Add parts of zxing library to generate qr codes

1 files changed, 192 insertions, 0 deletions

diff --git a/OpenPGP-Keychain/src/com/google/zxing/common/StringUtils.java b/OpenPGP-Keychain/src/com/google/zxing/common/StringUtils.java
new file mode 100644
index 000000000..97999f997
--- /dev/null
+++ b/OpenPGP-Keychain/src/com/google/zxing/common/StringUtils.java
@@ -0,0 +1,192 @@
+/*
+ * Copyright (C) 2010 ZXing authors
+ *
+ * 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.google.zxing.common;
+
+import java.util.Hashtable;
+
+import com.google.zxing.DecodeHintType;
+
+/**
+ * Common string-related functions.
+ *
+ * @author Sean Owen
+ */
+public final class StringUtils {
+
+  private static final String PLATFORM_DEFAULT_ENCODING =
+      System.getProperty("file.encoding");
+  public static final String SHIFT_JIS = "SJIS";
+  public static final String GB2312 = "GB2312";
+  private static final String EUC_JP = "EUC_JP";
+  private static final String UTF8 = "UTF8";
+  private static final String ISO88591 = "ISO8859_1";
+  private static final boolean ASSUME_SHIFT_JIS =
+      SHIFT_JIS.equalsIgnoreCase(PLATFORM_DEFAULT_ENCODING) ||
+      EUC_JP.equalsIgnoreCase(PLATFORM_DEFAULT_ENCODING);
+
+  private StringUtils() {}
+
+  /**
+   * @param bytes bytes encoding a string, whose encoding should be guessed
+   * @param hints decode hints if applicable
+   * @return name of guessed encoding; at the moment will only guess one of:
+   *  {@link #SHIFT_JIS}, {@link #UTF8}, {@link #ISO88591}, or the platform
+   *  default encoding if none of these can possibly be correct
+   */
+  public static String guessEncoding(byte[] bytes, Hashtable hints) {
+    if (hints != null) {
+      String characterSet = (String) hints.get(DecodeHintType.CHARACTER_SET);
+      if (characterSet != null) {
+        return characterSet;
+      }
+    }
+    // Does it start with the UTF-8 byte order mark? then guess it's UTF-8
+    if (bytes.length > 3 &&
+        bytes[0] == (byte) 0xEF &&
+        bytes[1] == (byte) 0xBB &&
+        bytes[2] == (byte) 0xBF) {
+      return UTF8;
+    }
+    // For now, merely tries to distinguish ISO-8859-1, UTF-8 and Shift_JIS,
+    // which should be by far the most common encodings. ISO-8859-1
+    // should not have bytes in the 0x80 - 0x9F range, while Shift_JIS
+    // uses this as a first byte of a two-byte character. If we see this
+    // followed by a valid second byte in Shift_JIS, assume it is Shift_JIS.
+    // If we see something else in that second byte, we'll make the risky guess
+    // that it's UTF-8.
+    int length = bytes.length;
+    boolean canBeISO88591 = true;
+    boolean canBeShiftJIS = true;
+    boolean canBeUTF8 = true;
+    int utf8BytesLeft = 0;
+    int maybeDoubleByteCount = 0;
+    int maybeSingleByteKatakanaCount = 0;
+    boolean sawLatin1Supplement = false;
+    boolean sawUTF8Start = false;
+    boolean lastWasPossibleDoubleByteStart = false;
+
+    for (int i = 0;
+         i < length && (canBeISO88591 || canBeShiftJIS || canBeUTF8);
+         i++) {
+
+      int value = bytes[i] & 0xFF;
+
+      // UTF-8 stuff
+      if (value >= 0x80 && value <= 0xBF) {
+        if (utf8BytesLeft > 0) {
+          utf8BytesLeft--;
+        }
+      } else {
+        if (utf8BytesLeft > 0) {
+          canBeUTF8 = false;
+        }
+        if (value >= 0xC0 && value <= 0xFD) {
+          sawUTF8Start = true;
+          int valueCopy = value;
+          while ((valueCopy & 0x40) != 0) {
+            utf8BytesLeft++;
+            valueCopy <<= 1;
+          }
+        }
+      }
+
+      // ISO-8859-1 stuff
+
+      if ((value == 0xC2 || value == 0xC3) && i < length - 1) {
+        // This is really a poor hack. The slightly more exotic characters people might want to put in
+        // a QR Code, by which I mean the Latin-1 supplement characters (e.g. u-umlaut) have encodings
+        // that start with 0xC2 followed by [0xA0,0xBF], or start with 0xC3 followed by [0x80,0xBF].
