cscg24-guacamole

CSCG 2024 Challenge 'Guacamole Mashup'
git clone https://git.sinitax.com/sinitax/cscg24-guacamole
Log | Files | Refs | sfeed.txt

hash.c (3717B)

      1/*
      2 * Licensed to the Apache Software Foundation (ASF) under one
      3 * or more contributor license agreements.  See the NOTICE file
      4 * distributed with this work for additional information
      5 * regarding copyright ownership.  The ASF licenses this file
      6 * to you under the Apache License, Version 2.0 (the
      7 * "License"); you may not use this file except in compliance
      8 * with the License.  You may obtain a copy of the License at
      9 *
     10 *   http://www.apache.org/licenses/LICENSE-2.0
     11 *
     12 * Unless required by applicable law or agreed to in writing,
     13 * software distributed under the License is distributed on an
     14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
     15 * KIND, either express or implied.  See the License for the
     16 * specific language governing permissions and limitations
     17 * under the License.
     18 */
     19
     20#include "config.h"
     21
     22#include <cairo/cairo.h>
     23
     24#include <stdint.h>
     25#include <string.h>
     26
     27/*
     28 * Arbitrary hash function whhich maps ALL 32-bit numbers onto 24-bit numbers
     29 * evenly, while guaranteeing that all 24-bit numbers are mapped onto
     30 * themselves.
     31 */
     32unsigned int _guac_hash_32to24(unsigned int value) {
     33
     34    /* Grab highest-order byte */
     35    unsigned int upper = value & 0xFF000000;
     36
     37    /* XOR upper with lower three bytes, truncate to 24-bit */
     38    return
     39          (value & 0xFFFFFF)
     40        ^ (upper >> 8)
     41        ^ (upper >> 16)
     42        ^ (upper >> 24);
     43
     44}
     45
     46/**
     47 * Rotates a given 32-bit integer by N bits.
     48 *
     49 * NOTE: We probably should check for available bitops.h macros first.
     50 */
     51unsigned int _guac_rotate(unsigned int value, int amount) {
     52
     53    /* amount = amount % 32 */
     54    amount &= 0x1F; 
     55
     56    /* Return rotated amount */
     57    return (value >> amount) | (value << (32 - amount));
     58
     59}
     60
     61unsigned int guac_hash_surface(cairo_surface_t* surface) {
     62
     63    /* Init to zero */
     64    unsigned int hash_value = 0;
     65
     66    int x, y;
     67
     68    /* Get image data and metrics */
     69    unsigned char* data = cairo_image_surface_get_data(surface);
     70    int width = cairo_image_surface_get_width(surface);
     71    int height = cairo_image_surface_get_height(surface);
     72    int stride = cairo_image_surface_get_stride(surface);
     73
     74    for (y=0; y<height; y++) {
     75
     76        /* Get current row */
     77        uint32_t* row = (uint32_t*) data;
     78        data += stride;
     79
     80        for (x=0; x<width; x++) {
     81
     82            /* Get color at current pixel */
     83            unsigned int color = *row;
     84            row++;
     85
     86            /* Compute next hash */
     87            hash_value =
     88                _guac_rotate(hash_value, 1) ^ color ^ 0x1B872E69;
     89
     90        }
     91
     92    } /* end for each row */
     93
     94    /* Done */
     95    return _guac_hash_32to24(hash_value);
     96
     97}
     98
     99int guac_surface_cmp(cairo_surface_t* a, cairo_surface_t* b) {
    100
    101    /* Surface A metrics */
    102    unsigned char* data_a = cairo_image_surface_get_data(a);
    103    int width_a = cairo_image_surface_get_width(a);
    104    int height_a = cairo_image_surface_get_height(a);
    105    int stride_a = cairo_image_surface_get_stride(a);
    106
    107    /* Surface B metrics */
    108    unsigned char* data_b = cairo_image_surface_get_data(b);
    109    int width_b = cairo_image_surface_get_width(b);
    110    int height_b = cairo_image_surface_get_height(b);
    111    int stride_b = cairo_image_surface_get_stride(b);
    112
    113    int y;
    114
    115    /* If core dimensions differ, just compare those. Done. */
    116    if (width_a != width_b) return width_a - width_b;
    117    if (height_a != height_b) return height_a - height_b;
    118
    119    for (y=0; y<height_a; y++) {
    120
    121        /* Compare row. If different, use that result. */
    122        int cmp_result = memcmp(data_a, data_b, width_a * 4);
    123        if (cmp_result != 0)
    124            return cmp_result;
    125
    126        /* Next row */
    127        data_a += stride_a;
    128        data_b += stride_b;
    129
    130    }
    131
    132    /* Otherwise, same. */
    133    return 0;
    134
    135}