cscg24-guacamole

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

png.c (3057B)

      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#include "log.h"
     22#include "png.h"
     23
     24#include <cairo/cairo.h>
     25
     26#include <stdlib.h>
     27#include <string.h>
     28
     29/**
     30 * The current state of the PNG decoder.
     31 */
     32typedef struct guacenc_png_read_state {
     33
     34    /**
     35     * The buffer of unread image data. This pointer will be updated to point
     36     * to the next unread byte when data is read.
     37     */
     38    unsigned char* data;
     39
     40    /**
     41     * The number of bytes remaining to be read within the buffer.
     42     */
     43    unsigned int length;
     44
     45} guacenc_png_read_state;
     46
     47/**
     48 * Attempts to fill the given buffer with read image data. The behavior of
     49 * this function is dictated by cairo_read_t.
     50 *
     51 * @param closure
     52 *     The current state of the PNG decoding process (an instance of
     53 *     guacenc_png_read_state).
     54 *
     55 * @param data
     56 *     The data buffer to fill.
     57 *
     58 * @param length
     59 *     The number of bytes to fill within the data buffer.
     60 *
     61 * @return
     62 *     CAIRO_STATUS_SUCCESS if all data was read successfully (the entire
     63 *     buffer was filled), CAIRO_STATUS_READ_ERROR otherwise.
     64 */
     65static cairo_status_t guacenc_png_read(void* closure, unsigned char* data,
     66        unsigned int length) {
     67
     68    guacenc_png_read_state* state = (guacenc_png_read_state*) closure;
     69
     70    /* If more data is requested than is available in buffer, fail */
     71    if (length > state->length)
     72        return CAIRO_STATUS_READ_ERROR;
     73
     74    /* Read chunk into buffer */
     75    memcpy(data, state->data, length);
     76
     77    /* Advance to next chunk */
     78    state->length -= length;
     79    state->data += length;
     80
     81    /* Read was successful */
     82    return CAIRO_STATUS_SUCCESS;
     83
     84}
     85
     86cairo_surface_t* guacenc_png_decoder(unsigned char* data, int length) {
     87
     88    guacenc_png_read_state state = {
     89        .data = data,
     90        .length = length
     91    };
     92
     93    /* Read PNG from data */
     94    cairo_surface_t* surface =
     95        cairo_image_surface_create_from_png_stream(guacenc_png_read, &state);
     96
     97    /* If surface returned with an error, just return NULL */
     98    if (surface != NULL &&
     99            cairo_surface_status(surface) != CAIRO_STATUS_SUCCESS) {
    100        guacenc_log(GUAC_LOG_WARNING, "Invalid PNG data");
    101        cairo_surface_destroy(surface);
    102        return NULL;
    103    }
    104
    105    /* PNG was read successfully */
    106    return surface;
    107
    108}
    109