A soft-core-based on-board high-speed solid-state file management method

Abstract

The application provides a file management method based on a soft core on-board high-speed solid storage, which comprises the following steps: dividing a solid storage logical space into a metadata fixed block area and a data block area, dividing the data block area according to a fixed block size and managing the data block area according to a block number; establishing a super block, a directory table, a file table, a free block linked list and a file block number sequence of each file in a memory; serializing the above structure to generate a metadata mirror, writing the metadata mirror into the metadata fixed block area and saving multiple redundant copies; when power is restored, reading the multiple copies to make a consistency judgment, selecting an effective mirror to analyze and rebuilding a memory index structure. Through integrated storage of metadata and data, the application avoids the life and reliability risks caused by storing metadata in an independent and vulnerable medium in a traditional scheme; a multiple-copy redundancy and consistency judgment mechanism is adopted to realize quick recovery after power failure; through a rebuilding mechanism of the memory index, the consistency of a file system state and physical data is ensured, and the reliability of an on-board storage system is improved.

Description

Technical Field

[0001] This invention relates to the field of data storage and management technology, and in particular to a file management method for onboard high-speed solid-state storage based on a soft core. Background Technology

[0002] During their on-orbit operation, spaceborne remote sensing, communication, and electronic reconnaissance missions generate massive amounts of continuous detection data. To meet the reliable storage requirements of this high-speed data, spacecraft storage systems generally use commercial off-the-shelf NVMe solid-state drives (SSDs) as high-speed storage media, which offer advantages such as high bandwidth, low latency, large capacity, and standardized interfaces. However, in aerospace engineering practice, on-board storage systems still face the following technical contradictions and challenges: First, there is a lack of file management mechanisms at the storage medium level: As an underlying block device, NVMe SSDs only support read and write operations in units of sectors or logical blocks in their logical space, and no general embedded file system is deployed; in engineering implementations, raw data streams are usually written directly at fixed granularity (such as DMA transfer blocks), resulting in the payload data appearing as continuous raw data blocks on the storage medium, lacking directory / file level organization and management capabilities; data playback, retrieval, or extraction by task requires reliance on external record tables or manual intervention, resulting in poor operational flexibility.

[0003] Second, the limited onboard resources impose strict constraints on the file system structure: the processor performance and memory capacity of aerospace embedded systems are highly limited. Traditional general-purpose file systems (such as FAT and EXT4) are difficult to meet the requirements of onboard systems for mission determinism and resource controllability due to their complex metadata structure, dynamic resource consumption, and unpredictable behavior. Specifically, the number of directories and files must have a clear upper limit, and the file index structure must be pre-allocated with controllable access time complexity to ensure that there will be no performance fluctuations or resource exhaustion during long-term on-orbit operation.

[0004] Third, metadata storage media suffers from lifespan and reliability bottlenecks: Traditional designs often store file system index information (directory entries, file allocation tables, etc.) in separate non-volatile memory (such as NOR Flash, eMMC, or NAND Flash). This type of media has a limited write lifespan (especially eMMC, which suffers from write amplification), while payload data is written frequently. Each metadata update adds to the number of writes to the small-capacity control media, accelerating its lifespan exhaustion. Furthermore, the separation of metadata from business data means that if the control media fails, all data becomes unreadable, creating a single point of failure.

[0005] Fourth, insufficient rapid recovery capability after on-orbit anomalies: Spacecraft may encounter anomalies such as system power failures during on-orbit operation. When recovering from an anomaly, it is necessary to quickly rebuild the data index and idle resource table to resume recording tasks. If the metadata is stored in volatile memory and not written to disk in time, a large amount of index information will be lost. If it is necessary to scan the entire disk to rebuild the index, the recovery time will be too long, and subsequent observation windows may be missed.

[0006] In summary, for high-speed onboard storage scenarios, there is an urgent need to design a file management method that runs on the FPGA soft-core processor side, has directory / file level management capabilities, integrates metadata and data storage, and supports redundancy protection and rapid consistency recovery, so as to achieve efficient organization and playback of high-speed payload data while meeting the high reliability and high determinism requirements of aerospace. Summary of the Invention

[0007] This invention proposes a file management method for high-speed onboard solid-state storage based on a soft core, which solves the above-mentioned problems existing in existing onboard storage systems.

