EVIO

EVIO is data format and corresponding software used at JLAB.

EVIO Manual version 2.0: pdf doc.

Event Building EVIO Scheme: pdf ppt pptx.

Not in the manual yet: 8-word EVIO block(record) header:

1. block length
2. block number
3. header length=8
4. event count (# of banks, without dictionary if it is inserted)
5. not used
6. bit info[31-8] version [7-0]; if dectionary is therer, bit 8 (starting from 0) will be set
7. unused
8. magic int = 0xc0da0100

CLAS12 guidelines:

• 'EVIO BANK' (not 'EVIO SEGMENT' or 'EVIO TAGSEGMENT' will be used for data banks; bank header has 2 words, first one is exclusive bank length in words, second one contains 3 fields: tag[31:16], contentType[15:8] and num[7:0]

• no mixed formats (for example 'int' and 'short') will be allowed in the same bank, format is described in 8-bit field contentType (or use type=0 and do custom swap ?)

• BOS bank name will be replaced with 16-bit field tag, BOS bank number will be replaced with 8-bit field num

• banks dictionary (former DDL replacement) will be provided in some form (ASCII ?) and will contains a notation on every bank tag, most important will be the number of 'columns' and the meaning of every column (for example id,tdcl,adcl,tdcr,tdcl), it will help to decode data from the bank and can be used by evio viewers; will be written at least in the beginning of every file

• data banks will be in 'unsigned short' or 'unsigned int' format; first element will be ID ('slot<<8+channel' without translation, 'layer<<8+wire' or similar with translation)

• some bank examples:

tdc version 1: ID, TDC
tdc version 2: ID, N_HITS, TDC_1, ... , TDC_N
adc (raw data hits): ID, N_SAMPLES(=window_width), ADC_1, ... , ADC_N
adc (window integral - 32bit): ID, ADC_SUM(can be 22 bits+1 bit overflow)
adc (pulse data hits): ID, N_SAMPLES, FIRST_SAMPLE, ADC_1, ..., ADC_N

• may give a tags to all existing CLAS banks and make sure CLAS12 bank tags do not overlap - will allow to process old and new banks together

EVIO possible extensions:

• file split - implemented in CLAS

• bank 'dictionary-based', or 'format-based' swap (will allow mixed format), can be enforced if contentType=0

EVIO format-based swap

Sergey B. proposed 2 functions to handle format-based banks in EVIO. The idea is to have designated contentType=0x11(or 0x12), which will contain 2 internal banks (or segments). First bank (or segment) will contain bank format description, and second bank (or segment) will contain data. Format can be stored in form of ascii string, or in binary form. Two evio swap functions are provided to handle format-based banks: eviofmt() converts format from character string form to binary form, and eviofmtswap() swaps data between big-endian and little-endian forms in according to the format (using binary form). Available formats are following FORTRAN rules in general, with some restrictions as shown in following examples: