Added allocator using buddy system

.gitignore

@@ -18,4 +18,5 @@ include/config.h*
 missing
 stamp-h1
 .deps
-tests/test_bitmapalloc
+tests/test_bitmapalloc
+tests/test_buddyalloc

include/Makefile.am

@@ -1 +1,2 @@
-nobase_include_HEADERS = libmalloc/bitmap_alloc.h libmalloc/memmap.h libmalloc/common.h
+nobase_include_HEADERS = libmalloc/bitmap_alloc.h libmalloc/buddy_alloc.h \
+    libmalloc/memmap.h libmalloc/common.h

include/libmalloc/bitmap_alloc.h

@@ -1,5 +1,5 @@
-#ifndef _LIBMALLOC_BUDDYALLOC_H
-#define _LIBMALLOC_BUDDYALLOC_H
+#ifndef _LIBMALLOC_BITMAPALLOC_H
+#define _LIBMALLOC_BITMAPALLOC_H
 
 #include "memmap.h"
 #include "common.h"

include/libmalloc/buddy_alloc.h

@@ -0,0 +1,55 @@
+#ifndef _LIBMALLOC_BUDDYALLOC_H
+#define _LIBMALLOC_BUDDYALLOC_H
+
+#include "memmap.h"
+#include "common.h"
+
+typedef struct buddy_block_t 
+{
+    struct buddy_block_t *linkb;
+
+    struct buddy_block_t *linkf;
+
+    unsigned long kval;
+
+    unsigned long tag;
+
+} buddy_block_t;
+
+typedef struct buddy_descriptor_t
+{
+    /**
+     * @brief An array of `buddy_block_t` structs serving as the heads of the
+     * lists of available blocks. avail[k] serves as the head of the list of
+     * blocks of size 2^k.
+     */
+    buddy_block_t *avail;
+
+    buddy_block_t *block_map;
+
+    unsigned long block_map_size;
+
+    unsigned long max_kval;
+
+    unsigned long block_size;
+
+    unsigned long offset;
+
+    unsigned long free_block_count;
+
+    int (*mmap)(void *location, unsigned long size);
+
+} buddy_descriptor_t;
+
+unsigned long buddy_map_size(const memory_map_t *map, unsigned long block_size);
+
+unsigned long buddy_reserve(buddy_descriptor_t *heap, unsigned long size);
+
+void buddy_free(buddy_descriptor_t *heap, unsigned long location);
+
+void buddy_free_size(buddy_descriptor_t *heap, unsigned long size, 
+    unsigned long location);
+
+int buddy_alloc_init(buddy_descriptor_t *heap, memory_map_t *map);
+
+#endif

src/Makefile.am

@@ -1,4 +1,4 @@
 lib_LIBRARIES = libmalloc.a
-libmalloc_a_SOURCES = bitmap_alloc.c memmap.c
+libmalloc_a_SOURCES = buddy_alloc.c bitmap_alloc.c memmap.c
 
