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Base64 Codec (base64)

Base64 encoding and decoding per RFC 4648.

API​

int base64_encode_size(int s);
int base64_decode_size(int s);
int base64_encode(const char * in, int len, char * out);
int base64_decode(const char * in, int len, char * out);
  • base64_encode_size — Calculate encoded buffer size (including trailing \0), formula: ((s + 2) / 3) * 4 + 1
  • base64_decode_size — Calculate decoded buffer size, formula: (s / 4) * 3
  • base64_encode — Encode, returns output length (excluding trailing \0)
  • base64_decode — Decode, returns output length

Example​

Encode​

const char * data = "Hello";
int enclen = base64_encode_size(xos_strlen(data));
char * out = xos_mem_malloc(enclen);
base64_encode(data, xos_strlen(data), out);
/* out = "SGVsbG8=" */
xos_mem_free(out);

Decode​

const char * b64 = "SGVsbG8=";
int declen = base64_decode_size(xos_strlen(b64));
char * out = xos_mem_malloc(declen);
int len = base64_decode(b64, xos_strlen(b64), out);
/* len = 5, out = "Hello" */
xos_mem_free(out);

Encode→Decode Round-Trip Verification​

char in[128] = { ... };
char enc[base64_encode_size(sizeof(in))];
char dec[base64_decode_size(sizeof(enc))];

base64_encode(in, sizeof(in), enc);
int len = base64_decode(enc, sizeof(enc), dec);
/* memcmp(in, dec, sizeof(in)) == 0 */