coffee_crisis_arcade_edition/source/external/gif.cpp

#include "gif.h"

#include <SDL3/SDL.h>  // Para SDL_LogError, SDL_LogCategory, SDL_LogInfo
#include <cstring>    // Para memcpy, size_t
#include <stdexcept>  // Para runtime_error
#include <string>     // Para char_traits, operator==, basic_string, string

namespace GIF {
inline void readBytes(const uint8_t *&buffer, void *dst, size_t size) {
    std::memcpy(dst, buffer, size);
    buffer += size;
}

void Gif::decompress(int code_length, const uint8_t *input, int input_length, uint8_t *out) {
    if (code_length < 2 || code_length > 12) {
        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Invalid LZW code length: %d", code_length);
        throw std::runtime_error("Invalid LZW code length");
    }

    int i, bit;
    int prev = -1;
    std::vector<DictionaryEntry> dictionary;
    int dictionary_ind;
    unsigned int mask = 0x01;
    int reset_code_length = code_length;
    int clear_code = 1 << code_length;
    int stop_code = clear_code + 1;
    int match_len = 0;

    dictionary.resize(1 << (code_length + 1));
    for (dictionary_ind = 0; dictionary_ind < (1 << code_length); dictionary_ind++) {
        dictionary[dictionary_ind].byte = static_cast<uint8_t>(dictionary_ind);
        dictionary[dictionary_ind].prev = -1;
        dictionary[dictionary_ind].len = 1;
    }
    dictionary_ind += 2;

    while (input_length > 0) {
        int code = 0;
        for (i = 0; i < (code_length + 1); i++) {
            if (input_length <= 0) {
                SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unexpected end of input in decompress");
                throw std::runtime_error("Unexpected end of input in decompress");
            }
            bit = ((*input & mask) != 0) ? 1 : 0;
            mask <<= 1;
            if (mask == 0x100) {
                mask = 0x01;
                input++;
                input_length--;
            }
            code |= (bit << i);
        }

        if (code == clear_code) {
            code_length = reset_code_length;
            dictionary.resize(1 << (code_length + 1));
            for (dictionary_ind = 0; dictionary_ind < (1 << code_length); dictionary_ind++) {
                dictionary[dictionary_ind].byte = static_cast<uint8_t>(dictionary_ind);
                dictionary[dictionary_ind].prev = -1;
                dictionary[dictionary_ind].len = 1;
            }
            dictionary_ind += 2;
            prev = -1;
            continue;
        } else if (code == stop_code) {
            break;
        }

        if (prev > -1 && code_length < 12) {
            if (code > dictionary_ind) {
                SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "LZW error: code (%d) exceeds dictionary_ind (%d)", code, dictionary_ind);
                throw std::runtime_error("LZW error: code exceeds dictionary_ind.");
            }

            int ptr;
            if (code == dictionary_ind) {
                ptr = prev;
                while (dictionary[ptr].prev != -1)
                    ptr = dictionary[ptr].prev;
                dictionary[dictionary_ind].byte = dictionary[ptr].byte;
            } else {
                ptr = code;
                while (dictionary[ptr].prev != -1)
                    ptr = dictionary[ptr].prev;
                dictionary[dictionary_ind].byte = dictionary[ptr].byte;
            }
            dictionary[dictionary_ind].prev = prev;
            dictionary[dictionary_ind].len = dictionary[prev].len + 1;
            dictionary_ind++;

            if ((dictionary_ind == (1 << (code_length + 1))) && (code_length < 11)) {
                code_length++;
                dictionary.resize(1 << (code_length + 1));
            }
        }

        prev = code;

        if (code < 0 || static_cast<size_t>(code) >= dictionary.size()) {
            SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Invalid LZW code %d, dictionary size %lu", code, static_cast<unsigned long>(dictionary.size()));
            throw std::runtime_error("LZW error: invalid code encountered");
        }

        int curCode = code;
        match_len = dictionary[curCode].len;
        while (curCode != -1) {
            out[dictionary[curCode].len - 1] = dictionary[curCode].byte;
            if (dictionary[curCode].prev == curCode) {
                SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Internal error; self-reference detected.");
                throw std::runtime_error("Internal error in decompress: self-reference");
            }
            curCode = dictionary[curCode].prev;
        }
        out += match_len;
    }
}

std::vector<uint8_t> Gif::readSubBlocks(const uint8_t *&buffer) {
    std::vector<uint8_t> data;
    uint8_t block_size = *buffer;
    buffer++;
    while (block_size != 0) {
        data.insert(data.end(), buffer, buffer + block_size);
        buffer += block_size;
        block_size = *buffer;
        buffer++;
    }
    return data;
}

std::vector<uint8_t> Gif::processImageDescriptor(const uint8_t *&buffer, const std::vector<RGB> &gct, int resolution_bits) {
    ImageDescriptor image_descriptor;
    readBytes(buffer, &image_descriptor, sizeof(ImageDescriptor));

