Class: FFI::Pointer

Inherits:
AbstractMemory show all
Defined in:
ext/ffi_c/Pointer.c,
lib/ffi/pointer.rb,
ext/ffi_c/Pointer.c

Overview

Pointer class is used to manage C pointers with ease. A Pointer object is defined by his #address (as a C pointer). It permits additions with an integer for pointer arithmetic.

Autorelease

A pointer object may autorelease his contents when freed (by default). This behaviour may be changed with #autorelease= method.

Constant Summary

SIZE =

Pointer size

Platform::ADDRESS_SIZE / 8
NULL =

NULL pointer

rbffi_NullPointerSingleton

Class Method Summary (collapse)

Instance Method Summary (collapse)

Methods inherited from AbstractMemory

#[], #__copy_from__, #clear, #get_array_of_float32, #get_array_of_float64, #get_array_of_pointer, #get_array_of_string, #get_bytes, #get_float32, #get_float64, #get_pointer, #get_string, #put_array_of_float32, #put_array_of_float64, #put_array_of_pointer, #put_bytes, #put_float32, #put_float64, #put_pointer, #put_string, #read_array_of_double, #read_array_of_float, #read_array_of_pointer, #read_bytes, #read_double, #read_float, #read_pointer, #total, #write_array_of_double, #write_array_of_float, #write_array_of_pointer, #write_bytes, #write_double, #write_float, #write_pointer

Constructor Details

- (self) initialize(pointer) - (self) initialize(type, address)

A new instance of Pointer.

Overloads:

  • - (self) initialize(pointer)

    Create a new pointer from another FFI::Pointer.

    Parameters:

    • pointer (Pointer)

      another pointer to initialize from

  • - (self) initialize(type, address)

    Create a new pointer from a Type and a base adresse

    Parameters:

    • type (Type)

      type for pointer

    • address (Integer)

      base address for pointer



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# File 'ext/ffi_c/Pointer.c', line 96

static VALUE
ptr_initialize(int argc, VALUE* argv, VALUE self)
{
    Pointer* p;
    VALUE rbType = Qnil, rbAddress = Qnil;
    int typeSize = 1;

    Data_Get_Struct(self, Pointer, p);

    switch (rb_scan_args(argc, argv, "11", &rbType, &rbAddress)) {
        case 1:
            rbAddress = rbType;
            typeSize = 1;
            break;
        case 2:
            typeSize = rbffi_type_size(rbType);
            break;
        default:
            rb_raise(rb_eArgError, "Invalid arguments");
    }

    switch (TYPE(rbAddress)) {
        case T_FIXNUM:
        case T_BIGNUM:
            p->memory.address = (void*) (uintptr_t) NUM2LL(rbAddress);
            p->memory.size = LONG_MAX;
            if (p->memory.address == NULL) {
                p->memory.flags = 0;
            }
            break;

        default:
            if (rb_obj_is_kind_of(rbAddress, rbffi_PointerClass)) {
                Pointer* orig;

                p->rbParent = rbAddress;
                Data_Get_Struct(rbAddress, Pointer, orig);
                p->memory = orig->memory;
            } else {
                rb_raise(rb_eTypeError, "wrong argument type, expected Integer or FFI::Pointer");
            }
            break;
    }

    p->memory.typeSize = typeSize;

    return self;
}

Class Method Details

+ (Numeric) size

Return the size of a pointer on the current platform, in bytes

Returns:

  • (Numeric)


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# File 'lib/ffi/pointer.rb', line 42

def self.size
  SIZE
end

Instance Method Details

- (Pointer) +(offset)

Return a new FFI::Pointer from an existing pointer and an offset.

Parameters:

  • offset (Numeric)

Returns:



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# File 'ext/ffi_c/Pointer.c', line 224

static VALUE
ptr_plus(VALUE self, VALUE offset)
{
    AbstractMemory* ptr;
    long off = NUM2LONG(offset);

    Data_Get_Struct(self, AbstractMemory, ptr);

    return slice(self, off, ptr->size == LONG_MAX ? LONG_MAX : ptr->size - off);
}

- (Object) ==(other)

Check equality between self and other. Equality is tested on #address.

