From 97ac78c1e595f2645dd14b053439319881ed97e6 Mon Sep 17 00:00:00 2001 From: Michael Jumper Date: Sun, 19 Aug 2012 20:46:02 -0700 Subject: [PATCH] Added hash.c and hash.h, including a basic image hash function. --- libguac/include/hash.h | 57 ++++++++++++++++++++ libguac/src/Makefile.am | 2 + libguac/src/hash.c | 113 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 172 insertions(+) create mode 100644 libguac/include/hash.h create mode 100644 libguac/src/hash.c diff --git a/libguac/include/hash.h b/libguac/include/hash.h new file mode 100644 index 00000000..8f7a8bfb --- /dev/null +++ b/libguac/include/hash.h @@ -0,0 +1,57 @@ + +/* ***** BEGIN LICENSE BLOCK ***** + * Version: MPL 1.1/GPL 2.0/LGPL 2.1 + * + * The contents of this file are subject to the Mozilla Public License Version + * 1.1 (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * http://www.mozilla.org/MPL/ + * + * Software distributed under the License is distributed on an "AS IS" basis, + * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License + * for the specific language governing rights and limitations under the + * License. + * + * The Original Code is libguac. + * + * The Initial Developer of the Original Code is + * Michael Jumper. + * Portions created by the Initial Developer are Copyright (C) 2010 + * the Initial Developer. All Rights Reserved. + * + * Contributor(s): + * + * Alternatively, the contents of this file may be used under the terms of + * either the GNU General Public License Version 2 or later (the "GPL"), or + * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), + * in which case the provisions of the GPL or the LGPL are applicable instead + * of those above. If you wish to allow use of your version of this file only + * under the terms of either the GPL or the LGPL, and not to allow others to + * use your version of this file under the terms of the MPL, indicate your + * decision by deleting the provisions above and replace them with the notice + * and other provisions required by the GPL or the LGPL. If you do not delete + * the provisions above, a recipient may use your version of this file under + * the terms of any one of the MPL, the GPL or the LGPL. + * + * ***** END LICENSE BLOCK ***** */ + + +#ifndef _GUAC_HASH_H +#define _GUAC_HASH_H + +#include + +/** + * Produces a 24-bit hash value from all pixels of the given surface. The + * surface provided must be RGB or ARGB with each pixel stored in 32 bits. + * The hashing algorithm used is a variant of the cyclic polynomial rolling + * hash. + * + * @param surface The Cairo surface to hash. + * @return An arbitrary 24-bit unsigned integer value intended to be well + * distributed across different images. + */ +int guac_hash_surface(cairo_surface_t* surface); + +#endif + diff --git a/libguac/src/Makefile.am b/libguac/src/Makefile.am index 8fc5ab8f..fdd595ed 100644 --- a/libguac/src/Makefile.am +++ b/libguac/src/Makefile.am @@ -42,6 +42,7 @@ libguacincdir = $(includedir)/guacamole libguacinc_HEADERS = \ ../include/client.h \ ../include/error.h \ + ../include/hash.h \ ../include/instruction.h \ ../include/layer.h \ ../include/plugin.h \ @@ -60,6 +61,7 @@ libguac_la_SOURCES = \ client.c \ client-handlers.c \ error.c \ + hash.c \ instruction.c \ palette.c \ plugin.c \ diff --git a/libguac/src/hash.c b/libguac/src/hash.c new file mode 100644 index 00000000..2ecf1961 --- /dev/null +++ b/libguac/src/hash.c @@ -0,0 +1,113 @@ + +/* ***** BEGIN LICENSE BLOCK ***** + * Version: MPL 1.1/GPL 2.0/LGPL 2.1 + * + * The contents of this file are subject to the Mozilla Public License Version + * 1.1 (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * http://www.mozilla.org/MPL/ + * + * Software distributed under the License is distributed on an "AS IS" basis, + * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License + * for the specific language governing rights and limitations under the + * License. + * + * The Original Code is libguac. + * + * The Initial Developer of the Original Code is + * Michael Jumper. + * Portions created by the Initial Developer are Copyright (C) 2010 + * the Initial Developer. All Rights Reserved. + * + * Contributor(s): + * + * Alternatively, the contents of this file may be used under the terms of + * either the GNU General Public License Version 2 or later (the "GPL"), or + * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), + * in which case the provisions of the GPL or the LGPL are applicable instead + * of those above. If you wish to allow use of your version of this file only + * under the terms of either the GPL or the LGPL, and not to allow others to + * use your version of this file under the terms of the MPL, indicate your + * decision by deleting the provisions above and replace them with the notice + * and other provisions required by the GPL or the LGPL. If you do not delete + * the provisions above, a recipient may use your version of this file under + * the terms of any one of the MPL, the GPL or the LGPL. + * + * ***** END LICENSE BLOCK ***** */ + + +#include +#include + +/* + * Arbitrary hash function whhich maps ALL 32-bit numbers onto 24-bit numbers + * evenly, while guaranteeing that all 24-bit numbers are mapped onto + * themselves. + */ +int _guac_hash_32to24(int value) { + + /* Grab highest-order byte */ + int upper = value & 0xFF000000; + + /* XOR upper with lower three bytes, truncate to 24-bit */ + return + (value & 0xFFFFFF) + ^ (upper >> 8) + ^ (upper >> 16) + ^ (upper >> 24); + +} + +/** + * Rotates a given 32-bit integer by N bits. + * + * NOTE: We probably should check for available bitops.h macros first. + */ +unsigned int _guac_rotate(unsigned int value, int amount) { + + /* amount = amount % 32 */ + amount &= 0x1F; + + /* Return rotated amount */ + return (value >> amount) | (value << (32 - amount)); + +} + +int guac_hash_surface(cairo_surface_t* surface) { + + /* Init to zero */ + int hash_value = 0; + + int x, y; + + /* Get image data and metrics */ + unsigned char* data = cairo_image_surface_get_data(surface); + int width = cairo_image_surface_get_width(surface); + int height = cairo_image_surface_get_height(surface); + int stride = cairo_image_surface_get_stride(surface); + + for (y=0; y