xref: /openbsd-src/lib/libcbor/src/cbor/encoding.h (revision 4dcc46c4d04180142eda526ce521dfb137776d05)

/*
 * Copyright (c) 2014-2020 Pavel Kalvoda <me@pavelkalvoda.com>
 *
 * libcbor is free software; you can redistribute it and/or modify
 * it under the terms of the MIT license. See LICENSE for details.
 */

#ifndef LIBCBOR_ENCODING_H
#define LIBCBOR_ENCODING_H

#include "cbor/cbor_export.h"
#include "cbor/common.h"

#ifdef __cplusplus
extern "C" {
#endif

/*
 * All cbor_encode_* methods take 2 or 3 arguments:
 * - a logical `value` to encode (except for trivial items such as NULLs)
 * - an output `buffer` pointer
 * - a `buffer_size` specification
 *
 * They serialize the `value` into one or more bytes and write the bytes to the
 * output `buffer` and return either the number of bytes written, or 0 if the
 * `buffer_size` was too small to small to fit the serialized value (in which
 * case it is not modified).
 */

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_uint8(uint8_t, unsigned char *,
                                                     size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_uint16(uint16_t, unsigned char *,
                                                      size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_uint32(uint32_t, unsigned char *,
                                                      size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_uint64(uint64_t, unsigned char *,
                                                      size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_uint(uint64_t, unsigned char *,
                                                    size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_negint8(uint8_t, unsigned char *,
                                                       size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_negint16(uint16_t,
                                                        unsigned char *,
                                                        size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_negint32(uint32_t,
                                                        unsigned char *,
                                                        size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_negint64(uint64_t,
                                                        unsigned char *,
                                                        size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_negint(uint64_t, unsigned char *,
                                                      size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_bytestring_start(size_t,
                                                                unsigned char *,
                                                                size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t
cbor_encode_indef_bytestring_start(unsigned char *, size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_string_start(size_t,
                                                            unsigned char *,
                                                            size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t
cbor_encode_indef_string_start(unsigned char *, size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_array_start(size_t,
                                                           unsigned char *,
                                                           size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t
cbor_encode_indef_array_start(unsigned char *, size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_map_start(size_t,
                                                         unsigned char *,
                                                         size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_indef_map_start(unsigned char *,
                                                               size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_tag(uint64_t, unsigned char *,
                                                   size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_bool(bool, unsigned char *,
                                                    size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_null(unsigned char *, size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_undef(unsigned char *, size_t);

/** Encodes a half-precision float
 *
 * Since there is no native representation or semantics for half floats
 * in the language, we use single-precision floats, as every value that
 * can be expressed as a half-float can also be expressed as a float.
 *
 * This however means that not all floats passed to this function can be
 * unambiguously encoded. The behavior is as follows:
 *  - Infinity, NaN are preserved
 *  - Zero is preserved
 *  - Denormalized numbers keep their sign bit and 10 most significant bit of
 * the significand
 *  - All other numbers
 *   - If the logical value of the exponent is < -24, the output is zero
 *   - If the logical value of the exponent is between -23 and -14, the output
 *     is cut off to represent the 'magnitude' of the input, by which we
 *     mean (-1)^{signbit} x 1.0e{exponent}. The value in the significand is
 * lost.
 *   - In all other cases, the sign bit, the exponent, and 10 most significant
 * bits of the significand are kept
 */
_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_half(float, unsigned char *,
                                                    size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_single(float, unsigned char *,
                                                      size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_double(double, unsigned char *,
                                                      size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_break(unsigned char *, size_t);

_CBOR_NODISCARD CBOR_EXPORT size_t cbor_encode_ctrl(uint8_t, unsigned char *,
                                                    size_t);

#ifdef __cplusplus
}
#endif

#endif  // LIBCBOR_ENCODING_H