[0008] The technical solution of this invention is implemented as follows: The first aspect of this invention provides a file management method for on-board high-speed solid-state storage based on a soft core, comprising: The fixed storage logical space is divided into a metadata fixed block area and a data block area. The data block area is divided into multiple data blocks according to the fixed block size and managed by block number. Create a superblock, directory table, file table, free block linked list, and file block number sequence for each file in memory; The superblock, directory table, file table, and file block number sequence of all files are serialized to generate a metadata image. The metadata image is then written into the fixed metadata block area and multiple redundant copies are saved. Upon power-on recovery, multiple redundant copies are read for consistency determination, and a valid metadata image is selected and parsed to reconstruct the superblock, directory table, file table, free block list, and file block number sequence in memory.

[0009] Specifically, the fixed block size is consistent with the DMA transfer granularity, and the number of directories and files is a preset fixed upper limit.

[0010] Specifically, the time complexity of the block allocation and reclamation operation of the free block list is O(1), that is, the block number is taken from the head of the free block list for allocation, and the released block number is inserted into the head of the free block list.

[0011] Specifically, the metadata mirror includes, in sequence, a mirror header, a superblock, a directory record array, a file record array, and a block number table; wherein, The image header includes a magic number, version number, image length, and a digest verification field; The superblock records the data block size, the total number of data blocks, the starting block number of the data block area, and the resource limit. The directory record array is used to persist the directory table in memory; The file record array is used to persist the file table in memory; The block number table is used to persist the sequence of file block numbers for all files.

[0012] Furthermore, the number of redundant copies is three, and the corresponding consistency decision rule is as follows: If the image header digests of at least two copies are identical, then the copy is selected as the valid metadata image. If only one copy passes verification, the system will enter a downgraded availability mode. If all replicas are invalid, then perform an empty index initialization.

[0013] Specifically, the method also includes the step of writing data: Receive write requests, create or search for directory entries based on task numbers, and create or search for file entries based on payload numbers, and set the file status to "writing". The requested data is divided into multiple blocks of fixed size based on the length of the requested data; For each block to be written, allocate a block number from the free block list and append the block number to the end of the corresponding file's block number sequence; Calculate the logical address based on the block number, and execute the write operation to write the data to the corresponding data block; Update the file length and block count after writing is complete; When a recording stop command is received, the file status is changed from writing to writing complete.

[0014] Specifically, the steps for rebuilding the free block linked list are as follows: Parse the valid metadata image to obtain the file block number sequence of all files; Summarize all occupied block numbers to form a set of used blocks; Traverse all block numbers in the data block area and add block numbers that are not in the used block set to the free block list in order.

[0015] Specifically, the file table records the read / write pointer and file status of each file, including writing in progress and writing completed; when the file is in the writing in progress state, reading operations are allowed on the written portion based on the read / write pointer.

[0016] A second aspect of the present invention provides an electronic device, including a memory and a processor, wherein the memory stores a computer program executable on the processor, and the processor executes the computer program to implement the steps of the file management method.

