275 lines
9.7 KiB
Markdown
275 lines
9.7 KiB
Markdown
liberasurecode API Definition
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=============================
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``` c
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/* liberasurecode frontend API functions */
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/**
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* Create a liberasurecode instance and return a descriptor
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* for use with EC operations (encode, decode, reconstruct)
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*
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* @param id - one of the supported backends as
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* defined by ec_backend_id_t
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* @param ec_args - arguments to the EC backend
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* arguments common to all backends
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* k - number of data fragments
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* m - number of parity fragments
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* w - word size, in bits
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* hd - hamming distance (=m for Reed-Solomon)
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* ct - fragment checksum type (stored with the fragment metadata)
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* backend-specific arguments
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* null_args - arguments for the null backend
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* flat_xor_hd, jerasure do not require any special args
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*
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* @return liberasurecode instance descriptor (int > 0)
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*/
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int liberasurecode_instance_create(const ec_backend_id_t id,
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struct ec_args *args);
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/**
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* Close a liberasurecode instance
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*
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* @param desc - liberasurecode descriptor to close
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*
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* @return 0 on success, otherwise non-zero error code
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*/
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int liberasurecode_instance_destroy(int desc);
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/**
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* Erasure encode a data buffer
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param orig_data - data to encode
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* @param orig_data_size - length of data to encode
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* @param encoded_data - pointer to _output_ array (char **) of k data
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* fragments (char *), allocated by the callee
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* @param encoded_parity - pointer to _output_ array (char **) of m parity
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* fragments (char *), allocated by the callee
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* @param fragment_len - pointer to _output_ length of each fragment, assuming
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* all fragments are the same length
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*
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* @return 0 on success, -error code otherwise
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*/
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int liberasurecode_encode(int desc,
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const char *orig_data, uint64_t orig_data_size, /* input */
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char ***encoded_data, char ***encoded_parity, /* output */
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uint64_t *fragment_len); /* output */
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/**
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* Cleanup structures allocated by librasurecode_encode
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*
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* The caller has no context, so cannot safely free memory
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* allocated by liberasurecode, so it must pass the
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* deallocation responsibility back to liberasurecode.
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param encoded_data - (char **) array of k data
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* fragments (char *), allocated by liberasurecode_encode
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* @param encoded_parity - (char **) array of m parity
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* fragments (char *), allocated by liberasurecode_encode
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*
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* @return 0 in success; -error otherwise
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*/
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int liberasurecode_encode_cleanup(int desc, char **encoded_data,
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char **encoded_parity);
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/**
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* Reconstruct original data from a set of k encoded fragments
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param fragments - erasure encoded fragments (> = k)
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* @param num_fragments - number of fragments being passed in
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* @param fragment_len - length of each fragment (assume they are the same)
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* @param force_metadata_checks - force fragment metadata checks (default: 0)
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* @param out_data - _output_ pointer to decoded data
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* @param out_data_len - _output_ length of decoded output
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* (both output data pointers are allocated by liberasurecode,
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* caller invokes liberasurecode_decode_clean() after it has
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* read decoded data in 'out_data')
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*
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* @return 0 on success, -error code otherwise
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*/
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int liberasurecode_decode(int desc,
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char **available_fragments, /* input */
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int num_fragments, uint64_t fragment_len, /* input */
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int force_metadata_checks, /* input */
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char **out_data, uint64_t *out_data_len); /* output */
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/**
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* Cleanup structures allocated by librasurecode_decode
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*
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* The caller has no context, so cannot safely free memory
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* allocated by liberasurecode, so it must pass the
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* deallocation responsibility back to liberasurecode.
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param data - (char *) buffer of data decoded by librasurecode_decode
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*
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* @return 0 on success; -error otherwise
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*/
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int liberasurecode_decode_cleanup(int desc, char *data);
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/**
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* Reconstruct a missing fragment from a subset of available fragments
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param available_fragments - erasure encoded fragments
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* @param num_fragments - number of fragments being passed in
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* @param fragment_len - size in bytes of the fragments
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* @param destination_idx - missing idx to reconstruct
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* @param out_fragment - output of reconstruct
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*
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* @return 0 on success, -error code otherwise
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*/
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int liberasurecode_reconstruct_fragment(int desc,
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char **available_fragments, /* input */
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int num_fragments, uint64_t fragment_len, /* input */
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int destination_idx, /* input */
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char* out_fragment); /* output */
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/**
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* Return a list of lists with valid rebuild indexes given
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* a list of missing indexes.
