passTwo

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

// Function to perform the Pass Two of the assembler process
void passTwo(char label[10], char opcode[10], char operand[10], char code[10], char mnemonic[3])
{
    FILE *f1, *f2, *f3, *f4, *f5;
    int locctr, start, length, recordLength = 0;
    char textRecord[70] = "";  // Holds the contents of the current text record
    int textStartAddr;  // Tracks the starting address of the current text record

    // Open all necessary files for reading and writing
    if ((f1 = fopen("intermediate.txt", "r")) == NULL ||
        (f2 = fopen("optab.txt", "r")) == NULL ||
        (f3 = fopen("symtab.txt", "r")) == NULL ||
        (f4 = fopen("output.txt", "w")) == NULL ||
        (f5 = fopen("length.txt", "r")) == NULL)
    {
        printf("Error opening one of the files.\n");
        exit(1);
    }

    // Read the program's starting label, opcode, and operand, then the program length
    fscanf(f1, "%s\t%s\t%s", label, opcode, operand);
    fscanf(f5, "%d", &length);

    // If the first opcode is "START", initialize the program's starting address
    if (strcmp(opcode, "START") == 0) {
        start = atoi(operand);  // Convert starting address to an integer
        fprintf(f4, "H^%s^%06d^%02d\n", label, start, length);  // Write header record
        fscanf(f1, "%X\t%s\t%s\t%s", &locctr, label, opcode, operand);  // Read next line
    } else {
        locctr = 0;  // If no START directive, start at address 0
    }

    textStartAddr = locctr;  // Initialize text record start address

    // Main loop to process each line until encountering the "END" opcode
    while (strcmp(opcode, "END") != 0) {
        rewind(f2);  // Reset optab file pointer to the beginning
        int found = 0;
        char objectCode[10] = "";  // String to hold generated object code

        // Search for the opcode in the optab to get its machine code
        while (fscanf(f2, "%s\t%s", code, mnemonic) != EOF) {
            if (strcmp(opcode, code) == 0) {  // Match found in optab
                if (strcmp(operand, "-") != 0) {  // If operand exists
                    rewind(f3);  // Reset symtab file pointer to search for operand
                    char symbol[10];
                    int address;

                    // Search for the operand's address in the symtab
                    while (fscanf(f3, "%s\t%X", symbol, &address) != EOF) {
                        if (strcmp(operand, symbol) == 0) {  // Match found in symtab
                            sprintf(objectCode, "%s%04X^", mnemonic, address);  // Format object code
                            recordLength += 3;
                            found = 1;
                            break;
                        }
                    }
                } else {  // If no operand, use 0000 as the address
                    sprintf(objectCode, "%s0000^", mnemonic);
                    recordLength += 3;
                    found = 1;
                }
                break;
            }
        }

        // Handle cases where the opcode is "WORD" or "BYTE"
        if (!found) {
            if (strcmp(opcode, "WORD") == 0) {  // For WORD, convert operand to object code
                sprintf(objectCode, "%06d^", atoi(operand));
                recordLength += 3;
            } else if (strcmp(opcode, "BYTE") == 0) {  // For BYTE, process character or hex constants
                if (operand[0] == 'C') {  // If BYTE operand is a character
                    for (int i = 2; i < strlen(operand) - 1; i++) {
                        sprintf(objectCode + strlen(objectCode), "%02X", operand[i]);  // Convert to ASCII hex
                        recordLength++;
                    }
                    strcat(objectCode, "^");
                } else if (operand[0] == 'X') {  // If BYTE operand is a hex constant
                    strcat(objectCode, operand + 2);  // Append hex digits to object code
                    strcat(objectCode, "^");
                    recordLength += (strlen(operand) - 3) / 2;
                }
            }
        }

        // Check if the current object code will exceed max record length (1E in hex, or 30 in decimal)
        if (recordLength > 30) {
            // Write the current text record to output and start a new record
            fprintf(f4, "T^%06X^%02llX^%s\n", textStartAddr, recordLength - strlen(objectCode) / 2, textRecord);
            textStartAddr = locctr;  // Reset text start address for new record
            strcpy(textRecord, "");  // Clear text record
            recordLength = strlen(objectCode) / 2;  // Reset record length
        }

        strcat(textRecord, objectCode);  // Add the generated object code to the text record

        // Read the next line in the intermediate file
        fscanf(f1, "%X\t%s\t%s\t%s", &locctr, label, opcode, operand);
    }

    // Write the final text record to the output file
    fprintf(f4, "T^%06X^%02X^%s\n", textStartAddr, recordLength, textRecord);

    // Write the end record, specifying the program start address
    fprintf(f4, "E^%06d\n", start);

    // Close all opened files
    fclose(f1); fclose(f2); fclose(f3); fclose(f4); fclose(f5);

    printf("Pass 2 completed. Object code generated in output.txt\n");  // Confirmation message
}

int main()
{
    char label[10], opcode[10], operand[10];
    char code[10], mnemonic[3];

    // Call the Pass Two function to generate object code
    passTwo(label, opcode, operand, code, mnemonic);
    return 0;
}



/*
---------------------------
    intermediate.txt
---------------------------
    SORT    START   1000
1000    -   LDA NUM1
1003    -   COMP    NUM2
1006    -   JLT SKIP
1009    -   LDA NUM1
100C    -   STA TEMP
100F    -   LDA NUM2
1012    -   STA NUM1
1015    -   LDA TEMP
1018    -   STA NUM2
101B    SKIP    J   SKIP
101E    NUM1    WORD    5
1021    NUM2    WORD    3
1024    TEMP    WORD    0
1027    -   END SORT


---------------------------
        optab.txt
---------------------------
LDA 00
STA 0C
COMP    28
JLT 38
J   3C


---------------------------
        symtab.txt
---------------------------
SKIP    101B
NUM1    101E
NUM2    1021
TEMP    1024



---------------------------
        length.txt
---------------------------
27


---------------------------
        output.txt
---------------------------
H^SORT^001000^27
T^001000^1E^00101E^281021^38101B^00101E^0C1024^001021^0C101E^001024^0C1021^3C101B^
T^00101E^09^000005^000003^000000^
E^001000
*/