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.

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, #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



96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
# File 'ext/ffi_c/Buffer.c', line 96

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) ~0x7UL);
    
        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).



167
168
169
170
171
# File 'ext/ffi_c/Buffer.c', line 167

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).



167
168
169
170
171
# File 'ext/ffi_c/Buffer.c', line 167

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).



167
168
169
170
171
# File 'ext/ffi_c/Buffer.c', line 167

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.



199
200
201
202
203
204
205
206
207
208
# File 'ext/ffi_c/Buffer.c', line 199

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)


140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
# File 'ext/ffi_c/Buffer.c', line 140

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) ~0x7UL);
    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)


228
229
230
231
232
233
234
235
236
237
238
239
# File 'ext/ffi_c/Buffer.c', line 228

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

    Parameters:

    • order (:big, :little, :network)

    Returns:

    • (self)


258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
# File 'ext/ffi_c/Buffer.c', line 258

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



217
218
219
220
221
# File 'ext/ffi_c/Buffer.c', line 217

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