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Add a helper method for reading/writing memory #123

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merged 3 commits into from
Mar 16, 2023
Merged

Add a helper method for reading/writing memory #123

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687f214
Add a helper methods for reading and writing memory
tenderlove Mar 15, 2023
9ba4f1c
Update ext/fiddle/pointer.c
tenderlove Mar 16, 2023
324c44d
Update test/fiddle/test_pointer.rb
tenderlove Mar 16, 2023
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29 changes: 29 additions & 0 deletions ext/fiddle/pointer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -799,6 +799,33 @@ rb_fiddle_ptr_s_to_ptr(VALUE self, VALUE val)
return ptr;
}

/*
* call-seq:
* Fiddle::Pointer.read(address, len) => string
*
* Or read the memory at address +address+ with length +len+ and return a
* string with that memory
*/

static VALUE
rb_fiddle_ptr_read_mem(VALUE klass, VALUE address, VALUE len)
{
return rb_str_new((char *)NUM2PTR(address), NUM2ULONG(len));
}

/*
* call-seq:
* Fiddle::Pointer.write(address, str)
*
* Write bytes in +str+ to the location pointed to by +address+.
*/
static VALUE
rb_fiddle_ptr_write_mem(VALUE klass, VALUE addr, VALUE str)
{
memcpy(NUM2PTR(addr), StringValuePtr(str), RSTRING_LEN(str));
return str;
}

void
Init_fiddle_pointer(void)
{
Expand All @@ -815,6 +842,8 @@ Init_fiddle_pointer(void)
rb_define_singleton_method(rb_cPointer, "malloc", rb_fiddle_ptr_s_malloc, -1);
rb_define_singleton_method(rb_cPointer, "to_ptr", rb_fiddle_ptr_s_to_ptr, 1);
rb_define_singleton_method(rb_cPointer, "[]", rb_fiddle_ptr_s_to_ptr, 1);
rb_define_singleton_method(rb_cPointer, "read", rb_fiddle_ptr_read_mem, 2);
rb_define_singleton_method(rb_cPointer, "write", rb_fiddle_ptr_write_mem, 2);
rb_define_method(rb_cPointer, "initialize", rb_fiddle_ptr_initialize, -1);
rb_define_method(rb_cPointer, "free=", rb_fiddle_ptr_free_set, 1);
rb_define_method(rb_cPointer, "free", rb_fiddle_ptr_free_get, 0);
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16 changes: 16 additions & 0 deletions test/fiddle/test_pointer.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,22 @@ def dlwrap arg
Fiddle.dlwrap arg
end

def test_can_read_write_memory
# Allocate some memory
address = Fiddle.malloc(Fiddle::SIZEOF_VOIDP)

bytes_to_write = Fiddle::SIZEOF_VOIDP.times.to_a.pack("C*")

# Write to the memory
Fiddle::Pointer.write(address, bytes_to_write)

# Read the bytes out again
bytes = Fiddle::Pointer.read(address, Fiddle::SIZEOF_VOIDP)
assert_equal bytes_to_write, bytes
ensure
Fiddle.free address
end

def test_cptr_to_int
null = Fiddle::NULL
assert_equal(null.to_i, null.to_int)
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