_MEMELEMENT - QB64Official/qb64 GitHub Wiki

The _MEMELEMENT function returns a _MEM block referring to a variable's memory, but not past it.

Syntax

memoryBlock = _MEMELEMENT(referenceVariable)

The referenceVariable parameter designates the existing variable name using the memory block.
_MEMELEMENT is the same as _MEM but in an array it returns the specifications of an element, not the entire array.
All values created by memory functions MUST be freed using _MEMFREE with a valid _MEM variable type.
The _MEMELEMENT type contains the following read-only elements where name is the variable name:
- name**.OFFSET** is the beginning offset of the memory block AS _OFFSET
- name**.SIZE** returns the largest available region of memory of the ELEMENT in bytes AS _OFFSET
- name**.ELEMENTSIZE** is the _BYTE size of the elements within the block AS _OFFSET
  - 2 = INTEGER values have an element size of 2 bytes
  - 4 = LONG integer and SINGLE float values have an element size of 4 bytes
  - 8 = DOUBLE float and _INTEGER64 values have an element size of 8 bytes
  - 32 = _FLOAT values have an element size of 32 bytes
  - LEN = STRING or _OFFSET byte sizes vary so use LEN(variable) for the number of bytes.
- name**.TYPE** is the type (represented as bits combined to form a value) AS LONG (see below).

.TYPE values (version 1.000 and up)

0 = UDT (TYPE) or memory created by _MEMNEW
1 = 1 bit. ELEMENT.SIZE=1 Only used along with specific types (currently integers or floats)
2 = 2 bit. ELEMENT.SIZE=2
4 = 4 bit. ELEMENT.SIZE=4
8 = 8 bit. ELEMENT.SIZE=8
16 = 16 bit. ELEMENT.SIZE=16
32 = 32 bit. ELEMENT.SIZE=32
64 = 64 bit. ELEMENT.SIZE=64
128 = 128 bit. ELEMENT.SIZE=128
256 = 256 bit. ELEMENT.SIZE=256
512(+ bit*) = integer types only(ie. whole numbers)
1024(+ bit*) = floating point types only(ie. numbers that can have a decimal point)
2048 = STRING type only
4096(+ 512 + bit*) = _UNSIGNED integer type only
8192 = _MEM type only
16384(+ 512 + bit*)= _OFFSET type only

Note: If a future integer, float or other type doesn't have a size that is 1,2,4,8,16,32,64,128 or 256 it won't have a size-bit set.

Versions prior to 1.000

1 = Integer types such as _BYTE, INTEGER, LONG, _INTEGER64 or _OFFSET
2 = _UNSIGNED variable types. Value must be added to the variable type value.(2 cannot be used by itself)
3 = ALL _UNSIGNED INTEGER type values.(add 1 + 2)
4 = Floating point types such as SINGLE, DOUBLE or _FLOAT
8 = STRING
0 = unknown(eg. created with _MEMNEW) or TYPE

Note: _MEM and _OFFSET values cannot be cast to other variable types.

Example(s)

Comparing the specifications returned by _MEM and _MEMELEMENT from an array.


DIM a(1 TO 100) AS _UNSIGNED _BYTE

DIM m1 AS _MEM
DIM m2 AS _MEM

m1 = _MEM(a(50)) 'function returns information about array up to specific element
PRINT m1.OFFSET, m1.SIZE, m1.TYPE, m1.ELEMENTSIZE

m2 = _MEMELEMENT(a(50)) 'function returns information about the specific element
PRINT m2.OFFSET, m2.SIZE, m2.TYPE, m2.ELEMENTSIZE

END

Output using VERSION .954 ONLY .TYPE values: 1 (integer) + 2 (unsigned)


28377205        51        3        1
28377205        1         3        1

Explanation: _MEM returns the info about the array to that element while _MEMELEMENT returns info about that element only.

_MEM value returns the available array .SIZE as 51 bytes from the designated array element.
_MEMELEMENT value returns the available element .SIZE as one byte.