Question about StrGet() Topic is solved

[iPhilip]

The code below behaves differently under v1.1 and v2. In v2 the last "|" doesn't show up.

Code: Select all

nSize := VarSetCapacity(lpFilename, 512, 0)
DllCall("GetModuleFileName", "Ptr", 0, "Ptr", &lpFilename, "UInt", nSize)
MsgBox % "|" StrGet(&lpFilename) "|`n|" StrGet(&lpFilename, 256) "|"

I am wondering if I missed something. Any insights would be appreciated.

[lexikos]

In v2, the string can and does contain null characters. MsgBox only shows up to the first null character.

You can pass the return value of GetModuleFileName to StrGet instead of the buffer size.

If the function succeeds, the return value is the length of the string that is copied to the buffer, in characters, not including the terminating null character.

[iPhilip]

Ok. Thank you. This seems inconsistent with the current documentation for StrGet():

Length

The maximum number of characters to read/write, including the null-terminator if required. See Return Value.

As implemented, it seems that Length represents the actual number of characters. That confused me.

Code: Select all

nSize := VarSetCapacity(lpFilename, 512, 0)
nSize := DllCall("GetModuleFileName", "Ptr", 0, "Ptr", &lpFilename, "UInt", nSize)
String1 := StrGet(&lpFilename, nSize)   ; C:\Program Files\AutoHotkey\AutoHotkey.exe
String2 := StrGet(&lpFilename, 256)
MsgBox % StrLen(String1) " vs " StrLen(String2)   ; 42 vs 256

Making Length the maximum number of characters would make StrGet() compatible with v1.1 and save people some work.

[lexikos]

"Full documentation is very much outdated, with the exception of v2-changes"
http://lexikos.github.io/v2/
https://autohotkey.com/v2/

The current behaviour is a direct result of adding support for binary zero in strings and wasn't originally intended.

[iPhilip]

Got it. Thank you. I figured there was a reason.

[lexikos]

v2.0-a075-02fab78

Changed StrGet to truncate the string at the first binary zero (null terminator), as in v1. Specifying a negative Length now causes it to extract exactly Abs(Length) characters (as previous builds did for positive values), utilizing v2's support for binary zero in strings.

[iPhilip]

Thank you! I appreciate the change.