Metalayers#

Metalayers are meta-information that can be attached to super-chunks. They can also be serialized to disk.

struct blosc2_metalayer#

This struct is meant to store metadata information inside a blosc2_schunk, allowing to specify, for example, how to interpret the contents included in the schunk.

Public Members

char *name#: The metalayer identifier for Blosc client (e.g. Blosc2 NDim).

uint8_t *content#: The serialized (msgpack preferably) content of the metalayer.

int32_t content_len#: The length in bytes of the content.

Fixed-length metalayers#

static inline int blosc2_meta_exists(blosc2_schunk *schunk, const char *name)#

Find whether the schunk has a metalayer or not.

Parameters:

schunk – The super-chunk from which the metalayer will be checked.
name – The name of the metalayer to be checked.

Returns:

If successful, return the index of the metalayer. Else, return a negative value.

int blosc2_meta_add(blosc2_schunk *schunk, const char *name, uint8_t *content, int32_t content_len)#

Add content into a new metalayer.

Parameters:

schunk – The super-chunk to which the metalayer should be added.
name – The name of the metalayer.
content – The content of the metalayer.
content_len – The length of the content.

Returns:

If successful, the index of the new metalayer. Else, return a negative value.

int blosc2_meta_update(blosc2_schunk *schunk, const char *name, uint8_t *content, int32_t content_len)#

Update the content of an existing metalayer.

Parameters:

schunk – The frame containing the metalayer.
name – The name of the metalayer to be updated.
content – The new content of the metalayer.
content_len – The length of the content.

Returns:

If successful, the index of the metalayer. Else, return a negative value.

Note

Contrarily to blosc2_meta_add the updates to metalayers are automatically serialized into a possible attached frame.

static inline int blosc2_meta_get(blosc2_schunk *schunk, const char *name, uint8_t **content, int32_t *content_len)#

Get the content out of a metalayer.

Parameters:

schunk – The frame containing the metalayer.
name – The name of the metalayer.
content – The pointer where the content will be put.
content_len – The length of the content.

Returns:

If successful, the index of the new metalayer. Else, return a negative value.

Note

This function is inlined so that external codec/filter plugins (like blosc2_grok) can use it without linking against libblosc2. This avoids pulling all of libblosc2’s symbols (e.g. internal ZFP, Zstd) into the global namespace at load time, which would otherwise shadow symbols from other libraries that need differently-configured builds of the same dependencies.

Warning

The **content receives a malloc’ed copy of the content. The user is responsible of freeing it.

Variable-length metalayers#

int blosc2_vlmeta_exists(blosc2_schunk *schunk, const char *name)#

Find whether the schunk has a variable-length metalayer or not.

Parameters:

schunk – The super-chunk from which the variable-length metalayer will be checked.
name – The name of the variable-length metalayer to be checked.

Returns:

If successful, return the index of the variable-length metalayer. Else, return a negative value.

int blosc2_vlmeta_add(blosc2_schunk *schunk, const char *name, uint8_t *content, int32_t content_len, blosc2_cparams *cparams)#

Add content into a new variable-length metalayer.

Parameters:

schunk – The super-chunk to which the variable-length metalayer should be added.
name – The name of the variable-length metalayer.
content – The content to be added.
content_len – The length of the content.
cparams – The parameters for compressing the variable-length metalayer content. If NULL, the BLOSC2_CPARAMS_DEFAULTS will be used.

Returns:

If successful, the index of the new variable-length metalayer. Else, return a negative value.

int blosc2_vlmeta_update(blosc2_schunk *schunk, const char *name, uint8_t *content, int32_t content_len, blosc2_cparams *cparams)#

Update the content of an existing variable-length metalayer.

Parameters:

schunk – The super-chunk containing the variable-length metalayer.
name – The name of the variable-length metalayer to be updated.
content – The new content of the variable-length metalayer.
content_len – The length of the content.
cparams – The parameters for compressing the variable-length metalayer content. If NULL, the BLOSC2_CPARAMS_DEFAULTS will be used.

Returns:

If successful, the index of the variable-length metalayer. Else, return a negative value.

int blosc2_vlmeta_get(blosc2_schunk *schunk, const char *name, uint8_t **content, int32_t *content_len)#

Get the content out of a variable-length metalayer.

Parameters:

schunk – The super-chunk containing the variable-length metalayer.
name – The name of the variable-length metalayer.
content – The pointer where the content will be put.
content_len – The pointer where the length of the content will be put.

Returns:

If successful, the index of the new variable-length metalayer. Else, return a negative value.

Warning

The **content receives a malloc’ed copy of the content. The user is responsible of freeing it.

int blosc2_vlmeta_delete(blosc2_schunk *schunk, const char *name)#

Delete the variable-length metalayer from the super-chunk.

Parameters:

schunk – The super-chunk containing the variable-length metalayer.
name – The name of the variable-length metalayer.

Returns:

If successful, the number of the variable-length metalayers in the super-chunk. Else, return a negative value.

int blosc2_vlmeta_get_names(blosc2_schunk *schunk, char **names)#

Get a list of all the variable-length metalayer names.

Parameters:

schunk – The super-chunk containing the variable-length metalayers.
names – The pointer to a char** to store the name pointers. This should be of size schunk->nvlmetalayers * sizeof(char).

Returns:

The number of the variable-length metalayers in the super-chunk. This cannot fail unless the user does not pass a names which is large enough to keep pointers to all names, in which case funny things (seg faults and such) will happen.