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Fastjson is a JSON processor (JSON parser + JSON generator) written in Java
package com.alibaba.fastjson.util;
import java.util.Arrays;
/**
* @author Mikael Grev Date: 2004-aug-02 Time: 11:31:11
* @version 2.2
* @deprecated internal api, don't use.
*/
public class Base64 {
public static final char[] CA = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();
public static final int[] IA = new int[256];
static {
Arrays.fill(IA, -1);
for (int i = 0, j = CA.length; i < j; i++) {
IA[CA[i]] = i;
}
IA['='] = 0;
}
/**
* Decodes a BASE64 encoded char array that is known to be resonably well formatted. The method is about twice as
* fast as #decode(char[]). The preconditions are:
* + The array must have a line length of 76 chars OR no line separators at all (one line).
* + Line separator must be "\r\n", as specified in RFC 2045 + The array must not contain illegal characters within
* the encoded string
* + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.
*
* @param chars The source array. Length 0 will return an empty array. null will throw an exception.
* @return The decoded array of bytes. May be of length 0.
*/
public static byte[] decodeFast(char[] chars, int offset, int charsLen) {
// Check special case
if (charsLen == 0) {
return new byte[0];
}
int sIx = offset, eIx = offset + charsLen - 1; // Start and end index after trimming.
// Trim illegal chars from start
while (sIx < eIx && IA[chars[sIx]] < 0) {
sIx++;
}
// Trim illegal chars from end
while (eIx > 0 && IA[chars[eIx]] < 0) {
eIx--;
}
// get the padding count (=) (0, 1 or 2)
int pad = chars[eIx] == '=' ? (chars[eIx - 1] == '=' ? 2 : 1) : 0; // Count '=' at end.
int cCnt = eIx - sIx + 1; // Content count including possible separators
int sepCnt = charsLen > 76 ? (chars[76] == '\r' ? cCnt / 78 : 0) << 1 : 0;
int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes
byte[] bytes = new byte[len]; // Preallocate byte[] of exact length
// Decode all but the last 0 - 2 bytes.
int d = 0;
for (int cc = 0, eLen = (len / 3) * 3; d < eLen; ) {
// Assemble three bytes into an int from four "valid" characters.
int i = IA[chars[sIx]] << 18
| IA[chars[sIx + 1]] << 12
| IA[chars[sIx + 2]] << 6
| IA[chars[sIx + 3]];
sIx += 4;
// Add the bytes
bytes[d] = (byte) (i >> 16);
bytes[d + 1] = (byte) (i >> 8);
bytes[d + 2] = (byte) i;
d += 3;
// If line separator, jump over it.
if (sepCnt > 0 && ++cc == 19) {
sIx += 2;
cc = 0;
}
}
if (d < len) {
// Decode last 1-3 bytes (incl '=') into 1-3 bytes
int i = 0;
for (int j = 0; sIx <= eIx - pad; j++) {
i |= IA[chars[sIx++]] << (18 - j * 6);
}
for (int r = 16; d < len; r -= 8) {
bytes[d++] = (byte) (i >> r);
}
}
return bytes;
}
public static byte[] decodeFast(String chars, int offset, int charsLen) {
// Check special case
if (charsLen == 0) {
return new byte[0];
}
int sIx = offset, eIx = offset + charsLen - 1; // Start and end index after trimming.
// Trim illegal chars from start
while (sIx < eIx && IA[chars.charAt(sIx)] < 0) {
sIx++;
}
// Trim illegal chars from end
while (eIx > 0 && IA[chars.charAt(eIx)] < 0) {
eIx--;
}
// get the padding count (=) (0, 1 or 2)
int pad = chars.charAt(eIx) == '=' ? (chars.charAt(eIx - 1) == '=' ? 2 : 1) : 0; // Count '=' at end.
