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-liberasurecode
-==============
-
-liberasurecode is an Erasure Code API library written in C with pluggable Erasure Code backends.
-
-----
-
-Highlights
-==========
-
- * Unified Erasure Coding interface for common storage workloads.
-
- * Pluggable Erasure Code backends - As of v1.0, liberasurecode supports the following backends:
-
- - 'Jerasure' - Erasure Coding library that supports Reed-Solomon, Cauchy backends [1]
- - 'ISA-L' - Intel Storage Acceleration Library - SIMD accelerated Erasure Coding backends [2]
- - 'SHSS' - NTT Lab Japan's hybrid Erasure Coding backend [4]
- - 'Flat XOR HD' - built-in to liberasurecode, based on [3]
- - 'NULL' template backend implemented to help future backend writers
-
-
- * True 'plugin' architecture - liberasurecode uses Dynamically Loaded (DL) libraries to realize a true 'plugin' architecture. This also allows one to build liberasurecode indepdendent of the Erasure Code backend libraries.
-
- * Cross-platform - liberasurecode is known to work on Linux (Fedora/Debian flavors), Solaris, BSD and Darwin/Mac OS X.
-
- * Community support - Developed alongside Erasure Code authority Kevin Greenan, liberasurecode is an actively maintained open-source project with growing community involvement (Openstack Swift, Ceph, PyECLib, NTT Labs).
-
-----
-
-License
-==========
-
-liberasurecode is distributed under the terms of the **BSD** license.
-
-----
-
-Active Users
-====================
-
- * PyECLib - Python EC library: https://pypi.python.org/pypi/PyECLib
- * Openstack Swift Object Store - https://wiki.openstack.org/wiki/Swift
-
-----
-
-liberasurecode API Definition
-=============================
-
-``` c
-
-/* liberasurecode frontend API functions */
-
-/**
- * Create a liberasurecode instance and return a descriptor
- * for use with EC operations (encode, decode, reconstruct)
- *
- * @param id - one of the supported backends as
- * defined by ec_backend_id_t
- * @param ec_args - arguments to the EC backend
- * arguments common to all backends
- * k - number of data fragments
- * m - number of parity fragments
- * w - word size, in bits
- * hd - hamming distance (=m for Reed-Solomon)
- * ct - fragment checksum type (stored with the fragment metadata)
- * backend-specific arguments
- * null_args - arguments for the null backend
- * flat_xor_hd, jerasure do not require any special args
- *
- * @return liberasurecode instance descriptor (int > 0)
- */
-int liberasurecode_instance_create(const ec_backend_id_t id,
- struct ec_args *args);
-
-/**
- * Close a liberasurecode instance
- *
- * @param desc - liberasurecode descriptor to close
- *
- * @return 0 on success, otherwise non-zero error code
- */
-int liberasurecode_instance_destroy(int desc);
-
-
-/**
- * Erasure encode a data buffer
- *
- * @param desc - liberasurecode descriptor/handle
- * from liberasurecode_instance_create()
- * @param orig_data - data to encode
- * @param orig_data_size - length of data to encode
- * @param encoded_data - pointer to _output_ array (char **) of k data
- * fragments (char *), allocated by the callee
- * @param encoded_parity - pointer to _output_ array (char **) of m parity
- * fragments (char *), allocated by the callee
- * @param fragment_len - pointer to _output_ length of each fragment, assuming
- * all fragments are the same length
- *
- * @return 0 on success, -error code otherwise
- */
-int liberasurecode_encode(int desc,
- const char *orig_data, uint64_t orig_data_size, /* input */
- char ***encoded_data, char ***encoded_parity, /* output */
- uint64_t *fragment_len); /* output */
-
-/**
- * Cleanup structures allocated by librasurecode_encode
- *
- * The caller has no context, so cannot safely free memory
- * allocated by liberasurecode, so it must pass the
- * deallocation responsibility back to liberasurecode.
