1 files changed, 314 insertions, 0 deletions
diff --git a/lib/sqfshelper/data_reader.c b/lib/sqfshelper/data_reader.c
new file mode 100644
index 0000000..4ad6266
--- /dev/null
+++ b/lib/sqfshelper/data_reader.c
@@ -0,0 +1,314 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * data_reader.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+
+#include "data_reader.h"
+#include "highlevel.h"
+#include "util.h"
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdio.h>
+
+struct data_reader_t {
+	sqfs_fragment_t *frag;
+	size_t num_fragments;
+	size_t current_frag_index;
+	size_t frag_used;
+
+	off_t current_block;
+
+	compressor_t *cmp;
+	size_t block_size;
+	int sqfsfd;
+
+	void *block;
+	void *scratch;
+	void *frag_block;
+};
+
+static ssize_t read_block(data_reader_t *data, off_t offset, uint32_t size,
+			  void *dst)
+{
+	bool compressed = SQFS_IS_BLOCK_COMPRESSED(size);
+	void *ptr = compressed ? data->scratch : dst;
+	ssize_t ret;
+
+	size = SQFS_ON_DISK_BLOCK_SIZE(size);
+
+	if (size > data->block_size)
+		goto fail_bs;
+
+	if (read_data_at("reading block", offset, data->sqfsfd, ptr, size))
+		return -1;
+
+	if (compressed) {
+		ret = data->cmp->do_block(data->cmp, data->scratch, size,
+					  dst, data->block_size);
+		if (ret <= 0) {
+			fputs("extracting block failed\n", stderr);
+			return -1;
+		}
+		size = ret;
+	}
+
+	return size;
+fail_bs:
+	fputs("found compressed block larger than block size\n", stderr);
+	return -1;
+}
+
+static int precache_data_block(data_reader_t *data, off_t location,
+			       uint32_t size)
+{
+	ssize_t ret;
+
+	if (data->current_block == location)
+		return 0;
+
+	ret = read_block(data, location, size, data->block);
+	if (ret < 0)
+		return -1;
+
+	if ((size_t)ret < data->block_size)
+		memset((char *)data->block + ret, 0, data->block_size - ret);
+
+	data->current_block = location;
+	return 0;
+}
+
+static int precache_fragment_block(data_reader_t *data, size_t idx)
+{
+	ssize_t ret;
+
+	if (idx == data->current_frag_index)
+		return 0;
+
+	if (idx >= data->num_fragments) {
+		fputs("fragment index out of bounds\n", stderr);
+		return -1;
+	}
+
+	ret = read_block(data, data->frag[idx].start_offset,
+			 data->frag[idx].size, data->frag_block);
+	if (ret < 0)
+		return -1;
+
+	data->current_frag_index = idx;
+	data->frag_used = ret;
+	return 0;
+}
+
+data_reader_t *data_reader_create(int fd, sqfs_super_t *super,
+				  compressor_t *cmp)
+{
+	data_reader_t *data = alloc_flex(sizeof(*data), super->block_size, 3);
+	size_t i, size;
+
+	if (data == NULL) {
+		perror("creating data reader");
+		return data;
+	}
+
+	data->num_fragments = super->fragment_entry_count;
+	data->current_frag_index = super->fragment_entry_count;
+	data->block = (char *)data + sizeof(*data);
+	data->scratch = (char *)data->block + super->block_size;
+	data->frag_block = (char *)data->scratch + super->block_size;
+	data->current_block = -1;
+	data->sqfsfd = fd;
+	data->block_size = super->block_size;
+	data->cmp = cmp;
+
+	if (super->fragment_entry_count == 0 ||
+	    (super->flags & SQFS_FLAG_NO_FRAGMENTS) != 0) {
+		return data;
+	}
+
+	if (super->fragment_table_start >= super->bytes_used) {
+		fputs("Fragment table start is past end of file\n", stderr);
+		free(data);
+		return NULL;
+	}
+
+	if (SZ_MUL_OV(sizeof(data->frag[0]), data->num_fragments, &size)) {
+		fputs("Too many fragments: overflow\n", stderr);
+		free(data);
+		return NULL;
+	}
+
+	data->frag = sqfs_read_table(fd, cmp, size,
+				     super->fragment_table_start,
+				     super->directory_table_start,
+				     super->fragment_table_start);
+	if (data->frag == NULL) {
+		free(data);
+		return NULL;
+	}
+
+	for (i = 0; i < data->num_fragments; ++i) {
