diff options
Diffstat (limited to 'src/com/android/providers/downloads/Helpers.java')
-rw-r--r-- | src/com/android/providers/downloads/Helpers.java | 793 |
1 files changed, 793 insertions, 0 deletions
diff --git a/src/com/android/providers/downloads/Helpers.java b/src/com/android/providers/downloads/Helpers.java new file mode 100644 index 00000000..7c6070f3 --- /dev/null +++ b/src/com/android/providers/downloads/Helpers.java @@ -0,0 +1,793 @@ +/* + * Copyright (C) 2008 The Android Open Source Project + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package com.android.providers.downloads; + +import android.content.ContentUris; +import android.content.Context; +import android.content.Intent; +import android.content.pm.PackageManager; +import android.content.pm.ResolveInfo; +import android.database.Cursor; +import android.drm.mobile1.DrmRawContent; +import android.net.ConnectivityManager; +import android.net.NetworkInfo; +import android.net.Uri; +import android.os.Environment; +import android.os.StatFs; +import android.os.SystemClock; +import android.provider.Downloads; +import android.telephony.TelephonyManager; +import android.util.Config; +import android.util.Log; +import android.webkit.MimeTypeMap; + +import java.io.File; +import java.io.FileNotFoundException; +import java.io.FileOutputStream; +import java.util.List; +import java.util.Random; +import java.util.regex.Matcher; +import java.util.regex.Pattern; +import java.util.Set; + +/** + * Some helper functions for the download manager + */ +public class Helpers { + + public static Random rnd = new Random(SystemClock.uptimeMillis()); + + /** Regex used to parse content-disposition headers */ + private static final Pattern CONTENT_DISPOSITION_PATTERN = + Pattern.compile("attachment;\\s*filename\\s*=\\s*\"([^\"]*)\""); + + private Helpers() { + } + + /* + * Parse the Content-Disposition HTTP Header. The format of the header + * is defined here: http://www.w3.org/Protocols/rfc2616/rfc2616-sec19.html + * This header provides a filename for content that is going to be + * downloaded to the file system. We only support the attachment type. + */ + private static String parseContentDisposition(String contentDisposition) { + try { + Matcher m = CONTENT_DISPOSITION_PATTERN.matcher(contentDisposition); + if (m.find()) { + return m.group(1); + } + } catch (IllegalStateException ex) { + // This function is defined as returning null when it can't parse the header + } + return null; + } + + /** + * Creates a filename (where the file should be saved) from a uri. + */ + public static DownloadFileInfo generateSaveFile( + Context context, + String url, + String hint, + String contentDisposition, + String contentLocation, + String mimeType, + int destination, + int contentLength) throws FileNotFoundException { + + /* + * Don't download files that we won't be able to handle + */ + if (destination == Downloads.DESTINATION_EXTERNAL + || destination == Downloads.DESTINATION_CACHE_PARTITION_PURGEABLE) { + if (mimeType == null) { + if (Config.LOGD) { + Log.d(Constants.TAG, "external download with no mime type not allowed"); + } + return new DownloadFileInfo(null, null, Downloads.STATUS_NOT_ACCEPTABLE); + } + if (!DrmRawContent.DRM_MIMETYPE_MESSAGE_STRING.equalsIgnoreCase(mimeType)) { + // Check to see if we are allowed to download this file. Only files + // that can be handled by the platform can be downloaded. + // special case DRM files, which we should always allow downloading. + Intent intent = new Intent(Intent.ACTION_VIEW); + + // We can provide data as either content: or file: URIs, + // so allow both. (I think it would be nice if we just did + // everything as content: URIs) + // Actually, right now the download manager's UId restrictions + // prevent use from using content: so it's got to be file: or + // nothing + + PackageManager pm = context.getPackageManager(); + intent.setDataAndType(Uri.fromParts("file", "", null), mimeType); + ResolveInfo