- *
- * @param desc - liberasurecode descriptor/handle
- * from liberasurecode_instance_create()
- * @param encoded_data - (char **) array of k data
- * fragments (char *), allocated by liberasurecode_encode
- * @param encoded_parity - (char **) array of m parity
- * fragments (char *), allocated by liberasurecode_encode
- *
- * @return 0 in success; -error otherwise
- */
-int liberasurecode_encode_cleanup(int desc, char **encoded_data,
- char **encoded_parity);
-
-/**
- * Reconstruct original data from a set of k encoded fragments
- *
- * @param desc - liberasurecode descriptor/handle
- * from liberasurecode_instance_create()
- * @param fragments - erasure encoded fragments (> = k)
- * @param num_fragments - number of fragments being passed in
- * @param fragment_len - length of each fragment (assume they are the same)
- * @param force_metadata_checks - force fragment metadata checks (default: 0)
- * @param out_data - _output_ pointer to decoded data
- * @param out_data_len - _output_ length of decoded output
- * (both output data pointers are allocated by liberasurecode,
- * caller invokes liberasurecode_decode_clean() after it has
- * read decoded data in 'out_data')
- *
- * @return 0 on success, -error code otherwise
- */
-int liberasurecode_decode(int desc,
- char **available_fragments, /* input */
- int num_fragments, uint64_t fragment_len, /* input */
- int force_metadata_checks, /* input */
- char **out_data, uint64_t *out_data_len); /* output */
-
-/**
- * Cleanup structures allocated by librasurecode_decode
- *
- * The caller has no context, so cannot safely free memory
- * allocated by liberasurecode, so it must pass the
- * deallocation responsibility back to liberasurecode.
- *
- * @param desc - liberasurecode descriptor/handle
- * from liberasurecode_instance_create()
- * @param data - (char *) buffer of data decoded by librasurecode_decode
- *
- * @return 0 on success; -error otherwise
- */
-int liberasurecode_decode_cleanup(int desc, char *data);
-
-/**
- * Reconstruct a missing fragment from a subset of available fragments
- *
- * @param desc - liberasurecode descriptor/handle
- * from liberasurecode_instance_create()
- * @param available_fragments - erasure encoded fragments
- * @param num_fragments - number of fragments being passed in
- * @param fragment_len - size in bytes of the fragments
- * @param destination_idx - missing idx to reconstruct
- * @param out_fragment - output of reconstruct
- *
- * @return 0 on success, -error code otherwise
- */
-int liberasurecode_reconstruct_fragment(int desc,
- char **available_fragments, /* input */
- int num_fragments, uint64_t fragment_len, /* input */
- int destination_idx, /* input */
- char* out_fragment); /* output */
-
-/**
- * Return a list of lists with valid rebuild indexes given
- * a list of missing indexes.
- *
- * @desc: liberasurecode instance descriptor (obtained with
- * liberasurecode_instance_create)
- * @fragments_to_reconstruct list of indexes to reconstruct
- * @fragments_to_exclude list of indexes to exclude from
- * reconstruction equation
- * @fragments_needed list of fragments needed to reconstruct
- * fragments in fragments_to_reconstruct
- *
- * @return 0 on success, non-zero on error
- */
-int liberasurecode_fragments_needed(int desc,
- int *fragments_to_reconstruct,
- int *fragments_to_exclude,
- int *fragments_needed);
-
-```
-
-Erasure Code Fragment Checksum Types Supported
-----------------------------------------------
-
-``` c
-
-/* Checksum types supported for fragment metadata stored in each fragment */
-typedef enum {
- CHKSUM_NONE = 0, /* "none" (default) */
- CHKSUM_CRC32 = 1, /* "crc32" */
- CHKSUM_TYPES_MAX,
-} ec_checksum_type_t;
-
-```
-
-Erasure Code Fragment Checksum API
-----------------------------------
-
-``` c
-
-struct __attribute__((__packed__))
-fragment_metadata
-{
- uint32_t idx; /* 4 */
- uint32_t size; /* 4 */
- uint32_t frag_backend_metadata_size; /* 4 */
- uint64_t orig_data_size; /* 8 */
- uint8_t chksum_type; /* 1 */
- uint32_t chksum[LIBERASURECODE_MAX_CHECKSUM_LEN]; /* 32 */
- uint8_t chksum_mismatch; /* 1 */
- uint8_t backend_id; /* 1 */
- uint32_t backend_version; /* 4 */
-} fragment_metadata_t;
-
-#define FRAGSIZE_2_BLOCKSIZE(fragment_size) \
- (fragment_size - sizeof(fragment_header_t))
-
-/**
- * Get opaque metadata for a fragment. The metadata is opaque to the
- * client, but meaningful to the underlying library. It is used to verify
- * stripes in verify_stripe_metadata().
