CVL - QB64Official/qb64 GitHub Wiki

The CVL function decodes a 4-byte STRING generated by MKL$ (or read from a file) to LONG numeric values.

Syntax

result& = CVL(stringData$)

Description

CV functions (CVD, CVS, CVI, CVL, CVDMBF, CVSMBF) are used to convert values encoded by MK$ functions (MKD$, MKS$, MKI$, MKL$, MKDMBF$, MKSMBF$).
QB64 has _CV and _MK$ functions which can also deal with extended Data types.
LONG values can range from -2147483648 to 2147483647.
Doesn't return _UNSIGNED values.

Example(s)

*Example 1: 4 byte ASCII character strings show how CVL multipliers convert MKL$ values into a 4 byte LONG value.


PRINT CVL(CHR$(1) + STRING$(3, 0)) 'ASC(CHR$(1)) * 1 = 1
PRINT CVL(CHR$(0) + CHR$(1) + STRING$(2, 0)) 'ASC(CHR$(1)) * 256 = 256
PRINT CVL(STRING$(2, 0) + CHR$(1) + CHR$(0)) 'ASC(CHR$(1)) * 256 * 256 = 65536
PRINT CVL(STRING$(3, 0) + CHR$(1)) 'ASC(CHR$(1)) * 256 * 256 * 256 = 16777216

Example 2:


FIELD #1, 4 AS N$, 12 AS B$...
GET #1
Y& = CVL(N$)

Explanation: Reads a field from file #1, and converts the first four bytes (N$) into a long integer value assigned to the variable Y&.

Since the representation of a long number can use up to 10 ASCII characters (ten bytes), writing to a file using MKL$ conversion, and then reading back with the CVL conversion can save up to 6 bytes of storage space.