当我在MemoryStream或FileStream中使用大文件时，会出现“内存不足”的错误。如何解决这个问题？
示例：
procedure button1.clıck(click);
var
mem:TMemoryStream;
str:string;
begin
mem:=Tmemorystream.create;
mem.loadfromfile('test.txt');----------> there test.txt size 1 gb..
compressstream(mem);
end;
你的实现非常凌乱。我不确定CompressStream到底做了什么，但如果你想以流的方式处理大文件，你可以简单地使用TFileStream而不是尝试一次性将整个文件读入TMemoryStream以节省内存。
此外，当你完成对TMemoryStream的使用后，你没有释放它，这意味着你将会泄漏大量的内存。(除非CompressStream负责处理，但从代码中并不清楚，使用这种方式的确不是一个好主意。)
由于文件太大，无法在32位地址空间中放入一个连续的块中，因此会出现内存不足错误。
将文件分成较小的部分进行读取，并逐个处理。
type THuffmanBuffer = array[0..1023] of Byte; // Because I need to pass the array as parameter
procedure DoActualHuffmanEncoding(const EncodeByte:Byte; var BitBuffer: THuffmanBuffer; var AtBit: Integer);
begin
// This is where the actual Huffman encoding would happen. This procedure will
// copy the correct encoding for EncodeByte in BitBuffer starting at AtBit bit index
// The procedure is expected to advance the AtBit counter with the number of bits
// that were actually written (that's why AtBit is a var parameter).
end;
procedure HuffmanEncoder(const FileNameIn, FileNameOut: string);
var InFile, OutFile: TFileStream;
InBuffer, OutBuffer: THuffmanBuffer;
InBytesCount: Integer;
OutBitPos: Integer;
i: Integer;
begin
// First open the InFile
InFile := TFileStream.Create(FileNameIn, fmOpenRead or fmShareDenyWrite);
try
// Now prepare the OutFile
OutFile := TFileStream.Create(FileNameOut, fmCreate);
try
// Start the out bit counter
OutBitPos := 0;
// Read from the input file, one buffer at a time (for efficiency)
InBytesCount := InFile.Read(InBuffer, SizeOf(InBuffer));
while InBytesCount <> 0 do
begin
// Process the input buffer byte-by-byte
for i:=0 to InBytesCount-1 do
begin
DoActualHuffmanEncoding(InBuffer[i], OutBuffer, OutBitPos);
// The function writes bits to the outer buffer, not full bytes, and the
// encoding for a rare byte might be significantly longer then 1 byte.
// Whenever the output buffer approaches it's capacity we'll flush it
// out to the OutFile
if (OutBitPos > ((SizeOf(OutBuffer)-10)*8) then
begin
// Ok, we've got less then 10 bytes available in the OutBuffer, time to
// flush!
OutFile.Write(OutBuffer, OutBitPos div 8);
// We're now possibly left with one incomplete byte in the buffer.
// We'll copy that byte to the start of the buffer and continue.
OutBuffer[0] := OutBuffer[OutBitPos div 8];
OutBitPos := OutBitPos mod 8;
end;
end;
// Read next chunk
InBytesCount := InFile.Read(InBuffer, SizeOf(InBuffer));
end;
// Flush the remaining of the output buffer. This time we want to flush
// the final (potentially incomplete) byte as well, because we've got no
// more input, there'll be no more output.
OutFile.Write(OutBuffer, (OutBitPos + 7) div 8);
finally OutFile.Free;
end;
finally InFile.Free;
end;
end;
Huffman 编码器并不难实现，但要做到正确和快速可能会是个挑战。我建议你从实现一个正确的编码器开始，一旦你已经完成了编码和解码的工作，再考虑如何实现一个快速的编码器。