index_hash.h File Reference

Validate Index by using a hash function. More...

Typedefs
typedef struct lzma_index_hash_s	lzma_index_hash
	Opaque data type to hold the Index hash.

Functions
lzma_index_hash *	lzma_index_hash_init (lzma_index_hash *index_hash, const lzma_allocator *allocator) lzma_nothrow lzma_attr_warn_unused_result
	Allocate and initialize a new lzma_index_hash structure.
void	lzma_index_hash_end (lzma_index_hash *index_hash, const lzma_allocator *allocator) lzma_nothrow
	Deallocate lzma_index_hash structure.
lzma_ret	lzma_index_hash_append (lzma_index_hash *index_hash, lzma_vli unpadded_size, lzma_vli uncompressed_size) lzma_nothrow lzma_attr_warn_unused_result
	Add a new Record to an Index hash.
lzma_ret	lzma_index_hash_decode (lzma_index_hash *index_hash, const uint8_t *in, size_t *in_pos, size_t in_size) lzma_nothrow lzma_attr_warn_unused_result
	Decode and validate the Index field.
lzma_vli	lzma_index_hash_size (const lzma_index_hash *index_hash) lzma_nothrow lzma_attr_pure
	Get the size of the Index field as bytes.

Detailed Description

Validate Index by using a hash function.

Note

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

Hashing makes it possible to use constant amount of memory to validate Index of arbitrary size.

Function Documentation

lzma_index_hash_init()

lzma_index_hash * lzma_index_hash_init	(	lzma_index_hash *	index_hash,
		const lzma_allocator *	allocator
	)

Allocate and initialize a new lzma_index_hash structure.

If index_hash is NULL, this function allocates and initializes a new lzma_index_hash structure and returns a pointer to it. If allocation fails, NULL is returned.

If index_hash is non-NULL, this function reinitializes the lzma_index_hash structure and returns the same pointer. In this case, return value cannot be NULL or a different pointer than the index_hash that was given as an argument.

Parameters

index_hash	Pointer to a lzma_index_hash structure or NULL.
allocator	lzma_allocator for custom allocator functions. Set to NULL to use malloc() and free().

Returns

Initialized lzma_index_hash structure on success or NULL on failure.

lzma_index_hash_end()

void lzma_index_hash_end	(	lzma_index_hash *	index_hash,
		const lzma_allocator *	allocator
	)

Deallocate lzma_index_hash structure.

Parameters

index_hash	Pointer to a lzma_index_hash structure to free.
allocator	lzma_allocator for custom allocator functions. Set to NULL to use malloc() and free().

lzma_index_hash_append()

lzma_ret lzma_index_hash_append	(	lzma_index_hash *	index_hash,
		lzma_vli	unpadded_size,
		lzma_vli	uncompressed_size
	)

Add a new Record to an Index hash.

Parameters

index_hash	Pointer to a lzma_index_hash structure
unpadded_size	Unpadded Size of a Block
uncompressed_size	Uncompressed Size of a Block

Returns

Possible lzma_ret values:

• LZMA_OK
• LZMA_DATA_ERROR: Compressed or uncompressed size of the Stream or size of the Index field would grow too big.
• LZMA_PROG_ERROR: Invalid arguments or this function is being used when lzma_index_hash_decode() has already been used.

lzma_index_hash_decode()

lzma_ret lzma_index_hash_decode	(	lzma_index_hash *	index_hash,
		const uint8_t *	in,
		size_t *	in_pos,
		size_t	in_size
	)

Decode and validate the Index field.

After telling the sizes of all Blocks with lzma_index_hash_append(), the actual Index field is decoded with this function. Specifically, once decoding of the Index field has been started, no more Records can be added using lzma_index_hash_append().

This function doesn't use lzma_stream structure to pass the input data. Instead, the input buffer is specified using three arguments. This is because it matches better the internal APIs of liblzma.

Parameters

	index_hash	Pointer to a lzma_index_hash structure
	in	Pointer to the beginning of the input buffer
[out]	in_pos	in[*in_pos] is the next byte to process
	in_size	in[in_size] is the first byte not to process

Returns

Possible lzma_ret values:

• LZMA_OK: So far good, but more input is needed.
• LZMA_STREAM_END: Index decoded successfully and it matches the Records given with lzma_index_hash_append().
• LZMA_DATA_ERROR: Index is corrupt or doesn't match the information given with lzma_index_hash_append().
• LZMA_BUF_ERROR: Cannot progress because *in_pos >= in_size.
• LZMA_PROG_ERROR

lzma_index_hash_size()

lzma_vli lzma_index_hash_size

(

const lzma_index_hash *

index_hash

)

Get the size of the Index field as bytes.

This is needed to verify the Backward Size field in the Stream Footer.

Parameters

index_hash

Pointer to a lzma_index_hash structure

Returns

Size of the Index field in bytes.