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t-io is a aio framework for java
package com.litongjava.tio.utils.encoder;
public class Base64Utils {
/**
* This array is a lookup table that translates 6-bit positive integer
* index values into their "Base64 Alphabet" equivalents as specified in
* Table 1 of RFC 2045.
*/
private static final char intToBase64[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',
'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8',
'9', '+', '/' };
/**
* This array is a lookup table that translates 6-bit positive integer
* index values into their "Alternate Base64 Alphabet" equivalents. This is
* NOT the real Base64 Alphabet as per in Table 1 of RFC 2045. This
* alternate alphabet does not use the capital letters. It is designed for
* use in environments where "case folding" occurs.
*/
private static final char intToAltBase64[] = { '!', '"', '#', '$', '%', '&', '\'', '(', ')', ',', '-', '.', ':', ';',
'<', '>', '@', '[', ']', '^', '`', '_', '{', '|', '}', '~', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k',
'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
'8', '9', '+', '?' };
/**
* This array is a lookup table that translates unicode characters drawn
* from the "Base64 Alphabet" (as specified in Table 1 of RFC 2045) into
* their 6-bit positive integer equivalents. Characters that are not in the
* Base64 alphabet but fall within the bounds of the array are translated
* to -1.
*/
private static final byte base64ToInt[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1,
-1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33,
34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 };
/**
* This array is the analogue of base64ToInt, but for the nonstandard
* variant that avoids the use of uppercase alphabetic characters.
*/
private static final byte altBase64ToInt[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, -1, 62, 9, 10, 11, -1, 52,
53, 54, 55, 56, 57, 58, 59, 60, 61, 12, 13, 14, -1, 15, 63, 16, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 17, -1, 18, 19, 21, 20, 26, 27, 28, 29, 30, 31, 32, 33,
34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 22, 23, 24, 25 };
/**
* Translates the specified "alternate representation" Base64 string into a
* byte array.
*/
public static byte[] altDecodeToBytes(String s) {
return decodeToBytes(s, true);
}
/**
* Translates the specified Base64 string (as per Preferences.get(byte[]))
* into a byte array.
*/
public static byte[] decodeToBytes(String s) {
return decodeToBytes(s, false);
}
private static byte[] decodeToBytes(String s, boolean alternate) {
byte[] alphaToInt = alternate ? altBase64ToInt : base64ToInt;
int sLen = s.length();
int numGroups = sLen / 4;
if (4 * numGroups != sLen) {
throw new IllegalArgumentException("String length must be a multiple of four. len=" + sLen);
}
int missingBytesInLastGroup = 0;
int numFullGroups = numGroups;
if (sLen != 0) {
if (s.charAt(sLen - 1) == '=') {
missingBytesInLastGroup++;
numFullGroups--;
}
if (s.charAt(sLen - 2) == '=') {
missingBytesInLastGroup++;
}
}
byte[] result = new byte[3 * numGroups - missingBytesInLastGroup];
// Translate all full groups from base64 to byte array elements
int inCursor = 0, outCursor = 0;
for (int i = 0; i < numFullGroups; i++) {
int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt);
result[outCursor++] = (byte) (ch0 << 2 | ch1 >> 4);
result[outCursor++] = (byte) (ch1 << 4 | ch2 >> 2);
result[outCursor++] = (byte) (ch2 << 6 | ch3);
}
// Translate partial group, if present
if (missingBytesInLastGroup != 0) {
int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
result[outCursor++] = (byte) (ch0 << 2 | ch1 >> 4);
if (missingBytesInLastGroup == 1) {
int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
result[outCursor++] = (byte) (ch1 << 4 | ch2 >> 2);
}
}
// assert inCursor == s.length()-missingBytesInLastGroup;
// assert outCursor == result.length;
return result;
}
/**
* Translates the specified character, which is assumed to be in the
* "Base 64 Alphabet" into its equivalent 6-bit positive integer.
*
* @throw IllegalArgumentException or ArrayOutOfBoundsException if c is not
* in the Base64 Alphabet.
*/
private static int base64toInt(char c, byte[] alphaToInt) {
int result = alphaToInt[c];
if (result < 0) {
throw new IllegalArgumentException("Illegal character " + c);
}
return result;
}
/**
* Translates the specified byte array into an "alternate representation"
* Base64 string. This non-standard variant uses an alphabet that does not
* contain the uppercase alphabetic characters, which makes it suitable for
* use in situations where case-folding occurs.
*/
public static String byteArrayToAltBase64(byte[] a) {
return encodeToString(a, true);
}
/**
* Translates the specified byte array into a Base64 string as per
* Preferences.put(byte[]).
*/
public static String encodeToString(byte[] a) {
return encodeToString(a, false);
}
private static String encodeToString(byte[] a, boolean alternate) {
int aLen = a.length;
int numFullGroups = aLen / 3;
int numBytesInPartialGroup = aLen - 3 * numFullGroups;
int resultLen = 4 * ((aLen + 2) / 3);
StringBuilder result = new StringBuilder(resultLen);
char[] intToAlpha = alternate ? intToAltBase64 : intToBase64;
// Translate all full groups from byte array elements to Base64
int inCursor = 0;
for (int i = 0; i < numFullGroups; i++) {
int byte0 = a[inCursor++] & 0xff;
int byte1 = a[inCursor++] & 0xff;
int byte2 = a[inCursor++] & 0xff;
result.append(intToAlpha[byte0 >> 2]);
result.append(intToAlpha[byte0 << 4 & 0x3f | byte1 >> 4]);
result.append(intToAlpha[byte1 << 2 & 0x3f | byte2 >> 6]);
result.append(intToAlpha[byte2 & 0x3f]);
}
// Translate partial group if present
if (numBytesInPartialGroup != 0) {
int byte0 = a[inCursor++] & 0xff;
result.append(intToAlpha[byte0 >> 2]);
if (numBytesInPartialGroup == 1) {
result.append(intToAlpha[byte0 << 4 & 0x3f]);
result.append("==");
} else {
// assert numBytesInPartialGroup == 2;
int byte1 = a[inCursor++] & 0xff;
result.append(intToAlpha[byte0 << 4 & 0x3f | byte1 >> 4]);
result.append(intToAlpha[byte1 << 2 & 0x3f]);
result.append('=');
}
}
// assert inCursor == a.length;
// assert result.length() == resultLen;
return result.toString();
}
/**
* Encode the given schoolId to Base64 string.
*
* @param schoolId The school ID to encode
* @return Encoded Base64 string
*/
public static String encodeToString(String str) {
return encodeToString(str.getBytes());
}
/**
* Decode the given Base64 string to original schoolId.
*
* @param base64SchoolId The Base64 encoded string
* @return The original school ID
*/
public static String decodeToString(String encoded) {
return new String(decodeToBytes(encoded));
}
/**
*
* @param imgageBase64Str "data:image/jpeg;base64,/9j/4QAYRXhpZgAASUkqAAgAAAAAAAAAAAAAAP/"
* @return
*/
public static ImageVo decodeImage(String imgageBase64Str) {
// 提取 MIME 类型和图片数据部分
String[] parts = imgageBase64Str.split(",");
String mimeType = parts[0].split(":")[1].split(";")[0];
return new ImageVo(mimeType, decodeToBytes(parts[1]));
}
}