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Compact implementation of Base64 encoding in C
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/** | |
BSD 3-Clause License | |
Copyright (c) 2019 Odzhan. All rights reserved. | |
Redistribution and use in source and binary forms, with or without | |
modification, are permitted provided that the following conditions are met: | |
* Redistributions of source code must retain the above copyright notice, this | |
list of conditions and the following disclaimer. | |
* Redistributions in binary form must reproduce the above copyright notice, | |
this list of conditions and the following disclaimer in the documentation | |
and/or other materials provided with the distribution. | |
* Neither the name of the copyright holder nor the names of its | |
contributors may be used to endorse or promote products derived from | |
this software without specific prior written permission. | |
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" | |
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE | |
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE | |
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR | |
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER | |
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, | |
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
*/ | |
#include <stdio.h> | |
#include <stdint.h> | |
#include <string.h> | |
#include <stdlib.h> | |
#include <inttypes.h> | |
#include <sys/stat.h> | |
#include <fcntl.h> | |
#ifndef _MSC_VER | |
#include <unistd.h> | |
#endif | |
#define ROTL32(v,n)(((v)<<(n))|((v)>>(32-(n)))) | |
#ifdef _MSC_VER | |
#define rev32(x) _byteswap_ulong(x) | |
#else | |
#define rev32(x) __builtin_bswap32(x) | |
#endif | |
// calculate length of buffer required for base64 encoding | |
#define B64_LEN(N) (((4 * (N / 3)) + 4) & -4) | |
static const char b64_tbl[] = | |
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; | |
// openssl base64 -A -e -in <binary> -out binary.base64 | |
// Compact implementation of base64 encoding. Probably slow as hell. | |
// The main encoding loop is inspired by Qkumba AKA Peter Ferrie, except this | |
// uses a lookup table. | |
// | |
static int b64_encode( | |
const void *src, uint64_t inlen, | |
void *dst, uint64_t *outlen, int last) | |
{ | |
uint64_t len; | |
uint32_t x; | |
int i = 0; | |
uint8_t *in = (uint8_t*)src, *out = (uint8_t*)dst; | |
// check arguments | |
if(outlen == NULL) return 0; | |
// calculate length of buffer required for encoded string | |
len = B64_LEN(inlen); | |
// return the length? | |
if(out == NULL) { | |
*outlen = len; | |
return 1; | |
} | |
// can buffer contain string? | |
if(len > *outlen) return 0; | |
// main encoding loop | |
while(inlen != 0) { | |
// load 3 bytes | |
for(x=i=0; i<3; i++) { | |
x |= ((i < inlen) ? *in++ : 0); | |
x <<= 8; | |
} | |
// increase by 1 | |
inlen++; | |
// encode 3 bytes | |
for(i=4; inlen && i>0; i--) { | |
x = ROTL32(x, 6); | |
*out++ = b64_tbl[x % 64]; | |
--inlen; | |
} | |
} | |
// if required, add padding | |
if(last) { | |
while(i!=0) { *out++ = '='; i--; } | |
// add null terminator | |
*out = 0; | |
} | |
// calculate output length by subtracting 2 pointers | |
*outlen = (out - (uint8_t*)dst); | |
return 1; | |
} | |
int main(int argc, char *argv[]) { | |
char *input; | |
uint64_t inlen, outlen; | |
void *output; | |
FILE *in, *out; | |
uint8_t buf[255], str[B64_LEN(sizeof(buf))]; | |
if(argc < 2) { | |
printf("usage: base64 <string> | <infile> <outfile>\n"); | |
return 0; | |
} | |
if(argc == 2) { | |
input = argv[1]; | |
inlen = strlen(argv[1]); | |
// calculate length | |
if(b64_encode(NULL, inlen, NULL, &outlen, 1)) { | |
// allocate memory | |
output = malloc(outlen); | |
if(output != NULL) { | |
// encode input | |
if(b64_encode(input, inlen, output, &outlen, 1)) { | |
printf("%s\n", (char*)output); | |
} | |
// release memory | |
free(output); | |
} | |
} | |
} else | |
if(argc == 3) { | |
in = fopen(argv[1], "rb"); | |
if(in == NULL) { | |
printf("unable to open %s\n", argv[1]); | |
return -1; | |
} | |
out = fopen(argv[2], "wb"); | |
if(out != NULL) { | |
for(;;) { | |
// read block | |
inlen = fread(buf, 1, sizeof(buf), in); | |
// nothing read? break | |
if(inlen == 0) break; | |
// encode | |
outlen = sizeof(str); | |
if(!b64_encode(buf, inlen, str, &outlen, inlen<sizeof(buf))) { | |
printf("encoding failed.\n"); | |
break; | |
} | |
// save to file | |
fwrite(str, 1, outlen, out); | |
} | |
fclose(out); | |
} else printf("unable to open %s\n", argv[2]); | |
fclose(in); | |
} | |
return 0; | |
} |
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