PEEK

• Source: https://www.freebasic.net/wiki/wikka.php?wakka=KeyPgPeek
• Last revised: 2021-03-04

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Gets the value of an arbitrary type at an address in memory

Syntax

declare function Peek ( byval address as any ptr ) byref as ubyte
declare function Peek ( datatype, byval address as any ptr ) byref as datatype

Usage

` Peek( [ datatype, ] address )

`

Parameters

address

The address in memory to get the value from.

datatype

The type of value to get. If omitted, ubyte is assumed.

Description

This procedure returns a reference to the value in memory given by a memory address, and is equivalent to:

*cast(ubyte ptr, address)

or

*cast(datatype ptr, address)

thus this keyword can also be used to assign a value to a memory location, similarly to Poke.

Note: When using Peek, the -exx compiler option does not add code for null-pointer checking (no nullity test on the value of address).

Examples

start GeSHi

Dim i As Integer, p As Integer Ptr
p = @i

Poke Integer, p, 420
Print Peek(Integer, p)

end GeSHi

will produce the output:

420

Differences from QB

• Peek did not support the datatype parameter in QB, and could only return individual bytes.
• Peek returns a reference in FB, so can be used to set the memory contents of the address, like with Operator * (Value of).
• DEF SEG isn't needed anymore because the address space is 32-bit flat in FreeBASIC.

See also

• Poke
• Operator * (Value of)

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