lzma_.container

File formats

Source:

Author:
Lasse Collin (original liblzma author), Johannes Pfau (D bindings)

License:
public domain

uint LZMA_PRESET_DEFAULT;

Default compression preset

It's not straightforward to recommend a default preset, because in some cases keeping the resource usage relatively low is more important that getting the maximum compression ratio.

uint LZMA_PRESET_LEVEL_MASK;

Mask for preset level

This is useful only if you need to extract the level from the preset variable. That should be rare.

uint LZMA_PRESET_EXTREME;

Extreme compression preset

This flag modifies the preset to make the encoding significantly slower while improving the compression ratio only marginally. This is useful when you don't mind wasting time to get as small result as possible.

This flag doesn't affect the memory usage requirements of the decoder (at least not significantly). The memory usage of the encoder may be increased a little but only at the lowest preset levels (0-3).

ulong lzma_easy_encoder_memusage(uint preset);

Calculate approximate memory usage of easy encoder

This function is a wrapper for lzma_raw_encoder_memusage().

Parameters:

uint preset

Compression preset (level and possible flags)

ulong lzma_easy_decoder_memusage(uint preset);

Calculate approximate decoder memory usage of a preset

This function is a wrapper for lzma_raw_decoder_memusage().

Parameters:

uint preset

Compression preset (level and possible flags)

lzma_ret lzma_easy_encoder(lzma_stream* strm, uint preset, lzma_check check);

Initialize .xz Stream encoder using a preset number

This function is intended for those who just want to use the basic features if liblzma (that is, most developers out there).

If initialization fails (return value is not LZMA_OK), all the memory allocated for *strm by liblzma is always freed. Thus, there is no need to call lzma_end() after failed initialization.

If initialization succeeds, use lzma_code() to do the actual encoding. Valid values for `action' (the second argument of lzma_code()) are LZMA_RUN, LZMA_SYNC_FLUSH, LZMA_FULL_FLUSH, and LZMA_FINISH. In future, there may be compression levels or flags that don't support LZMA_SYNC_FLUSH.

Parameters:

lzma_stream* strm	Pointer to lzma_stream that is at least initialized with LZMA_STREAM_INIT.
uint preset	Compression preset to use. A preset consist of level number and zero or more flags. Usually flags aren't used, so preset is simply a number [0, 9] which match the options -0 ... -9 of the xz command line tool. Additional flags can be be set using bitwise-or with the preset level number, e.g. 6 | LZMA_PRESET_EXTREME.
lzma_check check	Integrity check type to use. See check.h for available checks. The xz command line tool defaults to LZMA_CHECK_CRC64, which is a good choice if you are unsure. LZMA_CHECK_CRC32 is good too as long as the uncompressed file is not many gigabytes.

Returns:
- LZMA_OK: Initialization succeeded. Use lzma_code() to encode your data. - LZMA_MEM_ERROR: Memory allocation failed. - LZMA_OPTIONS_ERROR: The given compression preset is not supported by this build of liblzma. - LZMA_UNSUPPORTED_CHECK: The given check type is not supported by this liblzma build. - LZMA_PROG_ERROR: One or more of the parameters have values that will never be valid. For example, strm == NULL.

lzma_ret lzma_easy_buffer_encode(uint preset, lzma_check check, lzma_allocator* allocator, const(ubyte)* in_, size_t in_size, ubyte* out_, uint* out_pos, size_t out_size);

Single-call .xz Stream encoding using a preset number

The maximum required output buffer size can be calculated with lzma_stream_buffer_bound().

Parameters:

uint preset	Compression preset to use. See the description in lzma_easy_encoder().
lzma_check check	Type of the integrity check to calculate from uncompressed data.
lzma_allocator* allocator	lzma_allocator for custom allocator functions. Set to NULL to use malloc() and free().
const(ubyte)* in_	Beginning of the input buffer
size_t in_size	Size of the input buffer
ubyte* out_	Beginning of the output buffer
uint* out_pos	The next byte will be written to out[*out_pos]. *out_pos is updated only if encoding succeeds.
size_t out_size	Size of the out buffer; the first byte into which no data is written to is out[out_size].

