Formerly shared.h.~13~

1 files changed, 58 insertions, 11 deletions

diff --git a/hurd/shared.h b/hurd/shared.h
index 8244eec0..9d7edb55 100644
--- a/hurd/shared.h
+++ b/hurd/shared.h
@@ -1,11 +1,11 @@
 /* Definitions for shared IO control pages
-   Copyright (C) 1991 Free Software Foundation
+   Copyright (C) 1992 Free Software Foundation
 
 This file is part of the GNU Hurd.
 
 The GNU Hurd is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 1, or (at your option)
+the Free Software Foundation; either version 2, or (at your option)
 any later version.
 
 The GNU Hurd is distributed in the hope that it will be useful, 
@@ -19,10 +19,11 @@ the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
 
 struct shared_io
 {
-  int shared_page_version;
+  int shared_page_magic;
 
   /* This lock protects against modification to it_status. */
   spin_lock_t lock;
+
   enum
     {
       USER_IT,			/* User is it */
@@ -40,10 +41,29 @@ struct shared_io
   int do_sigio;			/* call io_sigio after each operation */
 
   int use_file_size;		/* file_size is meaningful */
-  off_t file_size;
 
   int use_read_size;		/* read_size is meaningful */
   int read_size;
+
+  enum
+    { 
+      /* This means that there isn't any data to be read */
+      RBR_NO_DATA,
+
+      /* This means that more data cannot be added to the buffer.  If 
+	 the rd_file_pointer is advanced, then more data might become 
+	 readable.  This condition has priority over NO_DATA: protocols
+	 might refuse to receive data when the buffer is full; then this
+	 will be BUFFER_FULL.  If file pointer gets advanced, then the
+	 protocol will tell the sender to go ahead, and the read_block_reason 
+	 will be NO_DATA until the first data arrives.  
+	 */
+      RBR_BUFFER_FULL,
+
+      /* These conditions are generally only meaningful for nonseekable
+	 objects.  */
+    }
+  read_block_reason;		/* identifies what holds up reading */
   
   int seekable;			/* the file pointer can be reduced */
 
@@ -62,19 +82,46 @@ struct shared_io
   off_t wr_file_pointer;
   off_t xx_file_pointer;
 
-
-  /* These are set by the user only:  */
+  off_t file_size;
 
   /* These two indicate that the appropriate times need updated */
   int written;
   int accessed;
 
-
-  /* Reserved for future extensions */
-  int reserved [32];
   
-  /* Owned by the user from here to the end of the page */
-  int user_owned[0];
+  /* File structuring: */
+
+  /* If the file is not seekable and read data is separate from write
+     data, then the read data might be structured.  Each record is
+     identified by one of these structures.  The "auxil" field
+     contains extra data which might be of interest to some readers,
+     but is not part of the data proper (for example, UDP and raw IP
+     put the internet headers there).
+
+     The IO server guarantees that these will be consecutive, and that
+     the file_pointer_start of each record will be that of the last
+     plus its data_length.  The last valid structure might grow
+     whenever the server is it.	 All previous records from the
+     rd_file_pointer to the current read_size/file_size will not
+     change.  Records before that can be dropped and the valid records
+     moved forward in the array (when the server is it); if this
+     happens indexes_changed will be set to the number of records 
+     dropped.  */
+
+  int indexes_changed;		/* users can clear this when they want */
+
+  /* Users should not modify the rest of this: */
+  int use_structure;		/* structure is being used */
+  struct iomap_structure
+    {
+      int file_pointer_start;	/* file pointer offset of data */
+      int object_start;		/* offset of auxil in memory object */
+      int auxil_length;		/* length of auxil data */
+      int data_length;		/* length of real data */
+    } structure[0];
 };
 
+/* Look at this value to determine the byte order the server is using,
+   and then use it.  */
+#define SHARED_PAGE_MAGIC 0xaabbccdd