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/* See LICENSE file for copyright and license details. */
#ifndef LIBLSS16_H
#define LIBLSS16_H
#include <stddef.h>
#include <stdint.h>
/**
* Image decoding state
*/
enum liblss16_decode_state {
/**
* End of image not yet reached
*
* File truncated if end of file reached
*/
LIBLSS16_DECODE_RUNNING,
/**
* End of image reached
*
* Note that pixels may still be returned
*
* File holds unused data if end of file not reached
*/
LIBLSS16_DECODE_END_OF_IMAGE,
/**
* A decoding error has occurred
*
* Processing most be aborted
*/
LIBLSS16_DECODE_ERROR
};
/**
* Error values for image decoding
*/
enum liblss16_decode_error {
/**
* The file was at most 3 bytes long, but first
* bytes where {0x3D, 0x3F, 0x41} (up to the
* length of the file)
*/
LIBLSS16_DECODE_TRUNCATED_MAGIC,
/**
* The file did not start with {0x3D, 0x3F, 0x41, 0x01}
*
* The number of consumed bytes, include the first bad
* byte in the magic. The number of consumed bytes is
* 1 if the first byte was wrong.
*/
LIBLSS16_DECODE_BAD_MAGIC,
/**
* The file was too short to contain the full header
*/
LIBLSS16_DECODE_TRUNCATED_HEADER,
/**
* At least one of the follow (you can check `.width`
* and `.height` to determine which apply):
*
* - The image width was set to 0
*
* - The image height was set to 0
*
* - The image height exceeded 32767
*/
LIBLSS16_DECODE_BAD_IMAGE_SIZE,
/**
* The colour map contain a colour that had at least
* once of the two high bits on the encoded byte set
*
* If you want to know which colour was bad (you can
* only find the first one), you have to calculate it
* from the number of bytes consumed before the failure
* occurred. If the number of consumed bytes is `N`,
* `(N - 9) / 3` is the index of the colour (the index
* of the first colour is 0), and the remainder maps
* to the channel: 0 = red, 1 = green, 2 = blue.
*/
LIBLSS16_DECODE_BAD_COLOUR,
/**
* Row padding was not all zeroes
*/
LIBLSS16_DECODE_BAD_ROW_PADDING,
/**
* Run-length encoding ran across two or more rows
*/
LIBLSS16_DECODE_EXCESSIVE_RUN_LENGTH,
/**
* The file was too short to contain the full image
*/
LIBLSS16_DECODE_TRUNCATED_IMAGE
};
/**
* sRGB colour values, with transfer function applied,
* encoded in values in [0, 255]
*/
struct liblss16_colour {
/**
* Red channel value
*/
uint8_t r;
/**
* Green channel value
*/
uint8_t g;
/**
* Blue channel value
*/
uint8_t b;
};
/**
* Decode state
*/
struct liblss16_decoder {
/**
* The width of the raster
*/
uint16_t width;
/**
* The height of the raster
*/
uint16_t height;
/**
* Image colour map
*/
struct liblss16_colour colour_map[16];
/**
* For internal use
*/
struct {
uint16_t x_rem; /**< number of pixels (after `.internal.kept`) until end of row */
uint16_t y_rem; /**< number of row completions until end of image */
uint16_t kept; /**< number of duplications held for next call */
uint8_t previous; /**< previous pixel */
uint8_t saved; /**< 0 or saved nibble plus 1 */
uint8_t init_state; /**< number of header bytes read */
uint8_t state;
} internal;
};
/**
* Initialise a decoder
*
* @param decoder The decoder
*/
void liblss16_decoder_init(struct liblss16_decoder *decoder);
/**
* @param decoder Decoder state, must have been initialised with
* `liblss16_decoder_init` before the first call
* @param data Data to decode image from (may be partial)
* @param length The number of bytes available in `data`;
* end of file can be indicated using the value 0
* @param consumed_out The number of bytes processed from `data`
* @param pixels Output buffer for the indicies of the colours
* for the pixels in the image. They are returned
* primarily from to the top down and secondarily
* from left to right.
* @param pixels_size The number of elements that may be stored in `pixels`
* @param npixels_out Output parameter for the number of elements stored
* in `pixels`. Always set.
* @param error_out Output parameter for the error; only set if
* `LIBLSS16_DECODE_ERROR` is returned; may be `NULL`
* @return The processing state: normally `LIBLSS16_DECODE_RUNNING`,
* but `LIBLSS16_DECODE_END_OF_IMAGE` when the image has
* been fully decoded, and `LIBLSS16_DECODE_ERROR` on error
*
* `decoder->width`, `decoder->height` and `decoder->colour_map` are
* set once `*npixels_out` is set to a non-zero value for the first
* time (or some time before that). `decoder->width` and `decoder->height`
* are also set if `LIBLSS16_DECODE_ERROR` is returned and `*error_out`
* is set to `LIBLSS16_DECODE_BAD_HEADER`
*/
enum liblss16_decode_state liblss16_decode_to_colour_index(
struct liblss16_decoder *decoder,
const void *data, size_t length, size_t *consumed_out,
uint8_t *pixels, size_t pixels_size, size_t *npixels_out,
enum liblss16_decode_error *error_out);
/**
* Get error description for an error code
*
* @param error The error code
* @return The error description
*/
#if defined(__GNUC__)
__attribute__((__const__))
#endif
const char *liblss16_decode_strerror(enum liblss16_decode_error error);
#endif
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