NAME
Image::Leptonica::Func::ptra
VERSION
version 0.04
ptra.c
ptra.c
Ptra creation and destruction
L_PTRA *ptraCreate()
void *ptraDestroy()
Add/insert/remove/replace generic ptr object
l_int32 ptraAdd()
static l_int32 ptraExtendArray()
l_int32 ptraInsert()
void *ptraRemove()
void *ptraRemoveLast()
void *ptraReplace()
l_int32 ptraSwap()
l_int32 ptraCompactArray()
Other array operations
l_int32 ptraReverse()
l_int32 ptraJoin()
Simple Ptra accessors
l_int32 ptraGetMaxIndex()
l_int32 ptraGetActualCount()
void *ptraGetPtrToItem()
Ptraa creation and destruction
L_PTRAA *ptraaCreate()
void *ptraaDestroy()
Ptraa accessors
l_int32 ptraaGetSize()
l_int32 ptraaInsertPtra()
L_PTRA *ptraaGetPtra()
Ptraa conversion
L_PTRA *ptraaFlattenToPtra()
Notes on the Ptra:
(1) The Ptra is a struct, not an array. Always use the accessors
in this file, never the fields directly.
(2) Items can be placed anywhere in the allocated ptr array,
including one index beyond the last ptr (in which case the
ptr array is realloc'd).
(3) Thus, the items on the ptr array need not be compacted. In
general there will be null pointers in the ptr array.
(4) A compacted array will remain compacted on removal if
arbitrary items are removed with compaction, or if items
are removed from the end of the array.
(5) For addition to and removal from the end of the array, this
functions exactly like a stack, and with the same O(1) cost.
(6) This differs from the generic stack in that we allow
random access for insertion, removal and replacement.
Removal can be done without compacting the array.
Insertion into a null ptr in the array has no effect on
the other pointers, but insertion into a location already
occupied by an item has a cost proportional to the
distance to the next null ptr in the array.
(7) Null ptrs are valid input args for both insertion and
replacement; this allows arbitrary swapping.
(8) The item in the array with the largest index is at pa->imax.
This can be any value from -1 (initialized; all array ptrs
are null) up to pa->nalloc - 1 (the last ptr in the array).
(9) In referring to the array: the first ptr is the "top" or
"beginning"; the last pointer is the "bottom" or "end";
items are shifted "up" towards the top when compaction occurs;
and items are shifted "down" towards the bottom when forced to
move due to an insertion.
(10) It should be emphasized that insertion, removal and replacement
are general:
* You can insert an item into any ptr location in the
allocated ptr array, as well as into the next ptr address
beyond the allocated array (in which case a realloc will occur).
* You can remove or replace an item from any ptr location
in the allocated ptr array.
* When inserting into an occupied location, you have
three options for downshifting.
* When removing, you can either leave the ptr null or
compact the array.
Notes on the Ptraa:
(1) The Ptraa is a fixed size ptr array for holding Ptra.
In that respect, it is different from other pointer arrays, which
are extensible and grow using the *Add*() functions.
(2) In general, the Ptra ptrs in the Ptraa can be randomly occupied.
A typical usage is to allow an O(n) horizontal sort of Pix,
where the size of the Ptra array is the width of the image,
and each Ptra is an array of all the Pix at a specific x location.FUNCTIONS
ptraAdd
l_int32 ptraAdd ( L_PTRA *pa, void *item )
ptraAdd()
Input: ptra
item (generic ptr to a struct)
Return: 0 if OK, 1 on error
Notes:
(1) This adds the element to the next location beyond imax,
which is the largest occupied ptr in the array. This is
what you expect from a stack, where all ptrs up to and
including imax are occupied, but here the occuption of
items in the array is entirely arbitrary.ptraCompactArray
l_int32 ptraCompactArray ( L_PTRA *pa )
ptraCompactArray()
Input: ptra
Return: 0 if OK, 1 on error
Notes:
(1) This compacts the items on the array, filling any empty ptrs.
(2) This does not change the size of the array of ptrs.ptraCreate
L_PTRA * ptraCreate ( l_int32 n )
ptraCreate()
Input: size of ptr array to be alloc'd (0 for default)
Return: pa, or null on errorptraDestroy
void ptraDestroy ( L_PTRA **ppa, l_int32 freeflag, l_int32 warnflag )
ptraDestroy()
Input: &ptra (<to be nulled>)
freeflag (TRUE to free each remaining item in the array)
warnflag (TRUE to warn if any remaining items are not destroyed)
Return: void
Notes:
(1) If @freeflag == TRUE, frees each item in the array.