+        int nextValue = bytes[i + 1] & 0xFF;
+        if (nextValue <= 0xBF &&
+            ((value == 0xC2 && nextValue >= 0xA0) || (value == 0xC3 && nextValue >= 0x80))) {
+          sawLatin1Supplement = true;
+        }
+      }
+      if (value >= 0x7F && value <= 0x9F) {
+        canBeISO88591 = false;
+      }
+
+      // Shift_JIS stuff
+
+      if (value >= 0xA1 && value <= 0xDF) {
+        // count the number of characters that might be a Shift_JIS single-byte Katakana character
+        if (!lastWasPossibleDoubleByteStart) {
+          maybeSingleByteKatakanaCount++;
+        }
+      }
+      if (!lastWasPossibleDoubleByteStart &&
+          ((value >= 0xF0 && value <= 0xFF) || value == 0x80 || value == 0xA0)) {
+        canBeShiftJIS = false;
+      }
+      if ((value >= 0x81 && value <= 0x9F) || (value >= 0xE0 && value <= 0xEF)) {
+        // These start double-byte characters in Shift_JIS. Let's see if it's followed by a valid
+        // second byte.
+        if (lastWasPossibleDoubleByteStart) {
+          // If we just checked this and the last byte for being a valid double-byte
+          // char, don't check starting on this byte. If this and the last byte
+          // formed a valid pair, then this shouldn't be checked to see if it starts
+          // a double byte pair of course.
+          lastWasPossibleDoubleByteStart = false;
+        } else {
+          // ... otherwise do check to see if this plus the next byte form a valid
+          // double byte pair encoding a character.
+          lastWasPossibleDoubleByteStart = true;
+          if (i >= bytes.length - 1) {
+            canBeShiftJIS = false;
+          } else {
+            int nextValue = bytes[i + 1] & 0xFF;
+            if (nextValue < 0x40 || nextValue > 0xFC) {
+              canBeShiftJIS = false;
+            } else {
+              maybeDoubleByteCount++;
+            }
+            // There is some conflicting information out there about which bytes can follow which in
+            // double-byte Shift_JIS characters. The rule above seems to be the one that matches practice.
+          }
+        }
+      } else {
+        lastWasPossibleDoubleByteStart = false;
+      }
+    }
+    if (utf8BytesLeft > 0) {
+      canBeUTF8 = false;
+    }
+
+    // Easy -- if assuming Shift_JIS and no evidence it can't be, done
+    if (canBeShiftJIS && ASSUME_SHIFT_JIS) {
+      return SHIFT_JIS;
+    }
+    if (canBeUTF8 && sawUTF8Start) {
+      return UTF8;
+    }
+    // Distinguishing Shift_JIS and ISO-8859-1 can be a little tough. The crude heuristic is:
+    // - If we saw
+    //   - at least 3 bytes that starts a double-byte value (bytes that are rare in ISO-8859-1), or
+    //   - over 5% of bytes could be single-byte Katakana (also rare in ISO-8859-1),
+    // - and, saw no sequences that are invalid in Shift_JIS, then we conclude Shift_JIS
+    if (canBeShiftJIS && (maybeDoubleByteCount >= 3 || 20 * maybeSingleByteKatakanaCount > length)) {
+      return SHIFT_JIS;
+    }
+    // Otherwise, we default to ISO-8859-1 unless we know it can't be
+    if (!sawLatin1Supplement && canBeISO88591) {
+      return ISO88591;
+    }
+    // Otherwise, we take a wild guess with platform encoding
+    return PLATFORM_DEFAULT_ENCODING;
+  }
+
+}