criscv/src/address_space.c

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

struct AddressSpace_s {
    // A pointer to a ROM array. The array can vary in length.
    uint8_t *rom;
    // The size of ROM.
    uint32_t romSize;

    // A pointer to a RAM array. The array can vary in length.
    uint8_t *ram;
    // The size of RAM.
    uint32_t ramSize;
};

typedef struct AddressSpace_s AddressSpace;


AddressSpace create_address_space(int romSize, int ramSize) {
    uint8_t rom[romSize];
    uint8_t ram[ramSize];

    AddressSpace addressSpace = { rom, romSize, ram, ramSize };

    return addressSpace;
}

int read_address_space(const AddressSpace *addressSpace, uint32_t address, const int n, void *dest) {
    uint32_t romSize = addressSpace->romSize;
    uint32_t ramSize = addressSpace->ramSize;

    if (address < romSize) {
        if (address + n < romSize) {
            fprintf(stderr, "Reading %d bytes from %d will exceed ROM address space of %d\n", n, address, romSize); // TODO maybe move to perror
            return 1;
        } else {
            memcpy(dest, addressSpace->rom + address, n);
        }
    } else if (address < romSize + ramSize) {
        if (address + n < romSize + ramSize) {
            fprintf(stderr, "Reading %d bytes from %d (total %d) will exceed RAM address space of %d (total %d)\n", n, address, address + romSize, ramSize, romSize + ramSize);
            return 1;
        } else {
            address -= romSize;
            memcpy(dest, addressSpace->ram + address, n);
        }

    } else {
        // TODO IO
    }

    return 0;
}

int write_address_space(const AddressSpace *addressSpace, uint32_t address, const int n, void *src) {
    uint32_t romSize = addressSpace->romSize;
    uint32_t ramSize = addressSpace->ramSize;

    if (address < romSize) {
        if (address + n < romSize) {
            fprintf(stderr, "Writing %d bytes to %d will exceed ROM address space of %d\n", n, address, romSize);
            return 1;
        } else {
            memcpy(addressSpace->rom + address, src, n);
        }
    } else if (address < romSize + ramSize) {
        if (address + n < romSize + ramSize) {
            fprintf(stderr, "Writing %d bytes to %d (total %d) will exceed RAM address space of %d (total %d)\n", n, address, address + romSize, ramSize, romSize + ramSize);
            return 1;
        } else {
            address -= romSize;
            memcpy(addressSpace->ram + address, src, n);
        }
    } else {
        // TODO IO
    }

    return 0;
}