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authorDavid Oberhollenzer <david.oberhollenzer@sigma-star.at>2019-05-03 17:35:37 +0200
committerDavid Oberhollenzer <david.oberhollenzer@sigma-star.at>2019-05-03 21:45:46 +0200
commit12c8196ad46808dc9d0e84b3a798509dcf1a41e7 (patch)
tree9069df66c14ca427540290ca1fb88688c859bb15
parent0903622b468136ef4354f33ebb24b12df0f549bb (diff)
Add utility functions to read the fragment data from an image
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
-rw-r--r--include/frag_reader.h31
-rw-r--r--lib/Makemodule.am3
-rw-r--r--lib/sqfs/frag_reader.c179
3 files changed, 212 insertions, 1 deletions
diff --git a/include/frag_reader.h b/include/frag_reader.h
new file mode 100644
index 0000000..6495f5b
--- /dev/null
+++ b/include/frag_reader.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#ifndef FRAG_READER_H
+#define FRAG_READER_H
+
+#include "squashfs.h"
+#include "compress.h"
+
+#include <stdint.h>
+#include <stddef.h>
+
+typedef struct {
+ 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[];
+} frag_reader_t;
+
+frag_reader_t *frag_reader_create(sqfs_super_t *super, int fd,
+ compressor_t *cmp);
+
+void frag_reader_destroy(frag_reader_t *f);
+
+int frag_reader_read(frag_reader_t *f, size_t index, size_t offset,
+ void *buffer, size_t size);
+
+#endif /* FRAG_READER_H */
diff --git a/lib/Makemodule.am b/lib/Makemodule.am
index 3b171c6..f23d9b7 100644
--- a/lib/Makemodule.am
+++ b/lib/Makemodule.am
@@ -14,7 +14,8 @@ libsquashfs_a_SOURCES += lib/sqfs/table.c include/table.h
libsquashfs_a_SOURCES += lib/sqfs/read_super.c lib/sqfs/meta_reader.c
libsquashfs_a_SOURCES += include/meta_reader.h lib/sqfs/id_table_write.c
libsquashfs_a_SOURCES += lib/sqfs/id_table_read.c lib/sqfs/read_inode.c
-libsquashfs_a_SOURCES += lib/sqfs/readdir.c
+libsquashfs_a_SOURCES += lib/sqfs/readdir.c lib/sqfs/frag_reader.c
+libsquashfs_a_SOURCES += include/frag_reader.h
libutil_a_SOURCES = lib/util/canonicalize_name.c lib/util/write_retry.c
libutil_a_SOURCES += lib/util/read_retry.c include/util.h
diff --git a/lib/sqfs/frag_reader.c b/lib/sqfs/frag_reader.c
new file mode 100644
index 0000000..1906376
--- /dev/null
+++ b/lib/sqfs/frag_reader.c
@@ -0,0 +1,179 @@
+/* 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>
+
+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);
+
+ if (ret <= 0) {
+ fputs("extracting fragment failed\n", stderr);
+ return -1;
+ }
+ }
+
+ 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);
+ if (f == NULL)
+ goto fail_rd;
+
+ tbl = malloc(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;
+}