mip_field.c

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#include "mip_field.h"
 
#include "mip_packet.h"
#include "mip_offsets.h"
#include "definitions/descriptors.h"
 
#include <assert.h>
 
 
void mip_field_init(mip_field* field, uint8_t descriptor_set, uint8_t field_descriptor, const uint8_t* payload, uint8_t payload_length)
{
    assert( payload_length <= MIP_FIELD_PAYLOAD_LENGTH_MAX );
    if( payload_length > MIP_FIELD_PAYLOAD_LENGTH_MAX )
        payload_length = MIP_FIELD_PAYLOAD_LENGTH_MAX;
 
    field->_payload          = payload;
    field->_payload_length   = payload_length;
    field->_field_descriptor = field_descriptor;
    field->_descriptor_set   = descriptor_set;
    field->_remaining_length = 0;
}
 
uint8_t mip_field_descriptor_set(const mip_field* field)
{
    return field->_descriptor_set;
}
 
uint8_t mip_field_field_descriptor(const mip_field* field)
{
    return field->_field_descriptor;
}
 
uint8_t mip_field_payload_length(const mip_field* field)
{
    assert(field->_payload_length <= MIP_FIELD_PAYLOAD_LENGTH_MAX);
 
    return field->_payload_length;
}
 
const uint8_t* mip_field_payload(const mip_field* field)
{
    return field->_payload;
}
 
bool mip_field_is_valid(const mip_field* field)
{
    return field->_field_descriptor != MIP_INVALID_FIELD_DESCRIPTOR;
}
 
 
 
void mip_field_init_empty(mip_field* field)
{
    mip_field_init(field, MIP_INVALID_DESCRIPTOR_SET, MIP_INVALID_FIELD_DESCRIPTOR, NULL, 0);
}
 
mip_field mip_field_from_header_ptr(const uint8_t* header, uint8_t total_length, uint8_t descriptor_set)
{
    mip_field field;
 
    // Default invalid values.
    field._payload          = NULL;
    field._descriptor_set   = descriptor_set;
    field._payload_length   = 0;
    field._field_descriptor = 0x00;  // This makes the field invalid.
    field._remaining_length = 0;
 
    if( total_length >= MIP_FIELD_HEADER_LENGTH )
    {
        // Field length is external input so it must be sanitized.
        uint8_t field_length = header[MIP_INDEX_FIELD_LEN];
 
        // Ensure field length does not exceed total_length.
        if( field_length > total_length )
            field_length = total_length;
 
        // Check for invalid field length.
        if( field_length >= MIP_FIELD_HEADER_LENGTH )
        {
            field._field_descriptor = header[MIP_INDEX_FIELD_DESC];
            field._payload_length   = field_length - MIP_FIELD_HEADER_LENGTH;
            field._payload          = header + MIP_INDEX_FIELD_PAYLOAD;
            field._remaining_length = total_length - field_length;
        }
    }
 
    return field;
}
 
mip_field mip_field_first_from_packet(const mip_packet* packet)
{
    return mip_field_from_header_ptr( mip_packet_payload(packet), mip_packet_payload_length(packet), mip_packet_descriptor_set(packet) );
}
 
mip_field mip_field_next_after(const mip_field* field)
{
    // Payload length must be zero if payload is NULL.
    assert(!(field->_payload == NULL) || (field->_payload_length == 0));
 
    const uint8_t* next_header = field->_payload + field->_payload_length;
 
    return mip_field_from_header_ptr(next_header, field->_remaining_length, field->_descriptor_set);
}
 
bool mip_field_next(mip_field* field)
{
    *field = mip_field_next_after(field);
 
    return mip_field_is_valid(field);
}
 
bool mip_field_next_in_packet(mip_field* field, const mip_packet* packet)
{
    if( field->_descriptor_set != MIP_INVALID_DESCRIPTOR_SET )
        *field = mip_field_next_after(field);
    else
        *field = mip_field_first_from_packet(packet);
 
    return mip_field_is_valid(field);
}