
 #include "kim_private.h"
 
+const char kim_empty_string[1] = "";
+
 /* ------------------------------------------------------------------------ */
 
 kim_error kim_string_create_from_format (kim_string *out_string, 
@@ -136,12 +138,19 @@ kim_error kim_string_copy (kim_string *out_string,
     if (!err && !in_string ) { err = check_error (KIM_NULL_PARAMETER_ERR); }
     
     if (!err) {
-        string = calloc (strlen (in_string) + 1, sizeof (char *));
-        if (!string) { err = check_error (KIM_OUT_OF_MEMORY_ERR); }
+        if (in_string[0]) {
+            string = calloc (strlen (in_string) + 1, sizeof (char *));
+            if (!string) { err = check_error (KIM_OUT_OF_MEMORY_ERR); }
+            
+            if (!err) {
+                strncpy ((char *) string, in_string, strlen (in_string) + 1);
+            }
+        } else {
+            string = kim_empty_string;
+        }
     }
     
     if (!err) {
-        strncpy ((char *) string, in_string, strlen (in_string) + 1);
         *out_string = string;
         string = NULL;
     }
@@ -167,7 +176,7 @@ kim_error kim_string_compare (kim_string      in_string,
 
 void kim_string_free (kim_string *io_string)
 {
-    if (io_string && *io_string) { 
+    if (io_string && *io_string && *io_string != kim_empty_string) { 
         free ((char *) *io_string);
         *io_string = NULL;
     }
diff --git a/src/kim/lib/kim_string_private.h b/src/kim/lib/kim_string_private.h
index 48d7bae13..6f4e0ad36 100644
--- a/src/kim/lib/kim_string_private.h
+++ b/src/kim/lib/kim_string_private.h
@@ -29,6 +29,8 @@
 
 #include <kim/kim.h>
 
+extern const char kim_empty_string[1];
+
 /* ------------------------------------------------------------------------ */
 
 static inline kim_count kim_string_buflen (kim_string in_string)