X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/mLib/blobdiff_plain/c6e0eaf00cd09a4e5237e70d8351049ec91d7653..a7f86da7e19ebf61011b313e107b17ae11fe7d5d:/sub.h

diff --git a/sub.h b/sub.h
index ffb708c..1b07703 100644
--- a/sub.h
+++ b/sub.h
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: sub.h,v 1.5 1999/12/10 23:42:04 mdw Exp $
+ * $Id: sub.h,v 1.6 2000/06/17 10:35:51 mdw Exp $
  *
  * Allocation of known-size blocks
  *
@@ -30,6 +30,9 @@
 /*----- Revision history --------------------------------------------------*
  *
  * $Log: sub.h,v $
+ * Revision 1.6  2000/06/17 10:35:51  mdw
+ * Major overhaul for arena support.
+ *
  * Revision 1.5  1999/12/10 23:42:04  mdw
  * Change header file guard names.
  *
@@ -58,27 +61,160 @@
 
 #include <stdlib.h>
 
-#ifndef MLIB_ALLOC_H
-#  include "alloc.h"
+#ifndef MLIB_ARENA_H
+#  include "arena.h"
 #endif
 
+/*----- Configuration and tuning ------------------------------------------*/
+
+/* --- The largest block I'll handle here --- *
+ *
+ * Anything larger will be handed on to the underlying @alloc@.
+ */
+
+#define SUB_MAXBIN 256
+
+/* --- Preferred chunk size --- *
+ *
+ * When a bin is empty, I'll allocate a large chunk of approximately this
+ * size and divvy it up into small bin-sized blocks.
+ */
+
+#define SUB_CHUNK 4096
+
+/*----- Other useful macros -----------------------------------------------*/
+
+/* --- The granularity of bin buffers --- *
+ *
+ * All blocks allocated by the binner are a multiple of this size.  I've
+ * chosen @void *@ because I need to store @void *@ things in here.
+ */
+
+#define SUB_GRANULE sizeof(void *)
+
+/* --- Finding the right bin for a given size --- *
+ *
+ * This chooses the correct bin for an allocation.  Input is the size of
+ * block wanted; result is the bin index.
+ */
+
+#define SUB_BIN(x) (((x) + SUB_GRANULE - 1) / SUB_GRANULE)
+
+/* --- Convert a bin back to the block size --- *
+ *
+ * This gives the size of block contained in a given bin.
+ */
+
+#define SUB_BINSZ(x) ((x) * SUB_GRANULE)
+
+/* --- Number of bins required --- */
+
+#define SUB_BINS (SUB_MAXBIN / SUB_GRANULE + 1)
+
+/*----- Data structures ---------------------------------------------------*/
+
+typedef struct subarena {
+  arena *a;
+  void *bin[SUB_BINS];
+} subarena;
+
+/*----- Global variables --------------------------------------------------*/
+
+extern subarena sub_global;
+
 /*----- Functions provided ------------------------------------------------*/
 
+/* --- @subarena_create@ --- *
+ *
+ * Arguments:	@subarena *s@ = pointer to arena to initialize
+ *		@arena *a@ = pointer to underlying arena block
+ *
+ * Returns:	---
+ *
+ * Use:		Initialize a suballocation arena based on an underlying large
+ *		blocks arena.
+ */
+
+extern void subarena_create(subarena */*s*/, arena */*a*/);
+
+/* --- @subarena_destroy@ --- *
+ *
+ * Arguments:	@subarena *s@ = pointer to arena to destroy
+ *
+ * Returns:	---
+ *
+ * Use:		Destroys a suballocation arena, freeing all of the memory it
+ *		contains back to the underlying large blocks arena.
+ */
+
+extern void subarena_destroy(subarena */*s*/);
+
+/* --- @subarena_alloc@ --- *
+ *
+ * Arguments:	@subarena *s@ = pointer to arena
+ *		@size_t s@ = size of chunk wanted
+ *
+ * Returns:     Pointer to a block at least as large as the one wanted.
+ *
+ * Use:         Allocates a small block of memory from the given pool.  The
+ *		exception @EXC_NOMEM@ is raised if the underlying arena is
+ *		full.
+ */
+
+extern void *subarena_alloc(subarena */*s*/, size_t /*sz*/);
+
+/* --- @subarena_free@ --- *
+ *
+ * Arguments:   @subarena *s@ = pointer to arena
+ *		@void *p@ = address of block to free
+ *              @size_t s@ = size of block
+ *
+ * Returns:     ---
+ *
+ * Use:         Frees a block allocated by @subarena_alloc@.
+ */
+
+extern void subarena_free(subarena */*s*/, void */*p*/, size_t /*sz*/);
+
+/* --- @A_CREATE@ --- *
+ *
+ * Arguments:	@subarena *s@ = pointer to arena
+ *		@type@ = type of object required; must be passable to
+ *			@sizeof@
+ *
+ * Returns:	Pointer to a block sufficiently big to hold an object of the
+ *		named type.
+ *
+ * Use:		Allocates a block of the required type.
+ */
+
+#define A_CREATE(a, type) subarena_alloc((a), sizeof(type))
+
+/* --- @A_DESTROY@ --- *
+ *
+ * Arguments:	@subarena *s@ = pointer to arena
+ *		@void *p@ = pointer to an object
+ *
+ * Returns:	---
+ *
+ * Use:		Frees the thing pointed to by @p@.
+ */
+
+#define A_DESTROY(a, p) subarena_free((a), (p), sizeof(*p))
+
+/*----- Shortcuts for the global pool -------------------------------------*/
+
 /* --- @sub_alloc@ --- *
  *
  * Arguments:   @size_t s@ = size of chunk wanted
  *
  * Returns:     Pointer to a block at least as large as the one wanted.
  *
- * Use:         Allocates a small block of memory.  If there is no more
- *		memory left, the exception @EXC_NOMEM@ is raised.
+ * Use:         Allocates a small block of memory from the @sub_global@ pool.
  */
 
-#ifdef TRACK_ENABLE
-#  define sub_alloc(s) xmalloc(s)
-#else
-void *sub_alloc(size_t s);
-#endif
+extern void *sub_alloc(size_t /*sz*/);
+#define sub_alloc(sz) subarena_alloc(&sub_global, (sz))
 
 /* --- @sub_free@ --- *
  *
@@ -90,11 +226,8 @@ void *sub_alloc(size_t s);
  * Use:         Frees a block allocated by @sub_alloc@.
  */
 
-#ifdef TRACK_ENABLE
-#  define sub_free(p, s) free(p)
-#else
-void sub_free(void *p, size_t s);
-#endif
+extern void sub_free(void */*p*/, size_t /*sz*/);
+#define sub_free(p, sz) subarena_free(&sub_global, (p), (sz))
 
 /* --- @CREATE@ --- *
  *
@@ -126,10 +259,11 @@ void sub_free(void *p, size_t s);
  *
  * Returns:     ---
  *
- * Use:         Initializes the magic allocator.
+ * Use:         Initializes the magic allocator.  This is no longer
+ *		necessary.
  */
 
-void sub_init(void);
+extern void sub_init(void);
 
 /*----- That's all, folks -------------------------------------------------*/