class Fiddle::Pointer

Fiddle::Pointer is a class to handle C pointers

Attributes

ffi_ptr[R]

Public Class Methods

[](value)

Get the underlying pointer for ruby object val and return it as a Fiddle::Pointer object.

Alias for: to_ptr

from_native(value, ctx) click to toggle source

# File fiddle/lib/fiddle/ffi_backend.rb, line 235
def self.from_native(value, ctx)
  self.new(value)
end

malloc(size, free = nil) { |pointer| ... } click to toggle source

Examples¶ ↑

# Automatically freeing the pointer when the block is exited - recommended
Fiddle::Pointer.malloc(size, Fiddle::RUBY_FREE) do |pointer|
  ...
end

# Manually freeing but relying on the garbage collector otherwise
pointer = Fiddle::Pointer.malloc(size, Fiddle::RUBY_FREE)
...
pointer.call_free

# Relying on the garbage collector - may lead to unlimited memory allocated before freeing any, but safe
pointer = Fiddle::Pointer.malloc(size, Fiddle::RUBY_FREE)
...

# Only manually freeing
pointer = Fiddle::Pointer.malloc(size)
begin
  ...
ensure
  Fiddle.free pointer
end

# No free function and no call to free - the native memory will leak if the pointer is garbage collected
pointer = Fiddle::Pointer.malloc(size)
...

Allocate size bytes of memory and associate it with an optional freefunc.

If a block is supplied, the pointer will be yielded to the block instead of being returned, and the return value of the block will be returned. A freefunc must be supplied if a block is.

If a freefunc is supplied it will be called once, when the pointer is garbage collected or when the block is left if a block is supplied or when the user calls call_free, whichever happens first. freefunc must be an address pointing to a function or an instance of Fiddle::Function.

# File fiddle/lib/fiddle/ffi_backend.rb, line 335
def self.malloc(size, free = nil)
  if block_given? and free.nil?
    message = "a free function must be supplied to #{self}.malloc " +
              "when it is called with a block"
    raise ArgumentError, message
  end

  pointer = new(LibC.malloc(size), size, free)
  if block_given?
    begin
      yield(pointer)
    ensure
      pointer.call_free
    end
  else
    pointer
  end
end

new(addr, size = nil, free = nil) click to toggle source

# File fiddle/lib/fiddle/ffi_backend.rb, line 299
def initialize(addr, size = nil, free = nil)
  ptr = if addr.is_a?(FFI::Pointer)
          addr

        elsif addr.is_a?(Integer)
          FFI::Pointer.new(addr)

        elsif addr.respond_to?(:to_ptr)
          fiddle_ptr = addr.to_ptr
          if fiddle_ptr.is_a?(Pointer)
            fiddle_ptr.ffi_ptr
          elsif fiddle_ptr.is_a?(FFI::AutoPointer)
            addr.ffi_ptr
          elsif fiddle_ptr.is_a?(FFI::Pointer)
            fiddle_ptr
          else
            raise DLError.new("to_ptr should return a Fiddle::Pointer object, was #{fiddle_ptr.class}")
          end
        elsif addr.is_a?(IO)
          raise NotImplementedError, "IO ptr isn't supported"
        end

  @size = size ? size : ptr.size
  @free = free
  @ffi_ptr = ptr
  @freed = false
end

Fiddle::Pointer.new(address) → fiddle_cptr click to toggle source

new(address, size) → fiddle_cptr

new(address, size, freefunc) → fiddle_cptr

Create a new pointer to address with an optional size and freefunc.

freefunc will be called when the instance is garbage collected.

static VALUE
rb_fiddle_ptr_initialize(int argc, VALUE argv[], VALUE self)
{
    VALUE ptr, sym, size, wrap = 0, funcwrap = 0;
    struct ptr_data *data;
    void *p = NULL;
    freefunc_t f = NULL;
    long s = 0;

    if (rb_scan_args(argc, argv, "12", &ptr, &size, &sym) >= 1) {
        VALUE addrnum = rb_Integer(ptr);
        if (addrnum != ptr) wrap = ptr;
        p = NUM2PTR(addrnum);
    }
    if (argc >= 2) {
        s = NUM2LONG(size);
    }
    if (argc >= 3) {
        f = get_freefunc(sym, &funcwrap);
    }

    if (p) {
        TypedData_Get_Struct(self, struct ptr_data, &fiddle_ptr_data_type, data);
        if (data->ptr && data->free) {
            /* Free previous memory. Use of inappropriate initialize may cause SEGV. */
            (*(data->free))(data->ptr);
        }
        RB_OBJ_WRITE(self, &data->wrap[0], wrap);
        RB_OBJ_WRITE(self, &data->wrap[1], funcwrap);
        data->ptr  = p;
        data->size = s;
        data->free = f;
    }

    return Qnil;
}

read(addr, len) click to toggle source

Or read the memory at address address with length len and return a string with that memory

