Goのスライスの挙動を理解するためにCでそれっぽいやつを再実装してみる

go-like-slice.c

#include <stdio.h>
#include <stdlib.h> // size_t

struct IntSlice {
  int    *ptr;
  size_t len;
  size_t cap;
};

struct IntSlice newIntSlice (int *ptr, size_t start, size_t end, size_t cap) {
  size_t len = end - start;
  struct IntSlice s = { ptr + start, len, cap };
  return s;
}

struct IntSlice newIntSliceFromSlice (struct IntSlice slice, size_t start, size_t end) {
  size_t len  = end - start;
  size_t ncap = slice.cap - start;
  struct IntSlice s = { slice.ptr + start, len, ncap };
  return s;
}

void dumpSlice (struct IntSlice slice) {
  printf("ptr:%p len:%d, cap:%d\t", slice.ptr, (int)slice.len, (int)slice.cap);
  for (int i = 0; i < slice.len; i++) {
    printf("%d ", slice.ptr[i]);
  }
  fputc('\n', stdout);
}

int main (void) {
  int a[5] = {1, 2, 3, 4, 5};

  struct IntSlice as1 = newIntSlice(a, 0, 5, 5);
  dumpSlice(as1);
  struct IntSlice as2 = newIntSliceFromSlice(as1, 0, 0);
  dumpSlice(as2);
  struct IntSlice as3 = newIntSliceFromSlice(as2, 0, 2);
  dumpSlice(as3);
  struct IntSlice as4 = newIntSliceFromSlice(as3, 2, 5);
  dumpSlice(as4);

  return 0;
}