libihash: generalize the interface to support non-integer keys

* libihash/ihash.c (hash, compare): New functions that are used
throughout libihash to hash and compare keys.
(hurd_ihash_set_gki): New function.
* libihash/ihash.h (hurd_ihash_fct_hash_t): New type for hash functions.
(hurd_ihash_fct_cmp_t): New type for comparison functions.
(struct hurd_ihash): New fields for hash and comparison functions.
(HURD_IHASH_INITIALIZER_GKI): New static initializer.
(hurd_ihash_set_gki): New prototype.

1 files changed, 35 insertions, 1 deletions

diff --git a/libihash/ihash.h b/libihash/ihash.h
index fdfc3673..28fefe80 100644
--- a/libihash/ihash.h
+++ b/libihash/ihash.h
@@ -1,5 +1,5 @@
 /* ihash.h - Integer keyed hash table interface.
-   Copyright (C) 1995, 2003, 2004 Free Software Foundation, Inc.
+   Copyright (C) 1995, 2003, 2004, 2014, 2015 Free Software Foundation, Inc.
    Written by Miles Bader <miles@gnu.org>.
    Revised by Marcus Brinkmann <marcus@gnu.org>.
 
@@ -57,6 +57,20 @@ typedef uintptr_t hurd_ihash_key_t;
 typedef hurd_ihash_value_t *hurd_ihash_locp_t;
 
 
+/* We support non-integer keys using the generalized key interface.
+
+   To use it, supply a pair of functions matching the following
+   specification, and use pointers to the key instead of the key
+   itself in all calls to libihash.  */
+
+/* The type of a function computing a hash for the given key.  */
+typedef hurd_ihash_key_t (*hurd_ihash_fct_hash_t) (const void *);
+
+/* The type of a function comparing two given keys.  Return true if
+   both keys are equal.  */
+typedef int (*hurd_ihash_fct_cmp_t) (const void *, const void *);
+
+
 /* The type of the cleanup function, which is called for every value
    removed from the hash table.  */
 typedef void (*hurd_ihash_cleanup_t) (hurd_ihash_value_t value, void *arg);
@@ -95,6 +109,10 @@ struct hurd_ihash
      second argument.  This does not happen if CLEANUP is NULL.  */
   hurd_ihash_cleanup_t cleanup;
   void *cleanup_data;
+
+  /* User-supplied functions for the generalized key interface.  */
+  hurd_ihash_fct_hash_t fct_hash;
+  hurd_ihash_fct_cmp_t fct_cmp;
 };
 typedef struct hurd_ihash *hurd_ihash_t;
 
@@ -118,6 +136,16 @@ typedef struct hurd_ihash *hurd_ihash_t;
     .max_load = HURD_IHASH_MAX_LOAD_DEFAULT,				\
     .locp_offset = (locp_offs)}
 
+#define HURD_IHASH_INITIALIZER_GKI(locp_offs, f_clean, f_clean_data,	\
+				   f_hash, f_compare)			\
+  { .nr_items = 0, .size = 0,						\
+    .cleanup = (f_clean),						\
+    .cleanup_data = (f_clean_data),					\
+    .max_load = HURD_IHASH_MAX_LOAD_DEFAULT,				\
+    .locp_offset = (locp_offs),						\
+    .fct_hash = (f_hash),						\
+    .fct_cmp = (f_compare)}						\
+
 /* Initialize the hash table at address HT.  If LOCP_OFFSET is not
    HURD_IHASH_NO_LOCP, then this is an offset (in bytes) from the
    address of a hash value where a location pointer can be found.  The
@@ -152,6 +180,12 @@ void hurd_ihash_free (hurd_ihash_t ht);
 void hurd_ihash_set_cleanup (hurd_ihash_t ht, hurd_ihash_cleanup_t cleanup,
 			     void *cleanup_data);
 
+/* Use the generalized key interface.  Must be called before any item
+   is inserted into the table.	*/
+void hurd_ihash_set_gki (hurd_ihash_t ht,
+			 hurd_ihash_fct_hash_t fct_hash,
+			 hurd_ihash_fct_cmp_t fct_cmp);
+
 /* Set the maximum load factor in binary percent to MAX_LOAD, which
    should be between 64 and 128.  The default is
    HURD_IHASH_MAX_LOAD_DEFAULT.  New elements are only added to the