- *
- * @param fragment - fragment data pointer
- * @param fragment_metadata - pointer to allocated buffer of size at least
- * sizeof(struct fragment_metadata) to hold fragment metadata struct
- *
- * @return 0 on success, non-zero on error
- */
-//EDL: This needs to be implemented
-int liberasurecode_get_fragment_metadata(char *fragment,
- fragment_metadata_t *fragment_metadata);
-
-/**
-* Verify that the specified pointer points to a well formed fragment that can
-* be processed by both this instance of liberasurecode and the specified
-* backend.
-*
-* @param desc - liberasurecode descriptor/handle
-* from liberasurecode_instance_create()
-* @param fragment - fragment to verify
-*
-* @return 1 if fragment validation fails, 0 otherwise.
-*/
-int is_invalid_fragment(int desc, char *fragment);
-
-/**
- * Verify a subset of fragments generated by encode()
- *
- * @param desc - liberasurecode descriptor/handle
- * from liberasurecode_instance_create()
- * @param fragments - fragments part of the EC stripe to verify
- * @param num_fragments - number of fragments part of the EC stripe
- *
- * @return 1 if stripe checksum verification is successful, 0 otherwise
- */
-int liberasurecode_verify_stripe_metadata(int desc,
- char **fragments, int num_fragments);
-
-/* ==~=*=~===~=*=~==~=*=~== liberasurecode Helpers ==~*==~=*=~==~=~=*=~==~= */
-
-/**
- * This computes the aligned size of a buffer passed into
- * the encode function. The encode function must pad fragments
- * to be algined with the word size (w) and the last fragment also
- * needs to be aligned. This computes the sum of the algined fragment
- * sizes for a given buffer to encode.
- *
- * @param desc - liberasurecode descriptor/handle
- * from liberasurecode_instance_create()
- * @param data_len - original data length in bytes
- *
- * @return aligned length, or -error code on error
- */
-int liberasurecode_get_aligned_data_size(int desc, uint64_t data_len);
-
-/**
- * This will return the minimum encode size, which is the minimum
- * buffer size that can be encoded.
- *
- * @param desc - liberasurecode descriptor/handle
- * from liberasurecode_instance_create()
- *
- * @return minimum data length length, or -error code on error
- */
-int liberasurecode_get_minimum_encode_size(int desc);
-
-/**
- * This will return the fragment size, which is each fragment data
- * length the backend will allocate when encoding.
- *
- * @param desc - liberasurecode descriptor/handle
- * from liberasurecode_instance_create()
- * @param data_len - original data length in bytes
- *
- * @return fragment size - sizeof(fragment_header) + size
- * + frag_backend_metadata_size
- */
-int liberasurecode_get_fragment_size(int desc, int data_len);
-```
-----
-
-
-Build and Install
-=================
-
-To build the liberasurecode repository, perform the following from the
-top-level directory:
-
-``` sh
- $ ./autogen.sh
- $ ./configure
- $ make
- $ make test
- $ sudo make install
-```
-
-----
-
-Code organization
-=================
-```
- |-- include
- | +-- erasurecode
- | | +-- erasurecode.h --> liberasurecode frontend API header
- | | +-- erasurecode_backend.h --> liberasurecode backend API header
- | +-- xor_codes --> headers for the built-in XOR codes
- |
- |-- src
- | |-- erasurecode.c --> liberasurecode API implementation
