LithosAnanake/src/memory_management.c

/*
  StarForth — Steady-State Virtual Machine Runtime

  Copyright (c) 2023–2025 Robert A. James
  All rights reserved.

  This file is part of the StarForth project.

  Licensed under the StarForth License, Version 1.0 (the "License");
  you may not use this file except in compliance with the License.

  You may obtain a copy of the License at:
      https://github.com/star.4th@proton.me/StarForth/LICENSE.txt

  This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
  express or implied, including but not limited to the warranties of
  merchantability, fitness for a particular purpose, and noninfringement.

 See the License for the specific language governing permissions and
 limitations under the License.

 StarForth — Steady-State Virtual Machine Runtime
  Copyright (c) 2023–2025 Robert A. James
  All rights reserved.

  This file is part of the StarForth project.

  Licensed under the StarForth License, Version 1.0 (the "License");
  you may not use this file except in compliance with the License.

  You may obtain a copy of the License at:
       https://github.com/star.4th@proton.me/StarForth/LICENSE.txt

  This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
  express or implied, including but not limited to the warranties of
  merchantability, fitness for a particular purpose, and noninfringement.

  See the License for the specific language governing permissions and
  limitations under the License.

 */

#include "../include/vm.h"
#include "../include/log.h"

/**
 * @brief Allocates memory from the VM's dictionary space
 * @param vm Pointer to the VM instance
 * @param bytes Number of bytes to allocate
 * @return Pointer to the allocated memory or NULL if allocation fails
 * @note The allocation is done from the VM's dictionary space which is limited to DICTIONARY_MEMORY_SIZE
 */
void *vm_allot(VM *vm, size_t bytes) {
    if (!vm || !vm->memory) {
        log_message(LOG_ERROR, "vm_allot: VM or memory is NULL");
        return NULL;
    }

    /* Ensure we don't allocate beyond dictionary space (first DICTIONARY_BLOCKS blocks = DICTIONARY_MEMORY_SIZE bytes) */
    log_message(LOG_DEBUG, "vm_allot: Requesting %zu bytes, current here=%zu, limit=%d",
                bytes, vm->here, DICTIONARY_MEMORY_SIZE);

    if (vm->here + bytes >= DICTIONARY_MEMORY_SIZE) {
        log_message(LOG_ERROR, "Dictionary space full (here=%zu, bytes=%zu, dict_limit=%d)",
                    vm->here, bytes, DICTIONARY_MEMORY_SIZE);
        vm->error = 1;
        return NULL;
    }

    void *ptr = vm->memory + vm->here;
    vm->here += bytes;

    /* Log which block we're using */
    int current_block = vm->here / BLOCK_SIZE;
    log_message(LOG_DEBUG, "ALLOT: Allocated %zu bytes at offset %zu (block %d)",
                bytes, vm->here - bytes, current_block);

    return ptr;
}

/**
 * @brief Aligns the VM's dictionary pointer (here) to the cell boundary
 * @param vm Pointer to the VM instance
 * @note Adds padding bytes if necessary to ensure proper alignment for cell_t type
 */
void vm_align(VM *vm) {
    size_t align = sizeof(cell_t);
    size_t misalignment = vm->here % align;

    if (misalignment != 0) {
        size_t padding = align - misalignment;
        void *pad = vm_allot(vm, padding);
        if (pad == NULL) {
            log_message(LOG_ERROR, "vm_align: Out of memory while aligning");
            vm->error = 1;
            return;
        }

        /* Optional: zero out the padding */
        unsigned char *bytes = (unsigned char *) pad;
        for (size_t i = 0; i < padding; ++i) {
            bytes[i] = 0;
        }

        log_message(LOG_DEBUG, "vm_align: Added %zu byte(s) of padding", padding);
    }
}

/**
 * @brief Gets the memory address for a specified block number
 * @param vm Pointer to the VM instance
 * @param block_num Block number to get the address for
 * @return Pointer to the start of the block or NULL if block number is invalid
 * @note Blocks are fixed-size memory regions of BLOCK_SIZE bytes
 */
void *vm_get_block_addr(VM *vm, int block_num) {
    if (block_num < 0 || block_num >= MAX_BLOCKS) {
        log_message(LOG_ERROR, "vm_get_block_addr: Invalid block number %d", block_num);
        return NULL;
    }
    return vm->memory + (block_num * BLOCK_SIZE);
}

/* Convert address to block number */
/**
 * @brief Converts a memory address to its corresponding block number
 * @param vm Pointer to the VM instance
 * @param addr Memory address to convert
 * @return Block number (0 to MAX_BLOCKS-1) or -1 if address is outside VM memory
 * @note Used for determining which block a memory address belongs to
 */
int vm_addr_to_block(VM *vm, void *addr) {
    if (addr < (void *) vm->memory ||
        addr >= (void *) (vm->memory + VM_MEMORY_SIZE)) {
        return -1; /* Outside VM memory */
    }

    uintptr_t offset = (uintptr_t) addr - (uintptr_t) vm->memory;
    return (int) (offset / BLOCK_SIZE);
}