Base64 Library

Base64 is an encoding for representing arbitrary data as a printable ASCII string. 4 Bytes in base64 encoding represent 3 Bytes of the data.

File information

File	common/ilib/base64.h
Public functions	encode_base64 decode_base64 decode_base64_bin encode_base64_buffer_len encode_base64url decode_base64url decode_base64url_bin
Examples	encode_base64 decode_base64 decode_base64_bin encode_base64_buffer_len

Two decode variants exist for each alphabet: *_bin takes an explicit output-buffer size and returns the byte-count actually written. The plain version (decode_base64, decode_base64url) assumes the buffer is large enough and returns the decoded length as dword.

The helper function encode_base64_buffer_len(len) isn’t a conversion routine; it just tells you how large the destination buffer must be when you call encode_base64.

From \ To	Binary	Base64	Base64URL
Binary		encode_base64	encode_base64url
Base64	decode_base64 decode_base64_bin		missing
Base64URL	decode_base64url decode_base64url_bin	missing

Public functions

encode_base64

Encodes arbitrary data into a null-terminated base64 string. This increases the needed space by 4/3 plus one byte for the null-termination.

Parameters

const byte * in	The data that shall be encoded.
char * out	The function writes the null-terminated base64 string to this buffer. The buffer has to be large enough to contain 4/3 * len + 1 bytes.
int len	The number of bytes that shall be encoded.

Return value

dword

The number of bytes that have been written to the out buffer.

decode_base64

Decodes a base64 string into a null-terminated plain string.

Parameters

const char * in	The base64 string to be decoded.
byte * out	The function writes the decoded data to this buffer and places an additional null byte at the end.
int n	The number of bytes in the in buffer to be decoded.

Return value

dword

The number of bytes that have been written to the out buffer.

decode_base64_bin

Decodes a null-terminated base64 string.

Parameters

const char * in	The null-terminated base64 string to be decoded.
byte * out	The function writes the decoded data to this buffer.
unsigned size_of_out	The size of the out buffer.

Return value

dword

The number of bytes that have been written to the out buffer.

encode_base64_buffer_len

Calculates the required buffer size for the `encode_base64` function.

Parameters

dword len

The number of bytes of the original data.

Return value

dword

The required size for the output buffer, including space for the null-terminator.

encode_base64url

Encodes arbitrary data into a null-terminated base64url string using the URL and filename safe alphabet (RFC 4648, section 5).

Parameters

const byte * in	The data that shall be encoded.
char * out	The function writes the null-terminated base64url string to this buffer.
int len	The number of bytes that shall be encoded.

Return value

dword

The number of bytes that have been written to the out buffer.

decode_base64url

Decodes a base64url string into a null-terminated plain string. It uses the URL and filename safe alphabet.

Parameters

const char * in	The base64url string to be decoded.
byte * out	The function writes the decoded data to this buffer and places an additional null byte at the end.
int n	The number of bytes in the in buffer to be decoded.

Return value

dword

The number of bytes that have been written to the out buffer.

decode_base64url_bin

Decodes a null-terminated base64url string using the URL and filename safe alphabet.

Parameters

const char * in	The null-terminated base64url string to be decoded.
byte * out	The function writes the decoded data to this buffer.
unsigned size_of_out	The size of the out buffer.

Return value

dword

The number of bytes that have been written to the out buffer.

Code Example

encode_base64

const char * in = "This is an example text";
char out[64];
dword out_len = encode_base64(in, out, strlen(in));

decode_base64

const char * in = "VGhpcyBpcyBhbiBleGFtcGxlIHRleHQ=";
char out[64];
dword out_len = decode_base64(in, out, strlen(in));

decode_base64_bin

const char * in = "VGhpcyBpcyBhbiBleGFtcGxlIHRleHQ=";
char out[64];
dword out_len = decode_base64_bin(in, out, sizeof(out));

encode_base64_buffer_len

const byte * data = (const byte *)"This is an example text";
dword data_len = strlen((const char *)data);
char * out = (char *)alloca(encode_base64_buffer_len(data_len));
encode_base64(data, out, data_len);