+		data->frag[i].size = le32toh(data->frag[i].size);
+		data->frag[i].start_offset =
+			le64toh(data->frag[i].start_offset);
+	}
+
+	return data;
+}
+
+void data_reader_destroy(data_reader_t *data)
+{
+	free(data->frag);
+	free(data);
+}
+
+int data_reader_dump_file(data_reader_t *data, file_info_t *fi, int outfd,
+			  bool allow_sparse)
+{
+	uint64_t filesz = fi->size;
+	size_t fragsz = fi->size % data->block_size;
+	size_t count = fi->size / data->block_size;
+	off_t off = fi->startblock;
+	size_t i, diff;
+
+	if (fragsz != 0 && !(fi->flags & FILE_FLAG_HAS_FRAGMENT)) {
+		fragsz = 0;
+		++count;
+	}
+
+	if (allow_sparse && ftruncate(outfd, filesz))
+		goto fail_sparse;
+
+	for (i = 0; i < count; ++i) {
+		diff = filesz > data->block_size ? data->block_size : filesz;
+		filesz -= diff;
+
+		if (SQFS_IS_SPARSE_BLOCK(fi->blocks[i].size)) {
+			if (allow_sparse) {
+				if (lseek(outfd, diff, SEEK_CUR) == (off_t)-1)
+					goto fail_sparse;
+				continue;
+			}
+			memset(data->block, 0, diff);
+		} else {
+			if (precache_data_block(data, off, fi->blocks[i].size))
+				return -1;
+			off += SQFS_ON_DISK_BLOCK_SIZE(fi->blocks[i].size);
+		}
+
+		if (write_data("writing uncompressed block",
+			       outfd, data->block, diff)) {
+			return -1;
+		}
+	}
+
+	if (fragsz > 0) {
+		if (precache_fragment_block(data, fi->fragment))
+			return -1;
+
+		if (fi->fragment_offset >= data->frag_used)
+			goto fail_range;
+
+		if ((fi->fragment_offset + fragsz - 1) >= data->frag_used)
+			goto fail_range;
+
+		if (write_data("writing uncompressed fragment", outfd,
+			       (char *)data->frag_block + fi->fragment_offset,
+			       fragsz)) {
+			return -1;
+		}
+	}
+
+	return 0;
+fail_range:
+	fputs("attempted to read past fragment block limits\n", stderr);
+	return -1;
+fail_sparse:
+	perror("creating sparse output file");
+	return -1;
+}
+
+ssize_t data_reader_read(data_reader_t *data, file_info_t *fi,
+			 uint64_t offset, void *buffer, size_t size)
+{
+	size_t i, diff, fragsz, count, total = 0;
+	off_t off;
+	char *ptr;
+
+	/* work out block count and fragment size */
+	fragsz = fi->size % data->block_size;
+	count = fi->size / data->block_size;
+
+	if (fragsz != 0 && !(fi->flags & FILE_FLAG_HAS_FRAGMENT)) {
+		fragsz = 0;
+		++count;
+	}
+
+	/* work out block index and on-disk location */
+	off = fi->startblock;
+	i = 0;
+
+	while (offset > data->block_size && i < count) {
+		off += SQFS_ON_DISK_BLOCK_SIZE(fi->blocks[i++].size);
+		offset -= data->block_size;
+	}
+
+	/* copy data from blocks */
+	while (i < count && size > 0) {
+		diff = data->block_size - offset;
+		if (size < diff)
+			size = diff;
+
+		if (SQFS_IS_SPARSE_BLOCK(fi->blocks[i].size)) {
+			memset(buffer, 0, diff);
+		} else {
+			if (precache_data_block(data, off, fi->blocks[i].size))
+				return -1;
+
+			memcpy(buffer, (char *)data->block + offset, diff);
+			off += SQFS_ON_DISK_BLOCK_SIZE(fi->blocks[i].size);
+		}
+
+		++i;
+		offset = 0;
+		size -= diff;
+		total += diff;
+		buffer = (char *)buffer + diff;
+	}
+
+	/* copy from fragment */
+	if (i == count && size > 0 && fragsz > 0) {
+		if (precache_fragment_block(data, fi->fragment))
+			return -1;
+
+		if (fi->fragment_offset >= data->frag_used)
+			goto fail_range;
+
+		if ((fi->fragment_offset + fragsz - 1) >= data->frag_used)
+			goto fail_range;
+
+		ptr = (char *)data->frag_block + fi->fragment_offset;
+		ptr += offset;
+
+		if (offset >= fragsz) {
+			offset = 0;
+			size = 0;
+		}
+
+		if (offset + size > fragsz)
+			size = fragsz - offset;
+
+		if (size > 0) {
+			memcpy(buffer, ptr + offset, size);
+			total += size;
+		}
+	}
+	return total;
+fail_range:
+	fputs("attempted to read past fragment block limits\n", stderr);
+	return -1;
+}