How to add a string to a big file in csharp !

zjut

I am not familiar with the stream,all help is welcome.thanx! The fallow is the java code and i want to write it in csharp ! import java.io.File; import java.io.* import java.util.Locale; import java.util.Comparator; import java.text.Collator; public class RandomAccessWordList implements WordList { /** The name of the random access word list. This name * is usually unique within a JVM. */ protected String name = null; /** The file this word list maps to. */ protected File file = null; /** The random access file object. This object is released * when there are no queries. */ protected RandomAccessFile raf = null; /** The comparator. */ protected Comparator comparator = DEFAULT_COMPARATOR; /** Reference count. It is incremented in notifyCheckStart() * method and decremented in notifyCheckEnd() method. So * we can tell the current number of queries on this word list. */ protected int inUse = 0; /** A lock used to synchonized access to the file. */ private Object lock = new Object(); /** Protected default construtor. */ protected RandomAccessWordList() { } /** Constructs a RandomAccessWordList from a File. * The name of this word list is defaultly the file name * (file.getName()). * * @param file the file to construct this word list * @throws WordListException if file is null, * or the file does not actually exists */ public RandomAccessWordList(File file) throws WordListException { if (file == null) { throw new WordListException( "file should not be null"); } if (!file.exists()) { throw new WordListException( file.getName() + " not exist."); } this.file = file; this.name = file.getName(); } /** Constructs a RandomAccessWordList from a File and * its name. * * @param file the file to construct this word list * @param name the name of this word list * @throws WordListException if file is null, * or the file does not actually exists, * or name is null or empty */ public RandomAccessWordList(File file, String name) throws WordListException { if (file == null) { throw new WordListException( "file should not be null"); } if (!file.exists()) { throw new WordListException( file.getName() + " not exist."); } if (name == null || name.length() == 0) { throw new WordListException( "name should not be null or empty."); } this.file = file; this.name = name; } /** TCSpellChecker calls this to notify that a query * finishes. RandomAccessWordList would close the * RandomAccessFile if it is there is no other queries * on this word list. */ public synchronized void notifyCheckEnd() { --inUse; if (inUse == 0) { try { raf.close(); raf = null; } catch (IOException ioe) { ; } } } /** TCSpellChecker calls this to notify that a query * is about to take place. RandomAccessWordList would * open a RandomAccessFile if it is not opened. */ public synchronized void notifyCheckStart() { if (inUse == 0) { try { raf = new RandomAccessFile(file, "r"); } catch (FileNotFoundException fnfe) { ; // should not reach here // we've checked in constructor } } ++inUse; } /** Add a word to this word list. For the fact that * the words in the word list should be ordered to * allow a binary search, the insertion of a word is * quite an expensive operation. A temporary file is * opened to help move the words. The file should be * writable for this method to succeed. * * @param word the word to be added to this word list * @throws WordNotAddedException if the word already * exists in this word list, or the file is * read-only, or other exception occurs */ public synchronized void addWord(String word) throws WordNotAddedException { if (word == null) { throw new WordNotAddedException(); } // first check whether the word exists // if does, just throw a WordNotAddedException notifyCheckStart(); try { if (findWord(word)) { notifyCheckEnd(); throw new WordNotAddedException( "Word already exists."); } } catch (WordNotAddedException wnae) { throw wnae; } catch (WordListException wle) { notifyCheckEnd(); throw new WordNotAddedException(wle.getMessage()); } notifyCheckEnd(); // if not, create a temp file and get prepared for the move File tempFile; try { tempFile = File.createTempFile("WordList", "tmp"); } catch (IOException ioe) { throw new WordNotAddedException( "IOException: Can't create temp file"); } // acquire the lock synchronized (lock) { try { // move all the words into the temp file PrintWriter pw = new PrintWriter( new BufferedWriter( new FileWriter(tempFile))); BufferedReader br = new BufferedReader( new FileReader(file)); while (br.ready()) { pw.println(br.readLine()); } pw.close(); br.close(); // move back pw = new PrintWriter( new BufferedWriter( new FileWriter(file))); br = new BufferedReader( new FileReader(tempFile)); boolean added = false; while (br.ready()) { String currentWord = br.readLine(); // this is the place where the word should be inserted if (!added && comparator.compare(word, currentWord) < 0) { pw.println(word); added = true; } pw.println(currentWord); } // oops, it becomes the last one if (!added) { pw.println(word); } pw.close(); br.close(); } catch (IOException ioe) { // still delete the temp file if something happens tempFile.delete(); throw new WordNotAddedException( "IOException: " + ioe); } } // clear up tempFile.delete(); } /** Check whether the specified word exists in this word list. * Since binary search is used, this operation is quite efficient * even for a large list file. * * @param word the word to be checked * @return whether the word exists * @throws WordListException if exception occurs */ public synchronized boolean findWord(String word) throws WordListException { if (word == null) { throw new WordListException(); } // acquire the lock synchronized (lock) { try { // check whether the first word matches raf.seek(0); String str = raf.readLine(); if (str == null) { return false; } if (comparator.compare(word, str.trim()) == 0) { return true; } // binary search starts long lower = 0; long upper = raf.length() - 1; while (lower <= upper) { long index = (lower + upper) / 2; raf.seek(index); // read off an incomplete line raf.readLine(); str = raf.readLine(); // the line might be null if it's the end of file int t = str == null ? -1 : comparator.compare(word, str.trim()); // found it ^_^ if (t == 0) { return true; } if (t > 0) { lower = index + 1; } else { upper = index - 1; } } } catch (IOException ioe) { throw new WordListException("IOException: " + ioe); } } // not found return false; } }