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*
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* @desc: liberasurecode instance descriptor (obtained with
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* liberasurecode_instance_create)
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* @fragments_to_reconstruct list of indexes to reconstruct
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* @fragments_to_exclude list of indexes to exclude from
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* reconstruction equation
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* @fragments_needed list of fragments needed to reconstruct
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* fragments in fragments_to_reconstruct
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*
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* @return 0 on success, non-zero on error
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*/
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int liberasurecode_fragments_needed(int desc,
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int *fragments_to_reconstruct,
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int *fragments_to_exclude,
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int *fragments_needed);
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```
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Erasure Code Fragment Checksum Types Supported
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----------------------------------------------
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``` c
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/* Checksum types supported for fragment metadata stored in each fragment */
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typedef enum {
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CHKSUM_NONE = 0, /* "none" (default) */
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CHKSUM_CRC32 = 1, /* "crc32" */
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CHKSUM_TYPES_MAX,
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} ec_checksum_type_t;
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```
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Erasure Code Fragment Checksum API
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----------------------------------
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``` c
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struct __attribute__((__packed__))
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fragment_metadata
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{
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uint32_t idx; /* 4 */
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uint32_t size; /* 4 */
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uint32_t frag_backend_metadata_size; /* 4 */
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uint64_t orig_data_size; /* 8 */
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uint8_t chksum_type; /* 1 */
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uint32_t chksum[LIBERASURECODE_MAX_CHECKSUM_LEN]; /* 32 */
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uint8_t chksum_mismatch; /* 1 */
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uint8_t backend_id; /* 1 */
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uint32_t backend_version; /* 4 */
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} fragment_metadata_t;
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#define FRAGSIZE_2_BLOCKSIZE(fragment_size) \
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(fragment_size - sizeof(fragment_header_t))
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/**
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* Get opaque metadata for a fragment. The metadata is opaque to the
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* client, but meaningful to the underlying library. It is used to verify
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* stripes in verify_stripe_metadata().
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*
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* @param fragment - fragment data pointer
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* @param fragment_metadata - pointer to allocated buffer of size at least
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* sizeof(struct fragment_metadata) to hold fragment metadata struct
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*
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* @return 0 on success, non-zero on error
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*/
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//EDL: This needs to be implemented
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int liberasurecode_get_fragment_metadata(char *fragment,
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fragment_metadata_t *fragment_metadata);
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/**
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* Verify that the specified pointer points to a well formed fragment that can
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* be processed by both this instance of liberasurecode and the specified
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* backend.
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param fragment - fragment to verify
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*
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* @return 1 if fragment validation fails, 0 otherwise.
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*/
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int is_invalid_fragment(int desc, char *fragment);
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/**
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* Verify a subset of fragments generated by encode()
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param fragments - fragments part of the EC stripe to verify
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* @param num_fragments - number of fragments part of the EC stripe
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*
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* @return 1 if stripe checksum verification is successful, 0 otherwise
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*/
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int liberasurecode_verify_stripe_metadata(int desc,
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char **fragments, int num_fragments);
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/* ==~=*=~===~=*=~==~=*=~== liberasurecode Helpers ==~*==~=*=~==~=~=*=~==~= */
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/**
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* This computes the aligned size of a buffer passed into
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* the encode function. The encode function must pad fragments
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* to be algined with the word size (w) and the last fragment also
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* needs to be aligned. This computes the sum of the algined fragment
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* sizes for a given buffer to encode.
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param data_len - original data length in bytes
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*
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* @return aligned length, or -error code on error
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*/
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int liberasurecode_get_aligned_data_size(int desc, uint64_t data_len);
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/**
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* This will return the minimum encode size, which is the minimum
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* buffer size that can be encoded.
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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*
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* @return minimum data length length, or -error code on error
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*/
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int liberasurecode_get_minimum_encode_size(int desc);
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/**
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* This will return the fragment size, which is each fragment data
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* length the backend will allocate when encoding.
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param data_len - original data length in bytes
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*
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* @return fragment size - sizeof(fragment_header) + size
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* + frag_backend_metadata_size
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*/
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int liberasurecode_get_fragment_size(int desc, int data_len);
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``` |