Base64 Encoding

Base64 Encoding — encodes and decodes data in Base64 format

Synopsis

#include <glib.h>

gsize               g_base64_encode_step                (const guchar *in,
                                                         gsize len,
                                                         gboolean break_lines,
                                                         gchar *out,
                                                         gint *state,
                                                         gint *save);
gsize               g_base64_encode_close               (gboolean break_lines,
                                                         gchar *out,
                                                         gint *state,
                                                         gint *save);
gchar*              g_base64_encode                     (const guchar *data,
                                                         gsize len);
gsize               g_base64_decode_step                (const gchar *in,
                                                         gsize len,
                                                         guchar *out,
                                                         gint *state,
                                                         guint *save);
guchar *            g_base64_decode                     (const gchar *text,
                                                         gsize *out_len);
guchar *            g_base64_decode_inplace             (gchar *text,
                                                         gsize *out_len);

Description

Base64 is an encoding that allows a sequence of arbitrary bytes to be encoded as a sequence of printable ASCII characters. For the definition of Base64, see RFC 1421 or RFC 2045. Base64 is most commonly used as a MIME transfer encoding for email.

GLib supports incremental encoding using g_base64_encode_step() and g_base64_encode_close(). Incremental decoding can be done with g_base64_decode_step(). To encode or decode data in one go, use g_base64_encode() or g_base64_decode(). To avoid memory allocation when decoding, you can use g_base64_decode_inplace().

Support for Base64 encoding has been added in GLib 2.12.

Details

g_base64_encode_step ()

gsize               g_base64_encode_step                (const guchar *in,
                                                         gsize len,
                                                         gboolean break_lines,
                                                         gchar *out,
                                                         gint *state,
                                                         gint *save);

Incrementally encode a sequence of binary data into its Base-64 stringified representation. By calling this function multiple times you can convert data in chunks to avoid having to have the full encoded data in memory.

When all of the data has been converted you must call g_base64_encode_close() to flush the saved state.

The output buffer must be large enough to fit all the data that will be written to it. Due to the way base64 encodes you will need at least: (len / 3 + 1) * 4 + 4 bytes (+ 4 may be needed in case of non-zero state). If you enable line-breaking you will need at least: ((len / 3 + 1) * 4 + 4) / 72 + 1 bytes of extra space.

break_lines is typically used when putting base64-encoded data in emails. It breaks the lines at 72 columns instead of putting all of the text on the same line. This avoids problems with long lines in the email system.

in :

 the binary data to encode

len :

 the length of in

break_lines :

 whether to break long lines

out :

 pointer to destination buffer

state :

 Saved state between steps, initialize to 0

save :

 Saved state between steps, initialize to 0

Returns :

 The number of bytes of output that was written

Since 2.12

g_base64_encode_close ()

gsize               g_base64_encode_close               (gboolean break_lines,
                                                         gchar *out,
                                                         gint *state,
                                                         gint *save);

Flush the status from a sequence of calls to g_base64_encode_step().

The output buffer must be large enough to fit all the data that will be written to it. It will need up to 4 bytes, or up to 5 bytes if line-breaking is enabled.

break_lines :

 whether to break long lines

out :

 pointer to destination buffer

state :

 Saved state from g_base64_encode_step()

save :

 Saved state from g_base64_encode_step()

Returns :

 The number of bytes of output that was written

Since 2.12

g_base64_encode ()

gchar*              g_base64_encode                     (const guchar *data,
                                                         gsize len);

Encode a sequence of binary data into its Base-64 stringified representation.

data :

 the binary data to encode

len :

 the length of data

Returns :

 a newly allocated, zero-terminated Base-64 encoded string representing data. The returned string must be freed with g_free().

Since 2.12

g_base64_decode_step ()

gsize               g_base64_decode_step                (const gchar *in,
                                                         gsize len,
                                                         guchar *out,
                                                         gint *state,
                                                         guint *save);

Incrementally decode a sequence of binary data from its Base-64 stringified representation. By calling this function multiple times you can convert data in chunks to avoid having to have the full encoded data in memory.

The output buffer must be large enough to fit all the data that will be written to it. Since base64 encodes 3 bytes in 4 chars you need at least: (len / 4) * 3 + 3 bytes (+ 3 may be needed in case of non-zero state).

in :

 binary input data

len :

 max length of in data to decode

out :

 output buffer

state :

 Saved state between steps, initialize to 0

save :

 Saved state between steps, initialize to 0

Returns :

 The number of bytes of output that was written

Since 2.12

g_base64_decode ()

guchar *            g_base64_decode                     (const gchar *text,
                                                         gsize *out_len);

Decode a sequence of Base-64 encoded text into binary data

text :

 zero-terminated string with base64 text to decode

out_len :

 The length of the decoded data is written here

Returns :

 a newly allocated buffer containing the binary data that text represents. The returned buffer must be freed with g_free().

Since 2.12

g_base64_decode_inplace ()

guchar *            g_base64_decode_inplace             (gchar *text,
                                                         gsize *out_len);

Decode a sequence of Base-64 encoded text into binary data by overwriting the input data.

text :

 zero-terminated string with base64 text to decode

out_len :

 The length of the decoded data is written here

Returns :

 The binary data that text responds. This pointer is the same as the input text.

Since 2.20

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