reStream lz4 streaming

receiver.c

#include <stdio.h>
#include <stdlib.h>

#include "lz4.h"

enum {
  HEIGHT = 1872,
  WIDTH = 1408,
  BYTES_PER_PIXEL = 2,
  WINDOW_BYTES = WIDTH*HEIGHT*BYTES_PER_PIXEL
};

int main(int argc, char const* argv[]) {
  LZ4_streamDecode_t lz4StreamDecode_body;
  LZ4_streamDecode_t* lz4StreamDecode = &lz4StreamDecode_body;

  LZ4_setStreamDecode(lz4StreamDecode, NULL, 0);

  char compressed[LZ4_COMPRESSBOUND(WINDOW_BYTES)];
  char *decompressed = malloc(WINDOW_BYTES);
  int compressed_size = 0;
  for (;;) {
    const size_t read_int = fread(&compressed_size, sizeof(compressed_size), 1, stdin);
    if (read_int != 1 || compressed_size <= 0)
      break;

    const size_t read_bytes = fread(compressed, 1, compressed_size, stdin);
    if (read_bytes != compressed_size)
      break;

    LZ4_decompress_safe_continue(lz4StreamDecode, compressed, decompressed, compressed_size, WINDOW_BYTES);
    /* puts("Decompressed a block"); */
    fwrite(decompressed, 1, WINDOW_BYTES, stdout);
  }

  puts("Error in decompression\n");
  free(decompressed);
  return 1;
}

streaming.c

#include <stdio.h>
#include <stdint.h>
#include <sys/mman.h>
#include <fcntl.h>

#include "lz4.h"

enum {
  HEIGHT = 1872,
  WIDTH = 1408,
  BYTES_PER_PIXEL = 2,
  WINDOW_BYTES = WIDTH*HEIGHT*BYTES_PER_PIXEL
};

int main(int argc, char const* argv[]) {
  int fb0 = open("/dev/fb0", O_RDONLY);
  char *fbp = mmap(NULL, WINDOW_BYTES, PROT_READ, MAP_SHARED, fb0, 0);

  // handle failed to open

  LZ4_stream_t lz4Stream_body;
  LZ4_stream_t* lz4Stream = &lz4Stream_body;

  LZ4_initStream(lz4Stream, sizeof(*lz4Stream));

  char compressed[LZ4_COMPRESSBOUND(WINDOW_BYTES)];

  for (;;) {
    int compressed_size = LZ4_compress_fast_continue(lz4Stream, fbp, compressed, WINDOW_BYTES, sizeof(compressed), 1);
    if (compressed_size == 0) {
      break;
    }

    fwrite(&compressed_size, sizeof(compressed_size), 1, stdout);
    fwrite(compressed, 1, compressed_size, stdout);
  };

  puts("Error in compression\n");
  return 1;
}

Usage:

ssh [email protected] -- /tmp/streaming | ./receiver | ffplay -vcodec rawvideo -loglevel info -f rawvideo -pixel_format gray16le -video_size "1408,1872" -i -

Precompiled reMarkable binary:
http://ix.io/2haI