77 lines
2.9 KiB
C
77 lines
2.9 KiB
C
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is libguac.
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*
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* The Initial Developer of the Original Code is
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* Michael Jumper.
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* Portions created by the Initial Developer are Copyright (C) 2010
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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#ifndef _GUAC_HASH_H
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#define _GUAC_HASH_H
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#include <cairo/cairo.h>
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/**
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* Provides functions and structures for producing likely-to-be-unique hash
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* values for images.
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*
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* @file hash.h
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*/
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/**
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* Produces a 24-bit hash value from all pixels of the given surface. The
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* surface provided must be RGB or ARGB with each pixel stored in 32 bits.
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* The hashing algorithm used is a variant of the cyclic polynomial rolling
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* hash.
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*
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* @param surface The Cairo surface to hash.
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* @return An arbitrary 24-bit unsigned integer value intended to be well
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* distributed across different images.
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*/
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unsigned int guac_hash_surface(cairo_surface_t* surface);
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/**
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* Given two Cairo surfaces, returns zero if the data contained within each
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* is identical, and a positive or negative value if the value of the first
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* is found to be lexically greater or less than the second respectively.
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*
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* @param a The first Cairo surface to compare.
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* @param b The Cairo surface to compare the first surface against.
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* @return Zero if the data contained within each is identical, and a positive
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* or negative value if the value of the first is found to be lexically
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* greater or less than the second respectively.
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*/
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int guac_surface_cmp(cairo_surface_t* a, cairo_surface_t* b);
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#endif
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