OpenEuphoria

getc/ReadFile after gets problem

• Posted by Pete Lomax <petelomax at blueyonder.co.uk> Dec 07, 2006
• 634 views

I think there is some wierd buffer-effect going on inside gets/getc.
After gets(0), getc(0) will wait for new input, whereas a call to the
windows API function, c_func(xReadFile,{stdin,chr,1,count,0}) yields
both the \r and \n, that I thought would have been "eaten" by gets(0)??

Here is some code that behaves strangely, any clues?:

include dll.e
include machine.e

atom xKernel32,xGetStdHandle,xReadFile

integer cinit
        cinit=0

constant C_PTR = C_POINTER
constant STD_INPUT_HANDLE = -10     -- #FFFFFFF6

atom stdin, character, bytes_count

procedure Cinit()
    xKernel32 = open_dll("kernel32.dll")
    if xKernel32 = 0 then ?9/0 end if

    xGetStdHandle = define_c_func(xKernel32,"GetStdHandle",
        {C_LONG},   --  DWORD  nStdHandle   // input, output, or error device
        C_PTR)      -- HANDLE

    xReadFile   = define_c_func(xKernel32,"ReadFile",
        {C_PTR,     --  HANDLE  hFile,  // handle of file to read
C_PTR,     --  LPVOID  lpBuffer,   // address of buffer that receives
         data
C_LONG,    --  DWORD  nNumberOfBytesToRead,    // number of bytes to
         read
C_PTR,     --  LPDWORD  lpNumberOfBytesRead,   // address of number of
         bytes read
C_PTR},    --  LPOVERLAPPED  lpOverlapped  // address of structure for
         data
        C_INT)      -- BOOL

    stdin = c_func(xGetStdHandle,{STD_INPUT_HANDLE})
    character = allocate(1)
    bytes_count = allocate(4)
    
    cinit=1
end procedure


function mygetc0()
integer ch
    if not cinit then Cinit() end if
    while 1 do
if not c_func(xReadFile,{stdin,character,1,bytes_count,0}) then return
        -1 end if
        ch = peek(character)
        if ch!='\r' then exit end if
    end while
    return ch
end function

?gets(0)
--?getc(0)        -- <<<--- swap me
?mygetc0()        -- <<<--- with me
?1.234

abort(0)

With getc(0), type in "ABC\n", it outputs {65,66,67,10} and waits for input.
With mygetc(0), it outputs the 10 twice, but you only need to key it once!

Does anyone (with some knowledge, perhaps, of C|be_runtime.c) have any Ideas?
There is something
Somewhere in there it (I think) shoves a read character back into the input 
stream, but I can't follow C code with all those #ifdefs...

Regards,
Pete