[0017] A third aspect of the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the file management method.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention avoids the lifespan and reliability risks caused by storing metadata on independent and vulnerable media in traditional solutions by storing metadata in an integrated manner with data; by using multiple redundant copies and a consistency decision mechanism, it ensures that after power failure and reset, a valid image can be quickly selected to complete system recovery, which greatly shortens the recovery time; by completely rebuilding the memory index structure, it ensures the consistency between the file system state and the physical storage data, which improves the overall reliability of the on-board storage system. (2) By setting the fixed block size of the data block area to be consistent with the DMA transfer granularity, the present invention enables data to be written without splitting or filling across granularities, realizing the direct transmission of data stream from the payload to the fixed storage, which significantly improves the writing efficiency; by setting the upper limit of the number of directories and files, the index structure in memory can be pre-allocated and the resource consumption can be predicted, avoiding the performance jitter and resource exhaustion problems caused by dynamic expansion of traditional file systems, and meeting the strict requirements of the on-board system for task determinism; (3) The present invention adopts a management method of taking the block number from the head of the linked list for allocation and inserting the released block number into the head of the linked list, which realizes that the time complexity of block allocation and reclamation operations is O(1). Regardless of the number of free blocks, each allocation or reclamation can be completed in constant time, ensuring the real-time requirements of high-speed data writing and avoiding the decline in write performance caused by fluctuations in block management overhead; (4) When writing data, the present invention automatically creates or searches for directory items based on task number and file items based on payload number, and sets the file status to writing. This mechanism enables payload data to be included in file-level management from the beginning of its generation, without the need for manual intervention or pre-configuration, thus realizing the automation of data management. At the same time, through the complete life cycle management of file status, it provides status basis for subsequent operations such as writing and reading simultaneously and data playback. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1This is a flowchart illustrating a file management method for on-board high-speed solid-state storage based on a soft core according to the present invention.

[0021] Figure 2 This is a schematic diagram illustrating the process of making a consistency decision on redundant copies in an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the data writing process in an embodiment of the present invention. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Reference Figure 1 The first aspect of this invention provides a file management method for on-board high-speed solid-state storage based on a soft core, comprising: Step S1, partition the fixed-length logical space: The fixed storage logical space is divided into a metadata fixed block area and a data block area. The data block area is divided into multiple data blocks according to the fixed block size and managed by block number.

[0025] In this step, the entire logical address space of solid-state media such as NVMe SSDs is logically divided into two regions: a fixed-block metadata region at the beginning, and a subsequent contiguous data block region. The fixed-block metadata region is specifically used to store the metadata image of the file system, and its size is pre-calculated and fixed based on the total amount of metadata and the number of redundant copies. The data block region is divided into consecutively numbered data blocks according to the fixed block size, and each data block has a unique block number. This partitioning method achieves physical isolation and integrated storage of metadata and business data: metadata no longer relies on external independent small-capacity storage, avoiding the media lifespan bottleneck in traditional solutions; at the same time, data blocks adopt unified granular management, laying the foundation for subsequent allocation and high-speed sequential writing.

[0026] Step S2, initialize the memory index structure: Create a superblock, directory table, file table, free block linked list, and file block number sequence for each file in memory.

[0027] When the system powers on or initializes, a complete index structure is dynamically constructed in the memory of the FPGA soft-core processor: the superblock is used to record global parameters (such as block size, total number of blocks, starting block number of the data area, maximum number of directories / files, etc.); the directory table is a first-level directory structure, and each directory entry contains information such as directory ID and status; the file table records the metadata of each file, including file ID, directory, file status (writing in progress / writing complete), file length, block count, read / write pointer, etc.; the free block list is a linked list structure that initially contains all free block numbers in the data block area for O(1) block allocation and reclamation; the file block number sequence corresponding to each file is used to dynamically record all block numbers already occupied by the file. The establishment of the memory index structure enables file-level operations (creation, writing, reading, deletion) to be completed quickly in memory without frequent access to the solid storage medium.

[0028] Step S3, Metadata Mirror Persistence: The superblock, directory table, file table, and file block number sequences of all files are serialized to generate a metadata image. The metadata image is then written into the fixed metadata block area and multiple redundant copies are saved.

[0029] This step converts the dynamic index structure in memory into a static, persistent metadata image. During serialization, the superblock, directory table, file table, and block number sequence of each file are sequentially packaged into a binary data block according to a predefined format, and an image header is added to form a complete metadata image. Subsequently, this image is written to multiple pre-allocated fixed locations in the metadata fixed block area using NVMe write commands, saving multiple redundant copies. Each metadata update (such as file creation, writing, or deletion) triggers an image update; the update strategy can be periodically triggered or command-triggered. By persisting the metadata to the SSD itself, the dependence on additional fragile media is eliminated, and the multi-copy redundancy design provides a foundation for subsequent reliability recovery.

