100% определяемости не добиться. Этот процент асимптотически растет с увеличением размера файла.
В одном факе нашел определение по методу каких-то там биграм (т.е. учитывается вроде частота встречаемости букв в русском алфавите). Вот, можешь применить метод alex-co, и если в результате не выяснилась кодировка - примени этот способ:
| Код | type
TCodePage = (cpWin1251, cp866);
PMap = ^TMap;
TMap = array [#$80..#$FF] of Char;
var
Map866: TMap;
function GetMap(CP : TCodePage) : PMap;
begin
case CP of
cpWin1251: GetMap := nil;
cp866: GetMap := @Map866;
end;
end;
function DetermineRussian (Buf : PChar; Count : Integer): TCodePage;
const
ModelBigrams : array [0..33, 0..33] of Byte = (
{АБВГДЕЖЗИЙКЛМHОПРСТУФХЦЧШЩЪЫЬЭЮЯ_Ё}
{А}(0,20,44,12,22,23,16,60,4,9,63,93,47,110,0,16,35,61,81,1,5,13,24,17,12,4,0,0,0,0,14,31,205,1),
{Б}(19,0,0,0,4,19,0,0,8,0,2,15,1,4,41,0,15,5,0,15,0,2,1,0,0,6,16,37,0,0,0,4,3,0),
{В}(97,0,1,0,2,57,0,5,40,0,4,25,2,23,78,2,8,28,4,12,0,1,0,0,8,1,0,40,1,0,0,5,106,3),
{Г}(13,0,0,0,9,5,0,0,15,0,1,17,1,2,96,0,24,0,0,7,0,0,0,0,0,0,0,0,0,0,0,0,8,0),
{Д}(63,0,9,1,2,71,1,0,35,0,3,16,2,22,50,2,19,9,2,25,0,2,1,0,1,0,1,9,4,0,1,5,17,4),
{Е}(4,14,15,34,56,22,13,14,2,34,39,77,73,150,6,9,101,64,81,1,0,15,5,12,10,6,0,0,0,0,3,4,235,1),
{Ж}(13,0,0,0,12,47,0,0,16,0,1,0,0,23,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,2,2),
{З}(76,2,11,3,11,4,1,0,7,0,2,4,11,24,17,0,6,1,0,8,0,0,0,0,0,0,0,16,6,0,1,4,17,0),
{И}(7,9,32,5,18,60,4,42,31,27,28,46,55,49,12,7,26,60,53,0,5,25,14,28,4,1,0,0,0,0,9,56,255,0),
{Й}(0,0,0,0,2,0,0,0,0,0,1,3,0,3,0,0,0,10,3,0,0,0,0,1,1,0,0,0,0,0,0,0,122,0),
{К}(92,0,3,0,0,7,2,1,39,0,0,27,0,14,110,0,18,5,35,18,0,0,11,0,0,0,0,0,0,0,0,5,5,0),
{Л}(85,1,0,2,1,70,6,0,85,0,5,3,0,9,67,1,0,9,0,15,0,0,0,2,0,0,0,9,66,0,15,43,57,4),
{М}(44,0,0,0,0,65,0,0,47,0,1,1,10,15,57,7,0,2,0,24,0,0,0,0,0,0,0,28,0,0,0,8,109,3),
{}(139,0,0,1,11,108,0,4,152,0,7,0,1,69,161,0,0,8,25,24,5,1,5,2,0,1,0,83,10,0,1,29,38,5),
{О}(0,72,139,76,74,32,32,19,12,52,21,93,68,72,7,34,93,102,98,1,2,6,6,19,15,2,0,0,0,1,4,9,252,2),
{П}(17,0,0,0,0,43,0,0,14,0,1,9,0,1,125,3,120,1,2,8,0,0,0,0,0,0,0,3,6,0,0,3,2,2),
{Р}(151,1,6,4,3,103,7,0,76,0,4,0,11,10,117,1,0,5,9,39,2,5,0,1,3,0,0,24,7,0,1,10,22,5),
{С}(24,1,21,0,3,39,0,0,33,0,56,41,11,15,58,30,5,30,183,16,0,4,1,4,1,0,0,8,25,0,1,50,41,2),
{Т}(83,0,43,0,3,87,0,0,71,0,9,3,2,26,180,0,55,33,1,23,1,0,1,4,0,0,0,20,78,0,0,5,82,4),
{У}(3,6,7,14,19,8,13,6,0,1,13,15,10,7,0,12,17,16,19,0,1,3,0,12,5,8,0,0,0,0,22,1,65,0),
{Ф}(4,0,0,0,0,4,0,0,11,0,0,1,0,0,9,0,3,0,0,4,1,0,0,0,0,0,0,0,0,0,0,0,2,0),
{Х}(9,0,2,0,0,2,0,0,5,0,0,1,0,5,26,0,4,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,76,0),
{Ц}(5,0,0,0,0,16,0,0,48,0,1,0,0,0,4,0,0,0,0,3,0,0,0,0,0,0,0,2,0,0,0,0,3,0),
{Ч}(30,0,0,0,0,52,0,0,23,0,3,1,0,14,1,0,0,0,36,5,0,0,0,0,1,0,0,0,1,0,0,0,2,2),
