前往Base64 解码【代码实现】
C
#include <stdio.h>
#include <stdlib.h>
#include <resolv.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>int main() {
int fin = open("favicon.ico", O_RDONLY);if (fin == -1)return 1;struct stat st;if (fstat(fin, &st))return 1;void *bi = mmap(0, st.st_size, PROT_READ, MAP_PRIVATE, fin, 0);if (bi == MAP_FAILED)return 1;int outLength = ((st.st_size + 2) / 3) * 4 + 1;char *outBuffer = malloc(outLength);if (outBuffer == NULL)return 1;int encodedLength = b64_ntop(bi, st.st_size, outBuffer, outLength);if (encodedLength < 0)return 1;puts(outBuffer);free(outBuffer);munmap(bi, st.st_size);close(fin);return 0;
}
C++
#include <iostream>
#include <fstream>
#include <vector>typedef unsigned char byte;
using namespace std;const unsigned m1 = 63 << 18, m2 = 63 << 12, m3 = 63 << 6;class base64
{
public:base64() {
char_set = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; }string encode( vector<byte> v ){
string res;unsigned d, a = 0, l = static_cast<unsigned>( v.size() );while( l > 2 ){
d = v[a++] << 16 | v[a++] << 8 | v[a++]; res.append( 1, char_set.at( ( d & m1 ) >> 18 ) ); res.append( 1, char_set.at( ( d & m2 ) >> 12 ) ); res.append( 1, char_set.at( ( d & m3 ) >> 6 ) );res.append( 1, char_set.at( d & 63 ) );l -= 3;}if( l == 2 ){
d = v[a++] << 16 | v[a++] << 8;res.append( 1, char_set.at( ( d & m1 ) >> 18 ) ); res.append( 1, char_set.at( ( d & m2 ) >> 12 ) ); res.append( 1, char_set.at( ( d & m3 ) >> 6 ) );res.append( 1, '=' );}else if( l == 1 ){
d = v[a++] << 16;res.append( 1, char_set.at( ( d & m1 ) >> 18 ) ); res.append( 1, char_set.at( ( d & m2 ) >> 12 ) ); res.append( "==", 2 );}return res;}private:string char_set;
};int main( int argc, char* argv[] )
{
base64 b;basic_ifstream<byte> f( "favicon.ico", ios::binary );string r = b.encode( vector<byte>( ( istreambuf_iterator<byte>( f ) ), istreambuf_iterator<byte>() ) );copy( r.begin(), r.end(), ostream_iterator<char>( cout ) );return 0;
}
输出：
AAABAAIAEBAAAAAAAABoBQAAJgAAACAgAAAAAAAAqAgAAI4FAAAoAAAAEAAAACAAAAABAAgAAAAAAEAB
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAP///wCGiYcARkhHAL/CwAAmKScAam1rAOPm5ACgo6EAV1pYABcZ
…
AAEAAAABAAAAAQAAAAEAAAABAAAAAQAAAAEAAAABAAAAAQAAAAEAAAABAAAAAQAAAAEAAAABAAAAAQAA
AAEAAAABAAAAAQAAAAEAAAABAAAAAQAAAAEAAAABAAAAAQAAAAE=
C#
namespace RosettaCode.Base64EncodeData
{
using System;using System.Net;internal static class Program{
private static void Main(){
const string path = "http://rosettacode.org/favicon.ico";byte[] input;using (var client = new WebClient()){
input = client.DownloadData(path);}var output = Convert.ToBase64String(input);Console.WriteLine(output);}}
}
输出：
AAABAAIAEBAAAAAAAABoBQAAJgAAACAg…AAABAAAAAQAAAAEAAAABAAAAAQAAAAE=
Go
- 使用标准库
package mainimport ("encoding/base64""fmt""io/ioutil""net/http"
)func main() {
r, err := http.Get("http://rosettacode.org/favicon.ico")if err != nil {
fmt.Println(err)return}defer r.Body.Close()d, err := ioutil.ReadAll(r.Body)if err != nil {
fmt.Println(err)return}fmt.Println(base64.StdEncoding.EncodeToString(d))
}
输出：
AAABAAIAEBAAAAAAAABoBQAAJg … AAAABAAAAAQAAAAE=
- 手动实现
/ base64 encoding
// A port, with slight variations, of the C version found here:
// http://rosettacode.org/wiki/Base64#C (manual implementation)
//
// go build ; cat favicon.ico | ./base64package mainimport ("bytes""fmt""io/ioutil""log""os""strings"
)const (B64_CHUNK_SIZE = 76
)type UL int64// Our lookup table.