    uint8_t lzw_code_size;
    readBytes(buffer, &lzw_code_size, sizeof(uint8_t));

    std::vector<uint8_t> compressed_data = readSubBlocks(buffer);
    int uncompressed_data_length = image_descriptor.image_width * image_descriptor.image_height;
    std::vector<uint8_t> uncompressed_data(uncompressed_data_length);

    decompress(lzw_code_size, compressed_data.data(), static_cast<int>(compressed_data.size()), uncompressed_data.data());
    return uncompressed_data;
}

std::vector<uint32_t> Gif::loadPalette(const uint8_t *buffer) {
    uint8_t header[6];
    std::memcpy(header, buffer, 6);
    buffer += 6;

    ScreenDescriptor screen_descriptor;
    std::memcpy(&screen_descriptor, buffer, sizeof(ScreenDescriptor));
    buffer += sizeof(ScreenDescriptor);

    std::vector<uint32_t> global_color_table;
    if (screen_descriptor.fields & 0x80) {
        int global_color_table_size = 1 << (((screen_descriptor.fields & 0x07) + 1));
        global_color_table.resize(global_color_table_size);
        for (int i = 0; i < global_color_table_size; ++i) {
            uint8_t r = buffer[0];
            uint8_t g = buffer[1];
            uint8_t b = buffer[2];
            global_color_table[i] = (r << 16) | (g << 8) | b;
            buffer += 3;
        }
    }
    return global_color_table;
}

std::vector<uint8_t> Gif::processGifStream(const uint8_t *buffer, uint16_t &w, uint16_t &h) {
    uint8_t header[6];
    std::memcpy(header, buffer, 6);
    buffer += 6;

    std::string headerStr(reinterpret_cast<char *>(header), 6);
    if (headerStr != "GIF87a" && headerStr != "GIF89a") {
        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Formato de archivo GIF inválido: %s", headerStr.c_str());
        throw std::runtime_error("Formato de archivo GIF inválido.");
    }

    SDL_LogInfo(SDL_LOG_CATEGORY_TEST, "Procesando GIF con cabecera: %s", headerStr.c_str());

    ScreenDescriptor screen_descriptor;
    readBytes(buffer, &screen_descriptor, sizeof(ScreenDescriptor));

    w = screen_descriptor.width;
    h = screen_descriptor.height;

    SDL_LogInfo(SDL_LOG_CATEGORY_TEST, "Resolución del GIF: %dx%d", w, h);

    int color_resolution_bits = ((screen_descriptor.fields & 0x70) >> 4) + 1;
    std::vector<RGB> global_color_table;
    if (screen_descriptor.fields & 0x80) {
        int global_color_table_size = 1 << (((screen_descriptor.fields & 0x07) + 1));
        global_color_table.resize(global_color_table_size);
        std::memcpy(global_color_table.data(), buffer, 3 * global_color_table_size);
        buffer += 3 * global_color_table_size;
    }

    uint8_t block_type = *buffer++;
    while (block_type != TRAILER) {
        if (block_type == EXTENSION_INTRODUCER) {
            uint8_t extension_label = *buffer++;
            switch (extension_label) {
                case GRAPHIC_CONTROL: {
                    uint8_t blockSize = *buffer++;
                    buffer += blockSize;
                    uint8_t subBlockSize = *buffer++;
                    while (subBlockSize != 0) {
                        buffer += subBlockSize;
                        subBlockSize = *buffer++;
                    }
                    break;
                }
                case APPLICATION_EXTENSION:
                case COMMENT_EXTENSION:
                case PLAINTEXT_EXTENSION: {
                    uint8_t blockSize = *buffer++;
                    buffer += blockSize;
                    uint8_t subBlockSize = *buffer++;
                    while (subBlockSize != 0) {
                        buffer += subBlockSize;
                        subBlockSize = *buffer++;
                    }
                    break;
                }
                default: {
                    uint8_t blockSize = *buffer++;
                    buffer += blockSize;
                    uint8_t subBlockSize = *buffer++;
                    while (subBlockSize != 0) {
                        buffer += subBlockSize;
                        subBlockSize = *buffer++;
                    }
                    break;
                }
            }
        } else if (block_type == IMAGE_DESCRIPTOR) {
            return processImageDescriptor(buffer, global_color_table, color_resolution_bits);
        } else {
            SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION, "Unrecognized block type: 0x%X", block_type);
            return std::vector<uint8_t>{};
        }
        block_type = *buffer++;
    }

    SDL_LogInfo(SDL_LOG_CATEGORY_TEST, "GIF procesado correctamente.");
    return std::vector<uint8_t>{};
}

std::vector<uint8_t> Gif::loadGif(const uint8_t *buffer, uint16_t &w, uint16_t &h) {
    return processGifStream(buffer, w, h);
}

}  // namespace GIF