Returns:
- LZMA_OK: Encoding was successful. - LZMA_BUF_ERROR: Not enough output buffer space. - LZMA_OPTIONS_ERROR - LZMA_MEM_ERROR - LZMA_DATA_ERROR - LZMA_PROG_ERROR

lzma_ret lzma_stream_encoder(lzma_stream* strm, const lzma_filter* filters, lzma_check check);

Initialize .xz Stream encoder using a custom filter chain

Parameters:

lzma_stream* strm	Pointer to properly prepared lzma_stream
lzma_filter* filters	Array of filters. This must be terminated with filters[n].id = LZMA_VLI_UNKNOWN. See filter.h for more information.
lzma_check check	Type of the integrity check to calculate from uncompressed data.

Returns:
- LZMA_OK: Initialization was successful. - LZMA_MEM_ERROR - LZMA_OPTIONS_ERROR - LZMA_PROG_ERROR

lzma_ret lzma_alone_encoder(lzma_stream* strm, const lzma_options_lzma* options);

Initialize .lzma encoder (legacy file format)

The .lzma format is sometimes called the LZMA_Alone format, which is the reason for the name of this function. The .lzma format supports only the LZMA1 filter. There is no support for integrity checks like CRC32.

Use this function if and only if you need to create files readable by legacy LZMA tools such as LZMA Utils 4.32.x. Moving to the .xz format is strongly recommended.

The valid action values for lzma_code() are LZMA_RUN and LZMA_FINISH. No kind of flushing is supported, because the file format doesn't make it possible.

Returns:
- LZMA_OK - LZMA_MEM_ERROR - LZMA_OPTIONS_ERROR - LZMA_PROG_ERROR

size_t lzma_stream_buffer_bound(size_t uncompressed_size);

Calculate output buffer size for single-call Stream encoder

When trying to compress uncompressible data, the encoded size will be slightly bigger than the input data. This function calculates how much output buffer space is required to be sure that lzma_stream_buffer_encode() doesn't return LZMA_BUF_ERROR.

The calculated value is not exact, but it is guaranteed to be big enough. The actual maximum output space required may be slightly smaller (up to about 100 bytes). This should not be a problem in practice.

If the calculated maximum size doesn't fit into size_t or would make the Stream grow past LZMA_VLI_MAX (which should never happen in practice), zero is returned to indicate the error.

Note:
The limit calculated by this function applies only to single-call encoding. Multi-call encoding may (and probably will) have larger maximum expansion when encoding uncompressible data. Currently there is no function to calculate the maximum expansion of multi-call encoding.

lzma_ret lzma_stream_buffer_encode(lzma_filter* filters, lzma_check check, lzma_allocator* allocator, const(ubyte)* in_, size_t in_size, ubyte* out_, uint* out_pos, size_t out_size);

Single-call .xz Stream encoder

Parameters:

lzma_filter* filters	Array of filters. This must be terminated with filters[n].id = LZMA_VLI_UNKNOWN. See filter.h for more information.
lzma_check check	Type of the integrity check to calculate from uncompressed data.
lzma_allocator* allocator	lzma_allocator for custom allocator functions. Set to NULL to use malloc() and free().
const(ubyte)* in_	Beginning of the input buffer
size_t in_size	Size of the input buffer
ubyte* out_	Beginning of the output buffer
uint* out_pos	The next byte will be written to out[*out_pos]. *out_pos is updated only if encoding succeeds.
size_t out_size	Size of the out buffer; the first byte into which no data is written to is out[out_size].

Returns:
- LZMA_OK: Encoding was successful. - LZMA_BUF_ERROR: Not enough output buffer space. - LZMA_OPTIONS_ERROR - LZMA_MEM_ERROR - LZMA_DATA_ERROR - LZMA_PROG_ERROR

uint LZMA_TELL_NO_CHECK;

Decoding *

This flag makes lzma_code() return LZMA_NO_CHECK if the input stream being decoded has no integrity check. Note that when used with lzma_auto_decoder(), all .lzma files will trigger LZMA_NO_CHECK if LZMA_TELL_NO_CHECK is used.

uint LZMA_TELL_UNSUPPORTED_CHECK;

This flag makes lzma_code() return LZMA_UNSUPPORTED_CHECK if the input stream has an integrity check, but the type of the integrity check is not supported by this liblzma version or build. Such files can still be decoded, but the integrity check cannot be verified.

uint LZMA_TELL_ANY_CHECK;

This flag makes lzma_code() return LZMA_GET_CHECK as soon as the type of the integrity check is known. The type can then be got with lzma_get_check().

uint LZMA_CONCATENATED;

This flag enables decoding of concatenated files with file formats that allow concatenating compressed files as is. From the formats currently supported by liblzma, only the .xz format allows concatenated files. Concatenated files are not allowed with the legacy .lzma format.

