FileDocCategorySizeDatePackage
File.javaAPI DocJ2ME MIDP 2.09129Thu Nov 07 12:02:22 GMT 2002com.sun.midp.io.j2me.storage

File

public class File extends Object
Provide the methods to manage files in a device's persistant storage.

Fields Summary
private static final char[]
NUMS
Table to speed up the unicodeToAsciiFilename conversion method.
private static String
storageRoot
Caches the storage root to save repeated native method calls.
Constructors Summary
public File()
Constructs a file object.

        MIDletSuite midletSuite = Scheduler.getScheduler().getMIDletSuite();

        // if a MIDlet suite is not scheduled, assume the JAM is calling.
        if (midletSuite != null) {
            midletSuite.checkIfPermissionAllowed(Permissions.MIDP);
        }
public File(com.sun.midp.security.SecurityToken callerSecurityToken)
Constructs a file object.

param
callerSecurityToken security token of the caller

        callerSecurityToken.checkIfPermissionAllowed(Permissions.MIDP);
Methods Summary
public static java.lang.StringasciiFilenameToUnicode(java.lang.String str)
Perform the reverse conversion of unicodeToAscii().

param
str a string previously returned by escape()
return
the original string before the conversion by escape().

        StringBuffer sbuf = new StringBuffer();

        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            if (c == '%") {
                int v = 0;

                v <<= 4; v += hexValue(str.charAt(i+1));
                v <<= 4; v += hexValue(str.charAt(i+2));
                v <<= 4; v += hexValue(str.charAt(i+3));
                v <<= 4; v += hexValue(str.charAt(i+4));

                i += 4;
                sbuf.append((char)(v & 0x0000ffff));
            } else if (c == '#") {
		// drop c
	    } else {
                sbuf.append(c);
            }
        }

        return sbuf.toString();
private static native intavailableStorage()
Gets the approximate number of free storage bytes remaining.

return
free storage space remaining, in bytes

public synchronized voiddelete(java.lang.String name)
Remove a file from storage if it exists.
param
name name of the file to delete
exception
IOException if an error occurs during delete
        byte[] asciiFilename = Util.toCString(name);

        deleteStorage(asciiFilename);
    
private static native voiddeleteStorage(byte[] szFilename)
Removes storage file szFilename.
param
szFilename storage file to delete
exception
IOException if an error occurs during deletion
public synchronized booleanexists(java.lang.String name)
Returns true if storage file name
exists.
param
name name of storage file
return
true if the named storage file exists
        byte[] asciiFilename = Util.toCString(name);

        return storageExists(asciiFilename);
    
public synchronized java.util.VectorfilenamesThatStartWith(java.lang.String root)
Finds the file names which start with prifix
root.
param
root prefix to match in file names
return
a Vector containing the matching file names.
        Vector list = new Vector();
        byte[] szRoot;
        String filename;

        szRoot = Util.toCString(root);
        filename = getFirstFileThatStartsWith(szRoot);
        while (filename != null) {
            list.addElement(filename);
            filename = getNextFileThatStartsWith(szRoot);
        }

        return list;
    
public intgetBytesAvailableForFiles()
Retrieves the approximate space available to grow or
create new storage files.
return
approximate number of free bytes in storage
        return availableStorage();
    
private static native java.lang.StringgetFirstFileThatStartsWith(byte[] szRoot)
The calling method should be synchronzed and call
getNextFileThatStartsWith until it returns null since
they share static state information.
param
szRoot prefix string to mach in return value
return
the first storage file to contain szRoot
as a prefix
private static native java.lang.StringgetNextFileThatStartsWith(byte[] szRoot)
getFirstFileThatStartsWith must becalled first since it sets up
some shared static state.
param
szRoot prefix string to match in return value
return
the 'next' storage file to contain szRoot
as a prefix
public static java.lang.StringgetStorageRoot()
Returns the root to build storage filenames including an needed
file separators, abstracting difference of the file systems
of development and device platforms. Note the root is never null.
return
root of any filename for accessing device persistant
storage.

                                                         
        
        if (storageRoot == null) {
            storageRoot = initStorageRoot();
        } 

        return storageRoot;
    
private static inthexValue(char c)
A utility method that convert a hex character 0-9a-f to the
numerical value represented by this hex char.
param
c the character to convert
return
the number represented by the character. E.g., '0' representes
the number 0x0, 'a' representes the number 0x0a, etc.
        if (c >= '0" && c <= '9") {
            return ((int)c) - '0";
        } else {
            return ((int)c) - 'a" + 10;
        }
    
private static native java.lang.StringinitStorageRoot()
Initializes storage root for this file instance.
return
path of the storage root
public synchronized voidrename(java.lang.String oldName, java.lang.String newName)
Replaces the current name of storage, oldName
with newName.
param
oldName original name of storage file
param
newName new name for storage file
exception
IOException if an error occurs during rename
        byte[] oldAsciiFilename = Util.toCString(oldName);
        byte[] newAsciiFilename = Util.toCString(newName);

        renameStorage(oldAsciiFilename, newAsciiFilename);
    
private static native voidrenameStorage(byte[] szOldName, byte[] szNewName)
Renames storage file.
param
szOldName old name of storage file
param
szNewName new name for storage file
private static native booleanstorageExists(byte[] szFilename)
Determines if a storage file matching szFilename exists.
param
szFilename storage file to match
return
true if storage indicated by
szFilename exists
public static java.lang.StringunicodeToAsciiFilename(java.lang.String str)
Convert a file name into a form that can be safely stored on
an ANSI-compatible file system. All characters that are not
[A-Za-z0-9] are converted into %uuuu, where uuuu is the hex
representation of the character's unicode value. Note even
though "_" is allowed it is converted because we use it for
for internal purposes. Potential file separators are converted
so the native layer does not have deal with sub-directory hierachies.
param
str a string that may contain any character
return
an equivalent string that contains only the "safe" characters.
        StringBuffer sbuf = new StringBuffer();

        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            if ((c >= 'a" && c <= 'z") ||
                (c >= '0" && c <= '9")) {
                sbuf.append(c);
            } else if (c >= 'A" && c <= 'Z") {
		sbuf.append('#");
		sbuf.append(c);
	    } else {
                int v = (int)(c & 0xffff);
                sbuf.append('%");
                sbuf.append(NUMS[(v & 0xf000) >> 12]);
                sbuf.append(NUMS[(v & 0x0f00) >>  8]);
                sbuf.append(NUMS[(v & 0x00f0) >>  4]);
                sbuf.append(NUMS[(v & 0x000f) >>  0]);
            }
        }

        return sbuf.toString();