Question

I’m opening a text file which can hold anywhere between 100 and 50,000 dataFrames, and assigning each line of the txt file to a dataFrame, where a dataFrame is defined as follows:

typedef struct {
  double x;
  double y;
  double z;
  double azimuth;
  double elevation;
  double roll;
} dataFrame;

I need the data to be accessible so that I can plot it in a graph in qwt, (which means I’ll need to create various other arrays from the data as well for instantaneous velocity etc.) but I’m a bit worried since I don’t know how much this is gonna slow down the system.
Currently, I read the number of lines, and then have

dataFrame*  left;
dataFrame*  right;
left = new dataFrame[lineCount/2];
right= new dataFrame[lineCount/2];

and then procede to fill it up as the data is read from the txt file.

Answer 1

If you only need fast indexing and you know the number of elements (lineCount) up front, nothing beats a good old array.*

If you also want fast appending, use a dynamic array such as std::vector or QVector.

If you want fast searching for an item by key, check out std::set, std::map, QSet, QHash.

[*] Almost nothing. Post your alternatives in the comments.