- | | (frontend + backend)
- | |-- backends
- | | +-- null
- | | +--- null.c --> 'null' erasure code backend (template backend)
- | | +-- xor
- | | +--- flat_xor_hd.c --> 'flat_xor_hd' erasure code backend (built-in)
- | | +-- jerasure
- | | +-- jerasure_rs_cauchy.c --> 'jerasure_rs_vand' erasure code backend (jerasure.org)
- | | +-- jerasure_rs_vand.c --> 'jerasure_rs_cauchy' erasure code backend (jerasure.org)
- | | +-- isa-l
- | | +-- isa_l_rs_vand.c --> 'isa_l_rs_vand' erasure code backend (Intel)
- | | +-- shss
- | | +-- shss.c --> 'shss' erasure code backend (NTT Labs)
- | |
- | |-- builtin
- | | +-- xor_codes --> XOR HD code backend, built-in erasure
- | | | code implementation (shared library)
- | | +-- xor_code.c
- | | +-- xor_hd_code.c
- | |
- | +-- utils
- | +-- chksum --> fragment checksum utils for erasure
- | +-- alg_sig.c coded fragments
- | +-- crc32.c
- |
- |-- doc --> API Documentation
- | +-- Doxyfile
- | +-- html
- |
- |--- test --> Test routines
- | +-- builtin
- | | +-- xor_codes
- | +-- liberasurecode_test.c
- | +-- utils
- |
- |-- autogen.sh
- |-- configure.ac
- |-- Makefile.am
- |-- README
- |-- NEWS
- |-- COPYING
- |-- AUTHORS
- |-- INSTALL
- +-- ChangeLog
-```
----
-
-References
-==========
-
- [1] Jerasure, C library that supports erasure coding in storage applications, http://jerasure.org
-
- [2] Intel(R) Storage Acceleration Library (Open Source Version), https://01.org/intel%C2%AE-storage-acceleration-library-open-source-version
-
- [3] Greenan, Kevin M et al, "Flat XOR-based erasure codes in storage systems", http://www.kaymgee.com/Kevin_Greenan/Publications_files/greenan-msst10.pdf
-
- [4] Kota Tsuyuzaki <tsuyuzaki.kota@lab.ntt.co.jp>, Ryuta Kon <kon.ryuta@po.ntts.co.jp>, "NTT SHSS Erasure Coding backend" \ No newline at end of file
+liberasurecode
+==============
+
+liberasurecode is an Erasure Code API library written in C with pluggable Erasure Code backends.
+
+----
+
+Highlights
+==========
+
+ * Unified Erasure Coding interface for common storage workloads.
+
+ * Pluggable Erasure Code backends - As of v1.0, liberasurecode supports the following backends:
+
+ - Native, software-only Erasure Coding implementation that supports a Reed-Solomon backend
+ - 'Jerasure' - Erasure Coding library that supports Reed-Solomon, Cauchy backends [1]
+ - 'ISA-L' - Intel Storage Acceleration Library - SIMD accelerated Erasure Coding backends [2]
+ - 'SHSS' - NTT Lab Japan's hybrid Erasure Coding backend [4]
+ - 'Flat XOR HD' - built-in to liberasurecode, based on [3]
+ - 'NULL' template backend implemented to help future backend writers
+
+
+ * True 'plugin' architecture - liberasurecode uses Dynamically Loaded (DL) libraries to realize a true 'plugin' architecture. This also allows one to build liberasurecode indepdendent of the Erasure Code backend libraries.
+
+ * Cross-platform - liberasurecode is known to work on Linux (Fedora/Debian flavors), Solaris, BSD and Darwin/Mac OS X.
+
+ * Community support - Developed alongside Erasure Code authority Kevin Greenan, liberasurecode is an actively maintained open-source project with growing community involvement (Openstack Swift, Ceph, PyECLib, NTT Labs).
+
+----
+
+License
+==========
+
+liberasurecode is distributed under the terms of the **BSD** license.