ri = pm.resolveActivity(intent, PackageManager.MATCH_DEFAULT_ONLY); + //Log.i(Constants.TAG, "*** FILENAME QUERY " + intent + ": " + list); + + if (ri == null) { + if (Config.LOGD) { + Log.d(Constants.TAG, "no handler found for type " + mimeType); + } + return new DownloadFileInfo(null, null, Downloads.STATUS_NOT_ACCEPTABLE); + } + } + } + String filename = chooseFilename( + url, hint, contentDisposition, contentLocation, destination); + + // Split filename between base and extension + // Add an extension if filename does not have one + String extension = null; + int dotIndex = filename.indexOf('.'); + if (dotIndex < 0) { + extension = chooseExtensionFromMimeType(mimeType, true); + } else { + extension = chooseExtensionFromFilename( + mimeType, destination, filename, dotIndex); + filename = filename.substring(0, dotIndex); + } + + /* + * Locate the directory where the file will be saved + */ + + File base = null; + StatFs stat = null; + // DRM messages should be temporarily stored internally and then passed to + // the DRM content provider + if (destination == Downloads.DESTINATION_CACHE_PARTITION + || destination == Downloads.DESTINATION_CACHE_PARTITION_PURGEABLE + || destination == Downloads.DESTINATION_CACHE_PARTITION_NOROAMING + || DrmRawContent.DRM_MIMETYPE_MESSAGE_STRING.equalsIgnoreCase(mimeType)) { + base = Environment.getDownloadCacheDirectory(); + stat = new StatFs(base.getPath()); + + /* + * Check whether there's enough space on the target filesystem to save the file. + * Put a bit of margin (in case creating the file grows the system by a few blocks). + */ + int blockSize = stat.getBlockSize(); + for (;;) { + int availableBlocks = stat.getAvailableBlocks(); + if (blockSize * ((long) availableBlocks - 4) >= contentLength) { + break; + } + if (!discardPurgeableFiles(context, + contentLength - blockSize * ((long) availableBlocks - 4))) { + if (Config.LOGD) { + Log.d(Constants.TAG, + "download aborted - not enough free space in internal storage"); + } + return new DownloadFileInfo(null, null, Downloads.STATUS_FILE_ERROR); + } + stat.restat(base.getPath()); + } + + } else { + if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) { + String root = Environment.getExternalStorageDirectory().getPath(); + base = new File(root + Constants.DEFAULT_DL_SUBDIR); + if (!base.isDirectory() && !base.mkdir()) { + if (Config.LOGD) { + Log.d(Constants.TAG, "download aborted - can't create base directory " + + base.getPath()); + } + return new DownloadFileInfo(null, null, Downloads.STATUS_FILE_ERROR); + } + stat = new StatFs(base.getPath()); + } else { + if (Config.LOGD) { + Log.d(Constants.TAG, "download aborted - no external storage"); + } + return new DownloadFileInfo(null, null, Downloads.STATUS_FILE_ERROR); + } + + /* + * Check whether there's enough space on the target filesystem to save the file. + * Put a bit of margin (in case creating the file grows the system by a few blocks). + */ + if (stat.getBlockSize() * ((long) stat.getAvailableBlocks() - 4) < contentLength) { + if (Config.LOGD) { + Log.d(Constants.TAG, "download aborted - not enough free space"); + } + return new DownloadFileInfo(null, null, Downloads.STATUS_FILE_ERROR); + } + + } + + boolean recoveryDir = Constants.RECOVERY_DIRECTORY.equalsIgnoreCase(filename + extension); + + filename = base.getPath() + File.separator + filename; + + /* + * Generate a unique filename, create the file, return it. + */ + if (Constants.LOGVV) { + Log.v(Constants.TAG, "target file: " + filename + extension); + } + + String fullFilename = chooseUniqueFilename( + destination, filename, extension, recoveryDir); + if (fullFilename != null) { + return new DownloadFileInfo(fullFilename, new FileOutputStream(fullFilename), 0); + } else { + return new DownloadFileInfo(null, null, Downloads.STATUS_FILE_ERROR); + } + } + + private static String chooseFilename(String url, String hint, String contentDisposition, + String contentLocation, int