box-intersect/lib/sort.js

Any dimensional box intersection

'use strict';

//This code is extracted from ndarray-sort
//It is inlined here as a temporary workaround

module.exports = wrapper;

var INSERT_SORT_CUTOFF = 32

function wrapper(data, n0) {
  if (n0 <= 4*INSERT_SORT_CUTOFF) {
    insertionSort(0, n0 - 1, data);
  } else {
    quickSort(0, n0 - 1, data);
  }
}

function insertionSort(left, right, data) {
  var ptr = 2*(left+1)
  for(var i=left+1; i<=right; ++i) {
    var a = data[ptr++]
    var b = data[ptr++]
    var j = i
    var jptr = ptr-2
    while(j-- > left) {
      var x = data[jptr-2]
      var y = data[jptr-1]
      if(x < a) {
        break
      } else if(x === a && y < b) {
        break
      }
      data[jptr]   = x
      data[jptr+1] = y
      jptr -= 2
    }
    data[jptr]   = a
    data[jptr+1] = b
  }
}

function swap(i, j, data) {
  i *= 2
  j *= 2
  var x = data[i]
  var y = data[i+1]
  data[i] = data[j]
  data[i+1] = data[j+1]
  data[j] = x
  data[j+1] = y
}

function move(i, j, data) {
  i *= 2
  j *= 2
  data[i] = data[j]
  data[i+1] = data[j+1]
}

function rotate(i, j, k, data) {
  i *= 2
  j *= 2
  k *= 2
  var x = data[i]
  var y = data[i+1]
  data[i] = data[j]
  data[i+1] = data[j+1]
  data[j] = data[k]
  data[j+1] = data[k+1]
  data[k] = x
  data[k+1] = y
}

function shufflePivot(i, j, px, py, data) {
  i *= 2
  j *= 2
  data[i] = data[j]
  data[j] = px
  data[i+1] = data[j+1]
  data[j+1] = py
}

function compare(i, j, data) {
  i *= 2
  j *= 2
  var x = data[i],
      y = data[j]
  if(x < y) {
    return false
  } else if(x === y) {
    return data[i+1] > data[j+1]
  }
  return true
}

function comparePivot(i, y, b, data) {
  i *= 2
  var x = data[i]
  if(x < y) {
    return true
  } else if(x === y) {
    return data[i+1] < b
  }
  return false
}

function quickSort(left, right, data) {
  var sixth = (right - left + 1) / 6 | 0, 
      index1 = left + sixth, 
      index5 = right - sixth, 
      index3 = left + right >> 1, 
      index2 = index3 - sixth, 
      index4 = index3 + sixth, 
      el1 = index1, 
      el2 = index2, 
      el3 = index3, 
      el4 = index4, 
      el5 = index5, 
      less = left + 1, 
      great = right - 1, 
      tmp = 0
  if(compare(el1, el2, data)) {
    tmp = el1
    el1 = el2
    el2 = tmp
  }
  if(compare(el4, el5, data)) {
    tmp = el4
    el4 = el5
    el5 = tmp
  }
  if(compare(el1, el3, data)) {
    tmp = el1
    el1 = el3
    el3 = tmp
  }
  if(compare(el2, el3, data)) {
    tmp = el2
    el2 = el3
    el3 = tmp
  }
  if(compare(el1, el4, data)) {
    tmp = el1
    el1 = el4
    el4 = tmp
  }
  if(compare(el3, el4, data)) {
    tmp = el3
    el3 = el4
    el4 = tmp
  }
  if(compare(el2, el5, data)) {
    tmp = el2
    el2 = el5
    el5 = tmp
  }
  if(compare(el2, el3, data)) {
    tmp = el2
    el2 = el3
    el3 = tmp
  }
  if(compare(el4, el5, data)) {
    tmp = el4
    el4 = el5
    el5 = tmp
  }

  var pivot1X = data[2*el2]
  var pivot1Y = data[2*el2+1]
  var pivot2X = data[2*el4]
  var pivot2Y = data[2*el4+1]

  var ptr0 = 2 * el1;
  var ptr2 = 2 * el3;
  var ptr4 = 2 * el5;
  var ptr5 = 2 * index1;
  var ptr6 = 2 * index3;
  var ptr7 = 2 * index5;
  for (var i1 = 0; i1 < 2; ++i1) {
    var x = data[ptr0+i1];
    var y = data[ptr2+i1];
    var z = data[ptr4+i1];
    data[ptr5+i1] = x;
    data[ptr6+i1] = y;
    data[ptr7+i1] = z;
  }

  move(index2, left, data)
  move(index4, right, data)
  for (var k = less; k <= great; ++k) {
    if (comparePivot(k, pivot1X, pivot1Y, data)) {
      if (k !== less) {
        swap(k, less, data)
      }
      ++less;
    } else {
      if (!comparePivot(k, pivot2X, pivot2Y, data)) {
        while (true) {
          if (!comparePivot(great, pivot2X, pivot2Y, data)) {
            if (--great < k) {
              break;
            }
            continue;
          } else {
            if (comparePivot(great, pivot1X, pivot1Y, data)) {
              rotate(k, less, great, data)
              ++less;
              --great;
            } else {
              swap(k, great, data)
              --great;
            }
            break;
          }
        }
      }
    }
  }
  shufflePivot(left, less-1, pivot1X, pivot1Y, data)
  shufflePivot(right, great+1, pivot2X, pivot2Y, data)
  if (less - 2 - left <= INSERT_SORT_CUTOFF) {
    insertionSort(left, less - 2, data);
  } else {
    quickSort(left, less - 2, data);
  }
  if (right - (great + 2) <= INSERT_SORT_CUTOFF) {
    insertionSort(great + 2, right, data);
  } else {
    quickSort(great + 2, right, data);
  }
  if (great - less <= INSERT_SORT_CUTOFF) {
    insertionSort(less, great, data);
  } else {
    quickSort(less, great, data);
  }
}