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Diffstat (limited to 'src/gif.c')
| -rw-r--r-- | src/gif.c | 2076 |
1 files changed, 2076 insertions, 0 deletions
diff --git a/src/gif.c b/src/gif.c new file mode 100644 index 0000000..73814bf --- /dev/null +++ b/src/gif.c @@ -0,0 +1,2076 @@ +/* + * Copyright 2004 Richard Wilson <richard.wilson@netsurf-browser.org> + * Copyright 2008 Sean Fox <dyntryx@gmail.com> + * Copyright 2013-2022 Michael Drake <tlsa@netsurf-browser.org> + * + * This file is part of NetSurf's libnsgif, http://www.netsurf-browser.org/ + * Licenced under the MIT License, + * http://www.opensource.org/licenses/mit-license.php + */ + +#include <assert.h> +#include <stdint.h> +#include <stdlib.h> +#include <string.h> +#include <stdbool.h> + +#include "lzw.h" +#include "nsgif.h" + +/** Default minimum allowable frame delay in cs. */ +#define NSGIF_FRAME_DELAY_MIN 2 + +/** + * Default frame delay to apply. + * + * Used when a frame delay lower than the minimum is requested. + */ +#define NSGIF_FRAME_DELAY_DEFAULT 10 + +/** GIF frame data */ +typedef struct nsgif_frame { + struct nsgif_frame_info info; + + /** offset (in bytes) to the GIF frame data */ + size_t frame_offset; + /** whether the frame has previously been decoded. */ + bool decoded; + /** whether the frame is totally opaque */ + bool opaque; + /** whether a full image redraw is required */ + bool redraw_required; + + /** Amount of LZW data found in scan */ + uint32_t lzw_data_length; + + /** the index designating a transparent pixel */ + uint32_t transparency_index; + + /** offset to frame colour table */ + uint32_t colour_table_offset; + + /* Frame flags */ + uint32_t flags; +} nsgif_frame; + +/** Pixel format: colour component order. */ +struct nsgif_colour_layout { + uint8_t r; /**< Byte offset within pixel to red component. */ + uint8_t g; /**< Byte offset within pixel to green component. */ + uint8_t b; /**< Byte offset within pixel to blue component. */ + uint8_t a; /**< Byte offset within pixel to alpha component. */ +}; + +/** GIF animation data */ +struct nsgif { + struct nsgif_info info; + + /** LZW decode context */ + void *lzw_ctx; + /** callbacks for bitmap functions */ + nsgif_bitmap_cb_vt bitmap; + /** decoded frames */ + nsgif_frame *frames; + /** current frame */ + uint32_t frame; + /** current frame decoded to bitmap */ + uint32_t decoded_frame; + + /** currently decoded image; stored as bitmap from bitmap_create callback */ + nsgif_bitmap_t *frame_image; + /** Row span of frame_image in pixels. */ + uint32_t rowspan; + + /** Minimum allowable frame delay. */ + uint16_t delay_min; + + /** Frame delay to apply when delay is less than \ref delay_min. */ + uint16_t delay_default; + + /** number of animation loops so far */ + int loop_count; + + /** number of frames partially decoded */ + uint32_t frame_count_partial; + + /** + * Whether all the GIF data has been supplied, or if there may be + * more to come. + */ + bool data_complete; + + /** pointer to GIF data */ + const uint8_t *buf; + /** current index into GIF data */ + size_t buf_pos; + /** total number of bytes of GIF data available */ + size_t buf_len; + + /** current number of frame holders */ + uint32_t frame_holders; + /** background index */ + uint32_t bg_index; + /** image aspect ratio (ignored) */ + uint32_t aspect_ratio; + /** size of global colour table (in entries) */ + uint32_t colour_table_size; + + /** current colour table */ + uint32_t *colour_table; + /** Client's colour component order. */ + struct nsgif_colour_layout colour_layout; + /** global colour table */ + uint32_t global_colour_table[NSGIF_MAX_COLOURS]; + /** local colour table */ + uint32_t local_colour_table[NSGIF_MAX_COLOURS]; + + /** previous frame for NSGIF_FRAME_RESTORE */ + void *prev_frame; + /** previous frame index */ + uint32_t prev_index; +}; + +/** + * Helper macro to get number of elements in an array. + * + * \param[in] _a Array to count elements of. + * \return NUlber of elements in array. + */ +#define NSGIF_ARRAY_LEN(_a) ((sizeof(_a)) / (sizeof(*_a))) + +/** + * + * \file + * \brief GIF image decoder + * + * The GIF format is thoroughly documented; a full description can be found at + * http://www.w3.org/Graphics/GIF/spec-gif89a.txt + * + * \todo Plain text and comment extensions should be implemented. + */ + +/** Internal flag that the colour table needs to be processed */ +#define NSGIF_PROCESS_COLOURS 0xaa000000 + +/** Internal flag that a frame is invalid/unprocessed */ +#define NSGIF_FRAME_INVALID UINT32_MAX + +/** Transparent colour */ +#define NSGIF_TRANSPARENT_COLOUR 0x00 + +/** No transparency */ +#define NSGIF_NO_TRANSPARENCY (0xFFFFFFFFu) + +/* GIF Flags */ +#define NSGIF_COLOUR_TABLE_MASK 0x80 +#define NSGIF_COLOUR_TABLE_SIZE_MASK 0x07 +#define NSGIF_BLOCK_TERMINATOR 0x00 +#define NSGIF_TRAILER 0x3b + +/** + * Convert an LZW result code to equivalent GIF result code. + * + * \param[in] l_res LZW response code. + * \return GIF result code. + */ +static nsgif_error nsgif__error_from_lzw(lzw_result l_res) +{ + static const nsgif_error g_res[] = { + [LZW_OK] = NSGIF_OK, + [LZW_NO_MEM] = NSGIF_ERR_OOM, + [LZW_OK_EOD] = NSGIF_ERR_END_OF_DATA, + [LZW_NO_DATA] = NSGIF_ERR_END_OF_DATA, + [LZW_EOI_CODE] = NSGIF_ERR_DATA_FRAME, + [LZW_BAD_ICODE] = NSGIF_ERR_DATA_FRAME, + [LZW_BAD_CODE] = NSGIF_ERR_DATA_FRAME, + }; + assert(l_res != LZW_BAD_PARAM); + assert(l_res != LZW_NO_COLOUR); + return g_res[l_res]; +} + +/** + * Updates the sprite memory size + * + * \param gif The animation context + * \param width The width of the sprite + * \param height The height of the sprite + * \return NSGIF_ERR_OOM for a memory error NSGIF_OK for success + */ +static nsgif_error nsgif__initialise_sprite( + struct nsgif *gif, + uint32_t width, + uint32_t height) +{ + /* Already allocated? */ + if (gif->frame_image) { + return NSGIF_OK; + } + + assert(gif->bitmap.create); + gif->frame_image = gif->bitmap.create(width, height); + if (gif->frame_image == NULL) { + return NSGIF_ERR_OOM; + } + + return NSGIF_OK; +} + +/** + * Helper to get the rendering bitmap for a gif. + * + * \param[in] gif The gif object we're decoding. + * \return Client pixel buffer for rendering into. + */ +static inline