LookingGlass/common/src/framebuffer.c

/**
 * Looking Glass
 * Copyright © 2017-2026 The Looking Glass Authors
 * https://looking-glass.io
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc., 59
 * Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include "common/framebuffer.h"
#include "common/cpuinfo.h"
#include "common/debug.h"
#include "common/time.h"

//#define FB_PROFILE
#ifdef FB_PROFILE
#include "common/runningavg.h"
#endif

#include <string.h>
#include <emmintrin.h>
#include <smmintrin.h>
#include <immintrin.h>
#include <unistd.h>

bool framebuffer_wait_timed(const FrameBuffer * frame, size_t size,
    uint64_t * waitTimeNs)
{
  if (atomic_load_explicit(&frame->wp, memory_order_acquire) >= size)
    return true;

  const uint64_t waitStart = waitTimeNs ? nanotime() : 0;

  while(atomic_load_explicit(&frame->wp, memory_order_acquire) < size)
  {
    int spinCount = 0;
    while(frame->wp < size)
    {
      if (++spinCount == FB_SPIN_LIMIT)
      {
        if (waitTimeNs)
          *waitTimeNs += nanotime() - waitStart;
        return false;
      }
      usleep(1);
    }
  }

  if (waitTimeNs)
    *waitTimeNs += nanotime() - waitStart;

  return true;
}

bool framebuffer_wait(const FrameBuffer * frame, size_t size)
{
  return framebuffer_wait_timed(frame, size, NULL);
}

static bool framebuffer_read_linear_timed(const FrameBuffer * frame,
    void * restrict dst, size_t size, uint64_t * waitTimeNs)
{
#ifdef FB_PROFILE
  static RunningAvg ra = NULL;
  static int raCount = 0;
  const uint64_t ts = microtime();
  if (!ra)
    ra = runningavg_new(100);
#endif

  uint8_t * restrict d     = (uint8_t*)dst;
  uint_least32_t rp        = 0;

  // copy in large 1MB chunks if the pitches match
  while(size)
  {
    const size_t copy = size < FB_CHUNK_SIZE ? size : FB_CHUNK_SIZE;
    if (!framebuffer_wait_timed(frame, rp + copy, waitTimeNs))
      return false;

    memcpy(d, frame->data + rp, copy);
    size -= copy;
    rp   += copy;
    d    += copy;
  }

#ifdef FB_PROFILE
  runningavg_push(ra, microtime() - ts);
  if (++raCount % 100 == 0)
    DEBUG_INFO("Average Copy Time: %.2fμs", runningavg_calc(ra));
#endif

  return true;
}

bool framebuffer_read_linear(const FrameBuffer * frame, void * restrict dst,
    size_t size)
{
  return framebuffer_read_linear_timed(frame, dst, size, NULL);
}

bool framebuffer_read_timed(const FrameBuffer * frame, void * restrict dst,
    size_t dstpitch, size_t height, size_t width, size_t bpp, size_t pitch,
    uint64_t * waitTimeNs)
{
  if (dstpitch == pitch)
    return framebuffer_read_linear_timed(
        frame, dst, height * pitch, waitTimeNs);

#ifdef FB_PROFILE
  static RunningAvg ra = NULL;
  static int raCount = 0;
  const uint64_t ts = microtime();
  if (!ra)
    ra = runningavg_new(100);
#endif

  uint8_t * restrict d     = (uint8_t*)dst;
  uint_least32_t rp        = 0;

  // copy per line to match the pitch of the destination buffer
  const size_t linewidth = width * bpp;
  for(size_t y = 0; y < height; ++y)
  {
    if (!framebuffer_wait_timed(frame, rp + linewidth, waitTimeNs))
      return false;

    memcpy(d, frame->data + rp, dstpitch);
    rp += pitch;
    d  += dstpitch;
  }

#ifdef FB_PROFILE
  runningavg_push(ra, microtime() - ts);
  if (++raCount % 100 == 0)
    DEBUG_INFO("Average Copy Time: %.2fμs", runningavg_calc(ra));
#endif

  return true;
}

bool framebuffer_read(const FrameBuffer * frame, void * restrict dst,
    size_t dstpitch, size_t height, size_t width, size_t bpp, size_t pitch)
{
  return framebuffer_read_timed(frame, dst, dstpitch, height, width, bpp,
      pitch, NULL);
}

bool framebuffer_read_fn(const FrameBuffer * frame, size_t height, size_t width,
    size_t bpp, size_t pitch, FrameBufferReadFn fn, void * opaque)
{
#ifdef FB_PROFILE
  static RunningAvg ra = NULL;
  static int raCount = 0;
  const uint64_t ts = microtime();
  if (!ra)
    ra = runningavg_new(100);
#endif

  uint_least32_t rp        = 0;
  size_t         y         = 0;
  const size_t   linewidth = width * bpp;

  while(y < height)
  {
    if (!framebuffer_wait(frame, rp + linewidth))
      return false;

    if (!fn(opaque, frame->data + rp, linewidth))
      return false;

    rp += pitch;
    ++y;
  }

#ifdef FB_PROFILE
  runningavg_push(ra, microtime() - ts);
  if (++raCount % 100 == 0)
    DEBUG_INFO("Average Copy Time: %.2fμs", runningavg_calc(ra));
#endif

  return true;
}

/**
 * Prepare the framebuffer for writing
 */
void framebuffer_prepare(FrameBuffer * frame)
{
  atomic_store_explicit(&frame->wp, 0, memory_order_release);
}

static bool framebuffer_write_sse4_1(FrameBuffer * frame,
    const void * restrict src, size_t size)
{
#ifdef FB_PROFILE
  static RunningAvg ra = NULL;
  static int raCount = 0;
  const uint64_t ts = microtime();
  if (!ra)
    ra = runningavg_new(100);
#endif

