/*
 * CS 261 PA2: Mini-ELF loader
 *
 * Name: Nicholas Tamassia
 * This code was developed in compliance with the JMU Honor Code.
 */

#include "p2-load.h"

/**********************************************************************
 *                         REQUIRED FUNCTIONS
 *********************************************************************/

bool read_phdr (FILE *file, uint16_t offset, elf_phdr_t *phdr)
{
    if (!file || !phdr || fseek(file, offset, SEEK_SET) != 0) {
        return false;
    }

    return ((fread(phdr, sizeof(elf_phdr_t), 1, file) == 1) && phdr->magic == 0xDEADBEEF);
}

bool load_segment (FILE *file, byte_t *memory, elf_phdr_t *phdr)
{
    if (!file || !memory || !phdr) {
        return false;
    }

    if (phdr->p_vaddr + phdr->p_size > MEMSIZE || fseek(file, phdr->p_offset, SEEK_SET) != 0) {
        return false;
    }

    if ((fread(memory + phdr->p_vaddr, phdr->p_size, 1, file) != 1) && phdr->p_size != 0) {
        return false;
    }

    return true;
}

/**********************************************************************
 *                         OPTIONAL FUNCTIONS
 *********************************************************************/

void dump_phdrs (uint16_t numphdrs, elf_phdr_t *phdrs)
{
    printf(" Segment   Offset    Size      VirtAddr  Type      Flags\n");

    for (int i = 0; i < numphdrs; i++) {
        elf_phdr_t phdr = phdrs[i];
        char flags[4] = "RWX";

        for (int j = 2; j >= 0; j--) {
            if ((phdr.p_flags & (1 << (2 - j))) == 0) {
                flags[j] = ' ';
            }
        }

        printf("  %02d       0x%04x    0x%04x    0x%04x    %-10s%s\n", i, phdr.p_offset, phdr.p_size, phdr.p_vaddr, p_type_mapper(phdr.p_type), flags);
    }
}

char* p_type_mapper(uint16_t type) {
    switch (type) {
        case 0: return "DATA"; break;
        case 1: return "CODE"; break;
        case 2: return "STACK"; break;
        case 3: return "HEAP"; break;
        default: return "UNKNOWN"; break;
    }
}

void dump_memory (byte_t *memory, uint16_t start, uint16_t end)
{
    printf("Contents of memory from %04x to %04x:\n", start, end);

    int aligned_start = start - (start % 16);

    for (int i = aligned_start; i < end; i++) {
        if (i % 16 == 0) {
            printf("  %04x ", i);
        }

        if (i >= start) {
            printf(" %02x", memory[i]);
        } else {
            printf("   ");
        }
        
        if (i % 16 == 15 || i == end - 1) {
            printf("\n");
        } else if (i % 16 == 7) {
            printf(" ");
        }
    }
}