Avoid eventual alignment problems

* src/gdbm.magic: Handle extended GDBM format.
* src/gdbmdefs.h (gdbm_file_standard_header)
(gdbm_file_extended_header): New data types.
* src/gdbmopen.c (gdbm_header_avail): Use casts to
gdbm_file_*_header to obtain data offsets.
* src/gdbmtool.c (print_header_handler): Improve formatting.

5 files changed, 75 insertions, 30 deletions

diff --git a/src/gdbm.h.in b/src/gdbm.h.in
index c4c8d88..ac71810 100644
--- a/src/gdbm.h.in
+++ b/src/gdbm.h.in
@@ -56,7 +56,7 @@ extern "C" {
 # define GDBM_CLOERROR  0x0400  /* Only for gdbm_fd_open: close fd on error. */
 # define GDBM_XVERIFY   0x0800  /* Additional consistency checks. */
 # define GDBM_PREREAD   0x1000  /* Enable pre-fault reading of mmapped regions. */
-# define GDBM_NUMSYNC   0x2000
+# define GDBM_NUMSYNC   0x2000  /* Enable the numsync extension */
 
   
 /* Parameters to gdbm_store for simple insertion or replacement in the
diff --git a/src/gdbm.magic b/src/gdbm.magic
index df3dc91..f685481 100644
--- a/src/gdbm.magic
+++ b/src/gdbm.magic
@@ -15,7 +15,7 @@
 # along with GDBM. If not, see <http://www.gnu.org/licenses/>. 
 
 0	lelong	0x13579acf	GNU DBM 64-bit, little endian
-!:mime	application/octet-stream
+!:mime	application/x-gdbm
 >4	lelong	x		\b; block size=%d
 >8	lequad	x		\b; dir offset=%lld
 >16	lelong	x		\b, size=%d
@@ -24,7 +24,7 @@
 >28	lelong	x		\b, elts=%d
 
 0	belong	0x13579acf	GNU DBM 64-bit, big endian
-!:mime	application/octet-stream
+!:mime	application/x-gdbm
 >4	belong	x		\b; block size=%d
 >8	bequad	x		\b; dir offset=%lld
 >16	belong	x		\b, size=%d
@@ -33,16 +33,16 @@
 >28	belong	x		\b, elts=%d
 
 0	lelong	0x13579acd	GNU DBM 32-bit, little endian
-!:mime	application/octet-stream
+!:mime	application/x-gdbm
 
 0	belong	0x13579acd	GNU DBM 32-bit, big endian
-!:mime	application/octet-stream
+!:mime	application/x-gdbm
 
 0	lelong	0x13579ace	GNU DBM old format, little endian
-!:mime	application/octet-stream
+!:mime	application/x-gdbm
 
 0	belong	0x13579ace	GNU DBM old format, big endian
-!:mime	application/octet-stream
+!:mime	application/x-gdbm
 
 0	string	\!\r\n
 >3	string	\!\040GDBM\040FLAT\040FILE\040DUMP\040--\040THIS\040IS\040NOT\040A\040TEXT\040FILE\r\n	GDBM flat dump file
@@ -58,3 +58,31 @@
 >>&0	string	>\0		\b, for file %s
 >0	string	#\040GDBM\040dump\040file\040created\040by\040GDBM\040version\040
 >>&0	regex	([0-9.]+)\.		\b, created by GDBM version %s
+
+0	lelong	0x13579ad1	GNU DBM extended 64-bit, little endian
+!:mime	application/x-gdbm
+>4	lelong	x		\b; block size=%d
+>8	lequad	x		\b; dir offset=%lld
+>16	lelong	x		\b, size=%d
+>20	lelong	x		\b, bits=%d
+>24	lelong	x		\b; bucket size=%d
+>28	lelong	x		\b, elts=%d
+>40     lelong  x               \b, version=%d
+>44     lelong  x               \b, numsync=%u
+
+0	belong	0x13579ad1	GNU DBM extended 64-bit, big endian
+!:mime	application/x-gdbm
+>4	belong	x		\b; block size=%d
+>8	bequad	x		\b; dir offset=%lld
+>16	belong	x		\b, size=%d
+>20	belong	x		\b, bits=%d
+>24	belong	x		\b; bucket size=%d
+>28	belong	x		\b, elts=%d
+>40     belong  x               \b, version=%d
+>44     belong  x               \b, numsync=%u
+
+0	lelong	0x13579ad0	GNU DBM extended 32-bit, little endian
+!:mime	application/x-gdbm
+
+0	belong	0x13579ad0	GNU DBM extended 32-bit, big endian
+!:mime	application/x-gdbm
diff --git a/src/gdbmdefs.h b/src/gdbmdefs.h
index a9c0c7f..ca88902 100644
--- a/src/gdbmdefs.h
+++ b/src/gdbmdefs.h
@@ -84,13 +84,6 @@ typedef struct
 
 typedef struct
 {
-  int version;
-  unsigned numsync;    /* Number of synchronizations */
-  int pad[6];
-} gdbm_ext_header;
-
-typedef struct
-{
   int   header_magic;  /* Version of file. */
   int   block_size;    /* The optimal i/o blocksize from stat. */
   off_t dir;           /* File address of hash directory table. */
@@ -99,13 +92,30 @@ typedef struct
   int   bucket_size;   /* Size in bytes of a hash bucket struct. */
   int   bucket_elems;  /* Number of elements in a hash bucket. */
   off_t next_block;    /* The next unallocated block address. */
-  /* In traditional GDBM database file, this header is followed by
-     avail_block with av_table occupying the rest of the disk block.
-     
-     In extended GDBM database file, it is followed by a gdbm_ext_header,
-     and then by avail_block. */
 } gdbm_file_header;
 
