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/* SPDX-License-Identifier: GPL-3.0-or-later */
#include "config.h"
#include "meta_reader.h"
#include "util.h"
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
struct meta_reader_t {
/* 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 */
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];
};
meta_reader_t *meta_reader_create(int fd, compressor_t *cmp)
{
meta_reader_t *m = calloc(1, sizeof(*m));
if (m == NULL) {
perror("creating meta data reader");
return NULL;
}
m->fd = fd;
m->cmp = cmp;
return m;
}
void meta_reader_destroy(meta_reader_t *m)
{
free(m);
}
int meta_reader_seek(meta_reader_t *m, uint64_t block_start, size_t offset)
{
bool compressed;
uint16_t header;
ssize_t ret;
size_t size;
if (offset >= sizeof(m->data)) {
fputs("Tried to seek past end of meta data block.\n", stderr);
return -1;
}
if (block_start == m->block_offset) {
m->offset = offset;
return 0;
}
if (lseek(m->fd, block_start, SEEK_SET) == (off_t)-1) {
perror("seek on image file");
return -1;
}
if (read_data("reading meta data header", m->fd, &header, 2))
return -1;
header = le16toh(header);
compressed = (header & 0x8000) == 0;
size = header & 0x7FFF;
if (size > sizeof(m->data)) {
fputs("found meta data block larger than maximum size\n",
stderr);
return -1;
}
m->block_offset = block_start;
m->offset = offset;
m->next_block = block_start + size + 2;
memset(m->data, 0, sizeof(m->data));
if (read_data("reading meta data block", 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);
if ((size_t)ret < sizeof(m->data))
memset(m->data + ret, 0, sizeof(m->data) - ret);
}
return 0;
}
int meta_reader_read(meta_reader_t *m, void *data, size_t size)
{
size_t diff;
while (size != 0) {
diff = sizeof(m->data) - m->offset;
if (diff == 0) {
if (meta_reader_seek(m, m->next_block, 0))
return -1;
diff = sizeof(m->data);
}
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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