C language implementation of the code at http://mechanical-sympathy.blogspot.com.au/2012/10/compact-off-heap-structurestuples-in.html

TestCMemoryLayout

#define _POSIX_C_SOURCE 200809L
 
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
 
#define NUM_RECORDS (50 * 1000 * 1000)
 
struct CMemoryTrade {
	long TradeId; long ClientId; int VenueCode; int InstrumentCode; long Price; long Quantity; char Side;
};
 
struct CMemoryTrade trades[NUM_RECORDS];
  
int pack(char* value, int len) {
	int result = 0;
 
	switch (len) {
	case 4:
		result = (int)value[3];
	case 3:
		result |= (int)value[2] << 8;
	case 2:
		result |= (int)value[1] << 16;
	case 1:
		result |= (int)value[0] << 24;
		break;
	}
	return result;
}
 
 
void initTrades() {
	char* londonStockExchange;
	londonStockExchange = (char[4]){'X', 'L', 'O', 'N'};
	int venueCode = pack(londonStockExchange,4);
	free(londonStockExchange);
 
	char* billiton;
	billiton = (char[3]){'B', 'H', 'P'};
	int instrumentCode = pack(billiton,3);
	free(billiton);
 
	for (long i = 0; i < NUM_RECORDS; i++) {
		struct CMemoryTrade *trade = &(trades[i]);
 
		trade->TradeId = i;
		trade->ClientId = 1;
		trade->VenueCode = venueCode;
		trade->InstrumentCode = instrumentCode;
 
		trade->Price = i;
		trade->Quantity = i;
 
		if ((i&1) == 0) {
			trade->Side = 'B';
		} else {
			trade->Side = 'S';
		}
	}
}
 
double getTime(){
	struct timespec spec;
	clock_gettime(CLOCK_REALTIME, &spec);	
	double s  = spec.tv_sec;
	double ms = spec.tv_nsec;
	return (s*1000 + ms / 1000000);
}
 
void perfRun(int runNum) {	
	double startT = getTime();
	initTrades();
 
//	var m runtime.MemStats   		This is the Go code; not sure how to easily get this information in C.
//	runtime.ReadMemStats(&m)
//	fmt.Printf("Memory %v total, %v free\n",
//		m.TotalAlloc,
//		m.TotalAlloc-m.Alloc)
	long buyCost = 0;
	long sellCost = 0;
 
	for (long i = 0; i < NUM_RECORDS; i++) {
		struct CMemoryTrade *trade = &(trades[i]);
		if (trade->Side == 'B') {
			buyCost += trade->Price * trade->Quantity;
		} else {
			sellCost += trade->Price * trade->Quantity;
		}
	}
	double endT = getTime();
	double duration =  endT - startT;
	printf("%d - duration %f ms\n", runNum, duration);
	printf("buyCost = %ld sellCost = %ld\n", buyCost, sellCost);
}
 
int main() {
	printf("%ld",sizeof(struct CMemoryTrade));
	for (int i = 0; i < 5; i++) {
		perfRun(i);
	}
}