Class: FFI::Buffer

Inherits:
AbstractMemory show all
Defined in:
ext/ffi_c/Buffer.c,
ext/ffi_c/Buffer.c

Overview

A Buffer is a function argument type. It should be use with functions playing with C arrays.

Constant Summary

Constants inherited from AbstractMemory

AbstractMemory::LONG_MAX

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from AbstractMemory

#[], #__copy_from__, #clear, #get, #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, #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, #size_limit?, #total, #type_size, #write_array_of_double, #write_array_of_float, #write_array_of_pointer, #write_bytes, #write_double, #write_float, #write_pointer

Constructor Details

#initialize(size, count = 1, clear = false) ⇒ self

A new instance of Buffer.

Parameters:

  • Type (Integer, Symbol, #size)

    or size in bytes of a buffer cell

  • count (Fixnum)

    number of cell in the Buffer

  • clear (Boolean)

    if true, set the buffer to all-zero

Raises:

  • (NoMemoryError)

    if failed to allocate memory for Buffer


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# File 'ext/ffi_c/Buffer.c', line 91

static VALUE
buffer_initialize(int argc, VALUE* argv, VALUE self)
{
    VALUE rbSize = Qnil, rbCount = Qnil, rbClear = Qnil;
    Buffer* p;
    int nargs;

    Data_Get_Struct(self, Buffer, p);

    nargs = rb_scan_args(argc, argv, "12", &rbSize, &rbCount, &rbClear);
    p->memory.typeSize = rbffi_type_size(rbSize);
    p->memory.size = p->memory.typeSize * (nargs > 1 ? NUM2LONG(rbCount) : 1);

    if (p->memory.size > BUFFER_EMBED_MAXLEN) {
        p->data.storage = xmalloc(p->memory.size + 7);
        if (p->data.storage == NULL) {
            rb_raise(rb_eNoMemError, "Failed to allocate memory size=%lu bytes", p->memory.size);
            return Qnil;
        }

        /* ensure the memory is aligned on at least a 8 byte boundary */
        p->memory.address = (void *) (((uintptr_t) p->data.storage + 0x7) & (uintptr_t) ~0x7ULL);
    
        if (p->memory.size > 0 && (nargs < 3 || RTEST(rbClear))) {
            memset(p->memory.address, 0, p->memory.size);
        }
    
    } else {
        p->memory.flags |= MEM_EMBED;
        p->memory.address = (void *) &p->data.embed[0];
    }

    if (rb_block_given_p()) {
        return rb_ensure(rb_yield, self, buffer_free, self);
    }

    return self;
}

Class Method Details

.alloc_in(*args) ⇒ Object

Create a new Buffer for in arguments (alias : new_in).


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# File 'ext/ffi_c/Buffer.c', line 162

static VALUE
buffer_alloc_inout(int argc, VALUE* argv, VALUE klass)
{
    return buffer_initialize(argc, argv, buffer_allocate(klass));
}

.alloc_inout(*args) ⇒ Object

Create a new Buffer for in and out arguments (alias : new_inout).


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# File 'ext/ffi_c/Buffer.c', line 162

static VALUE
buffer_alloc_inout(int argc, VALUE* argv, VALUE klass)
{
    return buffer_initialize(argc, argv, buffer_allocate(klass));
}

.alloc_out(*args) ⇒ Object

Create a new Buffer for out arguments (alias : new_out).


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# File 'ext/ffi_c/Buffer.c', line 162

static VALUE
buffer_alloc_inout(int argc, VALUE* argv, VALUE klass)
{
    return buffer_initialize(argc, argv, buffer_allocate(klass));
}

Instance Method Details

#+(offset) ⇒ Buffer

Add a Buffer with an offset

Parameters:

  • offset (Numeric)

Returns:

  • (Buffer)

    a new instance of Buffer pointing from offset until end of previous buffer.


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# File 'ext/ffi_c/Buffer.c', line 194

static VALUE
buffer_plus(VALUE self, VALUE rbOffset)
{
    Buffer* ptr;
    long offset = NUM2LONG(rbOffset);

    Data_Get_Struct(self, Buffer, ptr);

    return slice(self, offset, ptr->memory.size - offset);
}

#initialize_copy(other) ⇒ self

DO NOT CALL THIS METHOD.

Returns:

  • (self)

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# File 'ext/ffi_c/Buffer.c', line 135

static VALUE
buffer_initialize_copy(VALUE self, VALUE other)
{
    AbstractMemory* src;
    Buffer* dst;
    
    Data_Get_Struct(self, Buffer, dst);
    src = rbffi_AbstractMemory_Cast(other, BufferClass);
    if ((dst->memory.flags & MEM_EMBED) == 0 && dst->data.storage != NULL) {
        xfree(dst->data.storage);
    }
    dst->data.storage = xmalloc(src->size + 7);
    if (dst->data.storage == NULL) {
        rb_raise(rb_eNoMemError, "failed to allocate memory size=%lu bytes", src->size);
        return Qnil;
    }
    
    dst->memory.address = (void *) (((uintptr_t) dst->data.storage + 0x7) & (uintptr_t) ~0x7ULL);
    dst->memory.size = src->size;
    dst->memory.typeSize = src->typeSize;
    
    /* finally, copy the actual buffer contents */
    memcpy(dst->memory.address, src->address, src->size);

    return self;
}

#inspectString

Inspect a Buffer.

Returns:

  • (String)

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# File 'ext/ffi_c/Buffer.c', line 223

static VALUE
buffer_inspect(VALUE self)
{
    char tmp[100];
    Buffer* ptr;

    Data_Get_Struct(self, Buffer, ptr);

    snprintf(tmp, sizeof(tmp), "#<FFI:Buffer:%p address=%p size=%ld>", ptr, ptr->memory.address, ptr->memory.size);
    
    return rb_str_new2(tmp);
}

#order:big, :little #order(order) ⇒ self

Set or get endianness of Buffer.

Overloads:

  • #order:big, :little

    Get endianness of Buffer.

    Returns:

    • (:big, :little)
  • #order(order) ⇒ self

    Set endianness of Buffer (:network is an alias for :big).

    Parameters:

    • order (:big, :little, :network)

    Returns:

    • (self)

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# File 'ext/ffi_c/Buffer.c', line 253

static VALUE
buffer_order(int argc, VALUE* argv, VALUE self)
{
    Buffer* ptr;

    Data_Get_Struct(self, Buffer, 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) {
            Buffer* p2;
            VALUE retval = slice(self, 0, ptr->memory.size);

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

        return self;
    }
}

#slice(offset, length) ⇒ Buffer

Slice an existing Buffer.

Parameters:

  • offset (Numeric)
  • length (Numeric)

Returns:

  • (Buffer)

    a new instance of Buffer


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# File 'ext/ffi_c/Buffer.c', line 212

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