Mega Code Archive
Header file format of interbase-firebird files
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A simple class to get information about the disk structure of an interbase/firebird database.
This simple class will allow you to specify an interbase/firebird database and it will retrive information about the database including
Secondary files
Page sizes
On disk structure number
Number of pages for each file
etc
To use it you can simply do this
GDBInfo := TGDBInfo.Create('c:\something.gdb');
try
for I := 0 to GDBInfo.Count - 1 do
ShowMessage(GDBInfo[I].Filename);
finally
GDBInfo.Free;
end;
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unit GDBInfo;
interface
uses
SysUtils, Classes;
const
cMAX_PAGE_SIZE = 32768;
type
SChar = Shortint;
SShort = Smallint;
UShort = Word;
SLong = Longint;
ULong = LongWord;
TPag = packed record
pag_type: SChar;
pag_flags: SChar;
pag_checksum: UShort;
pag_generation: ULong;
pag_seqno: ULong;
pg_offset: ULong;
end;
THdr = packed record
hdr_header: TPag;
hdr_page_size: UShort;
hdr_ods_version: UShort;
hdr_pages: SLong;
hdr_next_page: ULong;
hdr_oldest_transaction: SLong;
hdr_oldest_active: SLong;
hdr_next_transaction: SLong;
hdr_sequence: UShort;
hdr_flags: UShort;
hdr_creation_date: array[0..1] of SLong;
hdr_attachment_id: SLong;
hdr_shadow_count: SLong;
hdr_implementation: SShort;
hdr_ods_minor: UShort;
hdr_ods_minor_original: UShort;
hdr_end: UShort;
hdr_page_buffers: ULong;
hdr_bumped_transaction: SLong;
hdr_oldest_snapshot: SLong;
hdr_misc: array[0..3] of SLong;
end;
THdrPage = packed record
fix_data: THdr;
var_data: array[0..cMAX_PAGE_SIZE - 1 - SizeOf(THdr)] of Byte;
end;
//Not IB related
EGDBError = class(Exception);
PGDBFile = ^TGDBFileInfo;
TGDBFileInfo = record
Header: THdr;
Filename: ShortString;
ContinuationFile: ShortString;
FirstLogicalPage: LongWord;
LastLogicalPage: LongWord;
TotalPages: LongWord;
end;
TGDBInfo = class
private
FList: TList;
FFilename: string;
procedure GetDBFiles;
function GetItem(I: Integer): TGDBFileInfo;
protected
public
constructor Create(const AFilename: string);
destructor Destroy; override;
function Count: Integer;
property Items[I: Integer]: TGDBFileInfo read GetItem; default;
end;
implementation
{ TGDBInfo }
function TGDBInfo.Count: Integer;
begin
Result := FList.Count;
end;
constructor TGDBInfo.Create(const AFilename: string);
begin
inherited Create;
FList := TList.Create;
FFilename := AFilename;
GetDBFiles;
end;
destructor TGDBInfo.Destroy;
var
I: Integer;
begin
for I := Count - 1 downto 0 do
begin
FreeMem(FList[I]);
FList.Delete(I);
end;
inherited;
end;
procedure TGDBInfo.GetDBFiles;
var
FS: TFileStream;
HeaderPage: THdrPage;
NewFile: PGDBFile;
CurrentFilename: ShortString;
FilenameSize: Byte;
StartPage: LongWord;
SourceDir: string;
DataOffset: Integer;
begin
if not FileExists(FFilename) then
raise EGDBError.Create('File does not exist - ' + FFilename);
SourceDir := ExtractFilePath(FFilename);
if SourceDir = '' then SourceDir := IncludeTrailingBackSlash(GetCurrentDir);
StartPage := 0;
CurrentFilename := SourceDir + ExtractFilename(FFilename);
repeat
FS := TFileStream.Create(CurrentFilename, fmOpenRead or fmShareDenyNone);
try
GetMem(NewFile, SizeOf(TGDBFileInfo));
FS.Read(HeaderPage, SizeOf(HeaderPage));
Move(HeaderPage, NewFile.Header, SizeOf(THdr));
DataOffset := 0;
//Format of var_data is repeated
//1 = Root file name
//2 = Journal server
//3 = Continuation file (this is the one we want)
//4 = Last logical page
//5 = Unlicensed accesses
//6 = Sweep interval
//7 = Replay logging file
//11= Shared cache file
while HeaderPage.var_data[DataOffset] <> 3 do
begin
if HeaderPage.var_data[DataOffset + 1] = 0 then Break;
Inc(DataOffset, HeaderPage.var_data[DataOffset + 1] + 2);
if DataOffset > HeaderPage.fix_data.hdr_page_size - SizeOf(HeaderPage.fix_data) then
raise EGDBError.Create('Continuation');
end;
FilenameSize := HeaderPage.var_data[DataOffset + 1];
NewFile.Filename := CurrentFileName;
SetLength(NewFile.ContinuationFile, FilenameSize);
if FilenameSize > 0 then
Move(HeaderPage.var_data[DataOffset + 2], NewFile.ContinuationFile[1], FilenameSize);
NewFile.FirstLogicalPage := StartPage;
Move(HeaderPage.var_data[DataOffset + FilenameSize + 4], NewFile.LastLogicalPage, SizeOf(LongWord));
NewFile.TotalPages := NewFile.LastLogicalPage - NewFile.FirstLogicalPage;
Inc(StartPage, NewFile.TotalPages);
FList.Add(NewFile);
CurrentFilename := NewFile.ContinuationFile;
if CurrentFilename = '' then
begin
NewFile.LastLogicalPage := 0;
NewFile.TotalPages := 0;
Break;
end;
finally
FS.Free;
end;
until False;
end;
function TGDBInfo.GetItem(I: Integer): TGDBFileInfo;
begin
Result := PGDBFile(FList[I])^;
end;
end.
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