[0030] Step S4, Power-on recovery and consistency determination: Upon power-on recovery, multiple redundant copies are read for consistency determination, and a valid metadata image is selected and parsed to reconstruct the superblock, directory table, file table, free block list, and file block number sequence in memory.

[0031] When the system restarts after a power outage or abnormal reset, it first reads all redundant copies from the metadata fixed block area. For each copy, it first verifies the magic number, version number, and length range of the image header, and then calculates the data digest and compares it with the header digest field. The parsing process follows the reverse process of serialization, sequentially restoring the superblock, directory table, file table, and the block number sequence of each file, and then reconstructing the directory table, file table, and file block number sequence in memory based on this. This mechanism ensures that even in harsh environments such as space radiation, even if some copies are damaged, the system can still quickly and reliably recover to the latest consistent state.

[0032] Specifically, the fixed block size is consistent with the DMA transfer granularity, and the number of directories and files is a preset fixed upper limit.

[0033] In this embodiment, the fixed block size is preferably 1MB, which is strictly consistent with the DMA transfer granularity of onboard data processing. This eliminates the need for cross-granularity splitting or padding at the driver layer during data writing. The data stream can be written directly from the payload to the fixed memory in whole blocks through the DMA channel, maximizing the use of bus bandwidth and achieving line-speed writing. Simultaneously, the number of directories and files is preset to a fixed upper limit (e.g., a maximum of 256 directories and a maximum of 512 files per directory). This allows the directory and file tables in memory to be pre-allocated using static arrays, avoiding the uncertainty and fragmentation issues caused by dynamic memory allocation and meeting the stringent requirements of onboard systems for resource controllability and task determinism.

[0034] Specifically, the time complexity of the block allocation and reclamation operation of the free block list is O(1), that is, the block number is taken from the head of the free block list for allocation, and the released block number is inserted into the head of the free block list.

[0035] The free block list is implemented using either a singly linked list or a doubly linked list, with the head pointer always pointing to the first free block. When a block needs to be allocated, the node is directly removed from the head of the list, the block number is retrieved, and the head pointer is set to the next node, resulting in a time complexity of O(1). When a file is deleted or a block is released, the node with the released block number is inserted into the head of the list, also requiring constant time. This design avoids traversing the linked list or sorting operations, ensuring that block allocation and reclamation do not become performance bottlenecks during high-speed data writing. Regardless of the proportion of used solid memory space, the system can maintain a stable write throughput.

[0036] Specifically, the metadata mirror includes, in sequence, a mirror header, a superblock, a directory record array, a file record array, and a block number table; wherein, The image header includes a magic number, version number, image length, and a digest verification field; The superblock records the data block size, the total number of data blocks, the starting block number of the data block area, and the resource limit. The directory record array is used to persist the directory table in memory; The file record array is used to persist the file table in memory; The block number table is used to persist the sequence of file block numbers for all files.

[0037] The image header is located at the very beginning of the metadata image. Its magic number field is used to quickly identify the image type, the version number supports future protocol upgrades, the image length facilitates reading the complete image, and the digest checksum field is used to verify the integrity of the image data. The superblock records the core configuration parameters of the file system, ensuring context consistency during parsing. The directory record array and file record array correspond one-to-one with the directory table and file table in memory, respectively. Each directory record / file record uses a fixed-length structure for fast indexing. The block number table arranges the block number sequence of all files consecutively, usually organized by file. It first records the block number of the file, and then records the block numbers sequentially. This contiguous storage method helps reduce random reads and writes and speeds up parsing during recovery.

[0038] Furthermore, such as Figure 2 As shown, the number of redundant replicas is three, and the corresponding consistency decision rule is: If the image header digests of at least two copies are identical, then the copy is selected as the valid metadata image. If only one copy passes verification, the system will enter a downgraded availability mode. If all replicas are invalid, then perform an empty index initialization.

