firedac数据集和字符串之间相互转换

最新推荐文章于 2020-07-18 12:24:21 发布

转载最新推荐文章于 2020-07-18 12:24:21 发布 · 81 阅读

本文介绍如何使用Firedac将数据集转换为字符串，以及如何从字符串还原为TFDMemTable。通过Base64编码和压缩技术，实现数据的高效存储和传输。

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firedac数据集和字符串之间相互转换

/// <author>cxg 2018-12-20</author>

unit DatasetString;

interface

uses
  System.NetEncoding, FireDAC.Stan.Intf, System.ZLib, System.Classes, FireDAC.Comp.Client,
  System.SysUtils;

function DataSetToString(const ADataSet: TFDAdaptedDataSet): string;

function MemTableFromString(const AValue: string): TFDMemTable;

implementation

function DataSetToString(const ADataSet: TFDAdaptedDataSet): string;
var
  LBinary64: string;
  LMemoryStream: TMemoryStream;
  LStringStream: TStringStream;
  LDstStream: TMemoryStream;
  Zipper: TZCompressionStream;
begin
  LDstStream := TMemoryStream.Create;
  try
    LMemoryStream := TMemoryStream.Create;
    try
      ADataSet.SaveToStream(LMemoryStream, TFDStorageFormat.sfBinary);
      LMemoryStream.Seek(0, TSeekOrigin.soBeginning);
      Zipper := TZCompressionStream.Create(clDefault, LDstStream);
      try
        Zipper.CopyFrom(LMemoryStream, LMemoryStream.Size);
      finally
        Zipper.Free;
      end;
    finally
      LMemoryStream.Free;
    end;
    LDstStream.Seek(0, TSeekOrigin.soBeginning);

    LStringStream := TStringStream.Create;
    try
      TNetEncoding.Base64.Encode(LDstStream, LStringStream);
      LBinary64 := LStringStream.DataString;
    finally
      LStringStream.Free;
    end;
  finally
    LDstStream.Free;
  end;
  Result := LBinary64;
end;

function MemTableFromString(const AValue: string): TFDMemTable;
var
  LMemTable: TFDMemTable;
  LStringStream: TStringStream;
  LMemoryStream: TMemoryStream;
  LOrgStream: TMemoryStream;
  Unzipper: TZDecompressionStream;
begin
  LMemTable := TFDMemTable.Create(nil);
  LMemoryStream := TMemoryStream.Create;
  try
    LStringStream := TStringStream.Create(AValue);
    try
      LOrgStream := TMemoryStream.Create;
      try
        TNetEncoding.Base64.Decode(LStringStream, LOrgStream);
        LOrgStream.Seek(0, TSeekOrigin.soBeginning);
        Unzipper := TZDecompressionStream.Create(LOrgStream);
        try
          LMemoryStream.CopyFrom(Unzipper, Unzipper.Size);
        finally
          Unzipper.Free;
        end;
        LMemoryStream.Seek(0, TSeekOrigin.soBeginning);
      finally
        LOrgStream.Free;
      end;
    finally
      LStringStream.Free;
    end;
    LMemTable.LoadFromStream(LMemoryStream, TFDStorageFormat.sfBinary);
  finally
    LMemoryStream.Free;
  end;
  Result := LMemTable;
end;

end.