#include "buffer.h"

#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <unistd.h>

void BufferCreate(struct Buffer* buffer) {
  memset(buffer, 0, sizeof(struct Buffer));
}

void* BufferReserve(struct Buffer* buffer, size_t size) {
  size_t alloc = buffer->size + size;
  if (alloc > buffer->alloc) {
    void* data = realloc(buffer->data, alloc);
    if (!data) return NULL;
    buffer->data = data;
    buffer->alloc = alloc;
  }
  return (char*)buffer->data + buffer->size;
}

int BufferAppendFrom(struct Buffer* buffer, int fd) {
  int nbytes;
  if (ioctl(fd, FIONREAD, &nbytes) == -1) return -1;
  if (!nbytes) return 0;
  void* data = BufferReserve(buffer, (size_t)nbytes);
  if (!data) return -1;
  ssize_t result = read(fd, data, (size_t)nbytes);
  if (result > 0) buffer->size += (size_t)result;
  return (int)result;
}

void BufferDiscard(struct Buffer* buffer, size_t size) {
  size_t tail_size = buffer->size - size;
  if (tail_size) {
    const char* tail = (const char*)buffer->data + size;
    memmove(buffer->data, tail, tail_size);
  }
  buffer->size = tail_size;
}

void BufferDestroy(struct Buffer* buffer) { free(buffer->data); }