J2ME 下的 Base64的编码与解码

基于J2ME的Base64的编码与解码的实现,原码如下:

1. importjava.io.*;
3. publicclassBase64{
4. privatestaticchar[]base64EncodeChars=newchar[]{
5. 'A','B','C','D','E','F','G','H',
6. 'I','J','K','L','M','N','O','P',
7. 'Q','R','S','T','U','V','W','X',
8. 'Y','Z','a','b','c','d','e','f',
9. 'g','h','i','j','k','l','m','n',
10. 'o','p','q','r','s','t','u','v',
11. 'w','x','y','z','0','1','2','3',
12. '4','5','6','7','8','9','+','/'};
14. privatestaticbyte[]base64DecodeChars=newbyte[]{
15. -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
16. -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
17. -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,62,-1,-1,-1,63,
18. 52,53,54,55,56,57,58,59,60,61,-1,-1,-1,-1,-1,-1,
19. -1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,
20. 15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1,
21. -1,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,
22. 41,42,43,44,45,46,47,48,49,50,51,-1,-1,-1,-1,-1};
24. privateBase64(){}
26. publicstaticStringencode(byte[]data){
27. StringBuffersb=newStringBuffer();
28. intlen=data.length;
29. inti=0;
30. intb1,b2,b3;
32. while(i<len){
33. b1=data[i++]&0xff;
34. if(i==len){
35. sb.append(base64EncodeChars[b1>>>2]);
36. sb.append(base64EncodeChars[(b1&0x3)<<4]);
37. sb.append("==");
38. break;
39. }
40. b2=data[i++]&0xff;
41. if(i==len){
42. sb.append(base64EncodeChars[b1>>>2]);
43. sb.append(
44. base64EncodeChars[((b1&0x03)<<4)|((b2&0xf0)>>>4)]);
45. sb.append(base64EncodeChars[(b2&0x0f)<<2]);
46. sb.append("=");
47. break;
48. }
49. b3=data[i++]&0xff;
50. sb.append(base64EncodeChars[b1>>>2]);
51. sb.append(
52. base64EncodeChars[((b1&0x03)<<4)|((b2&0xf0)>>>4)]);
53. sb.append(
54. base64EncodeChars[((b2&0x0f)<<2)|((b3&0xc0)>>>6)]);
55. sb.append(base64EncodeChars[b3&0x3f]);
56. }
57. returnsb.toString();
58. }
60. publicstaticbyte[]decode(Stringstr){
61. byte[]data=str.getBytes();
62. intlen=data.length;
63. ByteArrayOutputStreambuf=newByteArrayOutputStream(len);
64. inti=0;
65. intb1,b2,b3,b4;
67. while(i<len){
69. /*b1*/
70. do{
71. b1=base64DecodeChars[data[i++]];
72. }while(i<len&&b1==-1);
73. if(b1==-1){
74. break;
75. }
77. /*b2*/
78. do{
79. b2=base64DecodeChars[data[i++]];
80. }while(i<len&&b2==-1);
81. if(b2==-1){
82. break;
83. }
84. buf.write((int)((b1<<2)|((b2&0x30)>>>4)));
86. /*b3*/
87. do{
88. b3=data[i++];
89. if(b3==61){
90. returnbuf.toByteArray();
91. }
92. b3=base64DecodeChars[b3];
93. }while(i<len&&b3==-1);
94. if(b3==-1){
95. break;
96. }
97. buf.write((int)(((b2&0x0f)<<4)|((b3&0x3c)>>>2)));
99. /*b4*/
100. do{
101. b4=data[i++];
102. if(b4==61){
103. returnbuf.toByteArray();
104. }
105. b4=base64DecodeChars[b4];
106. }while(i<len&&b4==-1);
107. if(b4==-1){
108. break;
109. }
110. buf.write((int)(((b3&0x03)<<6)|b4));
111. }
112. returnbuf.toByteArray();
113. }
114. }