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zjut22y ago
hi: i solve my problem as fallow : static void Main(string[] args) { StreamReader sr = new StreamReader("c:\\1.txt"); StreamWriter sw = new StreamWriter("c:\\2.txt"); string s = ""; while((s = sr.ReadLine()) != null) { if (s.Equals("hello")) { sr.BaseStream.Seek(0,SeekOrigin.Current); sw.WriteLine("hello"); sw.WriteLine(s); } sw.WriteLine(s); } sr.Close(); sw.Close(); } and i can insert "hello" into "1.txt" in the needed position. Also i have a try in ur function,but it outputs bad results. static void Main(string[] args) { Class1 c1 = new Class1(); FileStream fs = new FileStream("c:\\1.txt",FileMode.Open); StreamWriter sw = new StreamWriter("c:\\2.txt"); string s = ""; while((s = c1.FileStreamReadLine(fs)) != null) { System.Console.WriteLine(s); //not output the correct string /*if(s.Equals("hello")) { fs.Seek(0,SeekOrigin.Current); sw.WriteLine("hello"); sw.WriteLine(s); }*/ sw.WriteLine(s); } sr.Close(); sw.Close(); } private string FileStreamReadLine(FileStream fs) { bool endline = false; byte b_tmp; string outstr = ""; while (endline == false) { b_tmp = (byte) fs.ReadByte(); if (b_tmp == '\n') { endline = true; return outstr; } else { outstr += b_tmp; } } return outstr; }
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zjut22y ago
i will try ! thanx for ur kind help !
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robin 022y ago
You know, IMHO, it could be faster and easier this way: when spell checking component is called (either by user, either by programm) it is loading into memory with all it's dictionary, I mean you read whole dictionary file into memory array. Then you are doing spell checking and after completion - unload dictionary from memory. If dictionary was changed (user has added words, for example) - befor unloading, dictionary (array) must be saved to the same file. Spell-checking engines of ICQ and Mozilla (Mozilla suite and Thunderbird) are based on this algorythm.
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zjut22y ago
Thanx of all ! nobrainer ,u are right, i can not add a word into file directly, and i need read the datas from file into a temp file ,and then , i adds the words .at last,i will read the datas from the temp file into the former file ! I am doing a component useing for check the spell of word !When i get a word ,i should compare it to the word in local file and check it is right or not !Maybe i can rewrite a method to read line until "/n". thanx !
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bilnaad22y ago
Let me get this straight ^_^ You can't just add bytes to a file somewhere in the middle. The only thing you can is overwrite bytes or append to the end of the file. If you want the file to be sorted you must rebuild the whole file in one way or another. The other thing is that I don't see the point of having a file in alphabetical order. If you need info from a file you need to read the file anyways(in most cases ^_^). If the data in the file is going to be some input into a array the case is simple. Arrays have a sort function to sort themselves. Could save you a lot of problems. But as I said... I don't know why you want the file to be alphabeticly ordered. Can you maybe tell the purpose for this concept? regards
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robin 022y ago
If I understood you correctly: FileStream is fiteable, but you need to make some functions by your own. something like this: private string FileStreamReadLine(FileStream fs) { bool endline = false; byte b_tmp; string outstr = ""; while (endline == false) { b_tmp = (byte) fs.ReadByte(); if (b_tmp == '\n') { endline = true; return outstr; } else { outstr += b_tmp; } } } I'm not sure, but I think that string.Compare is ok for it....
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zjut22y ago
Thanx for ur reply ! I am afraid i did not declare it enough! i want to add a string to the file and the file is sort by letter! for examply: ////////////////////// abort black cabbage dog egg fly //////////////////// and now i want to add "dad" into it ! Just after "cabbage" and at the front of "dog"! Because of so many word in file so i need to adopt binary search to find the location ! ///
/// want to find the word from given file ///
/// private bool find(string word) { if (word == null) { throw new ArgumentNullException("word is null."); } StreamReader sr = new StreamReader(file.FullName); //file is object of FileInfo lock(this) { //Check the word is in the first! string str = sr.ReadLine(); if (str == null) { return false; } if (string.Compare(str.Trim(),word)) return true; } // binary search starts FileStream fs = File.OpenRead(file.FullName); long lower = 0; long upper = fs.Length - 1; while (lower <= upper) { long index = (lower + upper) / 2; fs.seek(index,SeekOrigin.End); // read off an incomplete line str = fs.Read(); ////i donot know how to set the parameters of Read() so that it can read a line // the line might be null if it's the end of file int t = str == null ? -1 : string.Compare(word, str.trim()); // found it if (t == 0) { return true; } if (t > 0) { lower = index + 1; } else { upper = index - 1; } } } that is the fuction of method and my question is 1: the FileStream is fitable in it ? 2 : string.Compare is fitable in it ? 3: is there any method i can do it better ? thanx of all !
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robin 022y ago
I do not know Java, so I can just answer on your topic question: StreamWriter sw; string tmpstr = "new line in big file....."; sw = new StreamWriter("somefile.txt", true); sw.BaseStream.Seek(0, System.IO.SeekOrigin.End); sw.WriteLine(tmpstr); sw.Close();
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