uint32_t* nsgif__bitmap_get( + struct nsgif *gif) +{ + nsgif_error ret; + + /* Make sure we have a buffer to decode to. */ + ret = nsgif__initialise_sprite(gif, gif->info.width, gif->info.height); + if (ret != NSGIF_OK) { + return NULL; + } + + gif->rowspan = gif->info.width; + if (gif->bitmap.get_rowspan) { + gif->rowspan = gif->bitmap.get_rowspan(gif->frame_image); + } + + /* Get the frame data */ + assert(gif->bitmap.get_buffer); + return (void *)gif->bitmap.get_buffer(gif->frame_image); +} + +/** + * Helper to tell the client that their bitmap was modified. + * + * \param[in] gif The gif object we're decoding. + */ +static inline void nsgif__bitmap_modified( + const struct nsgif *gif) +{ + if (gif->bitmap.modified) { + gif->bitmap.modified(gif->frame_image); + } +} + +/** + * Helper to tell the client that whether the bitmap is opaque. + * + * \param[in] gif The gif object we're decoding. + * \param[in] frame The frame that has been decoded. + */ +static inline void nsgif__bitmap_set_opaque( + const struct nsgif *gif, + const struct nsgif_frame *frame) +{ + if (gif->bitmap.set_opaque) { + gif->bitmap.set_opaque( + gif->frame_image, frame->opaque); + } +} + +/** + * Helper to get the client to determine if the bitmap is opaque. + * + * \todo: We don't really need to get the client to do this for us. + * + * \param[in] gif The gif object we're decoding. + * \return true if the bitmap is opaque, false otherwise. + */ +static inline bool nsgif__bitmap_get_opaque( + const struct nsgif *gif) +{ + if (gif->bitmap.test_opaque) { + return gif->bitmap.test_opaque( + gif->frame_image); + } + + return false; +} + +static void nsgif__record_frame( + struct nsgif *gif, + const uint32_t *bitmap) +{ + size_t pixel_bytes = sizeof(*bitmap); + size_t height = gif->info.height; + size_t width = gif->info.width; + uint32_t *prev_frame; + + if (gif->decoded_frame == NSGIF_FRAME_INVALID || + gif->decoded_frame == gif->prev_index) { + /* No frame to copy, or already have this frame recorded. */ + return; + } + + bitmap = nsgif__bitmap_get(gif); + if (bitmap == NULL) { + return; + } + + if (gif->prev_frame == NULL) { + prev_frame = realloc(gif->prev_frame, + width * height * pixel_bytes); + if (prev_frame == NULL) { + return; + } + } else { + prev_frame = gif->prev_frame; + } + + memcpy(prev_frame, bitmap, width * height * pixel_bytes); + + gif->prev_frame = prev_frame; + gif->prev_index = gif->decoded_frame; +} + +static nsgif_error nsgif__recover_frame( + const struct nsgif *gif, + uint32_t *bitmap) +{ + const uint32_t *prev_frame = gif->prev_frame; + size_t pixel_bytes = sizeof(*bitmap); + size_t height = gif->info.height; + size_t width = gif->info.width; + + memcpy(bitmap, prev_frame, height * width * pixel_bytes); + + return NSGIF_OK; +} + +/** + * Get the next line for GIF decode. + * + * Note that the step size must be initialised to 24 at the start of the frame + * (when y == 0). This is because of the first two passes of the frame have + * the same step size of 8, and the step size is used to determine the current + * pass. + * + * \param[in] height Frame height in pixels. + * \param[in,out] y Current row, starting from 0, updated on exit. + * \param[in,out] step Current step starting with 24, updated on exit. + * \return true if there is a row to process, false at the end of the frame. + */ +static inline bool nsgif__deinterlace(uint32_t height, uint32_t *y, uint8_t *step) +{ + *y += *step & 0xf; + + if (*y < height) return true; + + switch (*step) { + case 24: *y = 4; *step = 8; if (*y < height) return true; + /* Fall through. */ + case 8: *y = 2; *step = 4; if (*y < height) return true; + /* Fall through. */ + case 4: *y = 1; *step = 2; if (*y < height) return true; + /* Fall through. */ + default: + break; + } + + return false; +} + +/** + * Get the next line for GIF decode. + * + * \param[in] interlace Non-zero if the frame is not interlaced. + * \param[in] height Frame height in pixels. + * \param[in,out] y Current row, starting from 0, updated on exit. + * \param[in,out] step Current step starting with 24, updated on exit. + * \return true if there is a row to process, false at the end of the frame. + */ +static inline bool nsgif__next_row(uint32_t interlace, + uint32_t height, uint32_t *y, uint8_t *step) +{ + if (!interlace) { + return (++*y != height); + } else { + return nsgif__deinterlace(height, y, step); + } +} + +/** + * Get any frame clip adjustment for the image extent. + * + * \param[in] frame_off Frame's X or Y offset. + * \param[in] frame_dim Frame width or height. + * \param[in] image_ext Image width or height constraint. + * \return the amount the frame needs to be clipped to fit the image in given + * dimension. + */ +static inline uint32_t gif__clip( + uint32_t frame_off, + uint32_t frame_dim, + uint32_t image_ext) +{ + uint32_t frame_ext = frame_off + frame_dim; + + if (frame_ext <= image_ext) { + return 0; + } + + return frame_ext - image_ext; +} + +/** + * Perform any jump over decoded data, to accommodate clipped portion of frame. + * + * \param[in,out] skip Number of pixels of data to jump. + * \param[in,out] available Number of pixels of data currently available. + * \param[in,out] pos Position in decoded pixel value data. + */ +static inline void gif__jump_data( + uint32_t *skip, + uint32_t *available, + const uint8_t **pos) +{ + uint32_t jump = (*skip < *available) ? *skip : *available; + + *skip -= jump; + *available -= jump; + *pos += jump; +} + +static nsgif_error nsgif__decode_complex( + struct nsgif *gif, + uint32_t width, + uint32_t height, + uint32_t offset_x, + uint32_t offset_y, + uint32_t interlace, + const uint8_t *data, + uint32_t transparency_index, + uint32_t *restrict frame_data, + uint32_t *restrict colour_table) +{ + lzw_result res; + nsgif_error ret = NSGIF_OK; + uint32_t clip_x = gif__clip(offset_x, width, gif->info.width); + uint32_t clip_y = gif__clip(offset_y, height, gif->info.height); + const uint8_t *uncompressed; + uint32_t available = 0; + uint8_t step = 24; + uint32_t skip = 0; + uint32_t y = 0; + + if (offset_x >= gif->info.width || + offset_y >= gif->info.height) { + return NSGIF_OK; + } + + width -= clip_x; + height -= clip_y; + + if (width == 0 || height == 