 libmalloc_a_CFLAGS = -I$(prefix)/include

src/buddy_alloc.c

@@ -0,0 +1,161 @@
+#include "libmalloc/buddy_alloc.h"
+#include "util.h"
+
+#define BLOCK_RESERVED 0
+#define BLOCK_FREE 1
+
+static unsigned long compute_memory_size(const memory_map_t *map)
+{
+    // Find the last available region in the memory map.
+    int map_index = map->size - 1;
+    while(map->array[map_index].type != M_AVAILABLE)
+    {
+        map_index--;
+    }
+
+    return map->array[map_index].location + map->array[map_index].size;
+}
+
+static void insert_block(buddy_descriptor_t *heap, unsigned long index,
+    unsigned long k)
+{
+    heap->free_block_count += 1UL << k;
+    while(k < heap->max_kval)
+    {
+        unsigned long buddy_index = index ^ (1UL << k);
+        if(heap->block_map[buddy_index].tag != BLOCK_FREE 
+            || heap->block_map[buddy_index].kval != k)
+        {
+            break;
+        }
+        heap->block_map[buddy_index].linkb->linkf = heap->block_map[buddy_index].linkf;
+        heap->block_map[buddy_index].linkf->linkb = heap->block_map[buddy_index].linkb;
+        heap->block_map[buddy_index].tag = BLOCK_RESERVED;
+        k++;
+        if(buddy_index < index)
+        {
+            index = buddy_index;
+        }
+    }
+    heap->block_map[index].tag = BLOCK_FREE;
+    buddy_block_t *p = heap->avail[k].linkf;
+    heap->block_map[index].linkf = p;
+    heap->block_map[index].linkb = &heap->avail[k];
+    p->linkb = &heap->block_map[index];
+    heap->avail[k].linkf = &heap->block_map[index];
+    heap->block_map[index].kval = k;
+}
+
+unsigned long buddy_map_size(const memory_map_t *map, unsigned long block_size)
+{
+    unsigned long memory_size = compute_memory_size(map);
+    return sizeof(buddy_block_t) * memory_size / block_size;
+}
+
+unsigned long buddy_reserve(buddy_descriptor_t *heap, unsigned long size)
+{
+    unsigned long k = llog2((size - 1) / heap->block_size + 1);
+    for(unsigned long j = k; j <= heap->max_kval; j++)
+    {
+        if(heap->avail[j].linkf != &heap->avail[j])
+        {
+            buddy_block_t *block = heap->avail[j].linkb;
+            heap->avail[j].linkb = block->linkb;
+            heap->avail[j].linkb->linkf = &heap->avail[j];
+            block->tag = BLOCK_RESERVED;
+            while(j > k)
+            {
+                j--;
+                buddy_block_t *buddy = block + (1UL << j);
+                buddy->tag = BLOCK_FREE;
+                buddy->kval = j;
+                block->kval = j;
+                buddy->linkb = &heap->avail[j];
+                buddy->linkf = &heap->avail[j];
+                heap->avail[j].linkb = buddy;
+                heap->avail[j].linkf = buddy;
+            }
+            unsigned long index = block - heap->block_map;
+            heap->free_block_count -= 1UL << k;
+            return (unsigned long)heap->offset + index * heap->block_size;
+        }
+    }
+    return NOMEM;
+}
+
+void buddy_free(buddy_descriptor_t *heap, unsigned long location)
+{
+    unsigned long index = (location - (unsigned long)heap->offset) / heap->block_size;
+    unsigned long k = llog2((heap->block_size * (1UL << heap->block_map[index].kval)) / heap->block_size);
+    insert_block(heap, index, k);
+}
+
+void buddy_free_size(buddy_descriptor_t *heap, unsigned long location,
+    unsigned long size)
+{
+    unsigned long index = (location - (unsigned long)heap->offset) / heap->block_size;
+    unsigned long k = llog2(size / heap->block_size);
+    insert_block(heap, index, k);
+}
+
+int buddy_alloc_init(buddy_descriptor_t *heap, memory_map_t *map)
+{
+    heap->block_map_size = buddy_map_size(map, heap->block_size);
+    heap->max_kval = llog2(heap->block_map_size / sizeof(buddy_block_t));
+    heap->free_block_count = 0;
+    for(int i = 0; i <= heap->max_kval; i++)
+    {
+        heap->avail[i].linkf = &heap->avail[i];
+        heap->avail[i].linkb = &heap->avail[i];
+    }
+
+    if(heap->block_map == (buddy_block_t*)0)
+    {
+        int map_index = 0;
+        while(map->array[map_index].type != M_AVAILABLE 
+            || map->array[map_index].size < heap->block_map_size)
+        {
+            map_index++;
+            if(map_index >= map->size)
+            {
+                return -1;
+            }
+        }
+
+        heap->block_map = (buddy_block_t*)(heap->offset + map->array[map_index].location);
+        memmap_insert_region(map, map->array[map_index].location, heap->block_map_size, M_UNAVAILABLE);
+        if(heap->mmap && heap->mmap(heap->block_map, heap->block_map_size))
+        {
+            return -1;
+        }
+    }
+
+    for(int i = 0; i < heap->block_map_size / sizeof(buddy_block_t); i++)
+    {
+        heap->block_map[i].tag = BLOCK_RESERVED;
+        heap->block_map[i].kval = 0;
+        heap->block_map[i].linkf = 0;
+        heap->block_map[i].linkb = 0;
+    }
+
+    for(int i = 0; i < map->size; i++)
+    {
+        if(map->array[i].type != M_AVAILABLE)
+        {
+            continue;
+        }
+
+        unsigned long location = (map->array[i].location + heap->block_size - 1);
+        location -= location % heap->block_size;
+        unsigned long region_end = map->array[i].location + map->array[i].size;
+        while(location + heap->block_size <= region_end)
+        {
+            unsigned long index = location / heap->block_size;
+            unsigned long k = 0;
+            insert_block(heap, index, k);
+            location += heap->block_size;
+            heap->free_block_count++;
+        }
+    }
+    return 0;
+}

