Need convert VC code to Delphi - delphi

Question

I need call a DLL file in my delphi code, here is the code snippet of the DLL Head file:
#define BookInfoDLL __declspec(dllexport)
struct _BookTime
{
unsigned char day;
unsigned char month;
unsigned short year;
};
struct _stBookData
{
unsigned char encrypt;
_BookTime bkTime;
unsigned int PageCount;
};
int BookInfoDLL UpdateBooks(const char * const pBookID,
const char cBookTypeWord,
const _stBookData * const pBookData,
const int nBookDataCounter);
I need invoke the dll function "UpdateBooks" in my delphi code.
How can I convert those code into delphi? Thank you!

Answer 1

Use h2pas! Although it is a freepascal tool, it should produce Delphi compatible code.

Answer 2

Snippet for non-managed Delphi code (not tested, but compiles and changed according suggestions in comments):
interface
type
TBookTime = packed record
day : byte; // unsigned 8-bit
month : byte;
year : word; // unsigned 16-bit
end;
TBookData = packed record
encrypt : byte;
bkTime : TBookTime;
PageCount : LongWord; // unsigned 32-bit
end;
TBookDataPtr = ^TBookData;
function UpdateBooks(
pBookID : PChar;
cBookTypeWord : byte;
pBookData : TBookDataPtr;
nBookDataCounter : integer
) : integer; stdcall; external 'dll_file_name.dll' name 'UpdateBooks';
implementation
// ...
end;
Simple call UpdateBooks(...) from delphi code.
Update: code changed, thanks for commenting!
Below is snippets for sample calls ...
Common functions and constants for all snippets:
// --- Test data fill utility and constants -----------------------------------
const
BOOK_ID = 'Test Book ID';
BOOK_TYPE_WORD = 'T';
BOOK_DATA_COUNT = 5;
procedure FillTestBookData(pBookData : TBookDataPtr; iTestNum : integer);
begin
if(pBookData = nil) then exit;
pBookData^.encrypt := iTestNum;
pBookData^.bkTime.day := iTestNum;
pBookData^.bkTime.month := iTestNum;
pBookData^.bkTime.year := 2000 + iTestNum;
pBookData^.PageCount := iTestNum;
end;
Calling function in common Delphi style:
// --- Test procedure in Delphi style -----------------------------------------
procedure TestBookUpdate_DelphiStyle;
var
bookArray : array of TBookData;
iBookNumber : integer;
begin
SetLength(bookArray, BOOK_DATA_COUNT);
try
for iBookNumber := Low(bookArray) to High(bookArray) do begin
FillTestBookData( #(bookArray[iBookNumber]), iBookNumber );
end;
UpdateBooks(
PChar(BOOK_ID), ord(BOOK_TYPE_WORD),
#(bookArray[Low(bookArray)]), BOOK_DATA_COUNT
);
finally
SetLength(bookArray, 0); // no explicit requirement to include in code
end;
end;
Bonus: same test calls in C-style and Pascal-style :-)
// --- Test procedure in Old Delphi (plain Pascal) style ----------------------
type
TBookDataOldArray = array[0..0] of TBookData;
TBookDataOldArrayPtr = ^TBookDataOldArray;
// Store range checking compiler option state
{$IFOPT R+}
{$DEFINE RANGE_CHECK_ON}
{$ENDIF}
procedure TestBookUpdate_OldDelphiStyle;
var
bookArrayPtr : TBookDataOldArrayPtr;
iBookNumber : integer;
begin
GetMem(bookArrayPtr, BOOK_DATA_COUNT*sizeof(TBookData));
try
// Disable range checking compiler option
{$R-}
for iBookNumber := 0 to BOOK_DATA_COUNT - 1 do begin
FillTestBookData(#(bookArrayPtr^[iBookNumber]), iBookNumber);
end;
// Restore range checking compiler option if turned on before disabling
{$IFDEF RANGE_CHECK_ON}{$R+}{$ENDIF}
UpdateBooks(
PChar(BOOK_ID), ord(BOOK_TYPE_WORD), TBookDataPtr(bookArrayPtr), BOOK_DATA_COUNT
);
finally
FreeMem(bookArrayPtr);
end;
end;
// --- Test procedure in C style ---------------------------------------------
procedure TestBookUpdate_CStyle;
var
bookArrayPtr : TBookDataPtr;
curBookPtr : TBookDataPtr;
curBookNumber : integer;
begin
bookArrayPtr := AllocMem( BOOK_DATA_COUNT * sizeof(TBookData) );
try
curBookNumber := 0;
curBookPtr := bookArrayPtr;
while(curBookNumber < BOOK_DATA_COUNT) do begin
FillTestBookData( curBookPtr, curBookNumber );
inc(curBookNumber);
inc(curBookPtr, 1);
// Another pointer increment solution is :
// curBookPtr := PChar(curBookPtr) + sizeof(TBookData);
end;
UpdateBooks( PChar(BOOK_ID), ord(BOOK_TYPE_WORD), bookArrayPtr, BOOK_DATA_COUNT );
finally
FreeMem(bookArrayPtr);
end;
end;

Answer 3

I have ended my first C header conversion yesterday. The articles and tools from TeamB member Rudy Velthuis were very, very helpful for me, specially
Pitfalls of converting
Conversion Helper Package