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109 lines
2.2 KiB
C
109 lines
2.2 KiB
C
#include "base64.h"
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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static const char* alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
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char* base64_strict_encode( void* v_binary, size_t len )
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{
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// RFC 4648 - https://www.rfc-editor.org/rfc/rfc4648.html
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enum { pad = '=' };
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uint8_t* binary = v_binary;
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const int groups = ( len + 2 ) / 3;
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char* result = malloc( groups * 4 + 1 );
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result[groups*4] = '\0';
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uint32_t word;
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char* out = result;
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for( int remain = len; remain > 0; remain -= 3, binary += 3, out += 4 ) {
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word = 0;
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switch( remain ) {
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default:
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word |= binary[2] << (8*0);
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case 2:
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word |= binary[1] << (8*1);
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case 1:
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word |= binary[0] << (8*2);
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}
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switch( remain ) {
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default:
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out[3] = alphabet[ ( word >> (6*0) ) % 64 ];
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case 2:
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out[2] = alphabet[ ( word >> (6*1) ) % 64 ];
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case 1:
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out[1] = alphabet[ ( word >> (6*2) ) % 64 ];
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out[0] = alphabet[ ( word >> (6*3) ) % 64 ];
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}
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switch( remain ) {
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case 1:
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out[3] = '=';
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out[2] = '=';
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break;
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case 2:
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out[3] = '=';
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break;
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}
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}
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return result;
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}
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bool base64_decode( const char* str, void** v_binary, size_t* len )
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{
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int input_length = strlen(str);
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uint8_t* data = malloc( ( input_length * 6 + 7 ) / 8 );
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*v_binary = data;
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*len = 0;
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uint32_t buffer = 0;
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int bits = 0;
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uint8_t part;
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for(;;) {
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//printf( " - Input %02X (%c)\n", *str, *str );
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switch( *str ) {
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case 'A' ... 'Z': part = *str - 'A'; break;
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case 'a' ... 'z': part = *str - 'a' + 26; break;
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case '0' ... '9': part = *str - '0' + 52; break;
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case '+': part = 62; break;
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case '/': part = 63; break;
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case '=': goto finish;
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case '\0':
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goto done;
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default:
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free( *v_binary );
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*len = 0;
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return false;
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};
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++str;
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buffer = ( buffer << 6 ) | part;
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bits += 6;
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//printf( "buffer=%08X, bits=%d\n", buffer, bits );
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if( bits > 8 ) {
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uint8_t byte = buffer >> ( bits % 8 );
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*data = byte;
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//printf( " - Output: %02X (%c)\n", byte, byte );
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buffer &= ( 1 << (bits%8) ) - 1;
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*len += 1;
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++data;
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bits -= 8;
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}
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}
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done:
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*len += 1;
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finish:
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uint8_t byte = buffer >> ( bits % 8 );
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*data = byte;
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++data;
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bits = 0;
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return true;
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}
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