## Sequence Sequence — Ordered sequence of items. |

## Synopsis

    typedef             raptor_sequence;
    raptor_sequence *   raptor_new_sequence                 (raptor_data_free_handler free_handler,
                                                             raptor_data_print_handler print_handler);
    raptor_sequence *   raptor_new_sequence_with_context    (raptor_data_context_free_handler free_handler,
                                                             raptor_data_context_print_handler print_handler,
                                                             void *handler_context);
    void                raptor_free_sequence                (raptor_sequence *seq);
    void *              raptor_sequence_delete_at           (raptor_sequence *seq,
                                                             int idx);
    void *              raptor_sequence_get_at              (raptor_sequence *seq,
                                                             int idx);
    int                 raptor_sequence_join                (raptor_sequence *dest,
                                                             raptor_sequence *src);
    int                 raptor_sequence_next_permutation    (raptor_sequence *seq,
                                                             raptor_data_compare_handler compare);
    void *              raptor_sequence_pop                 (raptor_sequence *seq);
    int                 raptor_sequence_print               (raptor_sequence *seq,
                                                             FILE *fh);
    int                 raptor_sequence_push                (raptor_sequence *seq,
                                                             void *data);
    int                 raptor_sequence_reverse             (raptor_sequence *seq,
                                                             int start_index,
                                                             int length);
    int                 raptor_sequence_set_at              (raptor_sequence *seq,
                                                             int idx,
                                                             void *data);
    int                 raptor_sequence_shift               (raptor_sequence *seq,
                                                             void *data);
    int                 raptor_sequence_size                (raptor_sequence *seq);
    void                raptor_sequence_sort                (raptor_sequence *seq,
                                                             raptor_data_compare_handler compare);
    int                 raptor_sequence_swap                (raptor_sequence *seq,
                                                             int i,
                                                             int j);
    void *              raptor_sequence_unshift             (raptor_sequence *seq);

## Description

A utility class that provides access to small sequence of items that grow at the end and require quick ordered and indexed access. Can be used as a queue/FIFO but less efficiently than a stack where the items are added and removed from the end.

## Details

### raptor_sequence

    raptor_sequence* raptor_sequence;

Raptor sequence class

### raptor_new_sequence ()

    raptor_sequence *   raptor_new_sequence                 (raptor_data_free_handler free_handler,
                                                             raptor_data_print_handler print_handler);

Constructor - create a new sequence with the given handlers.

This creates a sequence over objects that need only the item data pointers in order to print or free the objects.

For example sequences of strings could use handlers (free, NULL) and sequences of raptor_uri could use (raptor_free_uri, raptor_print_uri)

`free_handler` : | handler to free a sequence item
`print_handler` : | handler to print a sequence item to a FILE*
Returns : | a new raptor_sequence or NULL on failure

### raptor_new_sequence_with_context ()

    raptor_sequence *   raptor_new_sequence_with_context    (raptor_data_context_free_handler free_handler,
                                                             raptor_data_context_print_handler print_handler,
                                                             void *handler_context);

Constructor - create a new sequence with the given handlers and handler context.

This creates a sequence over objects that need context + item data pointers in order to print or free the objects.

`free_handler` : | handler to free a sequence item
`print_handler` : | handler to print a sequence item to a FILE*
`handler_context` : | context information to pass to free/print handlers
Returns : | a new raptor_sequence or NULL on failure

### raptor_free_sequence ()

    void                raptor_free_sequence                (raptor_sequence *seq);

Destructor - free a raptor_sequence

`seq` : | sequence to destroy

### raptor_sequence_delete_at ()

    void *              raptor_sequence_delete_at           (raptor_sequence *seq,
                                                             int idx);

Remove an item from a position a sequence, returning it

The item at the offset `idx` in the sequence is replaced with a NULL pointer and any existing item is returned. The caller owns the resulting item.

`seq` : | sequence object
`idx` : | index into sequence to operate at
Returns : | NULL on failure

### raptor_sequence_get_at ()

    void *              raptor_sequence_get_at              (raptor_sequence *seq,
                                                             int idx);

Retrieve an item at offset `index` in the sequence.

This is efficient to perform. raptor_sequence is optimised to append/remove from the end of the sequence.

After this call the item is still owned by the sequence.

`seq` : | sequence to use
`idx` : | index of item to get
Returns : | the object or NULL if `index` is out of range (0... sequence size - 1)

### raptor_sequence_join ()

    int                 raptor_sequence_join                (raptor_sequence *dest,
                                                             raptor_sequence *src);

Join two sequences moving all items from one sequence to the end of another.

