vn/code/vn_memory.h

/* date = April 26th 2023 10:11 pm */

#ifndef VN_MEMORY_H
#define VN_MEMORY_H

struct memory_arena
{
    platform_memory_block *CurrentBlock;
    umm MinimumBlockSize;
    s32 TemporaryMemoryCount;
};

struct temporary_memory
{
    memory_arena *Arena;
    platform_memory_block *Block;
    umm Used;
};

inline temporary_memory BeginTemporaryMemory(memory_arena *Arena)
{
    temporary_memory Result;
    Result.Arena = Arena;
    Result.Block = Arena->CurrentBlock;
    Result.Used = Arena->CurrentBlock ? Arena->CurrentBlock->Used : 0;
    
    ++Arena->TemporaryMemoryCount;
    
    return(Result);
}

inline void EndTemporaryMemory(temporary_memory Temp)
{
    memory_arena *Arena = Temp.Arena;
    while(Arena->CurrentBlock != Temp.Block)
    {
        platform_memory_block *MemoryBlock = Arena->CurrentBlock;
        Arena->CurrentBlock = MemoryBlock->ArenaPrev;
        Platform.DeallocateMemory(MemoryBlock);
    }
    
    if(Arena->CurrentBlock)
    {
        Assert(Arena->CurrentBlock->Used >= Temp.Used);
        Arena->CurrentBlock->Used = Temp.Used;
    }
    
    Assert(Arena->TemporaryMemoryCount > 0);
    --Arena->TemporaryMemoryCount;
} 

static void Release(memory_arena *Arena)
{
    while(Arena->CurrentBlock != 0)
    {
        platform_memory_block *MemoryBlock = Arena->CurrentBlock;
        b32 IsLastBlock = MemoryBlock->ArenaPrev  == 0;
        Arena->CurrentBlock = MemoryBlock->ArenaPrev;
        Platform.DeallocateMemory(MemoryBlock);
        
        if(IsLastBlock)
        {
            break;
        }
    }
}

enum arena_push_flag
{
    ArenaFlag_ClearToZero = 0x1,
};

struct arena_push_params
{
    u32 Flags;
    u32 Alignment;
};

inline arena_push_params DefaultArenaParams(void)
{
    arena_push_params Params = {};
    Params.Flags = ArenaFlag_ClearToZero;
    Params.Alignment = 4;
    return(Params);
}

inline arena_push_params NoClear(void)
{
    arena_push_params Params = DefaultArenaParams();
    Params.Flags &= ~ArenaFlag_ClearToZero;
    return(Params);
}

inline umm GetAlignmentOffset(memory_arena *Arena, umm Alignment)
{
    umm AlignmentOffset = 0;
    
    umm ResultPointer = (umm)Arena->CurrentBlock + Arena->CurrentBlock->Used;
    umm AlignmentMask = Alignment - 1;
    if(ResultPointer & AlignmentMask)
    {
        AlignmentOffset = Alignment - (ResultPointer & AlignmentMask);
    }
    
    return(AlignmentOffset);
}

inline umm GetEffectiveSizeFor(memory_arena *Arena, umm InitialSize, arena_push_params Params)
{
    umm Size = InitialSize;
    
    umm AlignmentOffset = GetAlignmentOffset(Arena, Params.Alignment);
    Size += AlignmentOffset;
    
    return(Size);
}

#define PushSize(Arena, InitialSize, ...) PushSize_(Arena, InitialSize, __VA_ARGS__)
#define PushStruct(Arena, type, ...) (type *)PushSize_(Arena, sizeof(type), __VA_ARGS__)
#define PushArray(Arena, type, Count, ...) (type *)PushSize_(Arena, sizeof(type)*Count, __VA_ARGS__)

inline void *PushSize_(memory_arena *Arena, umm InitialSize, arena_push_params Params = DefaultArenaParams())
{
    void *Result = 0;
    
    umm Size = 0;
    if(Arena->CurrentBlock)
    {
        Size = GetEffectiveSizeFor(Arena, InitialSize, Params);
    }
    
    if(!Arena->CurrentBlock || ((Arena->CurrentBlock->Used + Size) > Arena->CurrentBlock->Size))
    {
        Size = InitialSize;
        
        if(!Arena->MinimumBlockSize)
        {
            Arena->MinimumBlockSize = 1024*1024;
        }
        
        umm BlockSize = Maximum(Size, Arena->MinimumBlockSize);
        
        platform_memory_block *NewBlock = Platform.AllocateMemory(BlockSize);
        NewBlock->ArenaPrev = Arena->CurrentBlock;
        Arena->CurrentBlock = NewBlock;
    }
    
    Assert((Arena->CurrentBlock->Used + Size) <= Arena->CurrentBlock->Size);
    
    umm AlignmentOffset = GetAlignmentOffset(Arena, Params.Alignment);
    umm OffsetInBlock = Arena->CurrentBlock->Used + AlignmentOffset;
    Result = Arena->CurrentBlock->Base + OffsetInBlock;
    Arena->CurrentBlock->Used += Size;
    
    Assert(Size >= InitialSize);
    Assert(Arena->CurrentBlock->Used <= Arena->CurrentBlock->Size);
    
    if(Params.Flags & ArenaFlag_ClearToZero)
    {
        ZeroSize(Result, InitialSize);
    }
    
    return(Result);
}

static void *BootstrapPushSize(umm Size, umm OffsetToArena)
{
    memory_arena Arena = {};
    void *Result = PushSize(&Arena, Size);
    *(memory_arena *)((u8 *)Result + OffsetToArena) = Arena;
    
    return(Result);
}

#define BootstrapPushStruct(type, Member) (type *)BootstrapPushSize(sizeof(type), OffsetOf(type, Member))

static string PushString(memory_arena *Arena, string String)
{
    string Result = MakeString(PushArray(Arena, char, String.Count + 1), String.Count);
    Copy(Result.Data, String.Data, String.Count);
    
    Result.Data[Result.Count] = 0;
    
    return(Result);
}

static string PushFormatVariadic(memory_arena *Arena, char *Format, va_list Arguments)
{
    va_list ArgumentsCopy;
    va_copy(ArgumentsCopy, Arguments);
    
    string Result;
    Result.Count = stbsp_vsnprintf(0, 0, Format, ArgumentsCopy);
    Result.Data = (u8 *)PushSize(Arena, Result.Count + 1, NoClear());
    Result.Data[Result.Count] = 0;
    
    stbsp_vsnprintf((char *)Result.Data, (s32)Result.Count + 1, Format, Arguments);
    
    return(Result);
}

inline string PushFormat(memory_arena *Arena, char *Format, ...)
{
    va_list Arguments;
    va_start(Arguments, Format);
    string Result = PushFormatVariadic(Arena, Format, Arguments);
    va_end(Arguments);
    
    return(Result);
}

inline string PushCString(memory_arena *Arena, char *CString)
{
    string Result;
    Result.Count = StringLength(CString);
    Result.Data = PushArray(Arena, u8, Result.Count);
    Copy(Result.Data, CString, Result.Count);
    
    return(Result);
}

#endif //VN_MEMORY_H