0) { + return NSGIF_OK; + } + + /* Initialise the LZW decoding */ + res = lzw_decode_init(gif->lzw_ctx, data[0], + gif->buf, gif->buf_len, + data + 1 - gif->buf); + if (res != LZW_OK) { + return nsgif__error_from_lzw(res); + } + + do { + uint32_t x; + uint32_t *frame_scanline; + + frame_scanline = frame_data + offset_x + + (y + offset_y) * gif->rowspan; + + x = width; + while (x > 0) { + unsigned row_available; + while (available == 0) { + if (res != LZW_OK) { + /* Unexpected end of frame, try to recover */ + if (res == LZW_OK_EOD || + res == LZW_EOI_CODE) { + ret = NSGIF_OK; + } else { + ret = nsgif__error_from_lzw(res); + } + return ret; + } + res = lzw_decode(gif->lzw_ctx, + &uncompressed, &available); + + if (available == 0) { + return NSGIF_OK; + } + gif__jump_data(&skip, &available, &uncompressed); + } + + row_available = x < available ? x : available; + x -= row_available; + available -= row_available; + if (transparency_index > 0xFF) { + while (row_available-- > 0) { + *frame_scanline++ = + colour_table[*uncompressed++]; + } + } else { + while (row_available-- > 0) { + register uint32_t colour; + colour = *uncompressed++; + if (colour != transparency_index) { + *frame_scanline = + colour_table[colour]; + } + frame_scanline++; + } + } + } + + skip = clip_x; + gif__jump_data(&skip, &available, &uncompressed); + } while (nsgif__next_row(interlace, height, &y, &step)); + + return ret; +} + +static nsgif_error nsgif__decode_simple( + struct nsgif *gif, + uint32_t height, + uint32_t offset_y, + const uint8_t *data, + uint32_t transparency_index, + uint32_t *restrict frame_data, + uint32_t *restrict colour_table) +{ + uint32_t pixels; + uint32_t written = 0; + nsgif_error ret = NSGIF_OK; + lzw_result res; + + if (offset_y >= gif->info.height) { + return NSGIF_OK; + } + + height -= gif__clip(offset_y, height, gif->info.height); + + if (height == 0) { + return NSGIF_OK; + } + + /* Initialise the LZW decoding */ + res = lzw_decode_init_map(gif->lzw_ctx, data[0], + transparency_index, colour_table, + gif->buf, gif->buf_len, + data + 1 - gif->buf); + if (res != LZW_OK) { + return nsgif__error_from_lzw(res); + } + + frame_data += (offset_y * gif->info.width); + pixels = gif->info.width * height; + + while (pixels > 0) { + res = lzw_decode_map(gif->lzw_ctx, + frame_data, pixels, &written); + pixels -= written; + frame_data += written; + if (res != LZW_OK) { + /* Unexpected end of frame, try to recover */ + if (res == LZW_OK_EOD || res == LZW_EOI_CODE) { + ret = NSGIF_OK; + } else { + ret = nsgif__error_from_lzw(res); + } + break; + } + } + + if (pixels == 0) { + ret = NSGIF_OK; + } + + return ret; +} + +static inline nsgif_error nsgif__decode( + struct nsgif *gif, + struct nsgif_frame *frame, + const uint8_t *data, + uint32_t *restrict frame_data) +{ + nsgif_error ret; + uint32_t width = frame->info.rect.x1 - frame->info.rect.x0; + uint32_t height = frame->info.rect.y1 - frame->info.rect.y0; + uint32_t offset_x = frame->info.rect.x0; + uint32_t offset_y = frame->info.rect.y0; + uint32_t transparency_index = frame->transparency_index; + uint32_t *restrict colour_table = gif->colour_table; + + if (frame->info.interlaced == false && offset_x == 0 && + width == gif->info.width && + width == gif->rowspan) { + ret = nsgif__decode_simple(gif, height, offset_y, + data, transparency_index, + frame_data, colour_table); + } else { + ret = nsgif__decode_complex(gif, width, height, + offset_x, offset_y, frame->info.interlaced, + data, transparency_index, + frame_data, colour_table); + } + + if (gif->data_complete && ret == NSGIF_ERR_END_OF_DATA) { + /* This is all the data there is, so make do. */ + ret = NSGIF_OK; + } + + return ret; +} + +/** + * Restore a GIF to the background colour. + * + * \param[in] gif The gif object we're decoding. + * \param[in] frame The frame to clear, or NULL. + * \param[in] bitmap The bitmap to clear the frame in. + */ +static void nsgif__restore_bg( + struct nsgif *gif, + struct nsgif_frame *frame, + uint32_t *bitmap) +{ + size_t pixel_bytes = sizeof(*bitmap); + + if (frame == NULL) { + size_t width = gif->info.width; + size_t height = gif->info.height; + + memset(bitmap, NSGIF_TRANSPARENT_COLOUR, + width * height * pixel_bytes); + } else { + uint32_t width = frame->info.rect.x1 - frame->info.rect.x0; + uint32_t height = frame->info.rect.y1 - frame->info.rect.y0; + uint32_t offset_x = frame->info.rect.x0; + uint32_t offset_y = frame->info.rect.y0; + + if (frame->info.display == false || + frame->info.rect.x0 >= gif->info.width || + frame->info.rect.y0 >= gif->info.height) { + return; + } + + width -= gif__clip(offset_x, width, gif->info.width); + height -= gif__clip(offset_y, height, gif->info.height); + + if (frame->info.transparency) { + for (uint32_t y = 0; y < height; y++) { + uint32_t *scanline = bitmap + offset_x + + (offset_y + y) * gif->info.width; + memset(scanline, NSGIF_TRANSPARENT_COLOUR, + width * pixel_bytes); + } + } else { + for (uint32_t y = 0; y < height; y++) { + uint32_t *scanline = bitmap + offset_x + + (offset_y + y) * gif->info.width; + for (uint32_t x = 0; x < width; x++) { + scanline[x] = gif->info.background; + } + } + } + } +} + +static nsgif_error nsgif__update_bitmap( + struct nsgif *gif, + struct nsgif_frame *frame, + const uint8_t *data, + uint32_t frame_idx) +{ + nsgif_error ret; + uint32_t *bitmap; + + gif->decoded_frame = frame_idx; + + bitmap = nsgif__bitmap_get(gif); + if (bitmap == NULL) { + return NSGIF_ERR_OOM; + } + + /* Handle any bitmap clearing/restoration required before decoding this + * frame. */ + if (frame_idx == 0 || gif->decoded_frame == NSGIF_FRAME_INVALID) { + nsgif__restore_bg(gif, NULL, bitmap); + + } else { + struct nsgif_frame *prev = &gif->frames[frame_idx - 1]; + + if (prev->info.disposal == NSGIF_DISPOSAL_RESTORE_BG) { + nsgif__restore_bg(gif, prev, bitmap); + + } else if (prev->info.disposal == NSGIF_DISPOSAL_RESTORE_PREV) { + ret = nsgif__recover_frame(gif, bitmap); + if (ret != NSGIF_OK) { + nsgif__restore_bg(gif, prev, bitmap); + } + } + } + + if (frame->info.disposal == NSGIF_DISPOSAL_RESTORE_PREV) { + /* Store the previous frame for later restoration */ + nsgif__record_frame(gif, bitmap); + } + + ret = nsgif__decode(gif, frame, data, bitmap); + + nsgif__bitmap_modified(gif); + + if (!frame->decoded) { + frame->opaque = nsgif__bitmap_get_opaque(gif); + frame->decoded = true; + } + nsgif__bitmap_set_opaque(gif, frame); + + return ret; +} + +/** + * Parse the graphic control extension + * + * \param[in] frame The gif frame object we're decoding. + * \param[in] data The data to decode. + * \param[in] len Byte length of data. + * \return NSGIF_ERR_END_OF_DATA if more data is needed, + * NSGIF_OK for success. + */ +static nsgif_error nsgif__parse_extension_graphic_control( + struct nsgif_frame *frame, + const uint8_t *data, + size_t len) +{ + enum { + GIF_MASK_TRANSPARENCY = 0x01, + GIF_MASK_DISPOSAL = 0x1c, + }; + + /* 6-byte Graphic Control Extension is: + * + * +0 CHAR Graphic Control Label + * +1 CHAR Block Size + * +2 CHAR __Packed Fields__ + * 3BITS Reserved + * 3BITS Disposal Method + * 1BIT User Input Flag + * 1BIT Transparent Color Flag + * +3 SHORT Delay Time + * +5 CHAR Transparent Color Index + */ + if (len < 6) { + return NSGIF_ERR_END_OF_DATA; + } + + frame->info.delay = data[3] | (data[4] << 8); + + if (data[2] & GIF_MASK_TRANSPARENCY) { + frame->info.transparency = true; + frame->transparency_index = data[5]; + } + + frame->info.disposal = ((data[2] & GIF_MASK_DISPOSAL) >> 2); + /* I have encountered documentation and GIFs in the + * wild that use 0x04 to restore the previous frame, + * rather than the officially documented 0x03. I + * believe some (older?) software may even actually + * export this way. We handle this as a type of + * "quirks" mode. */ + if (frame->info.disposal == NSGIF_DISPOSAL_RESTORE_QUIRK) { + frame->info.disposal = NSGIF_DISPOSAL_RESTORE_PREV; + } + + /* if we are clearing the background then we need to + * redraw enough to cover the previous frame too. */ + frame->redraw_required = + frame->info.disposal == NSGIF_DISPOSAL_RESTORE_BG || + frame->info.disposal == NSGIF_DISPOSAL_RESTORE_PREV; + + return NSGIF_OK; +} + +/** + * Check an app ext identifier and authentication code for loop count extension. + * + * \param[in] data The data to decode. + * \param[in] len Byte length of data. + * \return true if extension is a loop count extension. + */ +static bool nsgif__app_ext_is_loop_count( + const uint8_t *data, + size_t len) +{ + enum { + EXT_LOOP_COUNT_BLOCK_SIZE = 0x0b, + }; + + assert(len > 13); + (void)(len); + + if (data[1] == EXT_LOOP_COUNT_BLOCK_SIZE) { + if (strncmp((const char *)data + 2, "NETSCAPE2.0", 11) == 0 || + strncmp((const char *)data + 2, "ANIMEXTS1.0", 11) == 0) { + return true; + } + } + + return false; +} + +/** + * Parse the application extension + * + * \param[in] gif The gif object we're decoding. + * \param[in] data The data to decode. + * \param[in] len Byte length of data. + * \return NSGIF_ERR_END_OF_DATA if more data is needed, + * NSGIF_OK for success. + */ +static nsgif_error nsgif__parse_extension_application( + struct nsgif *gif, + const uint8_t *data, + size_t len) +{ + /* 14-byte+ Application Extension is: + * + * +0 CHAR Application Extension Label + * +1 CHAR Block Size + * +2 8CHARS Application Identifier + * +10 3CHARS Appl. Authentication Code + * +13 1-256 Application Data (Data sub-blocks) + */ + if (len < 17) { + return NSGIF_ERR_END_OF_DATA; + } + + if (nsgif__app_ext_is_loop_count(data, len)) { + enum { + EXT_LOOP_COUNT_SUB_BLOCK_SIZE = 0x03, + EXT_LOOP_COUNT_SUB_BLOCK_ID = 0x01, + }; + if ((data[13] == EXT_LOOP_COUNT_SUB_BLOCK_SIZE) && + (data[14] == EXT_LOOP_COUNT_SUB_BLOCK_ID)) { + gif->info.loop_max = data[15] | (data[16] << 8); + + /* The value in the source data means repeat N times + * after the first implied play. A value of zero has + * the special meaning of loop forever. (The only way + * to play the animation once is not to have this + * extension at all. */ + if (gif->info.loop_max > 0) { + gif->info.loop_max++; + } + } + } + + return NSGIF_OK; +} + +/** + * Parse the frame's extensions + * + * \param[in] gif The gif object we're decoding. + * \param[in] frame The frame to parse extensions for. + * \param[in] pos Current position in data, updated on exit. + * \param[in] decode Whether to decode or skip over the extension. + * \return NSGIF_ERR_END_OF_DATA if more data is needed, + * NSGIF_OK for success. + */ +static nsgif_error nsgif__parse_frame_extensions( + struct nsgif *gif, + struct nsgif_frame *frame, + const uint8_t **pos, + bool decode) +{ + enum { + GIF_EXT_INTRODUCER = 0x21, + GIF_EXT_GRAPHIC_CONTROL = 0xf9, + GIF_EXT_COMMENT = 0xfe, + GIF_EXT_PLAIN_TEXT = 0x01, + GIF_EXT_APPLICATION = 0xff, + }; + const uint8_t *nsgif_data = *pos; + const uint8_t *nsgif_end = gif->buf + gif->buf_len; + int nsgif_bytes = nsgif_end - nsgif_data; + + /* Initialise the extensions */ + while (nsgif_bytes > 0 && nsgif_data[0] == GIF_EXT_INTRODUCER) { + bool block_step = true; + nsgif_error ret; + + nsgif_data++; + nsgif_bytes--; + + if (nsgif_bytes == 0) { + return NSGIF_ERR_END_OF_DATA; + } + + /* Switch on extension label */ + switch (nsgif_data[0]) { + case GIF_EXT_GRAPHIC_CONTROL: + if (decode) { + ret = nsgif__parse_extension_graphic_control( + frame, + nsgif_data, + nsgif_bytes); + if (ret != NSGIF_OK) { + return ret; + } + } + break; + + case GIF_EXT_APPLICATION: + if (decode) { + ret = nsgif__parse_extension_application( + gif, nsgif_data, nsgif_bytes); + if (ret != NSGIF_OK) { + return ret; + } + } + break; + + case GIF_EXT_COMMENT: + /* Move the pointer to the first data sub-block Skip 1 + * byte for the extension label. */ + ++nsgif_data; + block_step = false; + break; + + default: + break; + } + + if (block_step) { + /* Move the pointer to the first data sub-block Skip 2 + * bytes for the extension label and size fields Skip + * the extension size itself + */ + if (nsgif_bytes < 2) { + return NSGIF_ERR_END_OF_DATA; + } + nsgif_data += 2 + nsgif_data[1]; + } + + /* Repeatedly skip blocks until we get a zero block or run out + * of data. This data is ignored by this gif decoder. */ + while (nsgif_data < nsgif_end && nsgif_data[0] != NSGIF_BLOCK_TERMINATOR) { + nsgif_data += nsgif_data[0] + 1; + if (nsgif_data >= nsgif_end) { + return NSGIF_ERR_END_OF_DATA; + } + } + nsgif_data++; + nsgif_bytes = nsgif_end - nsgif_data; + } + + if (nsgif_data > nsgif_end) { + nsgif_data = nsgif_end; + } + + /* Set buffer position and return */ + *pos = nsgif_data; + return NSGIF_OK; +} + +/** + * Parse a GIF Image Descriptor. + * + * The format is: + * + * +0 CHAR Image Separator (0x2c) + * +1 SHORT Image Left Position + * +3 SHORT Image Top Position + * +5 SHORT Width + * +7 SHORT Height + * +9 CHAR __Packed Fields__ + * 1BIT Local Colour Table Flag + * 1BIT Interlace Flag + * 1BIT Sort Flag + * 2BITS Reserved + * 3BITS Size of Local Colour Table + * + * \param[in] gif The gif object we're decoding. + * \param[in] frame The frame to parse an image descriptor for. + * \param[in] pos Current position in data, updated on exit. + * \param[in] decode Whether to decode the image descriptor. + * \return NSGIF_OK on success, appropriate error otherwise. + */ +static nsgif_error nsgif__parse_image_descriptor( + struct nsgif *gif, + struct nsgif_frame *frame, + const uint8_t **pos, + bool decode) +{ + const uint8_t *data = *pos; + size_t len = gif->buf + gif->buf_len - data; + enum { + NSGIF_IMAGE_DESCRIPTOR_LEN = 10u, + NSGIF_IMAGE_SEPARATOR = 0x2Cu, + NSGIF_MASK_INTERLACE = 0x40u, + }; + + assert(gif != NULL); + assert(frame != NULL); + + if (len < NSGIF_IMAGE_DESCRIPTOR_LEN) { + return NSGIF_ERR_END_OF_DATA; + } + + if (decode) { + uint32_t x, y, w, h; + + if (data[0] != NSGIF_IMAGE_SEPARATOR) { + return NSGIF_ERR_DATA_FRAME; + } + + x = data[1] | (data[2] << 8); + y = data[3] | (data[4] << 8); + w = data[5] | (data[6] << 8); + h = data[7] | (data[8] << 8); + frame->flags = data[9]; + + frame->info.rect.x0 = x; + frame->info.rect.y0 = y; + frame->info.rect.x1 = x + w; + frame->info.rect.y1 = y + h; + + frame->info.interlaced = frame->flags & NSGIF_MASK_INTERLACE; + + /* Allow first frame to grow image dimensions. */ + if (gif->info.frame_count == 0) { + if (x + w > gif->info.width) { + gif->info.width = x + w; + } + if (y + h > gif->info.height) { + gif->info.height = y + h; + } + } + } + + *pos += NSGIF_IMAGE_DESCRIPTOR_LEN; + return NSGIF_OK; +} + +/** + * Extract a GIF colour table into a LibNSGIF colour table buffer. + * + * \param[in] colour_table The colour table to populate. + * \param[in] layout la. + * \param[in] colour_table_entries The number of colour table entries. + * \param[in] data Raw colour table data. + */ +static void nsgif__colour_table_decode( + uint32_t colour_table[NSGIF_MAX_COLOURS], + const struct nsgif_colour_layout *layout, + size_t colour_table_entries, + const uint8_t *data) +{ + uint8_t *entry = (uint8_t *)colour_table; + + while (colour_table_entries--) { + /* Gif colour map contents are r,g,b. + * + * We want to pack them bytewise into the colour table, + * according to the client colour layout. + */ + + entry[layout->r] = *data++; + entry[layout->g] = *data++; + entry[layout->b] = *data++; + entry[layout->a] = 0xff; + + entry += sizeof(uint32_t); + } +} + +/** + * Extract a GIF colour table into a LibNSGIF colour table buffer. + * + * \param[in] colour_table The colour table to populate. + * \param[in] layout The target pixel format to decode to. + * \param[in] colour_table_entries The number of colour table entries. + * \param[in] data Current position in data. + * \param[in] data_len The available length of `data`. + * \param[out] used Number of colour table bytes read. + * \param[in] decode Whether to decode the colour table. + * \return NSGIF_OK on success, appropriate error otherwise. + */ +static inline nsgif_error nsgif__colour_table_extract( + uint32_t colour_table[NSGIF_MAX_COLOURS], + const struct nsgif_colour_layout *layout, + size_t colour_table_entries, + const uint8_t *data, + size_t data_len, + size_t *used, + bool decode) +{ + if (data_len < colour_table_entries * 3) { + return NSGIF_ERR_END_OF_DATA; + } + + if (decode) { + nsgif__colour_table_decode(colour_table, layout, + colour_table_entries, data); + } + + *used = colour_table_entries * 3; + return NSGIF_OK; +} + +/** + * Get a frame's colour table. + * + * Sets up gif->colour_table for the frame. + * + * \param[in] gif The gif object we're decoding. + * \param[in] frame The frame to get the colour table for. + * \param[in] pos Current position in data, updated on exit. + * \param[in] decode Whether to decode the colour table. + * \return NSGIF_OK on success, appropriate error otherwise. + */ +static nsgif_error nsgif__parse_colour_table( + struct nsgif *gif, + struct nsgif_frame *frame, + const uint8_t **pos, + bool decode) +{ + nsgif_error ret; + const uint8_t *data = *pos; + size_t len = gif->buf + gif->buf_len - data; + size_t used_bytes; + + assert(gif != NULL); + assert(frame != NULL); + + if ((frame->flags & NSGIF_COLOUR_TABLE_MASK) == 0) { + gif->colour_table = gif->global_colour_table; + return NSGIF_OK; + } + + if (decode == false) { + frame->colour_table_offset = *pos - gif->buf; + } + + ret = nsgif__colour_table_extract( + gif->local_colour_table, &gif->colour_layout, + 2 << (frame->flags & NSGIF_COLOUR_TABLE_SIZE_MASK), + data, len, &used_bytes, decode); + if (ret != NSGIF_OK) { + return ret; + } + *pos += used_bytes; + + if (decode) { + gif->colour_table = gif->local_colour_table; + } else { + frame->info.local_palette = true; + } + + return NSGIF_OK; +} + +/** + * Parse the image data for a gif frame. + * + * Sets up gif->colour_table for the frame. + * + * \param[in] gif The gif object we're decoding. + * \param[in] frame The frame to parse image data for. + * \param[in] pos Current position in data, updated on exit. + * \param[in] decode Whether to decode the image data. + * \return NSGIF_OK on success, appropriate error otherwise. + */ +static nsgif_error nsgif__parse_image_data( + struct nsgif *gif, + struct nsgif_frame *frame, + const uint8_t **pos, + bool decode) +{ + const uint8_t *data = *pos; + size_t len = gif->buf + gif->buf_len - data; + uint32_t frame_idx = frame - gif->frames; + uint8_t minimum_code_size; + nsgif_error ret; + + assert(gif != NULL); + assert(frame != NULL); + + 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 { + uint32_t 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; +} + +static struct nsgif_frame *nsgif__get_frame( + struct nsgif *gif, + uint32_t frame_idx) +{ + struct nsgif_frame *frame; + + if (gif->frame_holders > frame_idx) { + frame = &gif->frames[frame_idx]; + } else { + /* Allocate more memory */ + size_t count = frame_idx + 1; + struct nsgif_frame *temp; + + temp = realloc(gif->frames, count * sizeof(*frame)); + if (temp == NULL) { + return NULL; + } + gif->frames = temp; + gif->frame_holders = count; + + frame = &gif->frames[frame_idx]; + + frame->info.local_palette = false; + frame->info.transparency = false; + frame->info.display = false; + frame->info.disposal = 0; + frame->info.delay = 10; + + frame->transparency_index = NSGIF_NO_TRANSPARENCY; + frame->frame_offset = gif->buf_pos; + frame->redraw_required = false; + frame->lzw_data_length = 0; + frame->decoded = false; + } + + return frame; +} + +/** + * Attempts to initialise the next frame + * + * \param[in] gif The animation context + * \param[in] frame_idx The frame number to decode. + * \param[in] decode Whether to decode the graphical image data. + * \return NSGIF_OK on success, appropriate error otherwise. +*/ +static nsgif_error nsgif__process_frame( + struct nsgif *gif, + uint32_t frame_idx, + bool decode) +{ + nsgif_error ret; + const uint8_t *pos; + const uint8_t *end; + struct nsgif_frame *frame; + + frame = nsgif__get_frame(gif, frame_idx); + if (frame == NULL) { + return NSGIF_ERR_OOM; + } + + end = gif->buf + gif->buf_len; + + if (decode) { + pos = gif->buf + frame->frame_offset; + + /* Ensure this frame is supposed to be decoded */ + if (frame->info.display == false) { + return NSGIF_OK; + } + + /* Ensure the frame is in range to decode */ + if (frame_idx > gif->frame_count_partial) { + return NSGIF_ERR_END_OF_DATA; + } + + /* Done if frame is already decoded */ + if (frame_idx == gif->decoded_frame) { + return NSGIF_OK; + } + } else { + pos = gif->buf + gif->buf_pos; + + /* Check if we've finished */ + if (pos < end && pos[0] == NSGIF_TRAILER) { + return NSGIF_OK; + } + } + + ret = nsgif__parse_frame_extensions(gif, frame, &pos, !decode); + if (ret != NSGIF_OK) { + goto cleanup; + } + + ret = nsgif__parse_image_descriptor(gif, frame, &pos, !decode); + if (ret != NSGIF_OK) { + goto cleanup; + } + + ret = nsgif__parse_colour_table(gif, frame, &pos, decode); + if (ret != NSGIF_OK) { + goto cleanup; + } + + ret = nsgif__parse_image_data(gif, frame, &pos, decode); + if (ret != NSGIF_OK) { + goto cleanup; + } + +cleanup: + if (!decode) { + gif->buf_pos = pos - gif->buf; + } + + return ret; +} + +/* exported function documented in nsgif.h */ +void nsgif_destroy(nsgif_t *gif) +{ + if (gif == NULL) { + return; + } + + /* Release all our memory blocks */ + if (gif->frame_image) { + assert(gif->bitmap.destroy); + gif->bitmap.destroy(gif->frame_image); + gif->frame_image = NULL; + } + + free(gif->frames); + gif->frames = NULL; + + free(gif->prev_frame); + gif->prev_frame = NULL; + + lzw_context_destroy(gif->lzw_ctx); + gif->lzw_ctx = NULL; + + free(gif); +} + +/** + * Check whether the host is little endian. + * + * Checks whether least significant bit is in the first byte of a `uint16_t`. + * + * \return true if host is little endian. + */ +static inline bool nsgif__host_is_little_endian(void) +{ + const uint16_t test = 1; + + return ((const uint8_t *) &test)[0]; +} + +static struct nsgif_colour_layout nsgif__bitmap_fmt_to_colour_layout( + nsgif_bitmap_fmt_t bitmap_fmt) +{ + bool le = nsgif__host_is_little_endian(); + + /* Map endian-dependant formats to byte-wise format for the host. */ + switch (bitmap_fmt) { + case NSGIF_BITMAP_FMT_RGBA8888: + bitmap_fmt = (le) ? NSGIF_BITMAP_FMT_A8B8G8R8 + : NSGIF_BITMAP_FMT_R8G8B8A8; + break; + case NSGIF_BITMAP_FMT_BGRA8888: + bitmap_fmt = (le) ? NSGIF_BITMAP_FMT_A8R8G8B8 + : NSGIF_BITMAP_FMT_B8G8R8A8; + break; + case NSGIF_BITMAP_FMT_ARGB8888: + bitmap_fmt = (le) ? NSGIF_BITMAP_FMT_B8G8R8A8 + : NSGIF_BITMAP_FMT_A8R8G8B8; + break; + case NSGIF_BITMAP_FMT_ABGR8888: + bitmap_fmt = (le) ? NSGIF_BITMAP_FMT_R8G8B8A8 + : NSGIF_BITMAP_FMT_A8B8G8R8; + break; + default: + break; + } + + /* Set up colour component order for bitmap format. */ + switch (bitmap_fmt) { + default: + /* Fall through. */ + case NSGIF_BITMAP_FMT_R8G8B8A8: + return (struct nsgif_colour_layout) { + .r = 0, + .g = 1, + .b = 2, + .a = 3, + }; + + case NSGIF_BITMAP_FMT_B8G8R8A8: + return (struct nsgif_colour_layout) { + .b = 0, + .g = 1, + .r = 2, + .a = 3, + }; + + case NSGIF_BITMAP_FMT_A8R8G8B8: + return (struct nsgif_colour_layout) { + .a = 0, + .r = 1, + .g = 2, + .b = 3, + }; + + case NSGIF_BITMAP_FMT_A8B8G8R8: + return (struct nsgif_colour_layout) { + .a = 0, + .b = 1, + .g = 2, + .r = 3, + }; + } +} + +/* exported function documented in nsgif.h */ +nsgif_error nsgif_create( + const nsgif_bitmap_cb_vt *bitmap_vt, + nsgif_bitmap_fmt_t bitmap_fmt, + nsgif_t **gif_out) +{ + nsgif_t *gif; + + gif = calloc(1, sizeof(*gif)); + if (gif == NULL) { + return NSGIF_ERR_OOM; + } + + gif->bitmap = *bitmap_vt; + gif->decoded_frame = NSGIF_FRAME_INVALID; + gif->prev_index = NSGIF_FRAME_INVALID; + + gif->delay_min = NSGIF_FRAME_DELAY_MIN; + gif->delay_default = NSGIF_FRAME_DELAY_DEFAULT; + + gif->colour_layout = nsgif__bitmap_fmt_to_colour_layout(bitmap_fmt); + + *gif_out = gif; + return NSGIF_OK; +} + +/* exported function documented in nsgif.h */ +void nsgif_set_frame_delay_behaviour( + nsgif_t *gif, + uint16_t delay_min, + uint16_t delay_default) +{ + gif->delay_min = delay_min; + gif->delay_default = delay_default; +} + +/** + * Read GIF header. + * + * 6-byte GIF file header is: + * + * +0 3CHARS Signature ('GIF') + * +3 3CHARS Version ('87a' or '89a') + * + * \param[in] gif The GIF object we're decoding. + * \param[in,out] pos The current buffer position, updated on success. + * \param[in] strict Whether to require a known GIF version. + * \return NSGIF_OK on success, appropriate error otherwise. + */ +static nsgif_error nsgif__parse_header( + struct nsgif *gif, + const uint8_t **pos, + bool strict) +{ + const uint8_t *data = *pos; + size_t len = gif->buf + gif->buf_len - data; + + if (len < 6) { + return NSGIF_ERR_END_OF_DATA; + } + + if (strncmp((const char *) data, "GIF", 3) != 0) { + return NSGIF_ERR_DATA; + } + data += 3; + + if (strict == true) { + if ((strncmp((const char *) data, "87a", 3) != 0) && + (strncmp((const char *) data, "89a", 3) != 0)) { + return