nsgif__parse_image_data()

static nsgif_error fl::third_party::nsgif__parse_image_data ( struct nsgif * gif, struct nsgif_frame * frame, const fl::u8 ** pos, bool decode )

static

Parse the image data for a gif frame.

Sets up gif->colour_table for the frame.

Parameters

[in]	gif	The gif object we're decoding.
[in]	frame	The frame to parse image data for.
[in]	pos	Current position in data, updated on exit.
[in]	decode	Whether to decode the image data.

Returns

NSGIF_OK on success, appropriate error otherwise.

Definition at line 1200 of file gif.cpp.hpp.

{
    const fl::u8 *data = *pos;
    fl::size len = gif->buf + gif->buf_len - data;
    fl::u32 frame_idx = frame - gif->frames;
    fl::u8 minimum_code_size;
    nsgif_error ret;
 
    FL_ASSERT(gif != nullptr, "GIF object required");
    FL_ASSERT(frame != nullptr, "Frame object required");
 
    if (!decode) {
        gif->frame_count_partial = frame_idx + 1;
    }
 
    /* Ensure sufficient data remains.  A gif trailer or a minimum lzw code
     * followed by a gif trailer is treated as OK, although without any
     * image data. */
    switch (len) {
        default: if (data[0] == NSGIF_TRAILER) return NSGIF_OK;
            break;
        case 2: if (data[1] == NSGIF_TRAILER) return NSGIF_OK;
            /* Fall through. */
        case 1: if (data[0] == NSGIF_TRAILER) return NSGIF_OK;
            /* Fall through. */
        case 0: return NSGIF_ERR_END_OF_DATA;
    }
 
    minimum_code_size = data[0];
    if (minimum_code_size >= LZW_CODE_MAX) {
        return NSGIF_ERR_DATA_FRAME;
    }
 
    if (decode) {
        ret = nsgif__update_bitmap(gif, frame, data, frame_idx);
    } else {
        fl::u32 block_size = 0;
 
        /* Skip the minimum code size. */
        data++;
        len--;
 
        while (block_size != 1) {
            if (len < 1) {
                return NSGIF_ERR_END_OF_DATA;
            }
            block_size = data[0] + 1;
            /* Check if the frame data runs off the end of the file */
            if (block_size > len) {
                frame->lzw_data_length += len;
                return NSGIF_ERR_END_OF_DATA;
            }
 
            len -= block_size;
            data += block_size;
            frame->lzw_data_length += block_size;
        }
 
        *pos = data;
 
        gif->info.frame_count = frame_idx + 1;
        gif->frames[frame_idx].info.display = true;
 
        return NSGIF_OK;
    }
 
    return ret;
}

References FL_ASSERT, FL_NOEXCEPT, LZW_CODE_MAX, nsgif__update_bitmap(), NSGIF_ERR_DATA_FRAME, NSGIF_ERR_END_OF_DATA, NSGIF_OK, NSGIF_TRAILER, and pos.

Referenced by nsgif__process_frame().

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