{Ш}(13,0,0,0,0,28,0,0,17,0,4,4,0,4,3,0,0,0,1,3,0,0,0,0,0,0,0,0,3,0,0,0,1,1),
{Щ}(6,0,0,0,0,23,0,0,16,0,0,0,0,1,0,0,0,0,0,1,0,0,0,0,0,0,0,0,1,0,0,0,0,1),
{Ъ}(0,0,0,0,0,16,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,0,0),
{Ы}(0,5,14,1,3,28,0,2,0,22,6,19,21,2,0,5,4,7,10,0,0,37,0,3,4,0,0,0,0,0,0,1,84,0),
{Ь}(0,1,0,0,0,9,0,10,1,0,13,0,2,26,0,0,0,10,3,0,0,0,1,0,6,0,0,0,0,0,6,4,117,0),
{Э}(0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,31,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0),
{Ю}(0,5,0,0,3,0,0,0,0,0,0,1,0,0,0,0,0,1,15,0,0,0,1,4,1,15,0,0,0,0,0,0,38,0),
{Я}(0,0,9,2,7,10,3,19,0,0,1,6,7,8,0,0,2,6,19,0,0,3,5,1,0,3,0,0,0,0,5,2,177,0),
{_}(42,80,193,43,109,41,18,53,159,0,144,27,83,176,187,229,70,231,99,47,15,13,6,58,7,0,0,0,0,38,0,22,0,2),
{Ё}(0,0,0,0,3,0,0,0,0,0,2,4,4,8,0,0,5,3,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0));
type
TVariation = array [0..33, 0..33] of Integer;
var
I, J, iC, iPredC, Max : Integer;
C : Char;
CP : TCodePage;
D, MinD, Factor : Double;
AMap : PMap;
PV : ^TVariation;
Vars : array [TCodePage] of TVariation;
begin
DetermineRussian := cpWin1251; { по yмолчанию }
{ вычисление распределений биграмм }
FillChar (Vars, SizeOf(Vars), 0);
for CP := Low(Vars) to High(Vars) do
begin
AMap := GetMap(CP);
PV := @Vars[CP];
iPredC := 32;
for I := 0 to Count-1 do
begin
C := Buf[I];
iC := 32;
if C >= #128 then
begin
if AMap <> nil then C := AMap^[C];
if not (C in ['Ё', 'ё']) then
begin
C := Chr(Ord(C) and not 32); { 'a'..'я' -> 'А'..'Я' }
if C in ['А'..'Я'] then iC := Ord(C) - Ord('А');
end
else iC := 33;
end;
Inc (PV^[iPredC, iC]);
iPredC := iC;
end;
end;
{ вычисление метрики и определение наиболее правдоподобной кодировки }
MinD := 0;
for CP := Low(Vars) to High(Vars) do
begin
PV := @Vars[CP];
PV^[32, 32]:=0;
Max := 1;
for I := 0 to 33 do
for J := 0 to 33 do
if PV^[I, J] > Max then Max := PV^[I, J];
Factor := 255 / Max; { ноpмализация }
D := 0;
for I := 0 to 33 do
for J := 0 to 33 do
D := D + Abs(PV^[I, J]*Factor - ModelBigrams[I, J]);
if (MinD = 0) or (D < MinD) then
begin
MinD := D;
DetermineRussian := CP;
end;
end;
end;
...................
var i : byte;
initialization
for i := $80 to $FF do Map866[Char(i)] := Char(i);
OEMToCharBuff(@Map866, @Map866, SizeOf(TMap));
finalization
end.
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Вот пример вызова:
| Код | procedure TfrmMain.Button3Click(Sender: TObject);
var
s : String;
cp : TCodePage;
begin
s := 'Абра-кадабра...';
cp := DetermineRussian(PChar(s), Length(s));
//...
end; |
Кстати, эта процедурина легко переделывается для нескольких кодировок - буквально пару-тройку строк нужно добавить, чтобы научилась определять любые другие кодировки...
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