/*
Copyright (C) 1997-2001 Id Software, Inc.

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.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

#include "shared/shared.h"
#include "system/hunk.h"
#include <windows.h>

void Hunk_Begin(memhunk_t *hunk, size_t maxsize)
{
    if (maxsize > SIZE_MAX - 4095)
        Com_Error(ERR_FATAL, "%s: size > SIZE_MAX", __func__);

    // reserve a huge chunk of memory, but don't commit any yet
    hunk->cursize = 0;
    hunk->maxsize = (maxsize + 4095) & ~4095;
    hunk->base = VirtualAlloc(NULL, hunk->maxsize, MEM_RESERVE, PAGE_NOACCESS);
    if (!hunk->base)
        Com_Error(ERR_FATAL,
                  "VirtualAlloc reserve %"PRIz" bytes failed with error %lu",
                  hunk->maxsize, GetLastError());
}

void *Hunk_Alloc(memhunk_t *hunk, size_t size)
{
    void *buf;

    if (size > SIZE_MAX - 63)
        Com_Error(ERR_FATAL, "%s: size > SIZE_MAX", __func__);

    // round to cacheline
    size = (size + 63) & ~63;

    if (hunk->cursize > hunk->maxsize)
        Com_Error(ERR_FATAL, "%s: cursize > maxsize", __func__);

    if (size > hunk->maxsize - hunk->cursize)
        Com_Error(ERR_FATAL, "%s: couldn't allocate %"PRIz" bytes", __func__, size);

    hunk->cursize += size;

    // commit pages as needed
    buf = VirtualAlloc(hunk->base, hunk->cursize, MEM_COMMIT, PAGE_READWRITE);
    if (!buf)
        Com_Error(ERR_FATAL,
                  "VirtualAlloc commit %"PRIz" bytes failed with error %lu",
                  hunk->cursize, GetLastError());

    return (byte *)hunk->base + hunk->cursize - size;
}

void Hunk_End(memhunk_t *hunk)
{
    if (hunk->cursize > hunk->maxsize)
        Com_Error(ERR_FATAL, "%s: cursize > maxsize", __func__);

    // for statistics
    hunk->mapped = (hunk->cursize + 4095) & ~4095;
}

void Hunk_Free(memhunk_t *hunk)
{
    if (hunk->base && !VirtualFree(hunk->base, 0, MEM_RELEASE))
        Com_Error(ERR_FATAL, "VirtualFree failed with error %lu", GetLastError());

    memset(hunk, 0, sizeof(*hunk));
}