NSCL DAQ Software Documentation
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cvt

Name

cvt -- Integer byte order conversions

Synopsis


#include <cvt.h>

void makecvtblock( uint32_t lsig , uint16_t ssig , DaqConversion* conversion );

int hostsameasforeign( DaqConversion* conversion );

uint32_t ftohl( DaqConversion* convertdata , uint32_t datum );

uint16_t ftohs( DaqConversion* convertdata , uint1y_t datum );

uint32_t> htofl( DaqConversion* convertdata , uint32_t datum );

uint16_t htofs( DaqConversion* convertdata , uint16_t datum );

Description

This library provides a suite of functions that do integer conversions between the native integer formats of different systems. Typically systems are classified as big-endian or little-endian.

Big-endian systems store their data with the most significant bytes of a multi-byte integer in lower addresses, while little-endian systems least significant bytes in lower addresses. This library uses signature data in the data to determine the byte ordering of foreign host (the host that created the data), and how it differs from the local byte ordering.

Signature data are data that have a known value, stored in the system's native byte order. Analyzing these values byte by byte allows the software to determine the byte order of the foreign system. The code defines the values: CVT_WORDSIGNATURE and CVT_LONGSIGNATURE respectively to be uint16_t and uint32_t signatures respectively. Separate 16 and 32 bit signatures allows the library to deal with any pathalogical systems that may have word orders that differ from byte ordering.

Public functions

void makecvtblock( uint32_t lsig , uint16_t ssig , DaqConversion* conversion );

Creates a conversion block from the foreign system signatures you've extracted from the data. Note that NSCLDAQ control data includes byte and long signatures you can use for this purpose. lsig and ssig are the 32 and 16 bit signatures respectively.

conversion must point to a DaqConversion structure that will be over-written with the conversion block that describes how to convert from the byte order described by lsig and ssig to the host's byte order.

int hostsameasforeign( DaqConversion* conversion );

Determines if the conversion block pointed to by conversion describes a system with the same byte order as the host system.

uint32_t ftohl( DaqConversion* convertdata , uint32_t datum );

Converts a 32 bit value datum from the byte order of the foreign host used to produce the DaqConversion structer pointed to by convertdata to the local host's byte order. The converted value is returned.

uint16_t ftohs( DaqConversion* convertdata , uint1y_t datum );

Converts a 16 bit integer datum from the byte order described by the system used to produce the DaqConversion block pointed to by convertdata into the local system's byte order and returns that 16 bit integer.

uint32_t> htofl( DaqConversion* convertdata , uint32_t datum );

Converts the 32 bit integer datum from the local host's native byte order to the byte order described by the foreign host used to create the DaqConversion conversion block convertdata, and returns the converted value.

uint16_t htofs( DaqConversion* convertdata , uint16_t datum );

Converts the 16 bit integer datum from the local host's native byte order to the byte order described by the foreign host used to create the DaqConversion conversion block convertdata, and returns the converted value.

Types and public data

CVT_WORDSIGNATURE is a 16 bit byte order signature you will need to supply in any data you originate, and CVT_LONGSIGNATURE is a 32 bit byte order signature you will need to supply in any data you originate.

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