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/* SPDX-License-Identifier: GPL-3.0-or-later */
#include "meta_reader.h"
#include "frag_reader.h"
#include "util.h"
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
struct frag_reader_t {
sqfs_fragment_t *tbl;
size_t num_fragments;
int fd;
compressor_t *cmp;
size_t block_size;
size_t used;
size_t current_index;
uint8_t buffer[];
};
static int precache_block(frag_reader_t *f, size_t i)
{
bool compressed;
size_t size;
ssize_t ret;
if (i == f->current_index)
return 0;
if (lseek(f->fd, f->tbl[i].start_offset, SEEK_SET) == (off_t)-1) {
perror("seeking to fragment location");
return -1;
}
compressed = (f->tbl[i].size & (1 << 24)) == 0;
size = f->tbl[i].size & ((1 << 24) - 1);
if (size > f->block_size) {
fputs("found fragment block larger than block size\n", stderr);
return -1;
}
ret = read_retry(f->fd, f->buffer, size);
if (ret < 0) {
perror("reading fragment");
return -1;
}
if ((size_t)ret < size) {
fputs("reading fragment: unexpected end of file\n", stderr);
return -1;
}
if (compressed) {
ret = f->cmp->do_block(f->cmp, f->buffer, size,
f->buffer + f->block_size, f->block_size);
if (ret <= 0) {
fputs("extracting fragment failed\n", stderr);
return -1;
}
memmove(f->buffer, f->buffer + f->block_size, ret);
}
f->current_index = i;
f->used = ret;
return 0;
}
frag_reader_t *frag_reader_create(sqfs_super_t *super, int fd,
compressor_t *cmp)
{
size_t i, blockcount, j, diff, count;
sqfs_fragment_t *tbl = NULL;
uint64_t *locations = NULL;
meta_reader_t *m = NULL;
frag_reader_t *f = NULL;
ssize_t ret;
count = super->fragment_entry_count;
blockcount = count / (SQFS_META_BLOCK_SIZE / sizeof(tbl[0]));
if (count % (SQFS_META_BLOCK_SIZE / sizeof(tbl[0])))
++blockcount;
/* pre allocate all the stuff */
f = calloc(1, sizeof(*f) + super->block_size * 2);
if (f == NULL)
goto fail_rd;
tbl = calloc(count, sizeof(tbl[0]));
if (tbl == NULL)
goto fail_rd;
locations = malloc(blockcount * sizeof(locations[0]));
if (locations == NULL)
goto fail_rd;
/* read the meta block offset table */
if (lseek(fd, super->fragment_table_start, SEEK_SET) == (off_t)-1)
goto fail_seek;
ret = read_retry(fd, locations, blockcount * sizeof(locations[0]));
if (ret < 0)
goto fail_rd;
if ((size_t)ret < (blockcount * sizeof(locations[0])))
goto fail_trunc;
for (i = 0; i < blockcount; ++i)
locations[i] = le64toh(locations[i]);
/* read the meta blocks */
m = meta_reader_create(fd, cmp);
if (m == NULL)
goto fail;
for (i = 0, j = 0; i < blockcount && j < count; ++i, j += diff) {
if (meta_reader_seek(m, locations[i], 0))
goto fail;
diff = SQFS_META_BLOCK_SIZE / sizeof(tbl[0]);
if (diff > count)
diff = count;
if (meta_reader_read(m, tbl + j, diff * sizeof(tbl[0])))
goto fail;
}
for (i = 0; i < count; ++i) {
tbl[i].start_offset = le64toh(tbl[i].start_offset);
tbl[i].size = le32toh(tbl[i].size);
}
/* cleanup and ship it */
meta_reader_destroy(m);
free(locations);
f->tbl = tbl;
f->num_fragments = count;
f->cmp = cmp;
f->fd = fd;
f->block_size = super->block_size;
f->current_index = count;
return f;
fail_seek:
perror("seek to fragment table");
goto fail;
fail_trunc:
fputs("reading fragment table: unexpected end of file\n", stderr);
goto fail;
fail_rd:
perror("reading fragment table");
goto fail;
fail:
if (m != NULL)
meta_reader_destroy(m);
free(tbl);
free(locations);
free(f);
return NULL;
}
void frag_reader_destroy(frag_reader_t *f)
{
free(f->tbl);
free(f);
}
int frag_reader_read(frag_reader_t *f, size_t index, size_t offset,
void *buffer, size_t size)
{
if (precache_block(f, index))
return -1;
if (offset >= f->used)
goto fail_range;
if (size == 0)
return 0;
if ((offset + size - 1) >= f->used)
goto fail_range;
memcpy(buffer, f->buffer + offset, size);
return 0;
fail_range:
fputs("attempted to read past fragment block limits\n", stderr);
return -1;
}
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