tests/Makefile.am

@@ -1,6 +1,9 @@
 if BUILD_TESTS
-    noinst_PROGRAMS = test_bitmapalloc
+    noinst_PROGRAMS = test_bitmapalloc test_buddyalloc
 
     test_bitmapalloc_SOURCES = test_bitmapalloc.c
     test_bitmapalloc_LDADD = ../src/libmalloc.a
+
+    test_buddyalloc_SOURCES = test_buddyalloc.c
+    test_buddyalloc_LDADD = ../src/libmalloc.a
 endif

tests/test_buddyalloc.c

@@ -0,0 +1,102 @@
+#include "libmalloc/buddy_alloc.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct memblock_t
+{
+    unsigned long size;
+    unsigned long location;
+} memblock_t;
+
+void print_heap(FILE *file, buddy_descriptor_t *heap)
+{
+    unsigned long count = 1UL << heap->max_kval;
+    fprintf(file, "heap {\n");
+    fprintf(file, "\t.block_size = %lu\n", heap->block_size);
+    fprintf(file, "\t.max_kval = %lu\n", heap->max_kval);
+    fprintf(file, "\t.offset = %lu\n", heap->offset);
+    fprintf(file, "\t.block_map = {\n");
+    for(unsigned int i = 0; i < count; i++)
+    {
+        unsigned long linkf_diff = heap->block_map[i].linkf - heap->block_map;
+        unsigned long linkb_diff = heap->block_map[i].linkb - heap->block_map;
+        fprintf(file, "\t\t%u: {.tag = %s, .kval = %lu, .linkf = %li, .linkb = %li}\n",
+            i,
+            heap->block_map[i].tag ? "BLOCK_FREE" : "BLOCK_RESERVED",
+            heap->block_map[i].kval,
+            linkf_diff < count ? linkf_diff : -1,
+            linkb_diff < count ? linkb_diff : -1);
+    }
+    fprintf(file, "\t}\n");
+    fprintf(file, "\t.avail = {\n");
+    for(unsigned int i = 0; i <= heap->max_kval; i++)
+    {
+        fprintf(file, "\t\t%u: {.linkf = %lu, .linkb = %lu}\n",
+            i,
+            heap->avail[i].linkf - heap->block_map,
+            heap->avail[i].linkb - heap->block_map);
+    }
+    fprintf(file, "\t}\n}\n");
+}
+
+int main(int argc, char **argv)
+{
+    unsigned long mem_size;
+    unsigned long block_size;
+    sscanf(argv[1], "%lu", &mem_size);
+    sscanf(argv[2], "%lu", &block_size);
+
+    FILE *out = fopen("debug_output.txt", "w");
+    if(out == NULL)
+    {
+        fprintf(stderr, "Failed to open debug output.\n");
+        return 0;
+    }
+
+    memory_map_t memory_map = {
+        .array = malloc(sizeof(memory_region_t) * 16),
+        .capacity = 16,
+        .size = 0
+    };
+
+    buddy_descriptor_t heap = {
+        .avail = malloc(sizeof(buddy_block_t) * 20),
+        .block_map = malloc(buddy_map_size(&memory_map, block_size)),
+        .block_size = block_size,
+        .mmap = NULL,
+        .offset = 0
+    };
+
+    memmap_insert_region(&memory_map, 0, mem_size, M_AVAILABLE);
+    if(buddy_alloc_init(&heap, &memory_map))
+    {
+        fprintf(stderr, "Failed to initialize buddy allocator.\n");
+        return 0;
+    }
+
+    print_heap(out, &heap);
+
+    memblock_t *blocks = calloc(mem_size / block_size, sizeof(memblock_t));
+
+    for(int i = 0; i < 1024; i++)
+    {
+        int index = rand() % (mem_size / block_size);
+        if(blocks[index].size == 0)
+        {
+            blocks[index].size = 1;
+            blocks[index].location = buddy_reserve(&heap, 1);
+            fprintf(out, "RESERVED %lu\n", blocks[index].location / heap.block_size);
+        }
+        else
+        {
+            buddy_free(&heap, blocks[index].location);
+            blocks[index].size = 0;
+            fprintf(out, "FREED %lu\n", blocks[index].location / heap.block_size);
+        }
+        print_heap(out, &heap);
+    }
+
+    print_heap(out, &heap);
+
+    return 0;
+}