%from IMP %include MCODE, FORMATS, Depio, SysSpecs

%externalroutine TT Input Empty %alias "3L___tt_input_empty"
   %record(SCB Fm) %name S
   %integer Size, H, A, L
   %label OK, L1, No

   *STR _ R1, S
   S_Position = S_Position + S_ThisB_Size ; S_ThisB_Size = 0

   Flush TTY                    {Flush chain of TTY output SCBs ...}
   %if Prompt String # "" %start
      A = Addr(Prompt String)
      *LDR   _ R5, A              {address of prompt string}
      *LDRB  _ R9, [R5], #1       {bytes to transfer}
L1:   *LDRB  _ R0, [R5], #1       {pick up the next byte}
      *CMPS  _ R0, #10            {newline?}
      *SWINE _ Brasil WriteC      {no, treat normally}
      *SWIEQ _ Brasil NewLine     {yes, treat specially}
      *SUBS  _ R9, R9, #1
      *BGT   _ L1
   %finish

   %signal 9,1 %if S_Flags&SCB Eof Pending # 0

   {Read block - User1 conventionally ignored for TT input}

   A = S_AllocB_Base
   L = S_AllocB_Size

   *LDR   _ R0, A
   *LDR   _ R1, L
   *MOV   _ R2, #0
   *MOV   _ R3, #255
   *SWI   _ Brasil ReadLine
         {The book is all lies. R0 = address of buffer, R1 = bytes transferred}
         {                      excluding the terminator}
   *BCC   _ Ok              {no escape}
   {deal with escape - treat as EOF}
   *MOV   _ R0, #124        {124 = clear escape condition}
   *SWI   _ 6               {osbyte}
No:S_Flags = S_Flags ! SCB Eof Pending {end of file pending}
   %signal 9,1                         {actually true eof now}

Ok:*MOV   _ R2, #10         {NL}
   *STRB  _ R2, [R0, R1]    {overwrite the CR with NL}
   *LDRB  _ R3, [R0]        {first character}
   *ADD   _ R0, R1, #1      {one more}
   *STR   _ R0, Size
   *CMPS  _ R3, #4          {EOT = ^D}
   *BEQ   _ No              {signal eof}

   {Successful record read, set buffer pointers and return}

   S_ThisB_Base = S_AllocB_Base
   S_ThisB_Size = Size
   S_Next       = S_ThisB_Base
   S_Limit      = S_Next+Size

   *LDR  _ R1, S         {restore pointer to SCB}
   *LDR  _ R2, [R1]      {character pointer, S_Next}
%end