+
+----
+
+Active Users
+====================
+
+ * PyECLib - Python EC library: https://pypi.python.org/pypi/PyECLib
+ * Openstack Swift Object Store - https://wiki.openstack.org/wiki/Swift
+
+----
+
+liberasurecode API Definition
+=============================
+
+``` c
+
+/* liberasurecode frontend API functions */
+
+/**
+ * Create a liberasurecode instance and return a descriptor
+ * for use with EC operations (encode, decode, reconstruct)
+ *
+ * @param id - one of the supported backends as
+ * defined by ec_backend_id_t
+ * @param ec_args - arguments to the EC backend
+ * arguments common to all backends
+ * k - number of data fragments
+ * m - number of parity fragments
+ * w - word size, in bits
+ * hd - hamming distance (=m for Reed-Solomon)
+ * ct - fragment checksum type (stored with the fragment metadata)
+ * backend-specific arguments
+ * null_args - arguments for the null backend
+ * flat_xor_hd, jerasure do not require any special args
+ *
+ * @return liberasurecode instance descriptor (int > 0)
+ */
+int liberasurecode_instance_create(const ec_backend_id_t id,
+ struct ec_args *args);
+
+/**
+ * Close a liberasurecode instance
+ *
+ * @param desc - liberasurecode descriptor to close
+ *
+ * @return 0 on success, otherwise non-zero error code
+ */
+int liberasurecode_instance_destroy(int desc);
+
+
+/**
+ * Erasure encode a data buffer
+ *
+ * @param desc - liberasurecode descriptor/handle
+ * from liberasurecode_instance_create()
+ * @param orig_data - data to encode
+ * @param orig_data_size - length of data to encode
+ * @param encoded_data - pointer to _output_ array (char **) of k data
+ * fragments (char *), allocated by the callee
+ * @param encoded_parity - pointer to _output_ array (char **) of m parity
+ * fragments (char *), allocated by the callee
+ * @param fragment_len - pointer to _output_ length of each fragment, assuming
+ * all fragments are the same length
+ *
+ * @return 0 on success, -error code otherwise
+ */
+int liberasurecode_encode(int desc,
+ const char *orig_data, uint64_t orig_data_size, /* input */
+ char ***encoded_data, char ***encoded_parity, /* output */
+ uint64_t *fragment_len); /* output */
+
+/**
+ * Cleanup structures allocated by librasurecode_encode
+ *
+ * The caller has no context, so cannot safely free memory
+ * allocated by liberasurecode, so it must pass the
+ * deallocation responsibility back to liberasurecode.
+ *
+ * @param desc - liberasurecode descriptor/handle
+ * from liberasurecode_instance_create()
+ * @param encoded_data - (char **) array of k data
+ * fragments (char *), allocated by liberasurecode_encode
+ * @param encoded_parity - (char **) array of m parity
+ * fragments (char *), allocated by liberasurecode_encode
+ *
+ * @return 0 in success; -error otherwise
+ */
+int liberasurecode_encode_cleanup(int desc, char **encoded_data,
+ char **encoded_parity);
+
+/**
+ * Reconstruct original data from a set of k encoded fragments
+ *
+ * @param desc - liberasurecode descriptor/handle
+ * from liberasurecode_instance_create()
+ * @param fragments - erasure encoded fragments (> = k)
+ * @param num_fragments - number of fragments being passed in
+ * @param fragment_len - length of each fragment (assume they are the same)
+ * @param force_metadata_checks - force fragment metadata checks (default: 0)
+ * @param out_data - _output_ pointer to decoded data
+ * @param out_data_len - _output_ length of decoded output
+ * (both output data pointers are allocated by liberasurecode,
+ * caller invokes liberasurecode_decode_clean() after it has
+ * read decoded data in 'out_data')
+ *
+ * @return 0 on success, -error code otherwise
+ */
+int liberasurecode_decode(int desc,
+ char **available_fragments, /* input */
+ int num_fragments, uint64_t fragment_len, /* input */
+ int force_metadata_checks, /* input */
+ char **out_data, uint64_t *out_data_len); /* output */
+
+/**
+ * Cleanup structures allocated by librasurecode_decode
+ *
+ * The caller has no context, so cannot safely free memory
+ * allocated by liberasurecode, so it must pass the
+ * deallocation responsibility back to liberasurecode.
+ *
+ * @param desc - liberasurecode descriptor/handle
+ * from liberasurecode_instance_create()
+ * @param data - (char *) buffer of data decoded by librasurecode_decode
+ *
+ * @return 0 on success; -error otherwise
+ */
+int liberasurecode_decode_cleanup(int desc, char *data);
+
+/**
+ * Reconstruct a missing fragment from a subset of available fragments
+ *
+ * @param desc - liberasurecode descriptor/handle
+ * from liberasurecode_instance_create()
+ * @param available_fragments - erasure encoded fragments
+ * @param num_fragments - number of fragments being passed in
+ * @param fragment_len - size in bytes of the fragments
+ * @param destination_idx - missing idx to reconstruct
+ * @param out_fragment - output of reconstruct
+ *
+ * @return 0 on success, -error code otherwise
+ */
+int liberasurecode_reconstruct_fragment(int desc,
+ char **available_fragments, /* input */
+ int num_fragments, uint64_t fragment_len, /* input */
+ int destination_idx, /* input */
+ char* out_fragment); /* output */
+
+/**
+ * Return a list of lists with valid rebuild indexes given
+ * a list of missing indexes.