NSGIF_ERR_DATA; + } + } + data += 3; + + *pos = data; + return NSGIF_OK; +} + +/** + * Read Logical Screen Descriptor. + * + * 7-byte Logical Screen Descriptor is: + * + * +0 SHORT Logical Screen Width + * +2 SHORT Logical Screen Height + * +4 CHAR __Packed Fields__ + * 1BIT Global Colour Table Flag + * 3BITS Colour Resolution + * 1BIT Sort Flag + * 3BITS Size of Global Colour Table + * +5 CHAR Background Colour Index + * +6 CHAR Pixel Aspect Ratio + * + * \param[in] gif The GIF object we're decoding. + * \param[in,out] pos The current buffer position, updated on success. + * \return NSGIF_OK on success, appropriate error otherwise. + */ +static nsgif_error nsgif__parse_logical_screen_descriptor( + struct nsgif *gif, + const uint8_t **pos) +{ + const uint8_t *data = *pos; + size_t len = gif->buf + gif->buf_len - data; + + if (len < 7) { + return NSGIF_ERR_END_OF_DATA; + } + + gif->info.width = data[0] | (data[1] << 8); + gif->info.height = data[2] | (data[3] << 8); + gif->info.global_palette = data[4] & NSGIF_COLOUR_TABLE_MASK; + gif->colour_table_size = 2 << (data[4] & NSGIF_COLOUR_TABLE_SIZE_MASK); + gif->bg_index = data[5]; + gif->aspect_ratio = data[6]; + gif->info.loop_max = 1; + + *pos += 7; + return NSGIF_OK; +} + +/* exported function documented in nsgif.h */ +nsgif_error nsgif_data_scan( + nsgif_t *gif, + size_t size, + const uint8_t *data) +{ + const uint8_t *nsgif_data; + nsgif_error ret; + uint32_t frames; + + if (gif->data_complete) { + return NSGIF_ERR_DATA_COMPLETE; + } + + /* Initialize values */ + gif->buf_len = size; + gif->buf = data; + + /* Get our current processing position */ + nsgif_data = gif->buf + gif->buf_pos; + + /* See if we should initialise the GIF */ + if (gif->buf_pos == 0) { + /* We want everything to be NULL before we start so we've no + * chance of freeing bad pointers (paranoia) + */ + gif->frame_image = NULL; + gif->frames = NULL; + gif->frame_holders = 0; + + /* The caller may have been lazy and not reset any values */ + gif->info.frame_count = 0; + gif->frame_count_partial = 0; + gif->decoded_frame = NSGIF_FRAME_INVALID; + gif->frame = NSGIF_FRAME_INVALID; + + ret = nsgif__parse_header(gif, &nsgif_data, false); + if (ret != NSGIF_OK) { + return ret; + } + + ret = nsgif__parse_logical_screen_descriptor(gif, &nsgif_data); + if (ret != NSGIF_OK) { + return ret; + } + + /* Remember we've done this now */ + gif->buf_pos = nsgif_data - gif->buf; + + /* Some broken GIFs report the size as the screen size they + * were created in. As such, we detect for the common cases and + * set the sizes as 0 if they are found which results in the + * GIF being the maximum size of the frames. + */ + if (((gif->info.width == 640) && (gif->info.height == 480)) || + ((gif->info.width == 640) && (gif->info.height == 512)) || + ((gif->info.width == 800) && (gif->info.height == 600)) || + ((gif->info.width == 1024) && (gif->info.height == 768)) || + ((gif->info.width == 1280) && (gif->info.height == 1024)) || + ((gif->info.width == 1600) && (gif->info.height == 1200)) || + ((gif->info.width == 0) || (gif->info.height == 0)) || + ((gif->info.width > 2048) || (gif->info.height > 2048))) { + gif->info.width = 1; + gif->info.height = 1; + } + + /* Set the first colour to a value that will never occur in + * reality so we know if we've processed it + */ + gif->global_colour_table[0] = NSGIF_PROCESS_COLOURS; + + /* Check if the GIF has no frame data (13-byte header + 1-byte + * termination block) Although generally useless, the GIF + * specification does not expressly prohibit this + */ + if (gif->buf_len == gif->buf_pos + 1) { + if (nsgif_data[0] == NSGIF_TRAILER) { + return NSGIF_OK; + } + } + } + + /* Do the colour map if we haven't already. As the top byte is always + * 0xff or 0x00 depending on the transparency we know if it's been + * filled in. + */ + if (gif->global_colour_table[0] == NSGIF_PROCESS_COLOURS) { + /* Check for a global colour map signified by bit 7 */ + if (gif->info.global_palette) { + size_t remaining = gif->buf + gif->buf_len - nsgif_data; + size_t used; + + ret = nsgif__colour_table_extract( + gif->global_colour_table, + &gif->colour_layout, + gif->colour_table_size, + nsgif_data, remaining, &used, true); + if (ret != NSGIF_OK) { + return ret; + } + + nsgif_data += used; + gif->buf_pos = (nsgif_data - gif->buf); + } else { + /* Create a default colour table with the first two + * colours as black and white. */ + uint8_t *entry = (uint8_t *)gif->global_colour_table; + + /* Black */ + entry[gif->colour_layout.r] = 0x00; + entry[gif->colour_layout.g] = 0x00; + entry[gif->colour_layout.b] = 0x00; + entry[gif->colour_layout.a] = 0xFF; + + entry += sizeof(uint32_t); + + /* White */ + entry[gif->colour_layout.r] = 0xFF; + entry[gif->colour_layout.g] = 0xFF; + entry[gif->colour_layout.b] = 0xFF; + entry[gif->colour_layout.a] = 0xFF; + + gif->colour_table_size = 2; + } + + if (gif->info.global_palette && + gif->bg_index < gif->colour_table_size) { + size_t bg_idx = gif->bg_index; + gif->info.background = gif->global_colour_table[bg_idx]; + } else { + gif->info.background = gif->global_colour_table[0]; + } + } + + if (gif->lzw_ctx == NULL) { + lzw_result res = lzw_context_create( + (struct lzw_ctx **)&gif->lzw_ctx); + if (res != LZW_OK) { + return nsgif__error_from_lzw(res); + } + } + + /* Try to initialise all frames. */ + do { + frames = gif->info.frame_count; + ret = nsgif__process_frame(gif, frames, false); + } while (gif->info.frame_count > frames); + + if (ret == NSGIF_ERR_END_OF_DATA && gif->info.frame_count > 0) { + ret = NSGIF_OK; + } + + return ret; +} + +/* exported function documented in nsgif.h */ +void nsgif_data_complete( + nsgif_t *gif) +{ + if (gif->data_complete == false) { + uint32_t start = gif->info.frame_count; + uint32_t end = gif->frame_count_partial; + + for (uint32_t f = start; f < end; f++) { + nsgif_frame *frame = &gif->frames[f]; + + if (frame->lzw_data_length > 0) { + frame->info.display = true; + gif->info.frame_count = f + 1; + + if (f == 0) { + frame->info.transparency = true; + } + break; + } + } + } + + gif->data_complete = true; +} + +static void nsgif__redraw_rect_extend( + const nsgif_rect_t *frame, + nsgif_rect_t *redraw) +{ + if (redraw->x1 == 0 || redraw->y1 == 0) { + *redraw = *frame; + } else { + if (redraw->x0 > frame->x0) { + redraw->x0 = frame->x0; + } + if (redraw->x1 < frame->x1) { + redraw->x1 = frame->x1; + } + if (redraw->y0 > frame->y0) { + redraw->y0 = frame->y0; + } + if (redraw->y1 < frame->y1) { + redraw->y1 = frame->y1; + } + } +} + +static uint32_t nsgif__frame_next( + const nsgif_t *gif, + bool partial, + uint32_t frame) +{ + uint32_t frames = partial ? + gif->frame_count_partial : + gif->info.frame_count; + + if (frames == 0) { + return NSGIF_FRAME_INVALID; + } + + frame++; + return (frame >= frames) ? 