Replace use of Cardinal with other types where necessary

[delphidabbler]

BDiff uses Cardinal wherever the original C code used size_t.

This is fine for 32 bit code, where both types are 32 bit, but size_t is 64 bit on 64 bit compilers whereas Cardinal remains 32 bit.

So it could be a good idea to replace Cardinal with NativeUInt, which changes size like size_t depending on the native word size.

This isn't necessary if BDiff is to remain 32 bit, and is not sufficient if BDiff moves to 64 bit, but it will help to smooth the transition if it is made.

[delphidabbler]

I'm not sure if NativeUInt is defined on Delphi XE, which BDiff is currently developed with.

So some code like the following in UBDiffTypes.pas may be needed:

{$IF not Declared(NativeUInt) }
type
  NativeUInt = Cardinal;
{$IFEND}

Will need to check the above syntax because I'm rusty on it and away don't have Delphi available to check.

[delphidabbler]

Check original C code to check where Cardinal has been used to stand in for size_t. Maybe some uses of Cardinal are still required to be 32 bit.

C code download

[delphidabbler]

This could get very buggy very quickly. Maybe leave the programs as 32 bit for now?

[delphidabbler]

Examination of the original C source code suggests that all Cardinal types in

bdiff/Src/BDiff/UBlockSort.pas

Line 20 in 464fe21

TBlockSort = class(TObject)

were substituted for size_t, and therefore should be changed to NativeUInt.

[delphidabbler]

All Cardinal types used in methods of

bdiff/Src/BDiff/UDiffer.pas

Line 28 in 464fe21

TDiffer = class(TObject)

would seem to be size_t replacements and so need to be NativeUInt.

But the type of the MinMatchLength property can remain Cardinal. In fact UInt16 might suffice. See the maximum size of a numeric parameter before deciding.

[delphidabbler]

The Size property of

bdiff/Src/BDiff/UFileData.pas

Line 16 in 464fe21

TFileData = class(TObject)

needs to be NativeUInt because the original C code always stored file sizes as size_t.

[delphidabbler]

All Cardinal types in

bdiff/Src/BDiff/UPatchWriters.pas

Line 10 in 464fe21

unit UPatchWriters;

replaced size_t types and so need to be NativeUInt. This includes the, perhaps less obvious,

bdiff/Src/BDiff/UPatchWriters.pas

Line 46 in 464fe21

function CheckSum(Data: PCChar; Length: Cardinal): Longint;

[delphidabbler]

Should

bdiff/Src/BPatch/UBPatchUtils.pas

Line 30 in 464fe21

class function Seek(Handle: Integer; Offset: Longint; Origin: Integer):

have its Offset &/or Origin parameter data types changed? Need to check if the SysUtils.FileSeek function that the method calls supports 64 bit offsets.

[delphidabbler]

The Size property of

bdiff/Src/BDiff/UFileData.pas

Line 16 in 464fe21

TFileData = class(TObject)

needs to be NativeUInt because the original C code always stored file sizes as size_t.

Maybe UInt32 is sufficient for the type of the Size property after all.

This is because the binary file header stores file sizes in 4 bytes.

In BPatch, file sizes are stored in LongInt = Int32 values, which limits the file size that can be handled to MaxInt. The choice of Int32 instead if UInt32 halves the maximum file size.

❓ Should BDiff and BPatch refuse to handle files larger than MaxInt bytes?

[delphidabbler]

To be consistent with BDiff,

bdiff/Src/BPatch/UPatcher.pas

Line 19 in 464fe21

class function CheckSum(Data: PAnsiChar; DataSize: Cardinal;

should possibly have its DataSize parameter changed to NativeUInt, but given the file size limitation noted above, it probably doesn't matter.

Furthermore the type of the method's BFCheckSum parameter differs between the interface & implementation sections. Should be LongInt.

[delphidabbler]

All length related variables in

bdiff/Src/BPatch/UPatcher.pas

Line 60 in 464fe21

class procedure TPatcher.Apply(const SourceFileName, DestFileName: string);

are LongInt instead of Cardinal as would be expected in BDiff. This is true of the original C code too. Given the size restrictions imposed by the binary diff header, this is OK, but ❗could with commenting an explanation❗

[delphidabbler]

Furthermore the type of the method's BFCheckSum parameter differs between the interface & implementation sections. Should be LongInt.

There's a similar inconsistency with the SourceFileHandle parameter of

bdiff/Src/BPatch/UPatcher.pas

Line 31 in 464fe21

class procedure CopyData(const SourceFileHandle, DestFileHandle: Integer;

[delphidabbler]

Consideration of Delphi XE now irrelevant since updated to Delphi 11. (Issue #12)

[delphidabbler]

Some uses of Cardinal in place of size_t get coerced to Longint a.k.a. Int32 when stored, so it would seem more sensible to change Cardinal to Int32 in these cases.

I'm choosing Int32 in preference to Longint or Integer since it expresses the intention better.

[delphidabbler]

Some uses of Cardinal in place of size_t get coerced to Longint a.k.a. Int32 when stored, so it would seem more sensible to change Cardinal to Int32 in these cases.

This is the approach I'm taking. Reviewing all used of Cardinal and deciding to replace with either Int32, NativeUInt or THandle as relevant.

[delphidabbler]

❓ Should BDiff and BPatch refuse to handle files larger than MaxInt bytes?

File size limited to 10MiB which can be overridden (see issue #22), will have absolute limit of MaxInt (see issue #32).

[delphidabbler]

Implemented by merge commit aa57c8d