(2) If @freeflag == FALSE and warnflag == TRUE, and there are
items on the array, this gives a warning and destroys the array.
If these items are not owned elsewhere, this will cause
a memory leak of all the items that were on the array.
So if the items are not owned elsewhere and require their
own destroy function, they must be destroyed before the ptra.
(3) If warnflag == FALSE, no warnings will be issued. This is
useful if the items are owned elsewhere, such as a
PixMemoryStore().
(4) To destroy the ptra, we destroy the ptr array, then
the ptra, and then null the contents of the input ptr.ptraGetActualCount
l_int32 ptraGetActualCount ( L_PTRA *pa, l_int32 *pcount )
ptraGetActualCount()
Input: ptra
&count (<return> actual number of items on the ptr array)
Return: 0 if OK; 1 on error
Notes:
(1) The actual number of items on the ptr array, pa->nactual,
will be smaller than pa->n if the array is not compacted.ptraGetMaxIndex
l_int32 ptraGetMaxIndex ( L_PTRA *pa, l_int32 *pmaxindex )
ptraGetMaxIndex()
Input: ptra
&maxindex (<return> index of last item in the array);
Return: 0 if OK; 1 on error
Notes:
(1) The largest index to an item in the array is @maxindex.
@maxindex is one less than the number of items that would be
in the array if there were no null pointers between 0
and @maxindex - 1. However, because the internal ptr array
need not be compacted, there may be null pointers at
indices below @maxindex; for example, if items have
been removed.
(2) When an item is added to the end of the array, it goes
into pa->array[maxindex + 1], and maxindex is then
incremented by 1.
(3) If there are no items in the array, this returns @maxindex = -1.ptraGetPtrToItem
void * ptraGetPtrToItem ( L_PTRA *pa, l_int32 index )
ptraGetPtrToItem()
Input: ptra
index (of element to be retrieved)
Return: a ptr to the element, or null on error
Notes:
(1) This returns a ptr to the item. You must cast it to
the type of item. Do not destroy it; the item belongs
to the Ptra.
(2) This can access all possible items on the ptr array.
If an item doesn't exist, it returns null.ptraInsert
l_int32 ptraInsert ( L_PTRA *pa, l_int32 index, void *item, l_int32 shiftflag )
ptraInsert()
Input: ptra
index (location in ptra to insert new value)
item (generic ptr to a struct; can be null)
shiftflag (L_AUTO_DOWNSHIFT, L_MIN_DOWNSHIFT, L_FULL_DOWNSHIFT)
Return: 0 if OK, 1 on error
Notes:
(1) This checks first to see if the location is valid, and
then if there is presently an item there. If there is not,
it is simply inserted into that location.
(2) If there is an item at the insert location, items must be
moved down to make room for the insert. In the downward
shift there are three options, given by @shiftflag.
- If @shiftflag == L_AUTO_DOWNSHIFT, a decision is made
whether, in a cascade of items, to downshift a minimum
amount or for all items above @index. The decision is
based on the expectation of finding holes (null ptrs)
between @index and the bottom of the array.
Assuming the holes are distributed uniformly, if 2 or more
holes are expected, we do a minimum shift.
- If @shiftflag == L_MIN_DOWNSHIFT, the downward shifting
cascade of items progresses a minimum amount, until
the first empty slot is reached. This mode requires
some computation before the actual shifting is done.
- If @shiftflag == L_FULL_DOWNSHIFT, a shifting cascade is
performed where pa[i] --> pa[i + 1] for all i >= index.
Then, the item is inserted at pa[index].
(3) If you are not using L_AUTO_DOWNSHIFT, the rule of thumb is
to use L_FULL_DOWNSHIFT if the array is compacted (each
element points to an item), and to use L_MIN_DOWNSHIFT
if there are a significant number of null pointers.
There is no penalty to using L_MIN_DOWNSHIFT for a
compacted array, however, because the full shift is required
and we don't do the O(n) computation to look for holes.
(4) This should not be used repeatedly on large arrays,
because the function is generally O(n).