[0039] This embodiment employs a three-replica redundancy strategy to achieve a balance between reliability, storage overhead, and recovery complexity. During consistency determination, each replica is first checked for integrity (magic number, version, digest), and replicas that pass the checks are added to the candidate set. If at least two replicas in the candidate set have completely identical content, the version is considered a valid image, and the system is rebuilt using this image. If only one replica is valid, it indicates that the other replicas are corrupted. In this case, the system can still use the valid replica for recovery, but it is marked as degraded mode, prompting the ground team to monitor the storage health status. If no replica passes the checks, it is considered a failure, and the system automatically performs empty index initialization, i.e., creates a blank file system, ensuring that new data can be recorded at least again. This decision rule fully utilizes multi-replica redundancy, significantly improving the system's survivability under failure.

[0040] Specifically, such as Figure 3 As shown, the method also includes the step of writing data: Receive write requests, create or search for directory entries based on task numbers, and create or search for file entries based on payload numbers, and set the file status to "writing". The requested data is divided into multiple blocks of fixed size based on the length of the requested data; For each block to be written, allocate a block number from the free block list and append the block number to the end of the corresponding file's block number sequence; Calculate the logical address based on the block number, and execute the write operation to write the data to the corresponding data block; Update the file length and block count after writing is complete; When a recording stop command is received, the file status is changed from writing to writing complete.

[0041] This embodiment takes a remote sensing imaging mission as an example: the ground command specifies the mission number and payload number. After receiving the write request, the system first checks if the mission number exists in the directory table. If not, a new directory entry is created. Then, it searches the file table for the file corresponding to the payload number. If not, a new file entry is created, and the file status is initialized to "writing". Next, the system calculates the number of data blocks required based on the length of the data to be written (rounded up by the fixed block size) and executes the following in a loop: a free block number is obtained from the head of the free block list and appended to the end of the file's block number sequence; the starting logical block address of the block in the SSD is calculated based on the block number, and a write command is issued to write the data; after each block is written, the file length and block count in the file table are updated; when all data is written and a recording stop command is received, the file status is changed from "writing" to "writing complete", indicating that the file has been completely recorded. This process realizes automated management from data generation to file encapsulation.

[0042] Specifically, the steps for rebuilding the free block linked list are as follows: Parse the valid metadata image to obtain the file block number sequence of all files; Summarize all occupied block numbers to form a set of used blocks; Traverse all block numbers in the data block area and add block numbers that are not in the used block set to the free block list in order.

[0043] During power-on recovery, after reconstructing the directory table, file table, and file block number sequence from the valid image, it is necessary to rebuild the free block list. Since the image does not directly store free block information, this step uses a reverse derivation method: First, it traverses the file block number sequence of all files, recording all occurrences of block numbers into a bitmap or hash table to form a set of used blocks; then, it traverses all block numbers in the entire data block area, checking whether each block number exists in the set of used blocks. If it does not exist, it means that the block is free, and it is added to the free block list in sequence. This method does not require additional storage of the free block list in the metadata image, saving storage space, while ensuring precise consistency between the free block list and file occupancy.

[0044] Specifically, the file table records the read / write pointer and file status of each file, including writing in progress and writing completed; when the file is in the writing in progress state, reading operations are allowed on the written portion based on the read / write pointer.

[0045] To enable simultaneous writing and reading, each file maintains a read pointer and a write pointer in its file table, in addition to recording the file length and block number sequence. The write pointer points to the offset within the currently being written data block, while the read pointer records the current position during playback. When a file is being written, although it is not completely closed, the system allows external read requests. During reading, the system looks up the corresponding block number and offset within the block based on the read pointer position, reads the data from the SSD, and simultaneously moves the read pointer forward. This mechanism allows payload data to be downloaded or processed online in real time during continuous recording. For example, remote sensing satellites can download partially imaged data to the ground while simultaneously imaging, greatly improving the timeliness of data acquisition.

[0046] A second aspect of the present invention provides an electronic device, including a memory and a processor, wherein the memory stores a computer program executable on the processor, and the processor executes the computer program to implement the steps of the file management method.