var alpha string = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"// Base64 encode a raw byte stream.
func B64Encode(raw []byte) (string, error) {
var buffer strings.Buildervar reader *bytes.Readervar u UL // w ULvar length intvar chunk []bytevar err errorlength = 3reader = bytes.NewReader(raw)chunk = make([]byte, 3)for length == 3 {
chunk[1] = 0chunk[2] = 0length, err = reader.Read(chunk)if err != nil || len(chunk) == 0 {
break}u = UL(chunk[0])<<16 | UL(chunk[1])<<8 | UL(chunk[2])buffer.WriteString(string(alpha[u>>18]))buffer.WriteString(string(alpha[u>>12&63]))if length < 2 {
buffer.WriteString("=")} else {
buffer.WriteString(string(alpha[u>>6&63]))}if length < 3 {
buffer.WriteString("=")} else {
buffer.WriteString(string(alpha[u&63]))}}return buffer.String(), nil
}// Prettifies the base64 result by interspersing \n chars every B64_CHUNK_SIZE bytes.
// Even though there's a performance hit, i'd rather compose these.
func B64EncodePretty(raw []byte) (string, error) {
var buffer strings.Builderencoded, err := B64Encode(raw)if err != nil {
return "", err}length := len(encoded)chunks := int(length/B64_CHUNK_SIZE) + 1for i := 0; i < chunks; i++ {
chunk := i * B64_CHUNK_SIZEend := chunk + B64_CHUNK_SIZEif end > length {
end = chunk + (length - chunk)}buffer.WriteString(encoded[chunk:end] + "\n")}return buffer.String(), err
}func main() {
contents, err := ioutil.ReadAll(os.Stdin)if err != nil {
log.Fatal("Error reading input: ", err)}encoded, err := B64EncodePretty(contents)if err != nil {
log.Fatal("Error base64 encoding the input: ", err)}fmt.Printf("%s", encoded)
}
输出：
AAABAAIAEBAAAAAAAABoBQAAJgAAACAgAAAAAAAAqAgAAI4FAAAoAAAAEAAAACAAAAABAAgAAAAA
AEABAAAAAAAAAAAAAAAAAAAAAAAAAAAAAP///wCGiYcARkhHAL/CwAAmKScAam1rAOPm5ACgo6EA
…
AAAAAQAAAAEAAAABAAAAAQAAAAEAAAABAAAAAQAAAAEAAAABAAAAAQAAAAEAAAABAAAAAQAAAAEA
AAABAAAAAQAAAAEAAAABAAAAAQAAAAEAAAABAAAAAQAAAAEAAAABAAAAAQAAAAE=
Java
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.Arrays;public class Base64 {
private static final char[] alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();static String base64(InputStream is) throws IOException {
StringBuilder sb = new StringBuilder();int blocks = 0;while (true) {
int c0 = is.read();if (c0 == -1)break;int c1 = is.read();int c2 = is.read();int block = ((c0 & 0xFF) << 16) | ((Math.max(c1, 0) & 0xFF) << 8) | (Math.max(c2, 0) & 0xFF);sb.append(alpha[block >> 18 & 63]);sb.append(alpha[block >> 12 & 63]);sb.append(c1 == -1 ? '=' : alpha[block >> 6 & 63]);sb.append(c2 == -1 ? '=' : alpha[block & 63]);if (++blocks == 19) {
blocks = 0;sb.append('\n');}}if (blocks > 0)sb.append('\n');return sb.toString();}private static void assertBase64(String expected, byte[] bytes) throws IOException {
String actual = base64(new ByteArrayInputStream(bytes));if (!actual.equals(expected)) {
throw new IllegalStateException(String.format("Expected %s for %s, but got %s.",expected, Arrays.toString(bytes), actual));}}private static void testBase64() throws IOException {
assertBase64("", new byte[]{
});assertBase64("AA==\n", new byte[]{
0});assertBase64("AAA=\n", new byte[]{
0, 0});assertBase64("AAAA\n", new byte[]{
0, 0, 0});assertBase64("AAAAAA==\n", new byte[]{
0, 0, 0, 0});assertBase64("/w==\n", new byte[]{
-1});assertBase64("//8=\n", new byte[]{
-1, -1});assertBase64("\n", new byte[]{
-1, -1, -1});assertBase64("/w==\n", new byte[]{
-1, -1, -1, -1});}public static void main(String[] args) throws IOException {