Parameters:



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# File 'ext/ffi_c/Pointer.c', line 294

static VALUE
ptr_equals(VALUE self, VALUE other)
{
    Pointer* ptr;
    
    Data_Get_Struct(self, Pointer, ptr);

    if (NIL_P(other)) {
        return ptr->memory.address == NULL ? Qtrue : Qfalse;
    }

    return ptr->memory.address == POINTER(other)->address ? Qtrue : Qfalse;
}

- (Numeric) address Also known as: to_i

Return self's base address (alias: #to_i).

Returns:

  • (Numeric)

    pointer's base address



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# File 'ext/ffi_c/Pointer.c', line 313

static VALUE
ptr_address(VALUE self)
{
    Pointer* ptr;
    
    Data_Get_Struct(self, Pointer, ptr);

    return ULL2NUM((uintptr_t) ptr->memory.address);
}

- (Boolean) autorelease=(autorelease)

Set autorelease attribute. See also Autorelease section.

Parameters:

  • autorelease (Boolean)

Returns:

  • (Boolean)

    autorelease



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# File 'ext/ffi_c/Pointer.c', line 421

static VALUE
ptr_autorelease(VALUE self, VALUE autorelease)
{
    Pointer* ptr;

    Data_Get_Struct(self, Pointer, ptr);
    ptr->autorelease = autorelease == Qtrue;

    return autorelease;
}

- (Boolean) autorelease?

Get autorelease attribute. See also Autorelease section.

Returns:

  • (Boolean)
  • (Boolean)


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# File 'ext/ffi_c/Pointer.c', line 437

static VALUE
ptr_autorelease_p(VALUE self)
{
    Pointer* ptr;

    Data_Get_Struct(self, Pointer, ptr);
    
    return ptr->autorelease ? Qtrue : Qfalse;
}

- (self) free

Free memory pointed by self.

Returns:

  • (self)


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# File 'ext/ffi_c/Pointer.c', line 382

static VALUE
ptr_free(VALUE self)
{
    Pointer* ptr;

    Data_Get_Struct(self, Pointer, ptr);

    if (ptr->allocated) {
        if (ptr->storage != NULL) {
            xfree(ptr->storage);
            ptr->storage = NULL;
        }
        ptr->allocated = false;

    } else {
        VALUE caller = rb_funcall(rb_funcall(Qnil, rb_intern("caller"), 0), rb_intern("first"), 0);
        
        rb_warn("calling free on non allocated pointer %s from %s", RSTRING_PTR(ptr_inspect(self)), RSTRING_PTR(rb_str_to_str(caller)));
    }

    return self;
}

- (self) initialize_copy(other)

DO NOT CALL THIS METHOD.

This method is internally used by #dup and #clone. Memory contents is copied from other.

Parameters:

  • other (Pointer)

    source for cloning or dupping

Returns:

  • (self)

Raises:

  • (RuntimeError)

    if other is an unbounded memory area, or is unreable/unwritable

  • (NoMemError)

    if failed to allocate memory for new object



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# File 'ext/ffi_c/Pointer.c', line 155

static VALUE
ptr_initialize_copy(VALUE self, VALUE other)
{
    AbstractMemory* src;
    Pointer* dst;
    
    Data_Get_Struct(self, Pointer, dst);
    src = POINTER(other);
    if (src->size == LONG_MAX) {
        rb_raise(rb_eRuntimeError, "cannot duplicate unbounded memory area");
        return Qnil;
    }
    
    if ((dst->memory.flags & (MEM_RD | MEM_WR)) != (MEM_RD | MEM_WR)) {
        rb_raise(rb_eRuntimeError, "cannot duplicate unreadable/unwritable memory area");
        return Qnil;
    }

    if (dst->storage != NULL) {
        xfree(dst->storage);
        dst->storage = NULL;
    }

    dst->storage = xmalloc(src->size + 7);
    if (dst->storage == NULL) {
        rb_raise(rb_eNoMemError, "failed to allocate memory size=%lu bytes", src->size);
        return Qnil;
    }
    
    dst->allocated = true;
    dst->autorelease = true;
    dst->memory.address = (void *) (((uintptr_t) dst->storage + 0x7) & (uintptr_t) ~0x7UL);
    dst->memory.size = src->size;
    dst->memory.typeSize = src->typeSize;
    
    /* finally, copy the actual memory contents */
    memcpy(dst->memory.address, src->address, src->size);

    return self;
}

- (String) inspect

Inspect pointer object.

