// Emacs style mode select   -*- C -*-
//-----------------------------------------------------------------------------
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
// 02111-1307, USA.
//
// Emulates the IO functions in C stdio.h reading and writing to
// memory.
//

// e6y
// All tabs are replaced with spaces.
// Fixed eol style of files.

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

#include "memio.h"

#include "z_zone.h"

typedef enum {
  MODE_READ,
  MODE_WRITE,
} memfile_mode_t;

struct _MEMFILE {
  unsigned char *buf;
  size_t buflen;
  size_t alloced;
  unsigned int position;
  memfile_mode_t mode;
};

// Open a memory area for reading

MEMFILE *mem_fopen_read(const void *buf, size_t buflen)
{
  MEMFILE *file;

  file = Z_Malloc(sizeof(MEMFILE));

  // The MEMFILE struct is overloaded for both read-only and write use cases
  // This is required to interface with 3rd party libraries (I think)
  #pragma GCC diagnostic push
  #pragma GCC diagnostic ignored "-Wcast-qual"
  file->buf = (unsigned char *) buf;
  #pragma GCC diagnostic pop
  file->buflen = buflen;
  file->position = 0;
  file->mode = MODE_READ;

  return file;
}

// Read bytes

size_t mem_fread(void *buf, size_t size, size_t nmemb, MEMFILE *stream)
{
  size_t items;

  if (stream->mode != MODE_READ)
  {
    printf("not a read stream\n");
    return -1;
  }

  // Trying to read more bytes than we have left?

  items = nmemb;

  if (items * size > stream->buflen - stream->position)
  {
    items = (stream->buflen - stream->position) / size;
  }

  // Copy bytes to buffer

  memcpy(buf, stream->buf + stream->position, items * size);

  // Update position

  stream->position += items * size;

  return items;
}

// Open a memory area for writing

MEMFILE *mem_fopen_write(void)
{
  MEMFILE *file;

  file = Z_Malloc(sizeof(MEMFILE));

  file->alloced = 1024;
  file->buf = Z_Malloc(file->alloced);
  file->buflen = 0;
  file->position = 0;
  file->mode = MODE_WRITE;

  return file;
}

// Write bytes to stream

size_t mem_fwrite(const void *ptr, size_t size, size_t nmemb, MEMFILE *stream)
{
  size_t bytes;

  if (stream->mode != MODE_WRITE)
  {
    return -1;
  }

  // More bytes than can fit in the buffer?
  // If so, reallocate bigger.

  bytes = size * nmemb;

  while (bytes > stream->alloced - stream->position)
  {
    unsigned char *newbuf;

    newbuf = Z_Malloc(stream->alloced * 2);
    memcpy(newbuf, stream->buf, stream->alloced);
    Z_Free(stream->buf);
    stream->buf = newbuf;
    stream->alloced *= 2;
  }

  // Copy into buffer

  memcpy(stream->buf + stream->position, ptr, bytes);
  stream->position += bytes;

  if (stream->position > stream->buflen)
    stream->buflen = stream->position;

  return nmemb;
}

void mem_get_buf(MEMFILE *stream, void **buf, size_t *buflen)
{
  *buf = stream->buf;
  *buflen = stream->buflen;
}

void mem_fclose(MEMFILE *stream)
{
  if (stream->mode == MODE_WRITE)
  {
    Z_Free(stream->buf);
  }

  Z_Free(stream);
}

long mem_ftell(MEMFILE *stream)
{
  return stream->position;
}

int mem_fseek(MEMFILE *stream, signed long position, mem_rel_t whence)
{
  unsigned int newpos;

  switch (whence)
  {
    case MEM_SEEK_SET:
      newpos = (int) position;
      break;

    case MEM_SEEK_CUR:
      newpos = (int) (stream->position + position);
      break;

    case MEM_SEEK_END:
      newpos = (int) (stream->buflen + position);
      break;
    default:
      return -1;
  }

  if (newpos <= stream->buflen)
  {
    stream->position = newpos;
    return 0;
  }
  else
  {
    printf("Error seeking to %i\n", newpos);
    return -1;
  }
}
