The sample contract serves as a demonstration of general QVM logic.
It is capable of:
registering users into the database
storing the last registered user's name in the database
echoing the previous user's name to STDOUT
incrementing the total registered user count
storing above counter in the database
Sample code
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static int envAtoi(const char* env) {
const char* val = getenv(env);
if (val == NULL) {
return 0;
}
return atoi(val);
}
int main(int argc, char *argv[]) {
// THIS SAMPLE ONLY SUPPORTS THE "register" FUNCTION
if (argc == 3 && strcmp(argv[1], "register") == 0) {
// GET THE CURRENT USER'S NAME
const char *previousName = getenv("DB_USER_CURRENT");
// OR DEFAULT TO "unknown" IF THIS IS THE FIRST CALL
if (previousName == NULL || strlen(previousName) == 0) {
previousName = "unknown";
}
// GET THE TOTAL USER COUNT
int totalUserCount = envAtoi("DB_TOTALUSERS");
// WRITE PREVIOUS USER NAME TO STDOUT
printf("OUT=prevname: %s\n", previousName);
// UPDATE CURRENT USER NAME BY WRITING IT TO DB
printf("DBW=USER_CURRENT=%s\n", argv[2]);
// STORE USER NAME UNDER A STORAGE SLOT FOR PERSISTENCE (CURRENT GETS OVERWRITTEN ON EACH CALL)
printf("DBW=USER_%d=%s\n", totalUserCount, argv[2]);
// INCREMENT THE TOTAL USER COUNT
printf("DBW=TOTALUSERS=%d\n", totalUserCount+1);
return 0;
}
if (argc >= 2) {
fprintf(stderr, "Wrong CMD: %s\n", argv[1]);
exit(1);
}
fprintf(stderr, "Wrong args!\n");
exit(1);
}
Save the contract
Open a text editor and save above sample contract as main.c file.