[0047] This electronic device can be an onboard computer, an FPGA soft-core processing system, or other embedded processing unit. The processor executes program code in memory to implement all steps of the aforementioned file management method, including space partitioning, index maintenance, metadata persistence, power-on recovery, and write processing. This device features high reliability, high determinism, and rapid recovery, making it suitable for spacecraft payload data management.

[0048] A third aspect of the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the file management method.

[0049] The computer-readable storage medium can be any non-volatile storage medium such as solid-state memory, flash memory chip, CD-ROM, or hard disk. The program code stored in the medium, after being loaded into the processor, can guide the system to execute the file management method of this invention, thereby realizing file-level management functionality for high-speed onboard solid-state storage. By distributing this storage medium, the technical solution of this invention can be quickly deployed on different hardware platforms.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A file management method for onboard high-speed solid-state storage based on a soft core, characterized in that, include: The fixed storage logical space is divided into a metadata fixed block area and a data block area. The data block area is divided into multiple data blocks according to the fixed block size and managed by block number. Create a superblock, directory table, file table, free block linked list, and file block number sequence for each file in memory; The superblock, directory table, file table, and file block number sequence of all files are serialized to generate a metadata image. The metadata image is then written into the fixed metadata block area and multiple redundant copies are saved. Upon power-on recovery, multiple redundant copies are read for consistency determination, and a valid metadata image is selected and parsed to reconstruct the superblock, directory table, file table, free block list, and file block number sequence in memory.

2. The file management method for on-board high-speed solid-state storage based on a soft core as described in claim 1, characterized in that, The fixed block size is consistent with the DMA transfer granularity, and the number of directories and files is a preset fixed upper limit.

3. The file management method for on-board high-speed solid-state storage based on a soft core as described in claim 1, characterized in that, The time complexity of block allocation and reclamation operations in the free block list is O(1), that is, the block number is taken from the head of the free block list for allocation, and the released block number is inserted into the head of the free block list.

4. The file management method for on-board high-speed solid-state storage based on a soft core as described in claim 1, characterized in that, The metadata image includes, in sequence, an image header, a superblock, a directory record array, a file record array, and a block number table; wherein, The image header includes a magic number, version number, image length, and a digest verification field; The superblock records the data block size, the total number of data blocks, the starting block number of the data block area, and the resource limit. The directory record array is used to persist the directory table in memory; The file record array is used to persist the file table in memory; The block number table is used to persist the sequence of file block numbers for all files.

5. The file management method for on-board high-speed solid-state storage based on a soft core as described in claim 4, characterized in that, The number of redundant replicas is three, and the corresponding consistency decision rule is as follows: If the image header digests of at least two copies are identical, then the copy is selected as the valid metadata image. If only one copy passes verification, the system will enter a downgraded availability mode. If all replicas are invalid, then perform an empty index initialization.

6. The file management method for on-board high-speed solid-state storage based on a soft core as described in claim 1, characterized in that, The method also includes steps for writing data: Receive write requests, create or search for directory entries based on task numbers, and create or search for file entries based on payload numbers, and set the file status to "writing". The requested data is divided into multiple blocks of fixed size based on the length of the requested data; For each block to be written, allocate a block number from the free block list and append the block number to the end of the corresponding file's block number sequence; Calculate the logical address based on the block number, and execute the write operation to write the data to the corresponding data block; Update the file length and block count after writing is complete; When a recording stop command is received, the file status is changed from writing to writing complete.

7. The file management method for on-board high-speed solid-state storage based on a soft core as described in claim 1, characterized in that, The specific steps for rebuilding the free block list are as follows: Parse the valid metadata image to obtain the file block number sequence of all files; Summarize all occupied block numbers to form a set of used blocks; Traverse all block numbers in the data block area and add block numbers that are not in the used block set to the free block list in order.

8. The file management method for on-board high-speed solid-state storage based on a soft core as described in claim 1, characterized in that, The file table records the read / write pointer and file status for each file, including writing in progress and writing completed. When a file is in the writing in progress state, reading operations are allowed on the written portion based on the read / write pointer.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the file management method as described in any one of claims 1 to 8.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the file management method as described in any one of claims 1 to 8.

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