Returns:

  • (String)


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# File 'ext/ffi_c/Pointer.c', line 254

static VALUE
ptr_inspect(VALUE self)
{
    char buf[100];
    Pointer* ptr;
    
    Data_Get_Struct(self, Pointer, ptr);

    if (ptr->memory.size != LONG_MAX) {
        snprintf(buf, sizeof(buf), "#<%s address=%p size=%lu>",
                rb_obj_classname(self), ptr->memory.address, ptr->memory.size);
    } else {
        snprintf(buf, sizeof(buf), "#<%s address=%p>", rb_obj_classname(self), ptr->memory.address);
    }

    return rb_str_new2(buf);
}

- (Boolean) null?

Return true if self is a NULL pointer.

Returns:

  • (Boolean)
  • (Boolean)


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# File 'ext/ffi_c/Pointer.c', line 278

static VALUE
ptr_null_p(VALUE self)
{
    Pointer* ptr;

    Data_Get_Struct(self, Pointer, ptr);

    return ptr->memory.address == NULL ? Qtrue : Qfalse;
}

- (:big, :little) order - (self) order(order)

Get or set self's endianness

Overloads:

  • - (:big, :little) order

    Returns endianness of self

    Returns:

    • (:big, :little)

      endianness of self

  • - (self) order(order)

    Parameters:

    • order (Symbol)

      endianness to set (:little, :big or :network). :big and :network are synonymous.

    Returns:

    • (self)


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# File 'ext/ffi_c/Pointer.c', line 338

static VALUE
ptr_order(int argc, VALUE* argv, VALUE self)
{
    Pointer* ptr;

    Data_Get_Struct(self, Pointer, ptr);
    if (argc == 0) {
        int order = (ptr->memory.flags & MEM_SWAP) == 0 ? BYTE_ORDER : SWAPPED_ORDER;
        return order == BIG_ENDIAN ? ID2SYM(rb_intern("big")) : ID2SYM(rb_intern("little"));
    } else {
        VALUE rbOrder = Qnil;
        int order = BYTE_ORDER;

        if (rb_scan_args(argc, argv, "1", &rbOrder) < 1) {
            rb_raise(rb_eArgError, "need byte order");
        }
        if (SYMBOL_P(rbOrder)) {
            ID id = SYM2ID(rbOrder);
            if (id == rb_intern("little")) {
                order = LITTLE_ENDIAN;

            } else if (id == rb_intern("big") || id == rb_intern("network")) {
                order = BIG_ENDIAN;
            }
        }
        if (order != BYTE_ORDER) {
            Pointer* p2;
            VALUE retval = slice(self, 0, ptr->memory.size);

            Data_Get_Struct(retval, Pointer, p2);
            p2->memory.flags |= MEM_SWAP;
            return retval;
        }

        return self;
    }
}

- (Array) read_array_of_type(type, reader, length)

Read an array of type of length length.

Examples:

ptr.read_array_of_type(TYPE_UINT8, :get_uint8, 4) # -> [1, 2, 3, 4]

Parameters:

  • type (Type)

    type of data to read from pointer's contents

  • reader (Symbol)

    method to send to self to read type

  • length (Numeric)

Returns:

  • (Array)


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# File 'lib/ffi/pointer.rb', line 106

def read_array_of_type(type, reader, length)
  ary = []
  size = FFI.type_size(type)
  tmp = self
  length.times { |j|
    ary << tmp.send(reader)
    tmp += size unless j == length-1 # avoid OOB
  }
  ary
end

- (String) read_string(len = nil)

Read pointer's contents as a string, or the first len bytes of the equivalent string if len is not nil.

