search-bounds.js

"use strict"

function compileSearch(funcName, predicate, reversed, extraArgs, earlyOut) {
  var code = [
    "function ", funcName, "(a,l,h,", extraArgs.join(","),  "){",
    earlyOut ? "" : "var i=", (reversed ? "l-1" : "h+1"),
    ";while(l<=h){var m=(l+h)>>>1,x=a[m]"]
  if(earlyOut) {
    if(predicate.indexOf("c") < 0) {
      code.push(";if(x===y){return m}else if(x<=y){")
    } else {
      code.push(";var p=c(x,y);if(p===0){return m}else if(p<=0){")
    }
  } else {
    code.push(";if(", predicate, "){i=m;")
  }
  if(reversed) {
    code.push("l=m+1}else{h=m-1}")
  } else {
    code.push("h=m-1}else{l=m+1}")
  }
  code.push("}")
  if(earlyOut) {
    code.push("return -1};")
  } else {
    code.push("return i};")
  }
  return code.join("")
}

function compileBoundsSearch(predicate, reversed, suffix, earlyOut) {
  var result = new Function([
  compileSearch("A", "x" + predicate + "y", reversed, ["y"], earlyOut),
  compileSearch("P", "c(x,y)" + predicate + "0", reversed, ["y", "c"], earlyOut),
"function dispatchBsearch", suffix, "(a,y,c,l,h){\
if(typeof(c)==='function'){\
return P(a,(l===void 0)?0:l|0,(h===void 0)?a.length-1:h|0,y,c)\
}else{\
return A(a,(c===void 0)?0:c|0,(l===void 0)?a.length-1:l|0,y)\
}}\
return dispatchBsearch", suffix].join(""))
  return result()
}

module.exports = {
  ge: compileBoundsSearch(">=", false,  "GE"),
  gt: compileBoundsSearch(">",  false,  "GT"),
  lt: compileBoundsSearch("<",  true,   "LT"),
  le: compileBoundsSearch("<=", true,   "LE"),
  eq: compileBoundsSearch("-",  true,   "EQ", true)
}