pic.bcpl

get "streams.d"
external
[
// Outgoing procedures
InitPic; DisplayPic;

// Incoming procedures
OpenFile; Gets; Ws; Wns; Allocate; SysErr;
sysZone; keys; dsp;
]

static [ dcb ]

let InitPic(filename) be
[
let f = OpenFile(filename, ksTypeReadOnly)
// File starts with x and y dimensions
let x = Gets(f)
let y = Gets(f)

let wordsPerLine = (x + 15) / 16
let words = wordsPerLine * y
if words ge 30705 do
[
   Ws("Image too big: ")
   Wns(dsp, words)
   Ws("*N")
   Gets(keys)
   SysErr()
]
// Remainder of file is raw data in Alto pixel format
let v = vec 30705
v = (v + 1) & -2 // double-word align
for i = 0 to words - 1 do
[
   v!i = Gets(f)
]

// Set up display control block, but don't use it yet
dcb = Allocate(sysZone, 5)
dcb = (dcb + 1) & -2
dcb!0 = 0 // End of display list
dcb!1 = 16384 % wordsPerLine // 16384 = white on black
dcb!2 = v // Data pointer
dcb!3 = y / 2 // # lines / 2
]

//-----------------------------------------------------------------------------------------
and DisplayPic() be
//-----------------------------------------------------------------------------------------
[
let lvdas = #420

dcb!0 = lvdas!0 // link into list
lvdas!0 = dcb
]