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