From 5ee7865458aa386a585aceb2fc4ecb555c18be89 Mon Sep 17 00:00:00 2001
From: Dan Hirsch <thequux@thequux.com>
Date: Mon, 23 Apr 2012 00:35:58 +0100
Subject: [PATCH] Added allocator and first cut at makefile
---
.gitignore | 2 ++
config.mk | 2 ++
lib/Makefile | 6 ++++
lib/allocator.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++
lib/allocator.h | 12 ++++++++
5 files changed, 95 insertions(+)
create mode 100644 .gitignore
create mode 100644 config.mk
create mode 100644 lib/Makefile
create mode 100644 lib/allocator.c
create mode 100644 lib/allocator.h
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 00000000..a70237a6
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+*.o
+*~
diff --git a/config.mk b/config.mk
new file mode 100644
index 00000000..16209be9
--- /dev/null
+++ b/config.mk
@@ -0,0 +1,2 @@
+CFLAGS := $(shell pkg-config --cflags glib-2.0)
+LDFLAGS := $(shell pkg-config --libs glib-2.0)
\ No newline at end of file
diff --git a/lib/Makefile b/lib/Makefile
new file mode 100644
index 00000000..de2a9af1
--- /dev/null
+++ b/lib/Makefile
@@ -0,0 +1,6 @@
+include ../config.mk
+
+all: allocator.o
+
+%.o: %.c
+ gcc $(CFLAGS) -c -o $@ $^
\ No newline at end of file
diff --git a/lib/allocator.c b/lib/allocator.c
new file mode 100644
index 00000000..77f14ea3
--- /dev/null
+++ b/lib/allocator.c
@@ -0,0 +1,73 @@
+#include <glib.h>
+#include <stdint.h>
+#include <sys/types.h>
+
+#include "allocator.h"
+
+struct arena_link {
+ // TODO:
+ // For efficiency, we should probably allocate the arena links in
+ // their own slice, and link to a block directly. That can be
+ // implemented later, though, with no change in interface.
+ struct arena_link *next; // It is crucial that this be the first item; so that
+ // any arena link can be casted to struct arena_link**.
+
+ size_t free;
+ size_t used;
+ uint8_t rest[];
+} ;
+
+struct arena {
+ struct arena_link *head;
+ size_t block_size;
+};
+
+arena_t new_arena(size_t block_size) {
+ struct arena *ret = g_new(struct arena, 1);
+ struct arena_link *link = (struct arena_link*)g_malloc0(sizeof(struct arena_link) + block_size);
+ link->free = block_size;
+ link->used = 0;
+ link->next = NULL;
+ ret->head = link;
+ ret->block_size = 0;
+
+ return ret;
+}
+
+void* arena_malloc(arena_t arena, size_t size) {
+ if (size <= arena->head->free) {
+ // fast path..
+ void* ret = arena->head->rest + arena->head->used;
+ arena->head->used += size;
+ arena->head->free -= size;
+ return ret;
+ } else if (size > arena->block_size) {
+ // We need a new, dedicated block for it, because it won't fit in a standard sized one.
+ // This involves some annoying casting...
+ void* link = g_malloc(size + sizeof(struct arena_link*));
+ *(struct arena_link**)link = arena->head->next;
+ arena->head->next = (struct arena_link*)link;
+ return (void*)((uint8_t*)link + sizeof(struct arena_link*));
+ } else {
+ // we just need to allocate an ordinary new block.
+ struct arena_link *link = (struct arena_link*)g_malloc0(sizeof(struct arena_link) + arena->block_size);
+ link->free = arena->block_size - size;
+ link->used = size;
+ link->next = arena->head;
+ arena->head = link;
+ return link->rest;
+ }
+}
+
+void delete_arena(arena_t arena) {
+ struct arena_link *link = arena->head;
+ while (link) {
+ struct arena_link *next = link->next;
+ // Even in the case of a special block, without the full arena
+ // header, this is correct, because the next pointer is the first
+ // in the structure.
+ g_free(link);
+ link = next;
+ }
+ g_free(arena);
+}
diff --git a/lib/allocator.h b/lib/allocator.h
new file mode 100644
index 00000000..3cea5906
--- /dev/null
+++ b/lib/allocator.h
@@ -0,0 +1,12 @@
+#ifndef LIB_ALLOCATOR__H__
+#define LIB_ALLOCATOR__H__
+#include <sys/types.h>
+
+typedef struct arena* arena_t; // hidden implementation
+
+arena_t new_arena(size_t block_size); // pass 0 for default...
+void* arena_malloc(arena_t arena, size_t count); // TODO: needs the malloc attribute
+void delete_arena(arena_t arena);
+
+
+#endif // #ifndef LIB_ALLOCATOR__H__
--
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