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Filename : memory_view.h
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#ifndef RUBY_MEMORY_VIEW_H
#define RUBY_MEMORY_VIEW_H 1
/**
 * @file
 * @author     Ruby developers <ruby-core@ruby-lang.org>
 * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
 *             Permission  is hereby  granted,  to  either redistribute  and/or
 *             modify this file, provided that  the conditions mentioned in the
 *             file COPYING are met.  Consult the file for details.
 * @brief      Memory View.
 */

#include "ruby/internal/dllexport.h"
#include "ruby/internal/stdbool.h"
#include "ruby/internal/value.h"
#include "ruby/intern.h"

enum ruby_memory_view_flags {
    RUBY_MEMORY_VIEW_SIMPLE            = 0,
    RUBY_MEMORY_VIEW_WRITABLE          = (1<<0),
    RUBY_MEMORY_VIEW_FORMAT            = (1<<1),
    RUBY_MEMORY_VIEW_MULTI_DIMENSIONAL = (1<<2),
    RUBY_MEMORY_VIEW_STRIDES           = (1<<3) | RUBY_MEMORY_VIEW_MULTI_DIMENSIONAL,
    RUBY_MEMORY_VIEW_ROW_MAJOR         = (1<<4) | RUBY_MEMORY_VIEW_STRIDES,
    RUBY_MEMORY_VIEW_COLUMN_MAJOR      = (1<<5) | RUBY_MEMORY_VIEW_STRIDES,
    RUBY_MEMORY_VIEW_ANY_CONTIGUOUS    = RUBY_MEMORY_VIEW_ROW_MAJOR | RUBY_MEMORY_VIEW_COLUMN_MAJOR,
    RUBY_MEMORY_VIEW_INDIRECT          = (1<<6) | RUBY_MEMORY_VIEW_STRIDES,
};

typedef struct {
    char format;
    unsigned native_size_p: 1;
    unsigned little_endian_p: 1;
    size_t offset;
    size_t size;
    size_t repeat;
} rb_memory_view_item_component_t;

typedef struct {
    /* The original object that has the memory exported via this memory view.
     * The consumer of this memory view has the responsibility to call rb_gc_mark
     * for preventing this obj collected by GC.  */
    VALUE obj;

    /* The pointer to the exported memory. */
    void *data;

    /* The number of bytes in data. */
    ssize_t byte_size;

    /* true for readonly memory, false for writable memory. */
    bool readonly;

    /* A string to describe the format of an element, or NULL for unsigned bytes.
     * The format string is a sequence of the following pack-template specifiers:
     *
     *   c, C, s, s!, S, S!, n, v, i, i!, I, I!, l, l!, L, L!,
     *   N, V, f, e, g, q, q!, Q, Q!, d, E, G, j, J, x
     *
     * For example, "dd" for an element that consists of two double values,
     * and "CCC" for an element that consists of three bytes, such as
     * an RGB color triplet.
     *
     * Also, the value endianness can be explicitly specified by '<' or '>'
     * following a value type specifier.
     *
     * The items are packed contiguously.  When you emulate the alignment of
     * structure members, put '|' at the beginning of the format string,
     * like "|iqc".  On x86_64 Linux ABI, the size of the item by this format
     * is 24 bytes instead of 13 bytes.
     */
    const char *format;

    /* The number of bytes in each element.
     * item_size should equal to rb_memory_view_item_size_from_format(format). */
    ssize_t item_size;

    struct {
        /* The array of rb_memory_view_item_component_t that describes the
         * item structure.  rb_memory_view_prepare_item_desc and
         * rb_memory_view_get_item allocate this memory if needed,
         * and rb_memory_view_release frees it. */
        const rb_memory_view_item_component_t *components;

        /* The number of components in an item. */
        size_t length;
    } item_desc;

    /* The number of dimension. */
    ssize_t ndim;

    /* ndim size array indicating the number of elements in each dimension.
     * This can be NULL when ndim == 1. */
    const ssize_t *shape;

    /* ndim size array indicating the number of bytes to skip to go to the
     * next element in each dimension. */
    const ssize_t *strides;

    /* The offset in each dimension when this memory view exposes a nested array.
     * Or, NULL when this memory view exposes a flat array. */
    const ssize_t *sub_offsets;

    /* the private data for managing this exported memory */
    void *const private;
} rb_memory_view_t;

typedef bool (* rb_memory_view_get_func_t)(VALUE obj, rb_memory_view_t *view, int flags);
typedef bool (* rb_memory_view_release_func_t)(VALUE obj, rb_memory_view_t *view);
typedef bool (* rb_memory_view_available_p_func_t)(VALUE obj);

typedef struct {
    rb_memory_view_get_func_t get_func;
    rb_memory_view_release_func_t release_func;
    rb_memory_view_available_p_func_t available_p_func;
} rb_memory_view_entry_t;

RBIMPL_SYMBOL_EXPORT_BEGIN()

/* memory_view.c */
bool rb_memory_view_register(VALUE klass, const rb_memory_view_entry_t *entry);

RBIMPL_ATTR_PURE()
bool rb_memory_view_is_row_major_contiguous(const rb_memory_view_t *view);
RBIMPL_ATTR_PURE()
bool rb_memory_view_is_column_major_contiguous(const rb_memory_view_t *view);
RBIMPL_ATTR_NOALIAS()
void rb_memory_view_fill_contiguous_strides(const ssize_t ndim, const ssize_t item_size, const ssize_t *const shape, const bool row_major_p, ssize_t *const strides);
RBIMPL_ATTR_NOALIAS()
bool rb_memory_view_init_as_byte_array(rb_memory_view_t *view, VALUE obj, void *data, const ssize_t len, const bool readonly);
ssize_t rb_memory_view_parse_item_format(const char *format,
                                         rb_memory_view_item_component_t **members,
                                         size_t *n_members, const char **err);
ssize_t rb_memory_view_item_size_from_format(const char *format, const char **err);
void *rb_memory_view_get_item_pointer(rb_memory_view_t *view, const ssize_t *indices);
VALUE rb_memory_view_extract_item_members(const void *ptr, const rb_memory_view_item_component_t *members, const size_t n_members);
void rb_memory_view_prepare_item_desc(rb_memory_view_t *view);
VALUE rb_memory_view_get_item(rb_memory_view_t *view, const ssize_t *indices);

bool rb_memory_view_available_p(VALUE obj);
bool rb_memory_view_get(VALUE obj, rb_memory_view_t* memory_view, int flags);
bool rb_memory_view_release(rb_memory_view_t* memory_view);

/* for testing */
RUBY_EXTERN VALUE rb_memory_view_exported_object_registry;
RUBY_EXTERN const rb_data_type_t rb_memory_view_exported_object_registry_data_type;

RBIMPL_SYMBOL_EXPORT_END()

RBIMPL_ATTR_PURE()
static inline bool
rb_memory_view_is_contiguous(const rb_memory_view_t *view)
{
    if (rb_memory_view_is_row_major_contiguous(view)) {
        return true;
    }
    else if (rb_memory_view_is_column_major_contiguous(view)) {
        return true;
    }
    else {
        return false;
    }
}

#endif /* RUBY_BUFFER_H */