+ *
+ * @desc: liberasurecode instance descriptor (obtained with
+ * liberasurecode_instance_create)
+ * @fragments_to_reconstruct list of indexes to reconstruct
+ * @fragments_to_exclude list of indexes to exclude from
+ * reconstruction equation
+ * @fragments_needed list of fragments needed to reconstruct
+ * fragments in fragments_to_reconstruct
+ *
+ * @return 0 on success, non-zero on error
+ */
+int liberasurecode_fragments_needed(int desc,
+ int *fragments_to_reconstruct,
+ int *fragments_to_exclude,
+ int *fragments_needed);
+
+```
+
+Erasure Code Fragment Checksum Types Supported
+----------------------------------------------
+
+``` c
+
+/* Checksum types supported for fragment metadata stored in each fragment */
+typedef enum {
+ CHKSUM_NONE = 0, /* "none" (default) */
+ CHKSUM_CRC32 = 1, /* "crc32" */
+ CHKSUM_TYPES_MAX,
+} ec_checksum_type_t;
+
+```
+
+Erasure Code Fragment Checksum API
+----------------------------------
+
+``` c
+
+struct __attribute__((__packed__))
+fragment_metadata
+{
+ uint32_t idx; /* 4 */
+ uint32_t size; /* 4 */
+ uint32_t frag_backend_metadata_size; /* 4 */
+ uint64_t orig_data_size; /* 8 */
+ uint8_t chksum_type; /* 1 */
+ uint32_t chksum[LIBERASURECODE_MAX_CHECKSUM_LEN]; /* 32 */
+ uint8_t chksum_mismatch; /* 1 */
+ uint8_t backend_id; /* 1 */
+ uint32_t backend_version; /* 4 */
+} fragment_metadata_t;
+
+#define FRAGSIZE_2_BLOCKSIZE(fragment_size) \
+ (fragment_size - sizeof(fragment_header_t))
+
+/**
+ * Get opaque metadata for a fragment. The metadata is opaque to the
+ * client, but meaningful to the underlying library. It is used to verify
+ * stripes in verify_stripe_metadata().
+ *
+ * @param fragment - fragment data pointer
+ * @param fragment_metadata - pointer to allocated buffer of size at least
+ * sizeof(struct fragment_metadata) to hold fragment metadata struct
+ *
+ * @return 0 on success, non-zero on error
+ */
+//EDL: This needs to be implemented
+int liberasurecode_get_fragment_metadata(char *fragment,
+ fragment_metadata_t *fragment_metadata);
+
+/**
+* Verify that the specified pointer points to a well formed fragment that can
+* be processed by both this instance of liberasurecode and the specified
+* backend.
+*
+* @param desc - liberasurecode descriptor/handle
+* from liberasurecode_instance_create()
+* @param fragment - fragment to verify
+*
+* @return 1 if fragment validation fails, 0 otherwise.
+*/
+int is_invalid_fragment(int desc, char *fragment);
+
+/**
+ * Verify a subset of fragments generated by encode()
+ *
+ * @param desc - liberasurecode descriptor/handle
+ * from liberasurecode_instance_create()
+ * @param fragments - fragments part of the EC stripe to verify
+ * @param num_fragments - number of fragments part of the EC stripe
+ *
+ * @return 1 if stripe checksum verification is successful, 0 otherwise
+ */
+int liberasurecode_verify_stripe_metadata(int desc,
+ char **fragments, int num_fragments);
+
+/* ==~=*=~===~=*=~==~=*=~== liberasurecode Helpers ==~*==~=*=~==~=~=*=~==~= */
+
+/**
+ * This computes the aligned size of a buffer passed into
+ * the encode function. The encode function must pad fragments
+ * to be algined with the word size (w) and the last fragment also
+ * needs to be aligned. This computes the sum of the algined fragment
+ * sizes for a given buffer to encode.