  __m128i * restrict s = (__m128i *)src;
  __m128i * restrict d = (__m128i *)frame->data;
  size_t wp = 0;

  _mm_mfence();

  /* copy in chunks */
  while(size > 63)
  {
    __m128i *_d = (__m128i *)d;
    __m128i *_s = (__m128i *)s;
    __m128i v1 = _mm_stream_load_si128(_s + 0);
    __m128i v2 = _mm_stream_load_si128(_s + 1);
    __m128i v3 = _mm_stream_load_si128(_s + 2);
    __m128i v4 = _mm_stream_load_si128(_s + 3);

    _mm_store_si128(_d + 0, v1);
    _mm_store_si128(_d + 1, v2);
    _mm_store_si128(_d + 2, v3);
    _mm_store_si128(_d + 3, v4);

    s    += 4;
    d    += 4;
    size -= 64;
    wp   += 64;

    if (wp % FB_CHUNK_SIZE == 0)
      atomic_store_explicit(&frame->wp, wp, memory_order_release);
  }

  if(size)
  {
    memcpy(frame->data + wp, s, size);
    wp += size;
  }

  atomic_store_explicit(&frame->wp, wp, memory_order_release);

#ifdef FB_PROFILE
  runningavg_push(ra, microtime() - ts);
  if (++raCount % 100 == 0)
    DEBUG_INFO("Average Copy Time: %.2fμs", runningavg_calc(ra));
#endif

  return true;
}

#ifdef __clang__
  #pragma clang attribute push (__attribute__((target("avx2"))), apply_to=function)
#else
  #pragma GCC push_options
  #pragma GCC target ("avx2")
#endif
bool framebuffer_write_avx2(FrameBuffer * frame,
    const void * restrict src, size_t size)
{
#ifdef FB_PROFILE
    static RunningAvg ra = NULL;
    static int raCount = 0;
    const uint64_t ts = microtime();
    if (!ra)
        ra = runningavg_new(100);
#endif

  __m256i *restrict s = (__m256i *)src;
  __m256i *restrict d = (__m256i *)frame->data;
  size_t wp = 0;

  _mm_mfence();

  /* copy in chunks */
  while (size > 127)
  {
    __m256i v1 = _mm256_stream_load_si256(s + 0);
    __m256i v2 = _mm256_stream_load_si256(s + 1);
    __m256i v3 = _mm256_stream_load_si256(s + 2);
    __m256i v4 = _mm256_stream_load_si256(s + 3);

    _mm256_stream_si256(d + 0, v1);
    _mm256_stream_si256(d + 1, v2);
    _mm256_stream_si256(d + 2, v3);
    _mm256_stream_si256(d + 3, v4);

    s    += 4;
    d    += 4;
    size -= 128;
    wp   += 128;

    if (wp % FB_CHUNK_SIZE == 0)
      atomic_store_explicit(&frame->wp, wp, memory_order_release);
  }

  if (size > 63)
  {
    __m256i v1 = _mm256_stream_load_si256(s);
    __m256i v2 = _mm256_stream_load_si256(s + 1);

    _mm256_stream_si256(d, v1);
    _mm256_stream_si256(d + 1, v2);

    s    += 2;
    d    += 2;
    size -= 64;
    wp   += 64;

    if (wp % FB_CHUNK_SIZE == 0)
      atomic_store_explicit(&frame->wp, wp, memory_order_release);
  }

  if (size)
  {
    memcpy(frame->data + wp, s, size);
    wp += size;
  }

  atomic_store_explicit(&frame->wp, wp, memory_order_release);

#ifdef FB_PROFILE
  runningavg_push(ra, microtime() - ts);
  if (++raCount % 100 == 0)
    DEBUG_INFO("Average Copy Time: %.2fμs", runningavg_calc(ra));
#endif

  return true;
}
#ifdef __clang__
  #pragma clang attribute pop
#else
  #pragma GCC pop_options
#endif

static bool _framebuffer_write(FrameBuffer * frame,
    const void * restrict src, size_t size)
{
  if (cpuInfo_getFeatures()->avx2)
    framebuffer_write = &framebuffer_write_avx2;
  else
    framebuffer_write = &framebuffer_write_sse4_1;

  return framebuffer_write(frame, src, size);
}

bool (*framebuffer_write)(FrameBuffer * frame,
  const void * restrict src, size_t size) = &_framebuffer_write;

const uint8_t * framebuffer_get_buffer(const FrameBuffer * frame)
{
  return frame->data;
}

uint8_t * framebuffer_get_data(FrameBuffer * frame)
{
  return frame->data;
}

void framebuffer_set_write_ptr(FrameBuffer * frame, size_t size)
{
  atomic_store_explicit(&frame->wp, size, memory_order_release);
}