Parameters:

  • len (nil, Numeric) (defaults to: nil)

    length of string to return

Returns:

  • (String)


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# File 'lib/ffi/pointer.rb', line 50

def read_string(len=nil)
  if len
    get_bytes(0, len)
  else
    get_string(0)
  end
end

- (String) read_string_length(len)

Read the first len bytes of pointer's contents as a string.

Same as:

ptr.read_string(len)  # with len not nil

Parameters:

  • len (Numeric)

    length of string to return

Returns:

  • (String)


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# File 'lib/ffi/pointer.rb', line 64

def read_string_length(len)
  get_bytes(0, len)
end

- (String) read_string_to_null

Read pointer's contents as a string.

Same as:

ptr.read_string  # with no len

Returns:

  • (String)


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# File 'lib/ffi/pointer.rb', line 73

def read_string_to_null
  get_string(0)
end

- (Pointer) slice(offset, length)

Return a new FFI::Pointer from an existing one. This pointer points on same contents from offset for a length length.

Parameters:

  • offset (Numeric)
  • length (Numeric)

Returns:



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# File 'ext/ffi_c/Pointer.c', line 243

static VALUE
ptr_slice(VALUE self, VALUE rbOffset, VALUE rbLength)
{
    return slice(self, NUM2LONG(rbOffset), NUM2LONG(rbLength));
}

- (String) inspect

Inspect pointer object.

Returns:

  • (String)


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# File 'ext/ffi_c/Pointer.c', line 254

static VALUE
ptr_inspect(VALUE self)
{
    char buf[100];
    Pointer* ptr;
    
    Data_Get_Struct(self, Pointer, ptr);

    if (ptr->memory.size != LONG_MAX) {
        snprintf(buf, sizeof(buf), "#<%s address=%p size=%lu>",
                rb_obj_classname(self), ptr->memory.address, ptr->memory.size);
    } else {
        snprintf(buf, sizeof(buf), "#<%s address=%p>", rb_obj_classname(self), ptr->memory.address);
    }

    return rb_str_new2(buf);
}

- (Object) type_size



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# File 'ext/ffi_c/Pointer.c', line 405

static VALUE
ptr_type_size(VALUE self)
{
    Pointer* ptr;

    Data_Get_Struct(self, Pointer, ptr);
    
    return INT2NUM(ptr->memory.typeSize);
}

- (self) write_array_of_type(type, writer, ary)

Write ary in pointer's contents as type.

Examples:

ptr.write_array_of_type(TYPE_UINT8, :put_uint8, [1, 2, 3 ,4])

Parameters:

  • type (Type)

    type of data to write to pointer's contents

  • writer (Symbol)

    method to send to self to write type

  • ary (Array)

Returns:

  • (self)


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# File 'lib/ffi/pointer.rb', line 124

def write_array_of_type(type, writer, ary)
  size = FFI.type_size(type)
  tmp = self
  ary.each_with_index {|i, j|
    tmp.send(writer, i)
    tmp += size unless j == ary.length-1 # avoid OOB
  }
  self
end

- (self) write_string(str, len = nil)

Write str in pointer's contents, or first len bytes if len is not nil.

Parameters:

  • str (String)

    string to write

  • len (Numeric) (defaults to: nil)

    length of string to return

Returns:

  • (self)


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# File 'lib/ffi/pointer.rb', line 93

def write_string(str, len=nil)
  len = str.bytesize unless len
  # Write the string data without NUL termination
  put_bytes(0, str, 0, len)
end

- (self) write_string_length(str, len)

Write len first bytes of str in pointer's contents.

Same as:

ptr.write_string(str, len)   # with len not nil

Parameters:

  • str (String)

    string to write

  • len (Numeric)

    length of string to return

Returns:

  • (self)


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# File 'lib/ffi/pointer.rb', line 84

def write_string_length(str, len)
  put_bytes(0, str, 0, len)
end