CondFormats/SiPixelObjects/src/SiPixelDbItem.cc - master - githubmirror/cmssw

CondFormats/SiPixelObjects/src/SiPixelDbItem.cc
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11 июн 2019, 11:29
11 июн 2019, 11:29e9d3fcc
#include "CondFormats/SiPixelObjects/interface/SiPixelDbItem.h"

#include <iostream>
#include <algorithm>

//! The logic of individual setters:
//! First, we put the new value into newXXX, which is a 32-bit word
//! which has the new value at the bits where it should go, and 0's
//! everywhere else.  To make it, we:
//! - assign the value
//! - AND with a mask -- so all others are zeroes
//! - shift up by noise_shift bits
//!
//! Next, we prepare the oldValue with a whole where newXXX needs to go.
//!  ~(mask << shift) has 1's everywhere except where the new value will go,
//! so AND-ing packedVal_ with it creates a `whole' for the new value.
//!
//! Finally, the new value is an OR of the two (since the wholes have 0's)
//!
//! Example:
//!   00 03 c3 02 -- old, new one must blow c3 away, so we AND with ff ff 00 ff,
//!   and get 00 03 00 02.
//!   The new number is now positioned to be ff ff a2 ff, and then we AND these
//!   two and get 00 03 a2 02.  We have replaced c3 with a2.

void SiPixelDbItem::setNoise(short n) {
  PackedPixDbType newNoise = (n & packing_.noise_mask) << packing_.noise_shift;
  PackedPixDbType oldValue = packedVal_ & (~(packing_.noise_mask << packing_.noise_shift));
  packedVal_ = oldValue | newNoise;
}

void SiPixelDbItem::setPedestal(short p) {
  PackedPixDbType newPedestal = (p & packing_.pedestal_mask) << packing_.pedestal_shift;
  PackedPixDbType oldValue = packedVal_ & (~(packing_.pedestal_mask << packing_.pedestal_shift));
  packedVal_ = oldValue | newPedestal;
}

void SiPixelDbItem::setGain(float g) {
  // Convert gain into a shifted-integer
  int mult_factor = 1 << packing_.gain_shift;  // TO DO: check
  unsigned short gInIntRep = int(g * mult_factor);

  PackedPixDbType newGain = (gInIntRep & packing_.gain_mask) << packing_.gain_shift;
  PackedPixDbType oldValue = packedVal_ & (~(packing_.gain_mask << packing_.gain_shift));
  packedVal_ = oldValue | newGain;
}

void SiPixelDbItem::setStatus(char s) {
  PackedPixDbType newStatus = (s & packing_.status_mask) << packing_.status_shift;
  PackedPixDbType oldValue = packedVal_ & (~(packing_.status_mask << packing_.status_shift));
  packedVal_ = oldValue | newStatus;
}

//! A fast version which sets all in one go.
void SiPixelDbItem::set(short noise, short pedestal, float gain, char status) {
  // Convert gain into a shifted-integer
  int mult_factor = 1 << packing_.gain_shift;  // TO DO: check usage here
  unsigned short gInIntRep = int(gain * mult_factor);

  packedVal_ = (noise << packing_.noise_shift) | (pedestal << packing_.pedestal_shift) |
               (gInIntRep << packing_.gain_shift) | (status << packing_.status_shift);
}

SiPixelDbItem::Packing::Packing(int noise_w, int pedestal_w, int gain_w, int status_w)
    : noise_width(noise_w), pedestal_width(pedestal_w), status_width(status_w) {
  // Constructor: pre-computes masks and shifts from field widths
  // Order of fields (from right to left) is
  // noise, pedestal, gain, status count.

  if (noise_w + pedestal_w + gain_w + status_w != 32) {
    std::cout << std::endl
              << "Error in SiPixelDbItem::Packing constructor:"
              << "sum of field widths != 32" << std::endl;
    // TO DO: throw an exception?
  }

  // Fields are counted from right to left!

  noise_shift = 0;
  pedestal_shift = noise_shift + noise_w;
  gain_shift = pedestal_shift + pedestal_w;
  status_shift = gain_shift + gain_w;

  // Ensure the complement of the correct
  // number of bits:
  PackedPixDbType zero32 = 0;  // 32-bit wide

  noise_mask = ~(~zero32 << noise_w);
  pedestal_mask = ~(~zero32 << pedestal_w);
  gain_mask = ~(~zero32 << gain_w);
  status_mask = ~(~zero32 << status_w);
}

//  Initialize the packing (order is: noise, pedestal, gain, status)
SiPixelDbItem::Packing SiPixelDbItem::packing_(8, 8, 8, 8);  // TO DO: TBD