+ *
+ * @param desc - liberasurecode descriptor/handle
+ * from liberasurecode_instance_create()
+ * @param data_len - original data length in bytes
+ *
+ * @return aligned length, or -error code on error
+ */
+int liberasurecode_get_aligned_data_size(int desc, uint64_t data_len);
+
+/**
+ * This will return the minimum encode size, which is the minimum
+ * buffer size that can be encoded.
+ *
+ * @param desc - liberasurecode descriptor/handle
+ * from liberasurecode_instance_create()
+ *
+ * @return minimum data length length, or -error code on error
+ */
+int liberasurecode_get_minimum_encode_size(int desc);
+
+/**
+ * This will return the fragment size, which is each fragment data
+ * length the backend will allocate when encoding.
+ *
+ * @param desc - liberasurecode descriptor/handle
+ * from liberasurecode_instance_create()
+ * @param data_len - original data length in bytes
+ *
+ * @return fragment size - sizeof(fragment_header) + size
+ * + frag_backend_metadata_size
+ */
+int liberasurecode_get_fragment_size(int desc, int data_len);
+```
+----
+
+
+Build and Install
+=================
+
+To build the liberasurecode repository, perform the following from the
+top-level directory:
+
+``` sh
+ $ ./autogen.sh
+ $ ./configure
+ $ make
+ $ make test
+ $ sudo make install
+```
+
+----
+
+Code organization
+=================
+```
+ |-- include
+ | +-- erasurecode
+ | | +-- erasurecode.h --> liberasurecode frontend API header
+ | | +-- erasurecode_backend.h --> liberasurecode backend API header
+ | +-- xor_codes --> headers for the built-in XOR codes
+ |
+ |-- src
+ | |-- erasurecode.c --> liberasurecode API implementation
+ | | (frontend + backend)
+ | |-- backends
+ | | +-- null
+ | | +--- null.c --> 'null' erasure code backend (template backend)
+ | | +-- xor
+ | | +--- flat_xor_hd.c --> 'flat_xor_hd' erasure code backend (built-in)
+ | | +-- jerasure
+ | | +-- jerasure_rs_cauchy.c --> 'jerasure_rs_vand' erasure code backend (jerasure.org)
+ | | +-- jerasure_rs_vand.c --> 'jerasure_rs_cauchy' erasure code backend (jerasure.org)
+ | | +-- isa-l
+ | | +-- isa_l_rs_vand.c --> 'isa_l_rs_vand' erasure code backend (Intel)
+ | | +-- shss
+ | | +-- shss.c --> 'shss' erasure code backend (NTT Labs)
+ | |
+ | |-- builtin
+ | | +-- xor_codes --> XOR HD code backend, built-in erasure
+ | | | code implementation (shared library)
+ | | +-- xor_code.c
+ | | +-- xor_hd_code.c
+ | |
+ | +-- utils
+ | +-- chksum --> fragment checksum utils for erasure
+ | +-- alg_sig.c coded fragments
+ | +-- crc32.c
+ |
+ |-- doc --> API Documentation
+ | +-- Doxyfile
+ | +-- html
+ |
+ |--- test --> Test routines
+ | +-- builtin
+ | | +-- xor_codes
+ | +-- liberasurecode_test.c
+ | +-- utils
+ |
+ |-- autogen.sh
+ |-- configure.ac
+ |-- Makefile.am
+ |-- README
+ |-- NEWS
+ |-- COPYING
+ |-- AUTHORS
+ |-- INSTALL
+ +-- ChangeLog
+```
+---
+
+References
+==========
+
+ [1] Jerasure, C library that supports erasure coding in storage applications, http://jerasure.org
+
+ [2] Intel(R) Storage Acceleration Library (Open Source Version), https://01.org/intel%C2%AE-storage-acceleration-library-open-source-version
+
+ [3] Greenan, Kevin M et al, "Flat XOR-based erasure codes in storage systems", http://www.kaymgee.com/Kevin_Greenan/Publications_files/greenan-msst10.pdf
+
+ [4] Kota Tsuyuzaki <tsuyuzaki.kota@lab.ntt.co.jp>, Ryuta Kon <kon.ryuta@po.ntts.co.jp>, "NTT SHSS Erasure Coding backend"