a fix (bug #4214: Table corruption with myisampack and large BLOB objects).

myisam/mi_check.c:
  a fix (bug #4214: Table corruption with myisampack and large BLOB objects).
  - pass version to the save_pack_length().
myisam/mi_packrec.c:
  a fix (bug #4214: Table corruption with myisampack and large BLOB objects).
  - code cleanup: read_pack_length() and calc_pack_length() introduced, 
                  save_pack_length() modified: now the behavior depends on packing version
  - save packing version in the share->pack.version
  - pass it to the read_pack_length()
myisam/mi_static.c:
  a fix (bug #4214: Table corruption with myisampack and large BLOB objects).
  - packing version set to 2
myisam/myisamdef.h:
  a fix (bug #4214: Table corruption with myisampack and large BLOB objects).
  - packing version slot introduced (see MI_PACK)
myisam/myisampack.c:
  a fix (bug #4214: Table corruption with myisampack and large BLOB objects).
  - code cleanup
  - pass version to the calc_pack_length() and save_pack_length()

myisam/mi_check.c

@@ -3189,9 +3189,11 @@ int sort_write_record(MI_SORT_PARAM *sort_param)
       break;
     case COMPRESSED_RECORD:
       reclength=info->packed_length;
-      length=save_pack_length(block_buff,reclength);
+      length= save_pack_length((uint) share->pack.version, block_buff,
+                               reclength);
       if (info->s->base.blobs)
-	length+=save_pack_length(block_buff+length,info->blob_length);
+	length+= save_pack_length((uint) share->pack.version,
+	                          block_buff + length, info->blob_length);
       if (my_b_write(&info->rec_cache,block_buff,length) ||
 	  my_b_write(&info->rec_cache,(byte*) sort_param->rec_buff,reclength))
       {

myisam/mi_packrec.c

@@ -149,11 +149,12 @@ my_bool _mi_read_pack_info(MI_INFO *info, pbool fix_keys)
       my_errno=HA_ERR_END_OF_FILE;
     goto err0;
   }
-  if (memcmp((byte*) header,(byte*) myisam_pack_file_magic,4))
+  if (memcmp((byte*) header, (byte*) myisam_pack_file_magic, 3))
   {
     my_errno=HA_ERR_WRONG_IN_RECORD;
     goto err0;
   }
+  share->pack.version= header[3];
   share->pack.header_length=	uint4korr(header+4);
   share->min_pack_length=(uint) uint4korr(header+8);
   share->max_pack_length=(uint) uint4korr(header+12);
@@ -1040,38 +1041,12 @@ uint _mi_pack_get_block_info(MI_INFO *myisam, MI_BLOCK_INFO *info, File file,
       return BLOCK_FATAL_ERROR;
     DBUG_DUMP("header",(byte*) header,ref_length);
   }
-  if (header[0] < 254)
-  {
-    info->rec_len=header[0];
-    head_length=1;
-  }
-  else if (header[0] == 254)
-  {
-    info->rec_len=uint2korr(header+1);
-    head_length=3;
-  }
-  else
-  {
-    info->rec_len=uint3korr(header+1);
-    head_length=4;
-  }
+  head_length= read_pack_length((uint) myisam->s->pack.version, header,
+                                &info->rec_len);
   if (myisam->s->base.blobs)
   {
-    if (header[head_length] < 254)
-    {
-      info->blob_len=header[head_length];
-      head_length++;
-    }
-    else if (header[head_length] == 254)
-    {
-      info->blob_len=uint2korr(header+head_length+1);
-      head_length+=3;
-    }
-    else
-    {
-      info->blob_len=uint3korr(header+head_length+1);
-      head_length+=4;
-    }
+    head_length+= read_pack_length((uint) myisam->s->pack.version,
+                                   header + head_length, &info->blob_len);
     if (!(mi_alloc_rec_buff(myisam,info->rec_len + info->blob_len,
 			    &myisam->rec_buff)))
       return BLOCK_FATAL_ERROR;			/* not enough memory */
@@ -1220,34 +1195,12 @@ void _mi_unmap_file(MI_INFO *info)
 static uchar *_mi_mempack_get_block_info(MI_INFO *myisam,MI_BLOCK_INFO *info,
 					 uchar *header)
 {
-  if (header[0] < 254)
-    info->rec_len= *header++;
-  else if (header[0] == 254)
-  {
-    info->rec_len=uint2korr(header+1);
-    header+=3;
-  }
-  else
-  {
-    info->rec_len=uint3korr(header+1);
-    header+=4;
-  }
+  header+= read_pack_length((uint) myisam->s->pack.version, header,
+                            &info->rec_len);
   if (myisam->s->base.blobs)
   {
-    if (header[0] < 254)
-    {
-      info->blob_len= *header++;
-    }
-    else if (header[0] == 254)
-    {
-      info->blob_len=uint2korr(header+1);
-      header+=3;
-    }
-    else
-    {
-      info->blob_len=uint3korr(header+1);
-      header+=4;
-    }
+    header+= read_pack_length((uint) myisam->s->pack.version, header,
+                              &info->blob_len);
     /* mi_alloc_rec_buff sets my_errno on error */
     if (!(mi_alloc_rec_buff(myisam, info->blob_len,
 			    &myisam->rec_buff)))
@@ -1319,7 +1272,7 @@ static int _mi_read_rnd_mempack_record(MI_INFO *info, byte *buf,
 