int cCnt = eIx - sIx + 1; // Content count including possible separators
int sepCnt = charsLen > 76 ? (chars.charAt(76) == '\r' ? cCnt / 78 : 0) << 1 : 0;
int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes
byte[] bytes = new byte[len]; // Preallocate byte[] of exact length
// Decode all but the last 0 - 2 bytes.
int d = 0;
for (int cc = 0, eLen = (len / 3) * 3; d < eLen; ) {
// Assemble three bytes into an int from four "valid" characters.
int i = IA[chars.charAt(sIx)] << 18
| IA[chars.charAt(sIx + 1)] << 12
| IA[chars.charAt(sIx + 2)] << 6
| IA[chars.charAt(sIx + 3)];
sIx += 4;
// Add the bytes
bytes[d] = (byte) (i >> 16);
bytes[d + 1] = (byte) (i >> 8);
bytes[d + 2] = (byte) i;
d += 3;
// If line separator, jump over it.
if (sepCnt > 0 && ++cc == 19) {
sIx += 2;
cc = 0;
}
}
if (d < len) {
// Decode last 1-3 bytes (incl '=') into 1-3 bytes
int i = 0;
for (int j = 0; sIx <= eIx - pad; j++) {
i |= IA[chars.charAt(sIx++)] << (18 - j * 6);
}
for (int r = 16; d < len; r -= 8) {
bytes[d++] = (byte) (i >> r);
}
}
return bytes;
}
/**
* Decodes a BASE64 encoded string that is known to be resonably well formatted. The method is about twice as fast
* as decode(String). The preconditions are:
* + The array must have a line length of 76 chars OR no line separators at all (one line).
* + Line separator must be "\r\n", as specified in RFC 2045 + The array must not contain illegal characters within
* the encoded string
* + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.
*
* @param s The source string. Length 0 will return an empty array. null will throw an exception.
* @return The decoded array of bytes. May be of length 0.
*/
public static byte[] decodeFast(String s) {
// Check special case
int sLen = s.length();
if (sLen == 0) {
return new byte[0];
}
int sIx = 0, eIx = sLen - 1; // Start and end index after trimming.
// Trim illegal chars from start
while (sIx < eIx && IA[s.charAt(sIx) & 0xff] < 0) {
sIx++;
}
// Trim illegal chars from end
while (eIx > 0 && IA[s.charAt(eIx) & 0xff] < 0) {
eIx--;
}
// get the padding count (=) (0, 1 or 2)
int pad = s.charAt(eIx) == '=' ? (s.charAt(eIx - 1) == '=' ? 2 : 1) : 0; // Count '=' at end.
int cCnt = eIx - sIx + 1; // Content count including possible separators
int sepCnt = sLen > 76 ? (s.charAt(76) == '\r' ? cCnt / 78 : 0) << 1 : 0;
int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes
byte[] dArr = new byte[len]; // Preallocate byte[] of exact length
// Decode all but the last 0 - 2 bytes.
int d = 0;
for (int cc = 0, eLen = (len / 3) * 3; d < eLen; ) {
// Assemble three bytes into an int from four "valid" characters.
int i = IA[s.charAt(sIx)] << 18
| IA[s.charAt(sIx + 1)] << 12
| IA[s.charAt(sIx + 2)] << 6
| IA[s.charAt(sIx + 3)];
sIx += 4;
// Add the bytes
dArr[d] = (byte) (i >> 16);
dArr[d + 1] = (byte) (i >> 8);
dArr[d + 2] = (byte) i;
d += 3;
// If line separator, jump over it.
if (sepCnt > 0 && ++cc == 19) {
sIx += 2;
cc = 0;
}
}
if (d < len) {
// Decode last 1-3 bytes (incl '=') into 1-3 bytes
int i = 0;
for (int j = 0; sIx <= eIx - pad; j++) {
i |= IA[s.charAt(sIx++)] << (18 - j * 6);
}
for (int r = 16; d < len; r -= 8) {
dArr[d++] = (byte) (i >> r);
}
}
return dArr;
}
}