Base64

An xsd:base64Binary is arbitrary binary data in base64 encoding.

size_t exess_base64_decoded_size(size_t length)

Return the maximum number of bytes required to decode length bytes of base64.

The returned value is an upper bound which is only exact for canonical strings.

Parameters

• length – The number of input (text) bytes to decode.

Returns

The size of a decoded value in bytes.

ExessResult exess_read_base64(ExessBlob *out, const char *str)

Read a binary value from a base64 string.

Canonical syntax is a multiple of 4 base64 characters, with either 1 or 2 trailing “=” characters as necessary, like “Zm9vYg==”, with no whitespace. All whitespace is skipped when reading.

The caller must allocate a large enough buffer to read the value, otherwise an ExessStatus.EXESS_NO_SPACE error will be returned. The required space can be calculated with exess_base64_decoded_size().

When this is called, the output blob must have the size of the available buffer in bytes, and a pointer to the buffer. On return, the size will be set to the exact size of the decoded data, which may be smaller than the initial available size. Only these first bytes are written, the rest of the buffer is not modified.

Parameters

• out – The blob to set to the decoded binary data.

• str – String to parse.

Returns

The count of characters read, and a status code.

ExessResult exess_write_base64(size_t data_size, const void *data, size_t buf_size, char *buf)

Write a canonical xsd:base64Binary string.

The data is always written in canonical form, as a multiple of 4 characters with no whitespace and 1 or 2 trailing “=” characters as padding if necessary.

Parameters

• data_size – The size of data in bytes.

• data – Data to write to a string.

• buf_size – The size of buf in bytes.

• buf – Output buffer, or null to only measure.

Returns

The count of characters in the output, and status ExessStatus.EXESS_SUCCESS, or ExessStatus.EXESS_NO_SPACE if the buffer is too small.