Move file extraction code to generic data_reader_t in libsquashfs.a

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

2 files changed, 159 insertions, 2 deletions

diff --git a/lib/Makemodule.am b/lib/Makemodule.am
index 3c1ef12..ddc78f6 100644
--- a/lib/Makemodule.am
+++ b/lib/Makemodule.am
@@ -23,8 +23,8 @@ libsquashfs_a_SOURCES += lib/sqfs/serialize_fstree.c
 libsquashfs_a_SOURCES += lib/sqfs/tree_node_from_inode.c
 libsquashfs_a_SOURCES += lib/sqfs/deserialize_fstree.c
 libsquashfs_a_SOURCES += lib/sqfs/data_writer.c lib/sqfs/write_xattr.c
-libsquashfs_a_SOURCES += include/data_writer.h
-libsquashfs_a_SOURCES += include/frag_reader.h
+libsquashfs_a_SOURCES += include/data_writer.h include/frag_reader.h
+libsquashfs_a_SOURCES += include/data_reader.h lib/sqfs/data_reader.c
 
 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/data_reader.c b/lib/sqfs/data_reader.c
new file mode 100644
index 0000000..22413f2
--- /dev/null
+++ b/lib/sqfs/data_reader.c
@@ -0,0 +1,157 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "data_reader.h"
+#include "frag_reader.h"
+#include "util.h"
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+
+struct data_reader_t {
+	compressor_t *cmp;
+	size_t block_size;
+	frag_reader_t *frag;
+	int sqfsfd;
+
+	void *buffer;
+	void *scratch;
+};
+
+data_reader_t *data_reader_create(int fd, sqfs_super_t *super,
+				  compressor_t *cmp)
+{
+	data_reader_t *data = calloc(1, sizeof(*data) + 2 * super->block_size);
+
+	if (data == NULL) {
+		perror("creating data reader");
+		return data;
+	}
+
+	if (super->fragment_entry_count > 0 &&
+	    !(super->flags & SQFS_FLAG_NO_FRAGMENTS)) {
+		if (super->fragment_table_start >= super->bytes_used) {
+			fputs("Fragment table start is past end of file\n",
+			      stderr);
+			free(data);
+			return NULL;
+		}
+
+		data->frag = frag_reader_create(super, fd, cmp);
+		if (data->frag == NULL) {
+			free(data);
+			return NULL;
+		}
+	}
+
+	data->buffer = (char *)data + sizeof(*data);
+	data->scratch = (char *)data->buffer + super->block_size;
+	data->sqfsfd = fd;
+	data->block_size = super->block_size;
+	data->cmp = cmp;
+	return data;
+}
+
+void data_reader_destroy(data_reader_t *data)
+{
+	if (data->frag != NULL)
+		frag_reader_destroy(data->frag);
+	free(data);
+}
+
+int data_reader_dump_file(data_reader_t *data, file_info_t *fi, int outfd)
+{
+	size_t i, count, fragsz;
+	bool compressed;
+	uint32_t bs;
+	ssize_t ret;
+	void *ptr;
+
+	count = fi->size / data->block_size;
+
+	if (count > 0) {
+		if (lseek(data->sqfsfd, fi->startblock, SEEK_SET) == (off_t)-1)
+			goto fail_seek;
+
+		for (i = 0; i < count; ++i) {
+			bs = fi->blocksizes[i];
+
+			compressed = (bs & (1 << 24)) == 0;
+			bs &= (1 << 24) - 1;
+
+			if (bs > data->block_size)
+				goto fail_bs;
+
+			ret = read_retry(data->sqfsfd, data->buffer, bs);
+			if (ret < 0)
+				goto fail_rd;
+
+			if ((size_t)ret < bs)
+				goto fail_trunc;
+
+			if (compressed) {
+				ret = data->cmp->do_block(data->cmp,
+							  data->buffer, bs,
+							  data->scratch,
+							  data->block_size);
+				if (ret <= 0)
+					return -1;
+
+				bs = ret;
+				ptr = data->scratch;
+			} else {
+				ptr = data->buffer;
+			}
+
+			ret = write_retry(outfd, ptr, bs);
+			if (ret < 0)
+				goto fail_wr;
+
+			if ((size_t)ret < bs)
+				goto fail_wr_trunc;
+		}
+	}
+
+	fragsz = fi->size % data->block_size;
+
+	if (fragsz > 0) {
+		if (data->frag == NULL)
+			goto fail_frag;
+
+		if (frag_reader_read(data->frag, fi->fragment,
+				     fi->fragment_offset, data->buffer,
+				     fragsz)) {
+			return -1;
+		}
+
+		ret = write_retry(outfd, data->buffer, fragsz);
+		if (ret < 0)
+			goto fail_wr;
+
+		if ((size_t)ret < fragsz)
+			goto fail_wr_trunc;
+	}
+
+	return 0;
+fail_seek:
+	perror("seek on squashfs");
+	return -1;
+fail_wr:
+	perror("writing uncompressed block");
+	return -1;
+fail_wr_trunc:
+	fputs("writing uncompressed block: truncated write\n", stderr);
+	return -1;
+fail_rd:
+	perror("reading from squashfs");
+	return -1;
+fail_trunc:
+	fputs("reading from squashfs: unexpected end of file\n", stderr);
+	return -1;
+fail_bs:
+	fputs("found compressed block larger than block size\n", stderr);
+	return -1;
+fail_frag:
+	fputs("file not a multiple of block size but no fragments available\n",
+	      stderr);
+	return -1;
+}