stream_flags.h File Reference

.xz Stream Header and Stream Footer encoder and decoder More...

Data Structures
struct	lzma_stream_flags
	Options for encoding/decoding Stream Header and Stream Footer. More...

Macros
#define	LZMA_STREAM_HEADER_SIZE   12
	Size of Stream Header and Stream Footer.
#define	LZMA_BACKWARD_SIZE_MIN   4
	Minimum value for lzma_stream_flags.backward_size.
#define	LZMA_BACKWARD_SIZE_MAX   (LZMA_VLI_C(1) << 34)
	Maximum value for lzma_stream_flags.backward_size.

Functions
lzma_ret	lzma_stream_header_encode (const lzma_stream_flags *options, uint8_t *out) lzma_nothrow lzma_attr_warn_unused_result
	Encode Stream Header.
lzma_ret	lzma_stream_footer_encode (const lzma_stream_flags *options, uint8_t *out) lzma_nothrow lzma_attr_warn_unused_result
	Encode Stream Footer.
lzma_ret	lzma_stream_header_decode (lzma_stream_flags *options, const uint8_t *in) lzma_nothrow lzma_attr_warn_unused_result
	Decode Stream Header.
lzma_ret	lzma_stream_footer_decode (lzma_stream_flags *options, const uint8_t *in) lzma_nothrow lzma_attr_warn_unused_result
	Decode Stream Footer.
lzma_ret	lzma_stream_flags_compare (const lzma_stream_flags *a, const lzma_stream_flags *b) lzma_nothrow lzma_attr_pure
	Compare two lzma_stream_flags structures.

Detailed Description

.xz Stream Header and Stream Footer encoder and decoder

Note

Never include this file directly. Use <lzma.h> instead.

Macro Definition Documentation

LZMA_STREAM_HEADER_SIZE

#define LZMA_STREAM_HEADER_SIZE   12

Size of Stream Header and Stream Footer.

Stream Header and Stream Footer have the same size and they are not going to change even if a newer version of the .xz file format is developed in future.

Function Documentation

lzma_stream_header_encode()

lzma_ret lzma_stream_header_encode	(	const lzma_stream_flags *	options,
		uint8_t *	out
	)

Encode Stream Header.

Parameters

	options	Stream Header options to be encoded. options->backward_size is ignored and doesn't need to be initialized.
[out]	out	Beginning of the output buffer of LZMA_STREAM_HEADER_SIZE bytes.

Returns

Possible lzma_ret values:

• LZMA_OK: Encoding was successful.
• LZMA_OPTIONS_ERROR: options->version is not supported by this liblzma version.
• LZMA_PROG_ERROR: Invalid options.

lzma_stream_footer_encode()

lzma_ret lzma_stream_footer_encode	(	const lzma_stream_flags *	options,
		uint8_t *	out
	)

Encode Stream Footer.

Parameters

	options	Stream Footer options to be encoded.
[out]	out	Beginning of the output buffer of LZMA_STREAM_HEADER_SIZE bytes.

Returns

Possible lzma_ret values:

• LZMA_OK: Encoding was successful.
• LZMA_OPTIONS_ERROR: options->version is not supported by this liblzma version.
• LZMA_PROG_ERROR: Invalid options.

lzma_stream_header_decode()

lzma_ret lzma_stream_header_decode	(	lzma_stream_flags *	options,
		const uint8_t *	in
	)

Decode Stream Header.

options->backward_size is always set to LZMA_VLI_UNKNOWN. This is to help comparing Stream Flags from Stream Header and Stream Footer with lzma_stream_flags_compare().

Note

When decoding .xz files that contain multiple Streams, it may make sense to print "file format not recognized" only if decoding of the Stream Header of the first Stream gives LZMA_FORMAT_ERROR. If non-first Stream Header gives LZMA_FORMAT_ERROR, the message used for LZMA_DATA_ERROR is probably more appropriate. For example, the Stream decoder in liblzma uses LZMA_DATA_ERROR if LZMA_FORMAT_ERROR is returned by lzma_stream_header_decode() when decoding non-first Stream.

Parameters

[out]	options	Target for the decoded Stream Header options.
	in	Beginning of the input buffer of LZMA_STREAM_HEADER_SIZE bytes.

Returns

Possible lzma_ret values:

• LZMA_OK: Decoding was successful.
• LZMA_FORMAT_ERROR: Magic bytes don't match, thus the given buffer cannot be Stream Header.
• LZMA_DATA_ERROR: CRC32 doesn't match, thus the header is corrupt.
• LZMA_OPTIONS_ERROR: Unsupported options are present in the header.

lzma_stream_footer_decode()

lzma_ret lzma_stream_footer_decode	(	lzma_stream_flags *	options,
		const uint8_t *	in
	)

Decode Stream Footer.

Note

If Stream Header was already decoded successfully, but decoding Stream Footer returns LZMA_FORMAT_ERROR, the application should probably report some other error message than "file format not recognized". The file likely is corrupt (possibly truncated). The Stream decoder in liblzma uses LZMA_DATA_ERROR in this situation.

Parameters

[out]	options	Target for the decoded Stream Footer options.
	in	Beginning of the input buffer of LZMA_STREAM_HEADER_SIZE bytes.

Returns

Possible lzma_ret values:

• LZMA_OK: Decoding was successful.
• LZMA_FORMAT_ERROR: Magic bytes don't match, thus the given buffer cannot be Stream Footer.
• LZMA_DATA_ERROR: CRC32 doesn't match, thus the Stream Footer is corrupt.
• LZMA_OPTIONS_ERROR: Unsupported options are present in Stream Footer.

lzma_stream_flags_compare()

lzma_ret lzma_stream_flags_compare	(	const lzma_stream_flags *	a,
		const lzma_stream_flags *	b
	)

Compare two lzma_stream_flags structures.

backward_size values are compared only if both are not LZMA_VLI_UNKNOWN.

Parameters

a	Pointer to lzma_stream_flags structure
b	Pointer to lzma_stream_flags structure

Returns

Possible lzma_ret values:

• LZMA_OK: Both are equal. If either had backward_size set to LZMA_VLI_UNKNOWN, backward_size values were not compared or validated.
• LZMA_DATA_ERROR: The structures differ.
• LZMA_OPTIONS_ERROR: version in either structure is greater than the maximum supported version (currently zero).
• LZMA_PROG_ERROR: Invalid value, e.g. invalid check or backward_size.