destination) { + String filename = null; + + // First, try to use the hint from the application, if there's one + if (filename == null && hint != null && !hint.endsWith("/")) { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "getting filename from hint"); + } + int index = hint.lastIndexOf('/') + 1; + if (index > 0) { + filename = hint.substring(index); + } else { + filename = hint; + } + } + + // If we couldn't do anything with the hint, move toward the content disposition + if (filename == null && contentDisposition != null) { + filename = parseContentDisposition(contentDisposition); + if (filename != null) { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "getting filename from content-disposition"); + } + int index = filename.lastIndexOf('/') + 1; + if (index > 0) { + filename = filename.substring(index); + } + } + } + + // If we still have nothing at this point, try the content location + if (filename == null && contentLocation != null) { + String decodedContentLocation = Uri.decode(contentLocation); + if (decodedContentLocation != null + && !decodedContentLocation.endsWith("/") + && decodedContentLocation.indexOf('?') < 0) { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "getting filename from content-location"); + } + int index = decodedContentLocation.lastIndexOf('/') + 1; + if (index > 0) { + filename = decodedContentLocation.substring(index); + } else { + filename = decodedContentLocation; + } + } + } + + // If all the other http-related approaches failed, use the plain uri + if (filename == null) { + String decodedUrl = Uri.decode(url); + if (decodedUrl != null + && !decodedUrl.endsWith("/") && decodedUrl.indexOf('?') < 0) { + int index = decodedUrl.lastIndexOf('/') + 1; + if (index > 0) { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "getting filename from uri"); + } + filename = decodedUrl.substring(index); + } + } + } + + // Finally, if couldn't get filename from URI, get a generic filename + if (filename == null) { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "using default filename"); + } + filename = Constants.DEFAULT_DL_FILENAME; + } + + filename = filename.replaceAll("[^a-zA-Z0-9\\.\\-_]+", "_"); + + + return filename; + } + + private static String chooseExtensionFromMimeType(String mimeType, boolean useDefaults) { + String extension = null; + if (mimeType != null) { + extension = MimeTypeMap.getSingleton().getExtensionFromMimeType(mimeType); + if (extension != null) { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "adding extension from type"); + } + extension = "." + extension; + } else { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "couldn't find extension for " + mimeType); + } + } + } + if (extension == null) { + if (mimeType != null && mimeType.toLowerCase().startsWith("text/")) { + if (mimeType.equalsIgnoreCase("text/html")) { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "adding default html extension"); + } + extension = Constants.DEFAULT_DL_HTML_EXTENSION; + } else if (useDefaults) { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "adding default text extension"); + } + extension = Constants.DEFAULT_DL_TEXT_EXTENSION; + } + } else if (useDefaults) { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "adding default binary extension"); + } + extension = Constants.DEFAULT_DL_BINARY_EXTENSION; + } + } + return extension; + } + + private static String chooseExtensionFromFilename(String mimeType, int destination, + String filename, int dotIndex) { + String extension = null; + if (mimeType != null) { + // Compare the last segment of the extension against the mime type. + // If there's a mismatch, discard the entire extension. + int lastDotIndex = filename.lastIndexOf('.'); + String typeFromExt = MimeTypeMap.getSingleton().getMimeTypeFromExtension( + filename.substring(lastDotIndex + 1)); + if (typeFromExt == null || !typeFromExt.equalsIgnoreCase(mimeType)) { + extension = chooseExtensionFromMimeType(mimeType, false); + if (extension != null) { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "substituting extension from type"); + } + } else { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "couldn't find extension for " + mimeType); + } + } + } + } + if (extension == null) { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "keeping extension"); + } + extension = filename.substring(dotIndex); + } + return extension; + } + + private static String chooseUniqueFilename(int destination, String filename, + String extension, boolean recoveryDir) { + String fullFilename = filename + extension; + if (!new File(fullFilename).exists() + && (!recoveryDir || + (destination != Downloads.DESTINATION_CACHE_PARTITION && + destination != Downloads.DESTINATION_CACHE_PARTITION_PURGEABLE && + destination != Downloads.DESTINATION_CACHE_PARTITION_NOROAMING))) { + return fullFilename; + } + filename = filename + Constants.FILENAME_SEQUENCE_SEPARATOR; + /* + * This number is used to generate partially randomized filenames to avoid + * collisions. + * It starts at 1. + * The next 9 iterations increment it by 1 at a time (up to 10). + * The next 9 iterations increment it by 1 to 10 (random) at a time. + * The next 9 iterations increment it by 1 to 100 (random) at a time. + * ... Up to the point where it increases by 100000000 at a time. + * (the maximum value that can be reached is 1000000000) + * As soon as a number is reached that generates a filename that doesn't exist, + * that filename is used. + * If the filename coming in is [base].[ext], the generated filenames are + * [base]-[sequence].[ext]. + */ + int sequence = 1; + for (int magnitude = 1; magnitude < 1000000000; magnitude *= 10) { + for (int iteration = 0; iteration < 9; ++iteration) { + fullFilename = filename + sequence + extension; + if (!new File(fullFilename).exists()) { + return fullFilename; + } + if (Constants.LOGVV) { + Log.v(Constants.TAG, "file with sequence number " + sequence + " exists"); + } + sequence += rnd.nextInt(magnitude) + 1; + } + } + return null; + } + + /** + * Deletes purgeable files from the cache partition. This also deletes + * the matching database entries. Files are deleted in LRU order until + * the total byte size is greater than targetBytes. + */ + public static final boolean discardPurgeableFiles(Context context, long targetBytes) { + Cursor cursor = context.getContentResolver().query( + Downloads.CONTENT_URI, + null, + "( " + + Downloads.STATUS + " = " + Downloads.STATUS_SUCCESS + " AND " + + Downloads.DESTINATION + " = " + Downloads.DESTINATION_CACHE_PARTITION_PURGEABLE + + " )", + null, + Downloads.LAST_MODIFICATION); + if (cursor == null) { + return false; + } + long totalFreed = 0; + try { + cursor.moveToFirst(); + while (!cursor.isAfterLast() && totalFreed < targetBytes) { + File file = new File(cursor.getString(cursor.getColumnIndex(Downloads._DATA))); + if (Constants.LOGVV) { + Log.v(Constants.TAG, "purging " + file.getAbsolutePath() + " for " + + file.length() + " bytes"); + } + totalFreed += file.length(); + file.delete(); + long id = cursor.getLong(cursor.getColumnIndex(Downloads._ID)); + context.getContentResolver().delete( + ContentUris.withAppendedId(Downloads.CONTENT_URI, id), null, null); + cursor.moveToNext(); + } + } finally { + cursor.close(); + } + if (Constants.LOGV) { + if (totalFreed > 0) { + Log.v(Constants.TAG, "Purged files, freed " + totalFreed + " for " + + targetBytes + " requested"); + } + } + return totalFreed > 0; + } + + /** + * Returns whether the network is available + */ + public static boolean isNetworkAvailable(Context context) { + ConnectivityManager connectivity = + (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE); + if (connectivity == null) { + Log.w(Constants.TAG, "couldn't get connectivity manager"); + } else { + NetworkInfo[] info = connectivity.getAllNetworkInfo(); + if (info != null) { + for (int i = 0; i < info.length; i++) { + if (info[i].getState() == NetworkInfo.State.CONNECTED) { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "network is available"); + } + return true; + } + } + } + } + if (Constants.LOGVV) { + Log.v(Constants.TAG, "network is not available"); + } + return false; + } + + /** + * Returns whether the network is roaming + */ + public static boolean isNetworkRoaming(Context context) { + ConnectivityManager connectivity = + (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE); + if (connectivity == null) { + Log.w(Constants.TAG, "couldn't get connectivity manager"); + } else { + NetworkInfo info = connectivity.getActiveNetworkInfo(); + if (info != null && info.getType() == ConnectivityManager.TYPE_MOBILE) { + if (TelephonyManager.getDefault().isNetworkRoaming()) { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "network is roaming"); + } + return true; + } else { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "network is not roaming"); + } + } + } else { + if (Constants.LOGVV) { + Log.v(Constants.TAG, "not using mobile network"); + } + } + } + return false; + } + + /** + * Checks whether the filename looks legitimate + */ + public static boolean isFilenameValid(String filename) { + File dir = new File(filename).getParentFile(); + return dir.equals(Environment.getDownloadCacheDirectory()) + || dir.equals(new File(Environment.getExternalStorageDirectory() + + Constants.DEFAULT_DL_SUBDIR)); + } + + /** + * Checks whether this looks like a legitimate selection parameter + */ + public static void validateSelection(String selection, Set<String> allowedColumns) { + try { + if (selection == null) { + return; + } + Lexer lexer = new Lexer(selection, allowedColumns); + parseExpression(lexer); + if (lexer.currentToken() != Lexer.TOKEN_END) { + throw new IllegalArgumentException("syntax error"); + } + } catch (RuntimeException ex) { + if (Constants.LOGV) { + Log.d(Constants.TAG, "invalid selection [" + selection + "] triggered " + ex); + } else if (Config.LOGD) { + Log.d(Constants.TAG, "invalid selection triggered " + ex); + } + throw ex; + } + + } + + // expression <- ( expression ) | statement [AND_OR ( expression ) | statement] * + // | statement [AND_OR expression]* + private static void parseExpression(Lexer lexer) { + for (;;) { + // ( expression ) + if (lexer.currentToken() == Lexer.TOKEN_OPEN_PAREN) { + lexer.advance(); + parseExpression(lexer); + if (lexer.currentToken() != Lexer.TOKEN_CLOSE_PAREN) { + throw new IllegalArgumentException("syntax error, unmatched parenthese"); + } + lexer.advance(); + } else { + // statement + parseStatement(lexer); + } + if (lexer.currentToken() != Lexer.TOKEN_AND_OR) { + break; + } + lexer.advance(); + } + } + + // statement <- COLUMN COMPARE VALUE + // | COLUMN IS NULL + private static void parseStatement(Lexer lexer) { + // both possibilities start with COLUMN + if (lexer.currentToken() != Lexer.TOKEN_COLUMN) { + throw new IllegalArgumentException("syntax error, expected column name"); + } + lexer.advance(); + + // statement <- COLUMN COMPARE VALUE + if (lexer.currentToken() == Lexer.TOKEN_COMPARE) { + lexer.advance(); + if (lexer.currentToken() != Lexer.TOKEN_VALUE) { + throw new IllegalArgumentException("syntax error, expected quoted string"); + } + lexer.advance(); + return; + } + + // statement <- COLUMN IS NULL + if (lexer.currentToken() == Lexer.TOKEN_IS) { + lexer.advance(); + if (lexer.currentToken() != Lexer.TOKEN_NULL) { + throw new IllegalArgumentException("syntax error, expected NULL"); + } + lexer.advance(); + return; + } + + // didn't get anything good after COLUMN + throw new IllegalArgumentException("syntax error after column name"); + } + + /** + * A simple lexer that recognizes the words of our restricted subset of SQL where clauses + */ + private static class Lexer { + public static final int TOKEN_START = 0; + public static final int TOKEN_OPEN_PAREN = 1; + public static final int TOKEN_CLOSE_PAREN = 2; + public static final int TOKEN_AND_OR = 3; + public static final int TOKEN_COLUMN = 4; + public static final int TOKEN_COMPARE = 5; + public static final int TOKEN_VALUE = 6; + public static final int TOKEN_IS = 7; + public static final int TOKEN_NULL = 8; + public static final int TOKEN_END = 9; + + private final String mSelection; + private final Set<String> mAllowedColumns; + private int mOffset = 0; + private int mCurrentToken = TOKEN_START; + private final char[] mChars; + + public Lexer(String selection, Set<String> allowedColumns) { + mSelection = selection; + mAllowedColumns = allowedColumns; + mChars = new char[mSelection.length()]; + mSelection.getChars(0, mChars.length, mChars, 0); + advance(); + } + + public int currentToken() { + return mCurrentToken; + } + + public void advance() { + char[] chars = mChars; + + // consume whitespace + while (mOffset < chars.length && chars[mOffset] == ' ') { + ++mOffset; + } + + // end of input + if (mOffset == chars.length) { + mCurrentToken = TOKEN_END; + return; + } + + // "(" + if (chars[mOffset] == '(') { + ++mOffset; + mCurrentToken = TOKEN_OPEN_PAREN; + return; + } + + // ")" + if (chars[mOffset] == ')') { + ++mOffset; + mCurrentToken = TOKEN_CLOSE_PAREN; + return; + } + + // "?" + if (chars[mOffset] == '?') { + ++mOffset; + mCurrentToken = TOKEN_VALUE; + return; + } + + // "=" and "==" + if (chars[mOffset] == '=') { + ++mOffset; + mCurrentToken = TOKEN_COMPARE; + if (mOffset < chars.length && chars[mOffset] == '=') { + ++mOffset; + } + return; + } + + // ">" and ">=" + if (chars[mOffset] == '>') { + ++mOffset; + mCurrentToken = TOKEN_COMPARE; + if (mOffset < chars.length && chars[mOffset] == '=') { + ++mOffset; + } + return; + } + + // "<", "<=" and "<>" + if (chars[mOffset] == '<') { + ++mOffset; + mCurrentToken = TOKEN_COMPARE; + if (mOffset < chars.length && (chars[mOffset] == '=' || chars[mOffset] == '>')) { + ++mOffset; + } + return; + } + + // "!=" + if (chars[mOffset] == '!') { + ++mOffset; + mCurrentToken = TOKEN_COMPARE; + if (mOffset < chars.length && chars[mOffset] == '=') { + ++mOffset; + return; + } + throw new IllegalArgumentException("Unexpected character after !"); + } + + // columns and keywords + // first look for anything that looks like an identifier or a keyword + // and then recognize the individual words. + // no attempt is made at discarding sequences of underscores with no alphanumeric + // characters, even though it's not clear that they'd be legal column names. + if (isIdentifierStart(chars[mOffset])) { + int startOffset = mOffset; + ++mOffset; + while (mOffset < chars.length && isIdentifierChar(chars[mOffset])) { + ++mOffset; + } + String word = mSelection.substring(startOffset, mOffset); + if (mOffset - startOffset <= 4) { + if (word.equals("IS")) { + mCurrentToken = TOKEN_IS; + return; + } + if (word.equals("OR") || word.equals("AND")) { + mCurrentToken = TOKEN_AND_OR; + return; + } + if (word.equals("NULL")) { + mCurrentToken = TOKEN_NULL; + return; + } + } + if (mAllowedColumns.contains(word)) { + mCurrentToken = TOKEN_COLUMN; + return; + } + throw new IllegalArgumentException("unrecognized column or keyword"); + } + + // quoted strings + if (chars[mOffset] == '\'') { + ++mOffset; + while(mOffset < chars.length) { + if (chars[mOffset] == '\'') { + if (mOffset + 1 < chars.length && chars[mOffset + 1] == '\'') { + ++mOffset; + } else { + break; + } + } + ++mOffset; + } + if (mOffset == chars.length) { + throw new IllegalArgumentException("unterminated string"); + } + ++mOffset; + mCurrentToken = TOKEN_VALUE; + return; + } + + // anything we don't recognize + throw new IllegalArgumentException("illegal character"); + } + + private static final boolean isIdentifierStart(char c) { + return c == '_' || + (c >= 'A' && c <= 'Z') || + (c >= 'a' && c <= 'z'); + } + + private static final boolean isIdentifierChar(char c) { + return c == '_' || + (c >= 'A' && c <= 'Z') || + (c >= 'a' && c <= 'z') || + (c >= '0' && c <= '9'); + } + } +} |