 	/* Save length of row */
 
-uint save_pack_length(byte *block_buff,ulong length)
+uint save_pack_length(uint version, byte *block_buff, ulong length)
 {
   if (length < 254)
   {
@@ -1333,6 +1286,46 @@ uint save_pack_length(byte *block_buff,ulong length)
     return 3;
   }
   *(uchar*) block_buff=255;
-  int3store(block_buff+1,(ulong) length);
+  if (version == 1) /* old format */
+  {
+    DBUG_ASSERT(length <= 0xFFFFFF);
+    int3store(block_buff + 1, (ulong) length);
     return 4;
+  }
+  else
+  {
+    int4store(block_buff + 1, (ulong) length);
+    return 5;
+  }
+}
+
+
+uint read_pack_length(uint version, const uchar *buf, ulong *length)
+{
+  if (buf[0] < 254)
+  {
+    *length= buf[0];
+    return 1;
+  }
+  else if (buf[0] == 254)
+  {
+    *length= uint2korr(buf + 1);
+    return 3;
+  }
+  if (version == 1) /* old format */
+  {
+    *length= uint3korr(buf + 1);
+    return 4;
+  }
+  else
+  {
+    *length= uint4korr(buf + 1);
+    return 5;
+  }
+}
+
+
+uint calc_pack_length(uint version, ulong length)
+{
+  return (length < 254) ? 1 : (length < 65536) ? 3 : (version == 1) ? 4 : 5;
 }

myisam/mi_static.c

@@ -27,7 +27,7 @@ LIST	*myisam_open_list=0;
 uchar	NEAR myisam_file_magic[]=
 { (uchar) 254, (uchar) 254,'\007', '\001', };
 uchar	NEAR myisam_pack_file_magic[]=
-{ (uchar) 254, (uchar) 254,'\010', '\001', };
+{ (uchar) 254, (uchar) 254,'\010', '\002', };
 my_string myisam_log_filename=(char*) "myisam.log";
 File	myisam_log_file= -1;
 uint	myisam_quick_table_bits=9;

myisam/myisamdef.h

@@ -149,6 +149,7 @@ typedef struct st_mi_blob		/* Info of record */
 typedef struct st_mi_isam_pack {
   ulong header_length;
   uint ref_length;
+  uchar version;
 } MI_PACK;
 
 
@@ -669,7 +670,9 @@ extern void _myisam_log_record(enum myisam_log_commands command,MI_INFO *info,
 			      int result);
 extern my_bool _mi_memmap_file(MI_INFO *info);
 extern void _mi_unmap_file(MI_INFO *info);
-extern uint save_pack_length(byte *block_buff,ulong length);
+extern uint save_pack_length(uint version, byte *block_buff, ulong length);
+extern uint read_pack_length(uint version, const uchar *buf, ulong *length);
+extern uint calc_pack_length(uint version, ulong length);
 
 uint mi_state_info_write(File file, MI_STATE_INFO *state, uint pWrite);
 char *mi_state_info_read(char *ptr, MI_STATE_INFO *state);

myisam/myisampack.c

@@ -1666,6 +1666,7 @@ static int compress_isam_file(PACK_MRG_INFO *mrg, HUFF_COUNTS *huff_counts)
   HUFF_COUNTS *count,*end_count;
   HUFF_TREE *tree;
   MI_INFO *isam_file=mrg->file[0];
+  uint pack_version= (uint) isam_file->s->pack.version;
   DBUG_ENTER("compress_isam_file");
 
   if (!(record=(byte*) my_alloca(isam_file->s->base.reclength)))
@@ -1693,23 +1694,10 @@ static int compress_isam_file(PACK_MRG_INFO *mrg, HUFF_COUNTS *huff_counts)
 	  huff_counts[i].tree->height+huff_counts[i].length_bits;
   }
   max_calc_length/=8;
-  if (max_calc_length < 254)
-    pack_ref_length=1;
-  else if (max_calc_length <= 65535)
-    pack_ref_length=3;
-  else
-    pack_ref_length=4;
+  pack_ref_length= calc_pack_length(pack_version, max_calc_length);
   record_count=0;
-  pack_blob_length=0;
-  if (isam_file->s->base.blobs)
-  {
-    if (mrg->max_blob_length < 254)
-      pack_blob_length=1;
-    else if (mrg->max_blob_length <= 65535)
-      pack_blob_length=3;
-    else
-      pack_blob_length=4;
-  }
+  pack_blob_length= isam_file->s->base.blobs ?
+                    calc_pack_length(pack_version, mrg->max_blob_length) : 0;
   max_pack_length=pack_ref_length+pack_blob_length;
 
   mrg_reset(mrg);
@@ -1865,9 +1853,10 @@ static int compress_isam_file(PACK_MRG_INFO *mrg, HUFF_COUNTS *huff_counts)
       }
       flush_bits();
       length=(ulong) (file_buffer.pos-record_pos)-max_pack_length;
-      pack_length=save_pack_length(record_pos,length);
+      pack_length= save_pack_length(pack_version, record_pos, length);
       if (pack_blob_length)
-	pack_length+=save_pack_length(record_pos+pack_length,tot_blob_length);
+	pack_length+= save_pack_length(pack_version, record_pos + pack_length,
+	                               tot_blob_length);
 
       /* Correct file buffer if the header was smaller */
       if (pack_length != max_pack_length)