# File fiddle/lib/fiddle/ffi_backend.rb, line 268
def self.read(addr, len)
  FFI::Pointer.new(addr).read_bytes(len)
end

to_native(value, ctx) click to toggle source

# File fiddle/lib/fiddle/ffi_backend.rb, line 223
def self.to_native(value, ctx)
  if value.is_a?(Pointer)
    value.ffi_ptr

  elsif value.is_a?(Integer)
    FFI::Pointer.new(value)

  elsif value.is_a?(String)
    value
  end
end

to_ptr(value) click to toggle source

Get the underlying pointer for ruby object val and return it as a Fiddle::Pointer object.

# File fiddle/lib/fiddle/ffi_backend.rb, line 239
def self.to_ptr(value)
  if value.is_a?(String)
    cptr = Pointer.malloc(value.bytesize)
    cptr.ffi_ptr.put_string(0, value)
    cptr

  elsif value.is_a?(Array)
    raise NotImplementedError, "array ptr"

  elsif value.respond_to?(:to_ptr)
    ptr = value.to_ptr
    case ptr
    when Pointer
      ptr
    when FFI::Pointer
      Pointer.new(ptr)
    else
      raise DLError.new("to_ptr should return a Fiddle::Pointer object, was #{ptr.class}")
    end

  else
    Pointer.new(value)
  end
end

Also aliased as: []

write(addr, bytes) click to toggle source

Write bytes in str to the location pointed to by address.

# File fiddle/lib/fiddle/ffi_backend.rb, line 264
def self.write(addr, bytes)
  FFI::Pointer.new(addr).write_bytes(bytes)
end

Public Instance Methods

+(delta) click to toggle source

Returns a new pointer instance that has been advanced n bytes.

# File fiddle/lib/fiddle/ffi_backend.rb, line 437
def +(delta)
  self.class.new(to_i + delta, @size - delta)
end

+@() click to toggle source

Returns a new Fiddle::Pointer instance that is a dereferenced pointer for this pointer.

Analogous to the star operator in C.

# File fiddle/lib/fiddle/ffi_backend.rb, line 465
def +@
  ptr
end

-(delta) click to toggle source

Returns a new pointer instance that has been moved back n bytes.

# File fiddle/lib/fiddle/ffi_backend.rb, line 441
def -(delta)
  self.class.new(to_i - delta, @size + delta)
end

-@() click to toggle source

Returns a new Fiddle::Pointer instance that is a reference pointer for this pointer.

Analogous to the ampersand operator in C.

# File fiddle/lib/fiddle/ffi_backend.rb, line 469
def -@
  ref
end

<=>(other) click to toggle source

Returns -1 if less than, 0 if equal to, 1 if greater than other.

Returns nil if ptr cannot be compared to other.

# File fiddle/lib/fiddle/ffi_backend.rb, line 445
def <=>(other)
  return unless other.is_a?(Pointer)
  diff = self.to_i - other.to_i
  return 0 if diff == 0
  diff > 0 ? 1 : -1
end

==(other) click to toggle source

Returns true if other wraps the same pointer, otherwise returns false.

# File fiddle/lib/fiddle/ffi_backend.rb, line 457
def ==(other)
  eql?(other)
end

[](index, length = nil) click to toggle source

Returns integer stored at index.

If start and length are given, a string containing the bytes from start of length will be returned.

# File fiddle/lib/fiddle/ffi_backend.rb, line 393
def [](index, length = nil)
  if length
    ffi_ptr.get_bytes(index, length)
  else
    ffi_ptr.get_char(index)
  end
rescue FFI::NullPointerError
  raise DLError.new("NULL pointer dereference")
end

[]=(*args, value) click to toggle source

Set the value at index to int.

Or, set the memory at start until length with the contents of string, the memory from dl_cptr, or the memory pointed at by the memory address addr.

# File fiddle/lib/fiddle/ffi_backend.rb, line 276
def []=(*args, value)
  if args.size == 2
    if value.is_a?(Integer)
      value = self.class.new(value)
    end
    if value.is_a?(Fiddle::Pointer)
      value = value.to_str(args[1])
    end

    @ffi_ptr.put_bytes(args[0], value, 0, args[1])
  elsif args.size == 1
    if value.is_a?(Fiddle::Pointer)
      value = value.to_str(args[0] + 1)
    else
      value = value.chr
    end

    @ffi_ptr.put_bytes(args[0], value, 0, 1)
  end
rescue FFI::NullPointerError
  raise DLError.new("NULL pointer access")
end

call_free() click to toggle source

Call the free function for this pointer. Calling more than once will do nothing. Does nothing if there is no free function attached.

