echo that will handle embedded nuls

nimecho-out.txt

See https://github.com/Araq/Nimrod/issues/1137 (nimecho0 and nimecho1 echo strings with embedded nuls)

$ nimrod c -x:off  --opt:speed --deadCodeElim:on --stackTrace:off --lineTrace:off   nimecho.nim

$ ./nimecho 0 > /dev/null
using nimecho0
1.8825269999999998e+00 seconds elapsed
1.8825269999999999e-06 seconds per iteration
string used: some very long string some very long string some very long string some very long string some very long string some very long string 

$ ./nimecho 1 > /dev/null
using nimecho1 (smallest code)
2.2058490000000002e+00 seconds elapsed
2.2058490000000000e-06 seconds per iteration
string used: some very long string some very long string some very long string some very long string some very long string some very long string 

$ ./nimecho e > /dev/null
using original echo
9.7179199999999999e-01 seconds elapsed
9.7179199999999994e-07 seconds per iteration
string used: some very long string some very long string some very long string some very long string some very long string some very long string 

$ ./nimecho 3
some very long string some very long string some very long string some very long string some very long string some very long string 1235.5999999999999996e+00
some very long string some very long string some very long string some very long string some very long string some very long string 1235.5999999999999996e+00
some very long string some very long string some very long string some very long string some very long string some very long string 1235.5999999999999996e+00


nulltest
nulltest
-----------------------------------------
My vote is for nimecho1 even though it is the slowest, because it is simplest code

nimecho.nim

import os, strutils, times

let argv = commandLineParams()

proc nimecho0 (a: varargs[string, `$`]) {.compilerProc.} =
  # declare external c functions. Use ints for pointers to avoid casting
  proc c_fwrite (buf: int, size, n: int, f: TFile) {.importc: "fwrite", noDecl.}
  proc c_memcpy (a: int, b: cstring, size: int) {.importc: "memcpy", noDecl.}
  proc c_alloca (n: int): int {.importc: "alloca", noDecl.}

  var size : int = 1                      # reserve space for trailing newline
  for i in 0..a.len-1: size += a [i].len  # add sum of string lengths
  let dst0 = c_alloca (size)              # allocate output buffer on the stack
  var dst = dst0                          # point to the start of the buffer
  for i in 0..a.len-1:                    # for all strings to be displayed
    c_memcpy (dst, a [i], a [i].len)      # append string to the output buffer
    dst += a [i].len                      # advance to the end of the buffer
    
  c_memcpy (dst, "\n", 1)                 # append the trailing newline
  c_fwrite (dst0, size, 1, stdout)        # write the buffer to standard out

proc nimecho1 (a: varargs[string, `$`]) =
  # join strings and append new line
  let buffer = join (a) & "\n";             
  # write the buffer to standard out
  discard writeBuffer (stdout, cstring (buffer), buffer.len);


proc test () =
  const testString = "some very long string some very long string some very long string some very long string some very long string some very long string " 
  proc usenimecho1 () = nimecho1 testString, 1, 2, 3, 5.6
  proc useorigecho () = echo testString, 1, 2, 3, 5.6
  proc usenimecho0 () = nimecho0 testString, 1, 2, 3, 5.6

  var testecho = usenimecho1
  if argv.len > 0:
    if argv [0][0] == 'e':
      writeln stderr, "using original echo"
      testecho = useorigecho
    if argv [0][0] == '0':
      writeln stderr, "using nimecho0"
      testecho = usenimecho0
    if argv [0][0] == '1':
      writeln stderr, "using nimecho1 (smallest code)"
      testecho = usenimecho1

    if argv [0][0] == '3':
      useorigecho ()
      usenimecho1 ()
      usenimecho0 ()
      nimecho0 ()
      nimecho1 ()
      nimecho0 ("null\0test")
      nimecho1 ("null\0test")
      return

  const loops = 1_000_000 
  let start = cpuTime ()
  for i in 1..loops: testecho () 
  let finish = cpuTime ()

  let elapsed = finish-start
  writeln stderr, elapsed, " seconds elapsed"
  writeln stderr, elapsed/float (loops), " seconds per iteration"
  writeln stderr, "string used: ", testString

test ()