0 : frame; +} + +static nsgif_error nsgif__next_displayable_frame( + const nsgif_t *gif, + uint32_t *frame, + uint32_t *delay) +{ + uint32_t next = *frame; + + do { + next = nsgif__frame_next(gif, false, next); + if (next <= *frame && *frame != NSGIF_FRAME_INVALID && + gif->data_complete == false) { + return NSGIF_ERR_END_OF_DATA; + + } else if (next == *frame || next == NSGIF_FRAME_INVALID) { + return NSGIF_ERR_FRAME_DISPLAY; + } + + if (delay != NULL) { + *delay += gif->frames[next].info.delay; + } + + } while (gif->frames[next].info.display == false); + + *frame = next; + return NSGIF_OK; +} + +static inline bool nsgif__animation_complete(int count, int max) +{ + if (max == 0) { + return false; + } + + return (count >= max); +} + +nsgif_error nsgif_reset( + nsgif_t *gif) +{ + gif->loop_count = 0; + gif->frame = NSGIF_FRAME_INVALID; + + return NSGIF_OK; +} + +/* exported function documented in nsgif.h */ +nsgif_error nsgif_frame_prepare( + nsgif_t *gif, + nsgif_rect_t *area, + uint32_t *delay_cs, + uint32_t *frame_new) +{ + nsgif_error ret; + nsgif_rect_t rect = { + .x1 = 0, + .y1 = 0, + }; + uint32_t delay = 0; + uint32_t frame = gif->frame; + + if (gif->frame != NSGIF_FRAME_INVALID && + gif->frame < gif->info.frame_count && + gif->frames[gif->frame].info.display) { + rect = gif->frames[gif->frame].info.rect; + } + + if (nsgif__animation_complete( + gif->loop_count, + gif->info.loop_max)) { + return NSGIF_ERR_ANIMATION_END; + } + + ret = nsgif__next_displayable_frame(gif, &frame, &delay); + if (ret != NSGIF_OK) { + return ret; + } + + if (gif->frame != NSGIF_FRAME_INVALID && frame < gif->frame) { + gif->loop_count++; + } + + if (gif->data_complete) { + /* Check for last frame, which has infinite delay. */ + + if (gif->info.frame_count == 1) { + delay = NSGIF_INFINITE; + } else if (gif->info.loop_max != 0) { + uint32_t frame_next = frame; + + ret = nsgif__next_displayable_frame(gif, + &frame_next, NULL); + if (ret != NSGIF_OK) { + return ret; + } + + if (gif->data_complete && frame_next < frame) { + if (nsgif__animation_complete( + gif->loop_count + 1, + gif->info.loop_max)) { + delay = NSGIF_INFINITE; + } + } + } + } + + gif->frame = frame; + nsgif__redraw_rect_extend(&gif->frames[frame].info.rect, &rect); + + if (delay < gif->delay_min) { + delay = gif->delay_default; + } + + *frame_new = gif->frame; + *delay_cs = delay; + *area = rect; + + return NSGIF_OK; +} + +/* exported function documented in nsgif.h */ +nsgif_error nsgif_frame_decode( + nsgif_t *gif, + uint32_t frame, + nsgif_bitmap_t **bitmap) +{ + uint32_t start_frame; + nsgif_error ret = NSGIF_OK; + + if (frame >= gif->info.frame_count) { + return NSGIF_ERR_BAD_FRAME; + } + + if (gif->decoded_frame == frame) { + *bitmap = gif->frame_image; + return NSGIF_OK; + + } else if (gif->decoded_frame >= frame || + gif->decoded_frame == NSGIF_FRAME_INVALID) { + /* Can skip to first frame or restart. */ + start_frame = 0; + } else { + start_frame = nsgif__frame_next( + gif, false, gif->decoded_frame); + } + + for (uint32_t f = start_frame; f <= frame; f++) { + ret = nsgif__process_frame(gif, f, true); + if (ret != NSGIF_OK) { + return ret; + } + } + + *bitmap = gif->frame_image; + return ret; +} + +/* exported function documented in nsgif.h */ +const nsgif_info_t *nsgif_get_info(const nsgif_t *gif) +{ + return &gif->info; +} + +/* exported function documented in nsgif.h */ +const nsgif_frame_info_t *nsgif_get_frame_info( + const nsgif_t *gif, + uint32_t frame) +{ + if (frame >= gif->info.frame_count) { + return NULL; + } + + return &gif->frames[frame].info; +} + +/* exported function documented in nsgif.h */ +void nsgif_global_palette( + const nsgif_t *gif, + uint32_t table[NSGIF_MAX_COLOURS], + size_t *entries) +{ + size_t len = sizeof(*table) * NSGIF_MAX_COLOURS; + + memcpy(table, gif->global_colour_table, len); + *entries = gif->colour_table_size; +} + +/* exported function documented in nsgif.h */ +bool nsgif_local_palette( + const nsgif_t *gif, + uint32_t frame, + uint32_t table[NSGIF_MAX_COLOURS], + size_t *entries) +{ + const nsgif_frame *f; + + if (frame >= gif->frame_count_partial) { + return false; + } + + f = &gif->frames[frame]; + if (f->info.local_palette == false) { + return false; + } + + *entries = 2 << (f->flags & NSGIF_COLOUR_TABLE_SIZE_MASK); + nsgif__colour_table_decode(table, &gif->colour_layout, + *entries, gif->buf + f->colour_table_offset); + + return true; +} + +/* exported function documented in nsgif.h */ +const char *nsgif_strerror(nsgif_error err) +{ + static const char *const str[] = { + [NSGIF_OK] = "Success", + [NSGIF_ERR_OOM] = "Out of memory", + [NSGIF_ERR_DATA] = "Invalid source data", + [NSGIF_ERR_BAD_FRAME] = "Requested frame does not exist", + [NSGIF_ERR_DATA_FRAME] = "Invalid frame data", + [NSGIF_ERR_END_OF_DATA] = "Unexpected end of GIF source data", + [NSGIF_ERR_DATA_COMPLETE] = "Can't add data to completed GIF", + [NSGIF_ERR_FRAME_DISPLAY] = "Frame can't be displayed", + [NSGIF_ERR_ANIMATION_END] = "Animation complete", + }; + + if (err >= NSGIF_ARRAY_LEN(str) || str[err] == NULL) { + return "Unknown error"; + } + + return str[err]; +} + +/* exported function documented in nsgif.h */ +const char *nsgif_str_disposal(enum nsgif_disposal disposal) +{ + static const char *const str[] = { + [NSGIF_DISPOSAL_UNSPECIFIED] = "Unspecified", + [NSGIF_DISPOSAL_NONE] = "None", + [NSGIF_DISPOSAL_RESTORE_BG] = "Restore background", + [NSGIF_DISPOSAL_RESTORE_PREV] = "Restore previous", + [NSGIF_DISPOSAL_RESTORE_QUIRK] = "Restore quirk", + }; + + if (disposal >= NSGIF_ARRAY_LEN(str) || str[disposal] == NULL) { + return "Unspecified"; + } + + return str[disposal]; +} |