After this operation, sequence src will be empty (zero size) but will have the same item capacity as before.

`dest` : | raptor_sequence destination sequence
`src` : | raptor_sequence source sequence
Returns : | non-0 on failure

### raptor_sequence_next_permutation ()

    int                 raptor_sequence_next_permutation    (raptor_sequence *seq,
                                                             raptor_data_compare_handler compare);

Get the next permutation of a sequence in lexicographic order

Assumes the initial order of the items is lexicographically increasing. This function alters the order of the items until the last permuatation is done at which point the contents is reset to the intial order.

Algorithm used is described in http://en.wikipedia.org/wiki/Permutation

The comparison function `compare` is compatible with that used for `qsort()` and provides the addresses of pointers to the data that must be dereferenced to get to the stored sequence data.

`seq` : | int seq
`compare` : | comparison function
Returns : | non-0 at the last permutation

### raptor_sequence_pop ()

    void *              raptor_sequence_pop                 (raptor_sequence *seq);

Retrieve the item at the end of the sequence.

Ownership of the item is transferred to the caller, i.e. caller is responsible of freeing the item.

`seq` : | sequence to use
Returns : | the object or NULL if the sequence is empty

### raptor_sequence_print ()

    int                 raptor_sequence_print               (raptor_sequence *seq,
                                                             FILE *fh);

Print the sequence contents using the print_handler to print the data items.

`seq` : | sequence to sort
`fh` : | file handle
Returns : | non-0 on failure

### raptor_sequence_push ()

    int                 raptor_sequence_push                (raptor_sequence *seq,
                                                             void *data);

Add an item to the end of the sequence.

The sequence takes ownership of the pushed item and frees it with the free_handler. On failure, the item is freed immediately.

`seq` : | sequence to add to
`data` : | item to add
Returns : | non-0 on failure

### raptor_sequence_reverse ()

    int                 raptor_sequence_reverse             (raptor_sequence *seq,
                                                             int start_index,
                                                             int length);

Reverse a range of elements

`seq` : | sequence
`start_index` : | starting index
`length` : | number of elements to reverse
Returns : | non-0 if arguments are out of range

### raptor_sequence_set_at ()

    int                 raptor_sequence_set_at              (raptor_sequence *seq,
                                                             int idx,
                                                             void *data);

Replace/set an item in a sequence.

The item at the offset `idx` in the sequence is replaced with the new item `data` (which may be NULL). Any existing item is freed with the sequence's free_handler. If necessary the sequence is extended (with NULLs) to handle a larger offset.

The sequence takes ownership of the new data item. On failure, the item is freed immediately.

`seq` : | sequence object
`idx` : | index into sequence to operate at
`data` : | new data item.
Returns : | non-0 on failure

### raptor_sequence_shift ()

    int                 raptor_sequence_shift               (raptor_sequence *seq,
                                                             void *data);

Add an item to the start of the sequence.

The sequence takes ownership of the shifted item and frees it with the free_handler. On failure, the item is freed immediately.

`seq` : | sequence to add to
`data` : | item to add
Returns : | non-0 on failure

### raptor_sequence_size ()

    int                 raptor_sequence_size                (raptor_sequence *seq);

Get the number of items in a sequence.

`seq` : | sequence object
Returns : | the sequence size (>=0)

### raptor_sequence_sort ()

    void                raptor_sequence_sort                (raptor_sequence *seq,
                                                             raptor_data_compare_handler compare);

Sort a sequence inline

The comparison function `compare` is compatible with that used for `qsort()` and provides the addresses of pointers to the data that must be dereferenced to get to the stored sequence data.

`seq` : | sequence to sort
`compare` : | comparison function

### raptor_sequence_swap ()

    int                 raptor_sequence_swap                (raptor_sequence *seq,
                                                             int i,
                                                             int j);

Swap a pair of elements in a sequence

`seq` : | sequence
`i` : | first data index
`j` : | second data index
Returns : | non-0 if arguments are out of range

### raptor_sequence_unshift ()

    void *              raptor_sequence_unshift             (raptor_sequence *seq);

Retrieve the item at the start of the sequence.

Ownership of the item is transferred to the caller, i.e. caller is responsible of freeing the item.

`seq` : | sequence to use
Returns : | the object or NULL if the sequence is empty