/**********************************************************************

  io_buffer.c

  Copyright (C) 2021 Samuel Grant Dawson Williams

**********************************************************************/

#include "ruby/io/buffer.h"
#include "ruby/fiber/scheduler.h"

// For `rb_nogvl`.
#include "ruby/thread.h"

#include "internal.h"
#include "internal/array.h"
#include "internal/bits.h"
#include "internal/error.h"
#include "internal/gc.h"
#include "internal/numeric.h"
#include "internal/string.h"
#include "internal/io.h"

VALUE rb_cIOBuffer;
VALUE rb_eIOBufferLockedError;
VALUE rb_eIOBufferAllocationError;
VALUE rb_eIOBufferAccessError;
VALUE rb_eIOBufferInvalidatedError;
VALUE rb_eIOBufferMaskError;

size_t RUBY_IO_BUFFER_PAGE_SIZE;
size_t RUBY_IO_BUFFER_DEFAULT_SIZE;

#ifdef _WIN32
#else
#include <unistd.h>
#include <sys/mman.h>
#endif

enum {
    RB_IO_BUFFER_HEXDUMP_DEFAULT_WIDTH = 16,

    RB_IO_BUFFER_INSPECT_HEXDUMP_MAXIMUM_SIZE = 256,
    RB_IO_BUFFER_INSPECT_HEXDUMP_WIDTH = 16,

    // This is used to validate the flags given by the user.
    RB_IO_BUFFER_FLAGS_MASK = RB_IO_BUFFER_EXTERNAL | RB_IO_BUFFER_INTERNAL | RB_IO_BUFFER_MAPPED | RB_IO_BUFFER_SHARED | RB_IO_BUFFER_LOCKED | RB_IO_BUFFER_PRIVATE | RB_IO_BUFFER_READONLY,

    RB_IO_BUFFER_DEBUG = 0,
};

struct rb_io_buffer {
    void *base;
    size_t size;
    enum rb_io_buffer_flags flags;

#if defined(_WIN32)
    HANDLE mapping;
#endif

    VALUE source;
};

static inline void *
io_buffer_map_memory(size_t size, int flags)
{
#if defined(_WIN32)
    void * base = VirtualAlloc(0, size, MEM_COMMIT, PAGE_READWRITE);

    if (!base) {
        rb_sys_fail("io_buffer_map_memory:VirtualAlloc");
    }
#else
    int mmap_flags = MAP_ANONYMOUS;
    if (flags & RB_IO_BUFFER_SHARED) {
        mmap_flags |= MAP_SHARED;
    }
    else {
        mmap_flags |= MAP_PRIVATE;
    }

    void * base = mmap(NULL, size, PROT_READ | PROT_WRITE, mmap_flags, -1, 0);

    if (base == MAP_FAILED) {
        rb_sys_fail("io_buffer_map_memory:mmap");
    }

    ruby_annotate_mmap(base, size, "Ruby:io_buffer_map_memory");
#endif

    return base;
}

static void
io_buffer_map_file(struct rb_io_buffer *buffer, int descriptor, size_t size, rb_off_t offset, enum rb_io_buffer_flags flags)
{
#if defined(_WIN32)
    HANDLE file = (HANDLE)_get_osfhandle(descriptor);
    if (!file) rb_sys_fail("io_buffer_map_descriptor:_get_osfhandle");

    DWORD protect = PAGE_READONLY, access = FILE_MAP_READ;

    if (flags & RB_IO_BUFFER_READONLY) {
        buffer->flags |= RB_IO_BUFFER_READONLY;
    }
    else {
        protect = PAGE_READWRITE;
        access = FILE_MAP_WRITE;
    }

    if (flags & RB_IO_BUFFER_PRIVATE) {
        protect = PAGE_WRITECOPY;
        access = FILE_MAP_COPY;
        buffer->flags |= RB_IO_BUFFER_PRIVATE;
    }
    else {
        // This buffer refers to external buffer.
        buffer->flags |= RB_IO_BUFFER_EXTERNAL;
        buffer->flags |= RB_IO_BUFFER_SHARED;
    }

    HANDLE mapping = CreateFileMapping(file, NULL, protect, 0, 0, NULL);
    if (RB_IO_BUFFER_DEBUG) fprintf(stderr, "io_buffer_map_file:CreateFileMapping -> %p\n", mapping);
    if (!mapping) rb_sys_fail("io_buffer_map_descriptor:CreateFileMapping");

    void *base = MapViewOfFile(mapping, access, (DWORD)(offset >> 32), (DWORD)(offset & 0xFFFFFFFF), size);

    if (!base) {
        CloseHandle(mapping);
        rb_sys_fail("io_buffer_map_file:MapViewOfFile");
    }

    buffer->mapping = mapping;
#else
    int protect = PROT_READ, access = 0;

    if (flags & RB_IO_BUFFER_READONLY) {
        buffer->flags |= RB_IO_BUFFER_READONLY;
    }
    else {
        protect |= PROT_WRITE;
    }

    if (flags & RB_IO_BUFFER_PRIVATE) {
        buffer->flags |= RB_IO_BUFFER_PRIVATE;
        access |= MAP_PRIVATE;
    }
    else {
        // This buffer refers to external buffer.
        buffer->flags |= RB_IO_BUFFER_EXTERNAL;
        buffer->flags |= RB_IO_BUFFER_SHARE