This flag also affects the usage of the `action' argument for lzma_code(). When LZMA_CONCATENATED is used, lzma_code() won't return LZMA_STREAM_END unless LZMA_FINISH is used as `action'. Thus, the application has to set LZMA_FINISH in the same way as it does when encoding.

If LZMA_CONCATENATED is not used, the decoders still accept LZMA_FINISH as `action' for lzma_code(), but the usage of LZMA_FINISH isn't required.

lzma_ret lzma_stream_decoder(lzma_stream* strm, ulong memlimit, uint flags);

Initialize .xz Stream decoder

Parameters:

lzma_stream* strm	Pointer to properly prepared lzma_stream
ulong memlimit	Memory usage limit as bytes. Use UINT64_MAX to effectively disable the limiter.
uint flags	Bitwise-or of zero or more of the decoder flags: LZMA_TELL_NO_CHECK, LZMA_TELL_UNSUPPORTED_CHECK, LZMA_TELL_ANY_CHECK, LZMA_CONCATENATED

Returns:
- LZMA_OK: Initialization was successful. - LZMA_MEM_ERROR: Cannot allocate memory. - LZMA_OPTIONS_ERROR: Unsupported flags - LZMA_PROG_ERROR

lzma_ret lzma_auto_decoder(lzma_stream* strm, ulong memlimit, uint flags);

Decode .xz Streams and .lzma files with autodetection

This decoder autodetects between the .xz and .lzma file formats, and calls lzma_stream_decoder() or lzma_alone_decoder() once the type of the input file has been detected.

Parameters:

lzma_stream* strm	Pointer to properly prepared lzma_stream
ulong memlimit	Memory usage limit as bytes. Use UINT64_MAX to effectively disable the limiter.
uint flags	Bitwise-or of flags, or zero for no flags.

Returns:
- LZMA_OK: Initialization was successful. - LZMA_MEM_ERROR: Cannot allocate memory. - LZMA_OPTIONS_ERROR: Unsupported flags - LZMA_PROG_ERROR

lzma_ret lzma_alone_decoder(lzma_stream* strm, ulong memlimit);

Initialize .lzma decoder (legacy file format)

Valid `action' arguments to lzma_code() are LZMA_RUN and LZMA_FINISH. There is no need to use LZMA_FINISH, but allowing it may simplify certain types of applications.

Returns:
- LZMA_OK - LZMA_MEM_ERROR - LZMA_PROG_ERROR

lzma_ret lzma_stream_buffer_decode(ulong* memlimit, uint flags, lzma_allocator* allocator, const(ubyte)* in_, uint* in_pos, size_t in_size, ubyte* out_, uint* out_pos, size_t out_size);

Single-call .xz Stream decoder

Parameters:

ulong* memlimit	Pointer to how much memory the decoder is allowed to allocate. The value pointed by this pointer is modified if and only if LZMA_MEMLIMIT_ERROR is returned.
uint flags	Bitwise-or of zero or more of the decoder flags: LZMA_TELL_NO_CHECK, LZMA_TELL_UNSUPPORTED_CHECK, LZMA_CONCATENATED. Note that LZMA_TELL_ANY_CHECK is not allowed and will return LZMA_PROG_ERROR.
lzma_allocator* allocator	lzma_allocator for custom allocator functions. Set to NULL to use malloc() and free().
const(ubyte)* in_	Beginning of the input buffer
uint* in_pos	The next byte will be read from in[*in_pos]. *in_pos is updated only if decoding succeeds.
size_t in_size	Size of the input buffer; the first byte that won't be read is in[in_size].
ubyte* out_	Beginning of the output buffer
uint* out_pos	The next byte will be written to out[*out_pos]. *out_pos is updated only if decoding succeeds.
size_t out_size	Size of the out buffer; the first byte into which no data is written to is out[out_size].

Returns:
- LZMA_OK: Decoding was successful. - LZMA_FORMAT_ERROR - LZMA_OPTIONS_ERROR - LZMA_DATA_ERROR - LZMA_NO_CHECK: This can be returned only if using the LZMA_TELL_NO_CHECK flag. - LZMA_UNSUPPORTED_CHECK: This can be returned only if using the LZMA_TELL_UNSUPPORTED_CHECK flag. - LZMA_MEM_ERROR - LZMA_MEMLIMIT_ERROR: Memory usage limit was reached. The minimum required memlimit value was stored to *memlimit. - LZMA_BUF_ERROR: Output buffer was too small. - LZMA_PROG_ERROR

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