Sample code to generate and read a CSV file for use in an integer mapping table

mapping.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#define MAX_TABLE_SIZE 100

// Define the struct to hold the table data
struct Transformation {
    int originalValue;
    int transformedValue;
};

// Function to create and initialize the CSV file
void createCSVFile(struct Transformation table[], int count) {
    FILE *csvFile = fopen("table.csv", "w");
    if (csvFile != NULL) {
        // Add column headers to the CSV file
        fprintf(csvFile, "OriginalValue,TransformedValue\n");

        // Add the data from the table to the CSV file
        for (int i = 0; i < count; i++) {
            fprintf(csvFile, "%d,%d\n", table[i].originalValue, table[i].transformedValue);
        }

        // Close the file after writing data
        fclose(csvFile);
    } else {
        printf("Error creating the CSV file. Exiting.\n");
    }
}

int main() {
    // Declare an array of structs to hold the table data
    struct Transformation table[MAX_TABLE_SIZE];

    // Check if the file exists
    FILE *csvFile = fopen("table.csv", "r");
    if (csvFile == NULL) {
        printf("CSV file doesn't exist. Creating a new CSV file.\n");
        // Add some sample values (replace with your desired values)
        int count = 3;
        struct Transformation sampleTable[] = {
            {1, 10},
            {2, 20},
            {3, 30}
        };
        createCSVFile(sampleTable, count);
        printf("New CSV file created with column headers and sample values.\n");
    } else {
    	fclose(csvFile);
    }

    // File exists, so close it and reopen in read-write mode (for further operations)
    csvFile = fopen("table.csv", "r+");
    if (csvFile == NULL) {
        printf("Error opening the CSV file for read-write access. Exiting.\n");
        return 1;
    }

    // Read data from the CSV file and populate the table
    int count = 0;
    char line[100]; // Assuming the line won't exceed 100 characters
    while (fgets(line, sizeof(line), csvFile) != NULL && count < MAX_TABLE_SIZE) {
        // Skip the first line (column headers)
        if (strstr(line, "OriginalValue,TransformedValue") != NULL) {
            continue;
        }

        // Use strtok to parse the CSV line and extract the two integers
        char *token = strtok(line, ",");
        char *endptr;
        errno = 0;

        // Parse originalValue
        int originalValue = strtol(token, &endptr, 10);
        if (errno == ERANGE || *endptr != '\0') {
            printf("Error: Invalid originalValue integer in the CSV file: %s\n", token);
            continue;
        }

        // Parse transformedValue
        token = strtok(NULL, ",");
        int transformedValue;
        if (sscanf(token, "%d", &transformedValue) != 1) {
            printf("Error: Invalid transformedValue integer in the CSV file: %s\n", token);
            continue;
        }

        // Store the valid values in the table
        table[count].originalValue = originalValue;
        table[count].transformedValue = transformedValue;
        count++;
    }

    // Close the CSV file
    fclose(csvFile);

    // Now, you have the table imported from the CSV file.
    // You can use it to transform specific integer values.

    int input_value = 3; // For example, the input value you want to transform
    int transformed_value = -1; // Initialize to a default value

    // Find the corresponding transformed value from the table
    for (int i = 0; i < count; i++) {
        if (table[i].originalValue == input_value) {
            transformed_value = table[i].transformedValue;
            break; // Exit the loop once we find the matching value
        }
    }

    if (transformed_value != -1) {
        printf("Input value: %d, Transformed value: %d\n", input_value, transformed_value);
    } else {
        printf("Input value not found in the table.\n");
    }

    return 0;
}