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/* SPDX-License-Identifier: GPL-3.0-or-later */
/*
* meta_reader.c
*
* Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
*/
#define SQFS_BUILDING_DLL
#include "config.h"
#include "sqfs/meta_reader.h"
#include "sqfs/compress.h"
#include "sqfs/data.h"
#include "util.h"
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
struct sqfs_meta_reader_t {
uint64_t start;
uint64_t limit;
size_t data_used;
/* The location of the current block in the image */
uint64_t block_offset;
/* The location of the next block after the current one */
uint64_t next_block;
/* A byte offset into the uncompressed data of the current block */
size_t offset;
/* The underlying file descriptor to read from */
int fd;
/* A pointer to the compressor to use for extracting data */
sqfs_compressor_t *cmp;
/* The raw data read from the input file */
uint8_t data[SQFS_META_BLOCK_SIZE];
/* The uncompressed data read from the input file */
uint8_t scratch[SQFS_META_BLOCK_SIZE];
};
sqfs_meta_reader_t *sqfs_meta_reader_create(int fd, sqfs_compressor_t *cmp,
uint64_t start, uint64_t limit)
{
sqfs_meta_reader_t *m = calloc(1, sizeof(*m));
if (m == NULL) {
perror("creating meta data reader");
return NULL;
}
m->start = start;
m->limit = limit;
m->fd = fd;
m->cmp = cmp;
return m;
}
void sqfs_meta_reader_destroy(sqfs_meta_reader_t *m)
{
free(m);
}
int sqfs_meta_reader_seek(sqfs_meta_reader_t *m, uint64_t block_start,
size_t offset)
{
bool compressed;
uint16_t header;
ssize_t ret;
size_t size;
if (block_start < m->start || block_start >= m->limit)
goto fail_range;
if (block_start == m->block_offset) {
if (offset >= m->data_used)
goto fail_offset;
m->offset = offset;
return 0;
}
if (read_data_at("reading meta data header", block_start,
m->fd, &header, 2)) {
return -1;
}
header = le16toh(header);
compressed = (header & 0x8000) == 0;
size = header & 0x7FFF;
if (size > sizeof(m->data))
goto fail_too_large;
if ((block_start + 2 + size) > m->limit)
goto fail_block_bounds;
if (read_data_at("reading meta data block", block_start + 2,
m->fd, m->data, size)) {
return -1;
}
if (compressed) {
ret = m->cmp->do_block(m->cmp, m->data, size,
m->scratch, sizeof(m->scratch));
if (ret <= 0) {
fputs("error uncompressing meta data block\n", stderr);
return -1;
}
memcpy(m->data, m->scratch, ret);
m->data_used = ret;
} else {
m->data_used = size;
}
if (offset >= m->data_used)
goto fail_offset;
m->block_offset = block_start;
m->next_block = block_start + size + 2;
m->offset = offset;
return 0;
fail_block_bounds:
fputs("found metadata block that exceeds filesystem bounds.\n",
stderr);
return -1;
fail_too_large:
fputs("found metadata block larger than maximum size.\n", stderr);
return -1;
fail_offset:
fputs("Tried to seek past end of metadata block.\n", stderr);
return -1;
fail_range:
fputs("Tried to read meta data block past filesystem bounds.\n",
stderr);
return -1;
}
void sqfs_meta_reader_get_position(sqfs_meta_reader_t *m, uint64_t *block_start,
size_t *offset)
{
*block_start = m->block_offset;
*offset = m->offset;
}
int sqfs_meta_reader_read(sqfs_meta_reader_t *m, void *data, size_t size)
{
size_t diff;
while (size != 0) {
diff = m->data_used - m->offset;
if (diff == 0) {
if (sqfs_meta_reader_seek(m, m->next_block, 0))
return -1;
diff = m->data_used;
}
if (diff > size)
diff = size;
memcpy(data, m->data + m->offset, diff);
m->offset += diff;
data = (char *)data + diff;
size -= diff;
}
return 0;
}
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