v4.0/src/MAPPER/READ.ASM

   1 page 80,132
   2
   3 title CP/DOS DosRead mapper   * * *
   4
   5 dosxxx  segment byte public 'dos'
   6         assume  cs:dosxxx,ds:nothing,es:nothing,ss:nothing
   7
   8 ;**********************************************************************
   9 ;*
  10 ;*   MODULE:   dosreade
  11 ;*
  12 ;*   FUNCTION: Read a specified number of bytes from the file
  13 ;*
  14 ;*   CALLING SEQUENCE:
  15 ;*
  16 ;*       push      word     file handle
  17 ;*       push@     other    buffer area
  18 ;*       push      word     buffer length
  19 ;*       push@     word     bytes read
  20 ;*       call      dosread
  21 ;*
  22 ;*   MODULES CALLED:  PC-DOS Int 21h, ah=3fh,
  23 ;*
  24 ;*********************************************************************
  25
  26             public   dosread
  27             .sall
  28             .xlist
  29             include  macros.inc
  30             .list
  31
  32 str         struc
  33 old_bp      dw       ?
  34 return      dd       ?
  35 Written     dd       ?       ; number of bytes actually read
  36 Bufflng     dw       ?       ; number of bytes to be read
  37 Buffer      dd       ?       ; read buffer
  38 Handle      dw       ?       ; handle
  39 str         ends
  40
  41 dosread     proc     far
  42             Enter    Dosread           ; save registers
  43
  44             mov      bx,[bp].handle    ; fill registers for
  45             lds      dx,[bp].buffer    ; function call
  46             mov      cx,[bp].bufflng   ; number of bytes to read
  47
  48             mov      ah,3fh            ; load opcode
  49             int      21h               ; read from file
  50             jc       exit              ; jump if error
  51
  52             lds      si,[bp].written   ; else, set return data area
  53             mov      word ptr [si],ax  ; save number of bytes read
  54             sub      ax,ax             ; set good return code
  55
  56 exit:       mexit                      ; pop registers
  57             ret      size str - 6      ; rturn
  58
  59 dosread     endp
  60
  61 dosxxx      ends
  62
  63             end