LEN - QB64Official/qb64 GitHub Wiki
The LEN function returns the number of bytes used by a variable value and the number of characters in a STRING.
Syntax
length% = LEN(literalTextOrVariable)
- Literal or variable STRING values return the number of string bytes which is the same as the number of string characters.
- A numerical variable will return the number of bytes used by a numerical variable type.
- _BYTE variable types return 1 byte.
- INTEGER variable types return 2 bytes.
- SINGLE and LONG integer variable types return 4 bytes.
- DOUBLE and _INTEGER64 variable types return 8 bytes.
- _FLOAT variable types return 32 bytes.
- _OFFSET and _MEM variable types return varying byte sizes.
- Note: _BIT variable types and bit multiples cannot be measured in bytes.
- LEN cannot return lengths of literal numerical values and will create a "variable required" status error in the IDE.
- LEN = can be used with a user defined TYPE variable to determine the number of bytes used in RANDOM file records:
[OPEN](OPEN) file$ FOR [RANDOM](RANDOM) AS #n LEN = LEN(recordTypeVariable)**
- If a LEN = statement is not used, RANDOM default record length is 128 or sequencial is 512 up to a maximum of 32767 bytes.
- BINARY OPEN statements will ignore LEN = statements. The byte size of a GET or PUT is determined by the Variable Types.
Example(s)
With a string variable the byte size is the same as the number of characters.
LastName$ = "Williams"
PRINT LEN(LastName$); "bytes"
8 bytes
Testing INPUT for numerical STRING entries from a user.
INPUT "number: ", num$
value$ = LTRIM$(STR$(VAL(num$)))
L = LEN(value$)
PRINT LEN(num$), L
Note: &H, &O, D and E will also be accepted as numerical type data in a VAL conversion, but will add to the entry length.
With numerical value types you MUST use a variable to find the inherent byte length when using LEN.
DIM I AS INTEGER
PRINT "INTEGER ="; LEN(I); "bytes"
DIM L AS LONG
PRINT "LONG ="; LEN(L); "bytes"
DIM I64 AS _INTEGER64
PRINT "_INTEGER64 ="; LEN(I64); "bytes"
DIM S AS SINGLE
PRINT "SINGLE ="; LEN(S); "bytes"
DIM D AS DOUBLE
PRINT "DOUBLE ="; LEN(D); "bytes"
DIM F AS _FLOAT
PRINT "_FLOAT ="; LEN(F); "bytes"
INTEGER = 2 bytes
LONG = 4 bytes
_INTEGER64 = 8 bytes
SINGLE = 4 bytes
DOUBLE = 8 bytes
_FLOAT = 32 bytes
Opening a RANDOM file using LEN to calculate and LEN = to designate the file record size.
TYPE variabletype
x AS INTEGER' '2 bytes
y AS STRING * 10' '10 bytes
z AS LONG' '4 bytes
END TYPE' '16 bytes total
DIM record AS variabletype
DIM newrec AS variabletype
file$ = "testrand.inf" '<<<< filename may overwrite existing file
number% = 1 '<<<<<<<<<< record number to write cannot be zero
RecordLEN% = LEN(record)
PRINT RecordLEN%; "bytes"
record.x = 255
record.y = "Hello world!"
record.z = 65535
PRINT record.x, record.y, record.z
OPEN file$ FOR RANDOM AS #1 LEN = RecordLEN%
PUT #1, number% , record 'change record position number to add records
CLOSE #1
OPEN file$ FOR RANDOM AS #2 LEN = RecordLEN%
NumRecords% = LOF(2) \ RecordLEN%
PRINT NumRecords%; "records"
GET #2, NumRecords% , newrec 'GET last record available
CLOSE #2
PRINT newrec.x, newrec.y, newrec.z
END
16 bytes
255 Hello worl 65535
1 records
255 Hello worl 65535
Explanation: The byte size of the record TYPE determines the LOF byte size of the file and can determine the number of records. To read the last record GET the number of records. To add a record, use the number of records + 1 to PUT new record data.