j-lang/src/memory/allocator.h

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

/*
    Custom Memory Allocator

    Implementacion custom de un memory allocator que opera sobre un array de
   bytes usandolo como "heap"
*/

#define JLANG_OK 0
#define JLANG_ERR 1
#define JLANG_FREE 0
#define JLANG_HEADER 1
#define JLANG_PAYLOAD 2

/*
    La estructura de Metadata se encarga de almacenar el tamaño del bloque y si
   está en uso. Se añadirá al principio de cada bloque [BLOCK_METADATA] +
   [BLOCK_BYTES]
*/
typedef struct {
  size_t size; // 8 bytes
  int in_use;  // 4 bytes
               // --- aquí el compilador mete 4 bytes invisibles ---
} JLANG_metadata;

/*
    La estructura de Memory Allocator se encarga de almancenar el array de
   memoria y el tamaño de esta.
*/
typedef struct {
  char *memory; // 8 bytes
  size_t size;  // 8 bytes
} JLANG_memory_allocator;

void *JLANG_CreateAllocator() {
  // Allocate memory in heap for JLANG_memory_allocator
  JLANG_memory_allocator *allocator =
      (JLANG_memory_allocator *)malloc(sizeof(JLANG_memory_allocator));

  // Assign default free bytes
  allocator->memory = (char *)malloc(1 * 1024);
  allocator->size = 1 * 1024;

  // ensure all memory is zero
  for (int i = 0; i < 1 * 1024; i++) {
    allocator->memory[i] = 0;
  }

  return allocator;
}

size_t JLANG_used(void *ptr) {
  JLANG_memory_allocator *allocPtr = (JLANG_memory_allocator *)ptr;

  // Iterate memory parsing only metadata
  JLANG_metadata *currentHeader = (JLANG_metadata *)allocPtr->memory;
  size_t used = 0;
  while (currentHeader->in_use != 0 && used < allocPtr->size) {
    used += sizeof(JLANG_metadata) + currentHeader->size;

    // Current block is in_use, jump to next block
    currentHeader =
        (JLANG_metadata *)((char *)currentHeader + sizeof(JLANG_metadata) +
                           currentHeader->size);
  }

  return used;
}

void *JLANG_last_free(void *ptr) {
  JLANG_memory_allocator *allocPtr = (JLANG_memory_allocator *)ptr;

  // Iterate memory parsing only metadata
  JLANG_metadata *currentHeader = (JLANG_metadata *)allocPtr->memory;
  size_t used = 0;
  while (currentHeader->in_use != 0 && used < allocPtr->size) {
    used += sizeof(JLANG_metadata) + currentHeader->size;

    // Current block is in_use, jump to next block
    currentHeader =
        (JLANG_metadata *)((char *)currentHeader + sizeof(JLANG_metadata) +
                           currentHeader->size);
  }

  return currentHeader;
}

void *JLANG_malloc(void *ptr, size_t size) {
  JLANG_memory_allocator *allocPtr = (JLANG_memory_allocator *)ptr;

  // 1. Hay bloques disponibles??
  size_t used = JLANG_used(ptr);
  size_t available = allocPtr->size - used;

  // chequear si hay suficiente espacio libre
  if (available > size + sizeof(JLANG_metadata)) {
    JLANG_metadata *freeHeader = (JLANG_metadata *)JLANG_last_free(ptr);
    freeHeader->size = size;
    freeHeader->in_use = 1;

    return (char *)freeHeader + sizeof(JLANG_metadata);
  }

  return NULL; // TODO
}

void JLANG_free(void *ptr, void *blockPtr) {
  JLANG_memory_allocator *allocPtr = (JLANG_memory_allocator *)ptr;

  // Get block header
  JLANG_metadata *blockHeader =
      (JLANG_metadata *)((char *)blockPtr - sizeof(JLANG_metadata));

  // Set block as not_used
  blockHeader->in_use = 0;
}

/*
    Debug Visualization

    [FF FF FF FF FF FF FF ]
*/

int _ceil(float v) {
  int n = (int)v;
  float r = v - n;

  if (r > 0) {
    return n + 1;
  }
  return n;
}

void JLANG_visualize(void *ptr) {
  JLANG_memory_allocator *allocPtr = (JLANG_memory_allocator *)ptr;

  // Step 1. Get byte type
  char *byteMapPtr = (char *)malloc(allocPtr->size);
  memset(byteMapPtr, 0, allocPtr->size);

  JLANG_metadata *currentHeader = (JLANG_metadata *)allocPtr->memory;
  long used = 0;
  while (used < allocPtr->size) {
    long blockIndex = (char *)currentHeader - (char *)allocPtr->memory;
    used += sizeof(JLANG_metadata) + currentHeader->size;

    /*
        HEADER
        blockIndex + sizeof(JLANG_metadata)
    */

    if (currentHeader->size > 0) {
      byteMapPtr[blockIndex] = JLANG_HEADER;
      for (int i = 0; i < sizeof(JLANG_metadata); i++) {
        byteMapPtr[blockIndex + i] = JLANG_HEADER;
      }

      /*
          PAYLOAD
      */
      for (int i = 0; i < currentHeader->size; i++) {
        byteMapPtr[blockIndex + sizeof(JLANG_metadata) + i] = JLANG_PAYLOAD;
      }
    } else {
      break;
    }

    // Jump to next block
    currentHeader =
        (JLANG_metadata *)((char *)currentHeader + sizeof(JLANG_metadata) +
                           currentHeader->size);
  }

  // Step 2. Draw

  int bytePerRow = 40;
  int totalRows = _ceil(allocPtr->size / bytePerRow);
  printf("totalRows=%d\n", totalRows);

  char *currentMemPtr = allocPtr->memory;

  for (int i = 0; i < totalRows; i++) {
    printf("[");
    for (int n = 0; n < bytePerRow; n++) {

      int index = n + i * bytePerRow;

      switch (byteMapPtr[index]) {
      case JLANG_HEADER:
        printf("\033[46m");
        break;
      case JLANG_FREE:
        printf("\033[32m");
        break;
      default:
        printf("\033[41m");
        break;
      }

      printf("%.2x", (unsigned char)*(currentMemPtr + (n + i * bytePerRow)));

      if (n < bytePerRow - 1) {
        printf(" ");
      }

      printf("\033[0m");
    }

    printf("]\n");
  }
}