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/*
* Contains a simple implementation of a data source that reads from a
* given file.
*/
#include <assert.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include "libisofs.h"
#define BLOCK_SIZE 2048
#define BLOCK_OUT_OF_FILE -1;
#define READ_ERROR -2;
#define SEEK_ERROR -3;
struct file_data_src {
int fd;
int nblocks;
};
static int
ds_read_block(struct data_source *src, int lba, unsigned char *buffer)
{
struct file_data_src *data;
assert(src && buffer);
data = (struct file_data_src*)src->data;
/* For block devices size is always 0, so this can't be used.
* if (lba >= data->nblocks)
* return BLOCK_OUT_OF_FILE;
*/
/* goes to requested block */
if ( lseek(data->fd, (off_t)lba * (off_t)BLOCK_SIZE, SEEK_SET) == (off_t) -1 )
return SEEK_ERROR;
if ( read(data->fd, buffer, BLOCK_SIZE) != BLOCK_SIZE )
return READ_ERROR;
return 0;
}
static int ds_get_size(struct data_source *src)
{
struct file_data_src *data;
assert(src);
data = (struct file_data_src*)src->data;
return data->nblocks;
}
static void ds_free_data(struct data_source *src)
{
struct file_data_src *data;
assert(src);
data = (struct file_data_src*)src->data;
/* close the file */
close(data->fd);
free(data);
}
struct data_source *data_source_from_file(const char *path)
{
int fd;
struct stat info;
struct file_data_src *data;
struct data_source *ret;
assert(path);
fd = open(path, O_RDONLY);
if (fd == -1)
return NULL;
fstat(fd, &info);
data = malloc(sizeof(struct file_data_src));
data->fd = fd;
data->nblocks = info.st_size / BLOCK_SIZE;
ret = malloc(sizeof(struct data_source));
ret->refcount = 1;
ret->read_block = ds_read_block;
ret->get_size = ds_get_size;
ret->free_data = ds_free_data;
ret->data = data;
return ret;
}
void data_source_free(struct data_source *src)
{
if (--src->refcount == 0) {
src->free_data(src);
free(src);
}
}