我想把任何类型的大型文件(音频,视频,图像......)分成小块。我尝试了很多算法,但我无法做到这一点。任何人都可以建议我使用算法吗?
答案 0 :(得分:0)
只需使用下一个开始位置将块复制到小文件中:
<?php
if ("" != trim($_FILES['fileToWrite']["tmp_name"])) {
if (!file_exists($_FILES['fileToWrite']["tmp_name"])) {
echo "File named: <span style='color:red;'>" . $_POST['fileToWrite'] . "</span> doesn't exist! <br>";
} else {
$fw = fopen($_FILES['fileToWrite']["tmp_name"], "w");
fwrite($fw, $_POST['write_file']);
echo 'File over-written successfully';
}
}
?>
示例:需要将7个字节的文件分成2个字节的块。 N = 3,RestSize = 1.三个2字节文件和一个1字节。
答案 1 :(得分:0)
即使我们有这样的记忆,你也无法一次性阅读大块文件。基本上对于每个拆分,您可以读取一个固定大小的字节数组,您知道在性能和内存方面应该是可行的。
public static void main(String[] args) throws Exception
{
RandomAccessFile raf = new RandomAccessFile("test.csv", "r");
long numSplits = 10; //from user input, extract it from args
long sourceSize = raf.length();
long bytesPerSplit = sourceSize/numSplits ;
long remainingBytes = sourceSize % numSplits;
int maxReadBufferSize = 8 * 1024; //8KB
for(int destIx=1; destIx <= numSplits; destIx++) {
BufferedOutputStream bw = new BufferedOutputStream(new FileOutputStream("split."+destIx));
if(bytesPerSplit > maxReadBufferSize) {
long numReads = bytesPerSplit/maxReadBufferSize;
long numRemainingRead = bytesPerSplit % maxReadBufferSize;
for(int i=0; i<numReads; i++) {
readWrite(raf, bw, maxReadBufferSize);
}
if(numRemainingRead > 0) {
readWrite(raf, bw, numRemainingRead);
}
}else {
readWrite(raf, bw, bytesPerSplit);
}
bw.close();
}
if(remainingBytes > 0) {
BufferedOutputStream bw = new BufferedOutputStream(new FileOutputStream("split."+(numSplits+1)));
readWrite(raf, bw, remainingBytes);
bw.close();
}
raf.close();
}
static void readWrite(RandomAccessFile raf, BufferedOutputStream bw, long numBytes) throws IOException {
byte[] buf = new byte[(int) numBytes];
int val = raf.read(buf);
if(val != -1) {
bw.write(buf);
}
}
您还应该在https://coderanch.com/t/458202/java/Approach-split-file-chunks和其他网站等各种网站上寻找一些讨论。 快乐的编码。