Merge branch 'feature/22-add-check-for-max-file-size' into develop

Fixes #22

Docs/BDiff.md

@@ -14,6 +14,8 @@ BDiff computes differences between two binary files. Text files are treated as a
 
 BDiff handles insertion and deletion of data as well as changed bytes.
 
+Files larger than 10MiB will not be processed unless the `--permit-large-files` option is specified (see _Options_ below).
+
 ## Options
 
 | Short option | Long option | Description |
@@ -24,9 +26,10 @@ BDiff handles insertion and deletion of data as well as changed bytes.
 |              | `--format=FMT`| Select format by name: `FMT` is one of `binary`, `filtered` or `quoted`. |
 |`-m N`        | `--min-equal=N`| Two chunks of data are recognized as being identical if they are at least `N` bytes long, the default is `24`. |
 | `-o FILENAME` | `--output=FILENAME`| Write diff to specified file instead of standard output. Specifying `--output=-` does nothing. Use as an alternative to shell redirection. |
-| `-V`          |  `--verbose`| Print status messages while processing input. |
-|`-h`           |  `--help`   | Show help screen and exit. |
-|`-v`           |  `--version`| Show version number and exit. |
+| `-V`          | `--verbose`| Print status messages while processing input. |
+|               | `--permit-large-files` | Ignore maximum file size limit and permit files larger than the limit to be processed. |
+|`-h`           | `--help`   | Show help screen and exit. |
+|`-v`           | `--version`| Show version number and exit. |
 
 ## Algorithm
 

Src/BDiff/BDiff.Main.pas

@@ -19,6 +19,10 @@ interface
   ///  <summary>Class containing main BDiff program logic.</summary>
   TMain = class(TObject)
   strict private
+    const
+      ///  <summary>Maximum file size for which diffs can be calculated.
+      ///  </summary>
+      MaxFileSize = 10_485_760;
     ///  <summary>Displays the program help screen.</summary>
     class procedure DisplayHelp;
     ///  <summary>Displays the program version information.</summary>
@@ -32,6 +36,14 @@   TMain = class(TObject)
     ///  <exception>Raises <c>EOSError</c> if file can't be redirected.
     ///  </exception>
     class procedure RedirectStdOut(const FileName: string);
+    ///  <summary>Checks that both input files are under the maximum supported
+    ///  file size. Does nothing if <c>--permit-large-files</c> option
+    ///  specified.</summary>
+    ///  <param name="Params">[in] Command line parameters object containing
+    ///  the old and new file names.</param>
+    ///  <exception>Raises <c>Exception</c> if either file is larger than
+    ///  maximum permitted.</exception>
+    class procedure CheckFileSizes(Params: TParams);
   public
     ///  <summary>Runs the program.</summary>
     class procedure Run;
@@ -44,6 +56,7 @@ implementation
 uses
   // Delphi
   System.SysUtils,
+  System.IOUtils,
   // Project
   BDiff.Differ,
   BDiff.InfoWriter,
@@ -55,6 +68,31 @@ implementation
 
 { TMain }
 
+class procedure TMain.CheckFileSizes(Params: TParams);
+
+  procedure SizeError(const FileName: string);
+  begin
+    Error(
+      '"%s" is too large (> %.0n bytes)',
+      [FileName, Extended(MaxFileSize)],
+      TFormatSettings.Create
+    );
+  end;
+
+  function IsFileTooLarge(const FileName: string): Boolean;
+  begin
+    Result := TFile.GetSize(FileName) > MaxFileSize;
+  end;
+
+begin
+  if Params.OverrideMaxSize then
+    Exit;
+  if IsFileTooLarge(Params.OldFileName) then
+    SizeError(Params.OldFileName);
+  if IsFileTooLarge(Params.NewFileName) then
+    SizeError(Params.NewFileName);
+end;
+
 class procedure TMain.CreateDiff(Params: TParams);
 begin
   var Logger := TLoggerFactory.CreateInstance(Params.Verbose);
@@ -103,6 +141,7 @@ class procedure TMain.Run;
         DisplayVersion
       else
       begin
+        CheckFileSizes(Params);
         if (Params.PatchFileName <> '') and (Params.PatchFileName <> '-') then
           RedirectStdOut(Params.PatchFileName);
         CreateDiff(Params);