(5) However, it can be used repeatedly if we start with an empty
ptr array and insert only once at each location. For example,
you can support an array of Numa, where at each ptr location
you store either 0 or 1 Numa, and the Numa can be added
randomly to the ptr array.ptraJoin
l_int32 ptraJoin ( L_PTRA *pa1, L_PTRA *pa2 )
ptraJoin()
Input: ptra1 (add to this one)
ptra2 (appended to ptra1, and emptied of items; can be null)
Return: 0 if OK, 1 on errorptraRemove
void * ptraRemove ( L_PTRA *pa, l_int32 index, l_int32 flag )
ptraRemove()
Input: ptra
index (element to be removed)
flag (L_NO_COMPACTION, L_COMPACTION)
Return: item, or null on error
Notes:
(1) If flag == L_NO_COMPACTION, this removes the item and
nulls the ptr on the array. If it takes the last item
in the array, pa->n is reduced to the next item.
(2) If flag == L_COMPACTION, this compacts the array for
for all i >= index. It should not be used repeatedly on
large arrays, because compaction is O(n).
(3) The ability to remove without automatic compaction allows
removal with cost O(1).ptraRemoveLast
void * ptraRemoveLast ( L_PTRA *pa )
ptraRemoveLast()
Input: ptra
Return: item, or null on error or if the array is emptyptraReplace
void * ptraReplace ( L_PTRA *pa, l_int32 index, void *item, l_int32 freeflag )
ptraReplace()
Input: ptra
index (element to be replaced)
item (new generic ptr to a struct; can be null)
freeflag (TRUE to free old item; FALSE to return it)
Return: item (old item, if it exists and is not freed),
or null on errorptraReverse
l_int32 ptraReverse ( L_PTRA *pa )
ptraReverse()
Input: ptra
Return: 0 if OK, 1 on errorptraSwap
l_int32 ptraSwap ( L_PTRA *pa, l_int32 index1, l_int32 index2 )
ptraSwap()
Input: ptra
index1
index2
Return: 0 if OK, 1 on errorptraaCreate
L_PTRAA * ptraaCreate ( l_int32 n )
ptraaCreate()
Input: size of ptr array to be alloc'd
Return: paa, or null on error
Notes:
(1) The ptraa is generated with a fixed size, that can not change.
The ptra can be generated and inserted randomly into this array.ptraaDestroy
void ptraaDestroy ( L_PTRAA **ppaa, l_int32 freeflag, l_int32 warnflag )
ptraaDestroy()
Input: &paa (<to be nulled>)
freeflag (TRUE to free each remaining item in each ptra)
warnflag (TRUE to warn if any remaining items are not destroyed)
Return: void
Notes:
(1) See ptraDestroy() for use of @freeflag and @warnflag.
(2) To destroy the ptraa, we destroy each ptra, then the ptr array,
then the ptraa, and then null the contents of the input ptr.ptraaFlattenToPtra
L_PTRA * ptraaFlattenToPtra ( L_PTRAA *paa )
ptraaFlattenToPtra()
Input: ptraa
Return: ptra, or null on error
Notes:
(1) This 'flattens' the ptraa to a ptra, taking the items in
each ptra, in order, starting with the first ptra, etc.
(2) As a side-effect, the ptra are all removed from the ptraa
and destroyed, leaving an empty ptraa.ptraaGetPtra
L_PTRA * ptraaGetPtra ( L_PTRAA *paa, l_int32 index, l_int32 accessflag )
ptraaGetPtra()
Input: ptraa
index (location in array)
accessflag (L_HANDLE_ONLY, L_REMOVE)
Return: ptra (at index location), or NULL on error or if there
is no ptra there.
Notes:
(1) This returns the ptra ptr. If @accessflag == L_HANDLE_ONLY,
the ptra is left on the ptraa. If @accessflag == L_REMOVE,
the ptr in the ptraa is set to NULL, and the caller
is responsible for disposing of the ptra (either putting it
back on the ptraa, or destroying it).
(2) This returns NULL if there is no Ptra at the index location.ptraaGetSize
l_int32 ptraaGetSize ( L_PTRAA *paa, l_int32 *psize )
ptraaGetSize()
Input: ptraa
&size (<return> size of ptr array)
Return: 0 if OK; 1 on errorptraaInsertPtra
l_int32 ptraaInsertPtra ( L_PTRAA *paa, l_int32 index, L_PTRA *pa )
ptraaInsertPtra()
Input: ptraa
index (location in array for insertion)
ptra (to be inserted)
Return: 0 if OK; 1 on error
Notes:
(1) Caller should check return value. On success, the Ptra
is inserted in the Ptraa and is owned by it. However,
on error, the Ptra remains owned by the caller.AUTHOR
Zakariyya Mughal <zmughal@cpan.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2014 by Zakariyya Mughal.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.