API Documentation

Supported Compression Methods

In the table below, "Name String" refers to the term that you should provide as the -Z option for the wandiocat tool to produce compressed output in that particular format. The "Identifier" is the enumerated type that corresponds to the compression_type argument that must be provided when calling wandio_wcreate().

Method	Name String	Identifier	Supports Read	Supports Write
No Compression	NA	WANDIO_COMPRESS_NONE	Yes	Yes
Gzip / Zlib	"gzip"	WANDIO_COMPRESS_ZLIB	Yes	Yes
Bzip2	"bzip2"	WANDIO_COMPRESS_BZ2	Yes	Yes
LZO	"lzo"	WANDIO_COMPRESS_LZO	No	Yes
LZMA (.xz)	"lzma"	WANDIO_COMPRESS_LZMA	Yes	Yes
zstd	"zstd"	WANDIO_COMPRESS_ZSTD	Yes	Yes
LZ4	"lz4"	WANDIO_COMPRESS_LZ4	Yes	Yes

Note that support for each compression method is dependent on you having the appropriate development library installed on your system at compile time, e.g. LZ4 support is only available if liblz4-dev (or equivalent) is present on your system. If you've installed libwandio via a package, all of the supported methods will be available.

File Reading API

File Writing API

The following functions comprise the API for writing a (compressed) file using libwandio.

iow_t *wandio_wcreate(const char *filename, int compression_type, int compression_level, int flags);

Creates a new libwandio writer instance and opens the output file for writing.

Arguments:

• filename -- the name of the output file to open
• compression_type -- the type of compression to be applied when writing to the file. Must be one of the "Identifier" values listed in the table at the top of this page.
• compression_level -- the compression level to use when writing to the file. This can range from 0 - 9 inclusive. 0 typically represents no compression. Larger values will often result in a better compression ratio, at the cost of requiring significantly more CPU time to run. Note that some compression methods do not support the use of levels to modify behaviour; in these cases, the value of the level does not matter. If you are unsure, 1 is a good starting point for the compression level.
• flags -- flags to apply when opening the file, just like those used by open(2). Examples of flags would be O_CREAT and O_DIRECT but consult the open(2) manpage for more information.

Returns a pointer to the new libwandio writer instance which will be required to call any of the other writing API functions.

void wandio_wdestroy(iow_t *iow);

int64_t wandio_wwrite(iow_t *iow, const void *buffer, int64_t len);

int wandio_wflush(iow_t *iow);