Src/BDiff/BDiff.Params.pas

@@ -28,6 +28,7 @@   TParams = class sealed(TBaseParams)
       fPatchFileName: string;
       fNewFileName: string;
       fFormat: TFormat;
+      fOverrideMaxSize: Boolean;
 
     ///  <summary>Write accessor for <c>Format</c> property.</summary>
     ///  <remarks>Parses and validates property value <c>Value</c>.</remarks>
@@ -99,6 +100,10 @@   TParams = class sealed(TBaseParams)
     ///  <summary>Format of patch output.</summary>
     property Format: TFormat read fFormat default FMT_QUOTED;
 
+    ///  <summary>Flag indicating whether to override maximum file size limit to
+    ///  permit oversize files to be diffed.</summary>
+    property OverrideMaxSize: Boolean read fOverrideMaxSize default False;
+
     ///  <summary>Flag indicating whether the program's help screen is to be
     ///  displayed or not.</summary>
     property Help;
@@ -130,6 +135,7 @@ constructor TParams.Create;
   fMinEqual := 24;
   fVerbose := False;
   fFormat := FMT_QUOTED;
+  fOverrideMaxSize := False;
 end;
 
 procedure TParams.Finalize;
@@ -160,8 +166,10 @@ function TParams.ParseLongOption(const Option: string; var ParamIdx: Integer;
   if Result then
     Exit;
   Result := True;
+
   if Option = '--verbose' then
     fVerbose := True
+
   else if Option = '--output' then
   begin
     Inc(ParamIdx);
@@ -171,20 +179,26 @@ function TParams.ParseLongOption(const Option: string; var ParamIdx: Integer;
   end
   else if AnsiStartsStr('--output=', Option) then
     fPatchFileName := StripLeadingChars(Option, Length('--output='))
+
   else if Option = '--format' then
   begin
     Inc(ParamIdx);
     SetFormat(ParamStr(ParamIdx));
   end
   else if AnsiStartsStr('--format=', Option) then
     SetFormat(StripLeadingChars(Option, Length('--format=')))
+
   else if Option = '--min-equal' then
   begin
     Inc(ParamIdx);
     SetMinEqual(ParamStr(ParamIdx));
   end
   else if AnsiStartsStr('--min-equal=', Option) then
     SetMinEqual(StripLeadingChars(Option, Length('--min-equal=')))
+
+  else if AnsiStartsStr('--permit-large-files', Option) then
+    fOverrideMaxSize := True
+
   else
     Result := False;
 end;

Src/Common/Common.Errors.pas

@@ -9,13 +9,21 @@
 interface
 
 
+uses
+  // Delphi
+  System.Sysutils;
+
+
 ///  <summary>Raises an exception with given message.</summary>
 procedure Error(const Msg: string); overload;
 
 ///  <summary>Raises an exception with message created from format string and
 ///  values.</summary>
 procedure Error(const Fmt: string; const Args: array of const); overload;
 
+procedure Error(const Fmt: string; const Args: array of const;
+  const FmtSettings: TFormatSettings); overload;
+
 ///  <summary>Raises exception determined by last operating system error.
 ///  </summary>
 procedure OSError;
@@ -24,11 +32,6 @@ procedure OSError;
 implementation
 
 
-uses
-  // Delphi
-  System.Sysutils;
-
-
 procedure Error(const Msg: string);
 begin
   raise Exception.Create(Msg);
@@ -39,6 +42,12 @@ procedure Error(const Fmt: string; const Args: array of const);
   raise Exception.CreateFmt(Fmt, Args);
 end;
 
+procedure Error(const Fmt: string; const Args: array of const;
+  const FmtSettings: TFormatSettings);
+begin
+  raise Exception.Create(Format(Fmt, Args, FmtSettings));
+end;
+
 procedure OSError;
 begin
   var Err: EOSError;