// Example of Ada-style tasking in XL
// Consumer and producer tasks with synchro buffer

import ASCII = XL.ASCII
import TASK = XL.TASKING

// Make all references to 'TASK' implicit
using TASK

// Buffer object used for synchronization
{protected} record Buffer with

    {entry} function Count() return unsigned
    {entry} function Available() return unsigned

    when Count() > 0:
       {entry} procedure Read(out character C)
    when Available() > 0:
       {entry} procedure Write(in character C)


// Producing task
task Producer is
   with character C
   loop
      // ... produce the next character
      Buffer.Write C
      exit if C = ASCII.EOT


// Consuming task
task Consumer is
   with character C
   loop
      Buffer.Read C
      exit if C = ASCII.EOT
      // ... consume the character


// Implementation of Buffer (possibly a separate file)
{protected} record Buffer body is
    with
       array Pool[1..100] of character
       unsigned Count := 0
       unsigned In_Index := 1, Out_Index := 1

    {entry} function Count() return unsigned is return Count

    {entry} function Available() return unsigned is return Size(Pool)-Count

    {entry} procedure Read(in character C) is
       Pool[In_Index] := C
       In_Index := (In_Index mod Size(Pool)) + 1
       Count += 1

    {entry} procedure Write(out character C) is
       C := Pool[Out_Index]
       Out_Index := (Out_Index mod Size(Pool)) + 1
       Count -= 1