Type 7 – Floats & control tokens¶

This type combines two completely unrelated types of items – floating point numbers and special values such as true, false, null, etc. We refer to these special values as ‘control values’ or ‘ctrls’ for short throughout the code.

Just like integers, they have different possible width (resulting in different value ranges and precisions).

enum cbor_float_width¶

Possible widths of CBOR_TYPE_FLOAT_CTRL items.

Values:

enumerator CBOR_FLOAT_0¶: Internal use - ctrl and special values.

enumerator CBOR_FLOAT_16¶: Half float.

enumerator CBOR_FLOAT_32¶: Single float.

enumerator CBOR_FLOAT_64¶: Double.

Corresponding `cbor_type`	`CBOR_TYPE_FLOAT_CTRL`
Number of allocations	One per lifetime
Storage requirements	`sizeof(cbor_item_t) + 1/4/8`

Getting metadata¶

bool cbor_float_ctrl_is_ctrl(const cbor_item_t *item)¶

Is this a ctrl value?

param item: A float or ctrl item
return: Is this a ctrl value?

cbor_float_width cbor_float_get_width(const cbor_item_t *item)¶

Get the float width.

param item: A float or ctrl item
return: The width.

Reading data¶

float cbor_float_get_float2(const cbor_item_t *item)¶

Get a half precision float.

The item must have the corresponding width

param item: A half precision float
return: half precision value

float cbor_float_get_float4(const cbor_item_t *item)¶

Get a single precision float.

The item must have the corresponding width

param item: A single precision float
return: single precision value

double cbor_float_get_float8(const cbor_item_t *item)¶

Get a double precision float.

The item must have the corresponding width

param item: A double precision float
return: double precision value

double cbor_float_get_float(const cbor_item_t *item)¶

Get the float value represented as double.

Can be used regardless of the width.

param item: Any float
return: double precision value

uint8_t cbor_ctrl_value(const cbor_item_t *item)¶

Reads the control value.

param item: A ctrl item
return: the simple value

bool cbor_get_bool(const cbor_item_t *item)¶

Get value from a boolean ctrl item.

param item: A ctrl item
return: boolean value

Creating new items¶

cbor_item_t *cbor_new_ctrl(void)¶

Constructs a new ctrl item.

The width cannot be changed once the item is created

return: Reference to the new ctrl item. The item’s reference count is initialized to one.
return: NULL if memory allocation fails

cbor_item_t *cbor_new_float2(void)¶

Constructs a new float item.

The width cannot be changed once the item is created

return: Reference to the new float item. The item’s reference count is initialized to one.
return: NULL if memory allocation fails

cbor_item_t *cbor_new_float4(void)¶

Constructs a new float item.

The width cannot be changed once the item is created

return: Reference to the new float item. The item’s reference count is initialized to one.
return: NULL if memory allocation fails

cbor_item_t *cbor_new_float8(void)¶

Constructs a new float item.

The width cannot be changed once the item is created

return: Reference to the new float item. The item’s reference count is initialized to one.
return: NULL if memory allocation fails

cbor_item_t *cbor_new_null(void)¶

Constructs new null ctrl item.

return: Reference to the new null item. The item’s reference count is initialized to one.
return: NULL if memory allocation fails

cbor_item_t *cbor_new_undef(void)¶

Constructs new undef ctrl item.

return: Reference to the new undef item. The item’s reference count is initialized to one.
return: NULL if memory allocation fails

Building items¶

cbor_item_t *cbor_build_bool(bool value)¶

Constructs new boolean ctrl item.

param value: The value to use
return: Reference to the new boolean item. The item’s reference count is initialized to one.
return: NULL if memory allocation fails

cbor_item_t *cbor_build_ctrl(uint8_t value)¶

Constructs a ctrl item.

param value: the value to use
return: Reference to the new ctrl item. The item’s reference count is initialized to one.
return: NULL if memory allocation fails

cbor_item_t *cbor_build_float2(float value)¶

Constructs a new float.

param value: the value to use
return: Reference to the new float item. The item’s reference count is initialized to one.
return: NULL if memory allocation fails

cbor_item_t *cbor_build_float4(float value)¶

Constructs a new float.

param value: the value to use
return: Reference to the new float item. The item’s reference count is initialized to one.
return: NULL if memory allocation fails

cbor_item_t *cbor_build_float8(double value)¶

Constructs a new float.

param value: the value to use
return: Reference to the new float item. The item’s reference count is initialized to one.
return: NULL if memory allocation fails

Manipulating existing items¶

void cbor_set_ctrl(cbor_item_t *item, uint8_t value)¶

Assign a control value.

Warning

It is possible to produce an invalid CBOR value by assigning a invalid value using this mechanism. Please consult the standard before use.

param item: A ctrl item
param value: The simple value to assign. Please consult the standard for allowed values

void cbor_set_bool(cbor_item_t *item, bool value)¶

Assign a boolean value to a boolean ctrl item.

param item: A ctrl item
param value: The simple value to assign.

void cbor_set_float2(cbor_item_t *item, float value)¶

Assigns a float value.

param item: A half precision float
param value: The value to assign

void cbor_set_float4(cbor_item_t *item, float value)¶

Assigns a float value.

param item: A single precision float
param value: The value to assign

void cbor_set_float8(cbor_item_t *item, double value)¶

Assigns a float value.

param item: A double precision float
param value: The value to assign

Half floats¶

CBOR supports two bytes wide (“half-precision”) floats which are not supported by the C language. libcbor represents them using float <https://en.cppreference.com/w/c/language/type> values throughout the API. Encoding will be performed by cbor_encode_half(), which will handle any values that cannot be represented as a half-float.