+/* The extension header keeps additional information. */
+typedef struct
+{
+  int version;         /* Version number (currently 0). */
+  unsigned numsync;    /* Number of synchronizations. */
+  int pad[6];          /* Reserve space for further use. */
+} gdbm_ext_header;
+
+/* Standard GDBM file header. */
+typedef struct
+{
+  gdbm_file_header hdr;
+  avail_block avail;
+} gdbm_file_standard_header;
+
+/* Extended GDBM file header. */
+typedef struct
+{
+  gdbm_file_header hdr;
+  gdbm_ext_header ext;
+  avail_block avail;
+} gdbm_file_extended_header;
 
 /* The dbm hash bucket element contains the full 31 bit hash value, the
    "pointer" to the key and data (stored together) with their sizes.  It also
diff --git a/src/gdbmopen.c b/src/gdbmopen.c
index 14685bc..360d113 100644
--- a/src/gdbmopen.c
+++ b/src/gdbmopen.c
@@ -57,15 +57,17 @@ gdbm_header_avail (gdbm_file_header const *hdr,
     { 
     case GDBM_OMAGIC:
     case GDBM_MAGIC: 
-      *avail_ptr = (avail_block *) (hdr + 1);
-      *avail_size = (hdr->block_size - sizeof (gdbm_file_header));
       *exhdr = NULL;
+      *avail_ptr = &((gdbm_file_standard_header*)hdr)->avail;
+      *avail_size = (hdr->block_size -
+		     offsetof (gdbm_file_standard_header, avail));
       break;
       
     case GDBM_NUMSYNC_MAGIC:
-      *exhdr = (gdbm_ext_header *) (hdr + 1);
-      *avail_ptr = (avail_block *) (*exhdr + 1);
-      *avail_size = (hdr->block_size - (sizeof (gdbm_file_header) + sizeof (gdbm_ext_header)));
+      *exhdr = &((gdbm_file_extended_header*)hdr)->ext;
+      *avail_ptr = &((gdbm_file_extended_header*)hdr)->avail;
+      *avail_size = (hdr->block_size -
+		     offsetof (gdbm_file_extended_header, avail));
       break;
     }
 }
@@ -587,7 +589,9 @@ gdbm_fd_open (int fd, const char *file_name, int block_size,
 	}
       gdbm_header_avail (dbf->header, &dbf->avail, &dbf->avail_size, &dbf->xheader);
 
-      if (((dbf->header->block_size - (((char*)dbf->avail-(char*)dbf->header) + sizeof (avail_block))) / sizeof (avail_elem) + 1) != dbf->avail->size)
+      if (((dbf->header->block_size -
+	    (((char*)dbf->avail - (char*)dbf->header) +
+	     sizeof (avail_block))) / sizeof (avail_elem) + 1) != dbf->avail->size)
 	{
 	  if (!(flags & GDBM_CLOERROR))
 	    dbf->desc = -1;
diff --git a/src/gdbmtool.c b/src/gdbmtool.c
index 10a5c03..c734ad3 100644
--- a/src/gdbmtool.c
+++ b/src/gdbmtool.c
@@ -790,15 +790,15 @@ print_header_handler (struct handler_param *param)
   switch (gdbm_file->header->header_magic)
     {
     case GDBM_OMAGIC:
-      type = "Old GDBM";
+      type = "GDBM (old)";
       break;
 
     case GDBM_MAGIC:
-      type = "GDBM";
+      type = "GDBM (standard)";
       break;
 
     case GDBM_NUMSYNC_MAGIC:
-      type = "GDBM numsync";
+      type = "GDBM (numsync)";
       break;
 
     default:
@@ -823,9 +823,12 @@ print_header_handler (struct handler_param *param)
   fprintf (fp, _("  avail nx blk = %lu\n"),
 	   (unsigned long) gdbm_file->avail->next_block);
 
-  // FIXME
   if (gdbm_file->xheader)
-    fprintf (fp, _("       numsync = %u\n"), gdbm_file->xheader->numsync);  
+    {
+      fprintf (fp, _("\nExtended Header: \n\n"));
+      fprintf (fp, _("       version = %d\n"), gdbm_file->xheader->version);  
+      fprintf (fp, _("       numsync = %u\n"), gdbm_file->xheader->numsync);
+    }
 }
 
 static void