# File fiddle/lib/fiddle/ffi_backend.rb, line 374
def call_free
  return if @free.nil?
  return if @freed
  if @free == RUBY_FREE
    LibC::FREE.call(@ffi_ptr)
  else
    @free.call(@ffi_ptr)
  end
  @freed = true
end

eql?(other) click to toggle source

Returns true if other wraps the same pointer, otherwise returns false.

# File fiddle/lib/fiddle/ffi_backend.rb, line 452
def eql?(other)
  return unless other.is_a?(Pointer)
  self.to_i == other.to_i
end

free() click to toggle source

Get the free function for this pointer.

Returns a new instance of Fiddle::Function.

See Fiddle::Function.new

# File fiddle/lib/fiddle/ffi_backend.rb, line 366
def free
  @free
end

free=(free) click to toggle source

Set the free function for this pointer to function in the given Fiddle::Function.

# File fiddle/lib/fiddle/ffi_backend.rb, line 370
def free=(free)
  @free = free
end

freed?() click to toggle source

Returns if the free function for this pointer has been called.

# File fiddle/lib/fiddle/ffi_backend.rb, line 385
def freed?
  @freed
end

inspect() click to toggle source

Returns a string formatted with an easily readable representation of the internal state of the pointer.

# File fiddle/lib/fiddle/ffi_backend.rb, line 433
def inspect
  "#<#{self.class.name} ptr=#{to_i.to_s(16)} size=#{@size} free=#{@free.inspect}>"
end

null?() click to toggle source

Returns true if this is a null pointer.

# File fiddle/lib/fiddle/ffi_backend.rb, line 354
def null?
  @ffi_ptr.null?
end

ptr() click to toggle source

Returns a new Fiddle::Pointer instance that is a dereferenced pointer for this pointer.

Analogous to the star operator in C.

# File fiddle/lib/fiddle/ffi_backend.rb, line 461
def ptr
  Pointer.new(ffi_ptr.get_pointer(0))
end

ref() click to toggle source

Returns a new Fiddle::Pointer instance that is a reference pointer for this pointer.

Analogous to the ampersand operator in C.

# File fiddle/lib/fiddle/ffi_backend.rb, line 473
def ref
  cptr = Pointer.malloc(FFI::Type::POINTER.size, RUBY_FREE)
  cptr.ffi_ptr.put_pointer(0, ffi_ptr)
  cptr
end

size() click to toggle source

Get the size of this pointer.

# File fiddle/lib/fiddle/ffi_backend.rb, line 362
def size
  defined?(@layout) ? @layout.size : @size
end

size=(size) click to toggle source

Set the size of this pointer to size

# File fiddle/lib/fiddle/ffi_backend.rb, line 389
def size=(size)
  @size = size
end

to_i() click to toggle source

Returns the integer memory location of this pointer.

# File fiddle/lib/fiddle/ffi_backend.rb, line 403
def to_i
  ffi_ptr.to_i
end

Also aliased as: to_int

to_int()

Returns the integer memory location of this pointer.

Alias for: to_i

to_ptr() click to toggle source

# File fiddle/lib/fiddle/ffi_backend.rb, line 358
def to_ptr
  @ffi_ptr
end

to_s(len = nil) click to toggle source

without 0

# File fiddle/lib/fiddle/ffi_backend.rb, line 409
def to_s(len = nil)
  if len
    ffi_ptr.get_string(0, len)
  else
    ffi_ptr.get_string(0)
  end
rescue FFI::NullPointerError
  raise DLError.new("NULL pointer access")
end

to_str(len = nil) click to toggle source

Returns the pointer contents as a string.

When called with no arguments, this method will return the contents with the length of this pointer’s size.

When called with len, a string of len bytes will be returned.

See to_s

# File fiddle/lib/fiddle/ffi_backend.rb, line 419
def to_str(len = nil)
  if len
    ffi_ptr.read_string(len)
  else
    ffi_ptr.read_string(@size)
  end
rescue FFI::NullPointerError
  raise DLError.new("NULL pointer access")
end

to_value() click to toggle source

Cast this pointer to a ruby object.

# File fiddle/lib/fiddle/ffi_backend.rb, line 429
def to_value
  raise NotImplementedError, "to_value isn't supported"
end