libb64

Library for Base64 encoding/decoding

Requirement

• gcc (C99)
• GNU Make
• GNU Binutils (ar)

Build

Build static library (libb64.a):

# build/release/libb64.a
$ make
# or
$ make static

Build shared library (libb64.so):

# build/release/libb64.so
$ make shared

Debug build (libb64d.***):

# build/debug/libb64d.a
$ make DEBUG=yes

# build/debug/libb64d.so
$ make shared DEBUG=yes

Build and run test:

# build/release/test_runner
$ make test

Build sample:

# build/release/***
$ make sample

Usage

Encoding

#include "b64.h"

void encode_sample(void) {
    // Input byte array
    uint8_t input_bytes[7] = {
        // "ABCDEFG"
        0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47
    };

    // Output string is allocated dynamically
    size_t length;
    char* base64_str = b64_std_encode(&length, input_bytes, sizeof(input_bytes));
    assert(length == 12);

    // "QUJDREVGRw=="
    printf("%s\n", base64_str);

    free(base64_str);
}

• b64_std_encode: standard encoding
  • 62nd/63rd encoding character: +//
  • Padding: =
  • No line breaks
• b64_url_encode: URL-safe encoding
  • 62nd/63rd encoding character: -/_
  • Padding: not used
  • No line breaks
• b64_mime_decode: MIME encoding
  • 62nd/63rd encoding character: +//
  • Padding: =
  • Line break by CR+LF is inserted every 76 characters in the decoded string

b64_encode provide the encoding with the following parameters can be specified:

• 62nd/63rd encoding characters
• Use padding or not
• Line length to insert CR+LF (no line breaks by 0)

Decoding

#include "b64.h"

void decode_sample(void) {
    // Input base64 string
    char base64_str[] = "QUJDREVGRw==";

    // Output byte array is allocated dynamically
    size_t size;
    uint8_t* decoded_bytes = b64_std_decode(&size, base64_str);

    // "0x41,0x42,0x43,0x44,0x45,0x46,0x47,"
    for (int i = 0; i < size; ++i) {
        printf("0x%2x,", decoded_bytes);
    }
    putchar('\n');

    free(decoded_bytes);
}

• b64_std_encode: standard decoding
  • 62nd/63rd encoding character: +//
  • Non-encoding characters are not allowed
• b64_url_encode: URL-safe decoding
  • 62nd/63rd encoding character: -/_
  • Non-encoding characters are not allowed
• b64_mime_decode: MIME encoding
  • 62nd/63rd encoding character: +//
  • Non-encoding characters are discarded

b64_decode provide the decoding with the following parameters can be specified:

• 62nd/63rd encoding characters
• Validate the input characters

Sample

• b64_encoder

  Encode an attached Jpeg image sample/sakura.jpg to sample/encoded.txt:

  $ ./build/release/sample/b64_encoder ./sample/sakura.jpg ./sample/encoded.txt 
  Base64 encoding of ./sample/sakura.jpg is finished (87269 to 116360 bytes).
  The string is written to './sample/encoded.txt'.
  $ cat output.txt
  /9j/4AAQSkZJRgABAQEASABIAAD/4T9eRXhpZgAATU0AKgAAAAgADAEPAAIAAAAGAAAAngEQAAIA
  ...

• b64_decoder

  Decode sample/encoded.txt to sample/decoded.bin:

  $ ./build/release/sample/b64_decoder ./sample/encoded.txt ./sample/decoded.bin 
  Base64 decoding of ./sample/encoded.txt is finished (116360 to 87269 bytes).
  The byte expression is written to './sample/decoded.bin'.
  
  $ diff ./sample/sakura.jpg ./sample/decoded.bin
  # No differences

License

MIT License