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/*
winnie - an experimental window system
Copyright (C) 2013 Eleni Maria Stea
This program 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 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
Author: Eleni Maria Stea <elene.mst@gmail.com>
*/
#include <assert.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include <map>
#include "shalloc.h"
#define BLOCK_SIZE 512
#define NUM_BLOCKS (POOL_SIZE / BLOCK_SIZE)
#define BITMAP_SIZE (NUM_BLOCKS / 32)
static bool is_allocated(int block_number);
static int addr_to_block(unsigned char *addr);
static unsigned char *block_to_addr(int block_number);
static void alloc_blocks(int block_pos, int num_blocks);
static void free_blocks(int block_pos, int num_blocks);
static void print_stats();
static int fd;
static unsigned char *pool;
static std::map<int, int> alloc_sizes; //starting block -> number of blocks
// 0 means not allocated 1 means allocated
static uint32_t bitmap[BITMAP_SIZE];
struct Statistics {
int alloc_num;
int free_num;
int alloc_memsize;
int free_memsize;
};
static Statistics stats;
bool init_shared_memory()
{
if(((fd = shm_open(SHMNAME, O_RDWR | O_CREAT, S_IRWXU)) == -1)) {
fprintf(stderr, "Failed to open shared memory: %s\n", strerror(errno));
return false;
}
ftruncate(fd, POOL_SIZE);
if((pool = (unsigned char*)mmap(0, POOL_SIZE, PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0)) == (void*)-1) {
fprintf(stderr, "Failed to map shared memory: %s\n", strerror(errno));
}
for(int i=0; i<BITMAP_SIZE; i++) {
bitmap[i] = 0;
}
alloc_sizes.clear();
memset(&stats, 0, sizeof stats);
return true;
}
void destroy_shared_memory()
{
print_stats();
if(munmap(pool, POOL_SIZE) == -1) {
fprintf(stderr, "Failed to unmap shared memory: %s\n", strerror(errno));
}
shm_unlink(SHMNAME);
}
void *sh_malloc(size_t bytes)
{
if(!bytes) {
return 0;
}
int num_blocks = (bytes + BLOCK_SIZE - 1) / BLOCK_SIZE;
int free_block;
int ctr = 0;
for(int i=0; i<NUM_BLOCKS; i++) {
if(!is_allocated(i)) {
if(!ctr) {
free_block = i;
}
ctr++;
}
else {
ctr = 0;
}
if(ctr == num_blocks) {
alloc_blocks(free_block, num_blocks);
return block_to_addr(free_block);
}
}
return 0;
}
void sh_free(void *ptr)
{
int block = addr_to_block((unsigned char*)ptr);
std::map<int, int>::iterator it;
if((it = alloc_sizes.find(block)) != alloc_sizes.end()) {
int num_blocks = it->second;
free_blocks(block, num_blocks);
alloc_sizes.erase(it);
}
else {
fprintf(stderr, "Attempt to free non-existent blocks from: %d\n", block);
}
}
void *get_pool()
{
return (void*)pool;
}
static bool is_allocated(int block_number)
{
int idx = block_number / 32;
int bit_num = block_number % 32;
if((bitmap[idx] >> bit_num) & 1) {
return true;
}
return false;
}
static int addr_to_block(unsigned char *addr)
{
assert(addr >= pool);
assert(addr < pool + POOL_SIZE);
return (addr - pool) / BLOCK_SIZE;
}
static unsigned char *block_to_addr(int block_number)
{
assert(block_number >= 0);
assert(block_number < NUM_BLOCKS);
return pool + block_number * BLOCK_SIZE;
}
static void alloc_blocks(int block_pos, int num_blocks)
{
for(int i=0; i<num_blocks; i++) {
int block_number = i + block_pos;
int idx = block_number / 32;
int bit_num = block_number % 32;
bitmap[idx] |= ((uint32_t)1 << bit_num); // or pow(2, i)
}
alloc_sizes[block_pos] = num_blocks;
stats.alloc_num++;
stats.alloc_memsize += BLOCK_SIZE * num_blocks;
}
static void free_blocks(int block_pos, int num_blocks)
{
for(int i=0; i<num_blocks; i++) {
int block_number = i + block_pos;
int idx = block_number / 32;
int bit_num = block_number % 32;
bitmap[idx] &= ~((uint32_t)1 << bit_num);
}
stats.free_num++;
stats.free_memsize += BLOCK_SIZE * num_blocks;
}
static void print_stats()
{
printf("Total allocated memory: %d\n", stats.alloc_memsize);
printf("Total deallocated memory: %d\n", stats.free_memsize);
printf("Number of allocations: %d\n", stats.alloc_num);
printf("Number of deallocations: %d\n", stats.free_num);
}
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