testBase64();URLConnection conn = new URL("http://rosettacode.org/favicon.ico").openConnection();conn.addRequestProperty("User-Agent", "Mozilla"); // To prevent an HTTP 403 error.try (InputStream is = conn.getInputStream()) {
System.out.println(base64(is));}}
}
//java8 version
import java.nio.file.*;
import java.util.Base64;public class Base64Task {
public static void main(String[] args) throws Exception {
byte[] bytes = Files.readAllBytes(Paths.get("favicon.ico"));String result = Base64.getEncoder().encodeToString(bytes);System.out.println(result);}
}
JavaScript
(function(){
//ECMAScript doesn't have an internal base64 function or method, so we have to do it ourselves, isn't that exciting?function stringToArrayUnicode(str){
for(var i=0,l=str.length,n=[];i<l;i++)n.push(str.charCodeAt(i));return n;}function generateOnesByLength(n){
//Attempts to generate a binary number full of ones given a length.. they don't redefine each other that much.var x=0;for(var i=0;i<n;i++){
x<<=1;x|=1;//I don't know if this is performant faster than Math.pow but seriously I don't think I'll need Math.pow, do I?}return x;}function paf(_offset,_offsetlength,_number){
//I don't have any name for this function at ALL, but I will explain what it does, it takes an offset, a number and returns the base64 number and the offset of the next number.//the next function will be used to extract the offset of the number..var a=6-_offsetlength,b=8-a;//Oh god, 8 is HARDCODED! Because 8 is the number of bits in a byte!!!//And 6 is the mini-byte used by wikipedia base64 article... at least on 2013.//I imagine this code being read in 2432 or something, that probably won't happen..return [_number&generateOnesByLength(b),b,(_offset<<a)|(_number>>b)];//offset & offsetlength & number }function toBase64(uint8array){
//of bits, each value may not have more than 255 bits... //a normal "array" should work fine too..//From 0x29 to 0x5a plus from 0x61 to 0x7A AND from 0x30 to 0x39//Will not report errors if an array index has a value bigger than 255.. it will likely fail.var a=[],i,output=[];for(i=0x41;i<=0x5a;i++){
//A-Za.push(String.fromCharCode(i));}for(i=0x61;i<=0x7A;i++){
//a-za.push(String.fromCharCode(i));}for(i=0x30;i<=0x39;i++){
//0-9a.push(String.fromCharCode(i));}a.push('+','/');var offset=0,offsetLength=0,x;for(var i=0,l=uint8array.length;i<l;i++){
if(offsetLength==6){
//if offsetlength is 6 that means that a whole offset is occupying the space of a byte, can you believe it.offsetLength=0;output.push(a[offset]);offset=0;i--;continue;}x=paf(offset,offsetLength,uint8array[i]);offset=x[0];offsetLength=x[1];output.push(a[x[2]]);}if(offsetLength){
if(offsetLength==6){
output.push(a[offset]);}else{
var y=(6-offsetLength)/2;x=paf(offset,offsetLength,0);offset=x[0];output.push(a[x[2]]);switch (y){
case 2:output.push('=');//This thingy right here, you know.. the offsets also, no break statement;case 1:output.push('=');break;}}}return output.join('');//You can change it so the result is an array instead!!!!}//Usagereturn toBase64(stringToArrayUnicode("Nothing seems hard to the people who don't know what they're talking about."))
}())
Kotlin
// version 1.1.2import java.io.File
import java.util.Base64fun main(args: Array<String>) {
val path = "favicon.ico" // already downloaded to current directoryval bytes = File(path).readBytes()val base64 = Base64.getEncoder().encodeToString(bytes)println(base64)
}
PHP
<?php echo base64_encode(file_get_contents("http://rosettacode.org/favicon.ico"));/*1 liner*/ ?>
Python
import urllib
import base64data = urllib.urlopen('http://rosettacode.org/favicon.ico').read()
print base64.b64encode(data)