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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.
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.
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.
L_PTRA * ptraCreate ( l_int32 n )
ptraCreate() Input: size of ptr array to be alloc'd (0 for default) Return: pa, or null on error
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.
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.
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.
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.
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.
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 error
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).
void * ptraRemoveLast ( L_PTRA *pa )
ptraRemoveLast() Input: ptra Return: item, or null on error or if the array is empty
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 error
l_int32 ptraReverse ( L_PTRA *pa )
ptraReverse() Input: ptra Return: 0 if OK, 1 on error
l_int32 ptraSwap ( L_PTRA *pa, l_int32 index1, l_int32 index2 )
ptraSwap() Input: ptra index1 index2 Return: 0 if OK, 1 on error
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.
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.
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.
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.
l_int32 ptraaGetSize ( L_PTRAA *paa, l_int32 *psize )
ptraaGetSize() Input: ptraa &size (<return> size of ptr array) Return: 0 if OK; 1 on error
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.
Zakariyya Mughal <email@example.com>
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.