StringCb... and similar windows functions

[jj2007]

ahhhh, Michael - the PSDK has the static library   :t

See reply #1. But it doesn't help much, at least with my machines, because the exe complains about the missing ntdll :(

However, StringCbLengthA works:

Intel(R) Celeron(R) M CPU        420  @ 1.60GHz (SSE3)

3948    cycles for 100 * MasmBasic Len
30580   cycles for 100 * StringCbLengthA

3936    cycles for 100 * MasmBasic Len
30588   cycles for 100 * StringCbLengthA

3936    cycles for 100 * MasmBasic Len
30676   cycles for 100 * StringCbLengthA

[TWell]

MichaelW's example with POAsm:

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.386
.model FLAT, c
option casemap:none
;==============================================================================
;include \masm32\include\masm32rt.inc
includelib kernel32.lib
includelib msvcrt.lib
includelib strsafe.lib
;==============================================================================
StringCbLengthA proto stdcall :DWORD,:DWORD,:DWORD
;  _In_   LPCTSTR psz,
;  _In_   size_t cbMax,
;  _Out_  size_t *pcb
;==============================================================================
ExitProcess proto stdcall :DWORD
printf proto C :DWORD,:VARARG

.data
    slength  dd 0
    string   db "my other brother darryl",0
    fmt      db "%d",9,"%d",13,10,0
.code
;==============================================================================
;==============================================================================
start:
;==============================================================================
    invoke StringCbLengthA, ADDR string, 24, ADDR slength
    invoke printf,addr fmt,eax,slength
    invoke  ExitProcess,0
;==============================================================================
end start


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LIBRARY msvcrt.dll
EXPORTS
printf

[dedndave]

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3948    cycles for 100 * MasmBasic Len
30580   cycles for 100 * StringCbLengthA

3936    cycles for 100 * MasmBasic Len
30588   cycles for 100 * StringCbLengthA

3936    cycles for 100 * MasmBasic Len
30676   cycles for 100 * StringCbLengthA

not very "zippy" - lol

[MichaelW]

I get Unresolved external symbol '_StringCbLengthA@12'. from my C:\Program Files\Microsoft SDKs\Windows\v7.0A\Lib\strsafe.lib of 30.09.2009...

Using the Microsoft Visual C++ Toolkit 2003 compiler it works fine for me, whether the function is inlined or linked in from the library. The attachment includes the EXE and assembly ouput for both.

Doing a dump of the EXEs I see that they both contain the name mscoree.dll. The description from the DLL properties is:

Microsoft .NET Runtime Execution Engine

Makes me wonder how portable the EXEs are...

It looks like all of the EXEs I built with that compiler contain the name, apparently associated with CorExitProcess.

[jj2007]

Thanks, Michael :t

Test_Inline.asm:
; Line 5165
   lea   ecx, DWORD PTR _cchLength$[ebp]
   push   ecx
   mov   edx, DWORD PTR _cchMax$[ebp]
   push   edx
   mov   eax, DWORD PTR _psz$[ebp]
   push   eax
   call   _StringLengthWorkerA@12

It's a mystery how they can release into the wild an algo that is eight times slower than a reasonable handcrafted one doing exactly the same ::)

Well, almost exactly. Just for fun:

include \masm32\MasmBasic\MasmBasic.inc        ; download
StringCbLengthA proto :DWORD,:DWORD,:DWORD
includelib strsafestatic.lib

  Init tc
  Let esi=FileRead$("\Masm32\include\Windows.inc")        ; get a source text
  invoke VirtualAlloc, 0, 4096, MEM_COMMIT, PAGE_READWRITE        ; create a 4k buffer
  xchg eax, edi
  pushad
  mov ecx, 4096
  rep movsb        ; copy
  popad
  Print Str$("Len=%i\twith MasmBasic Len\n", Len(edi))
  push eax
  invoke StringCbLengthA, edi, 4096, esp
  pop ecx
  Print Str$("Len=%i   \twith StringCbLengthA\n", ecx)
  Print Str$("Len=%i\twith Masm32 len\n", len(edi))
  Exit
  TryCatchEnd
end start

Output:
Len=4096        with MasmBasic Len
Len=0           with StringCbLengthA
The instruction at "0040149A" referred to the memory location...

And of course, StringCbLengthA reports "The operation completed successfully" - what else would you expect from such a "safe" function?  ;)

[traphunter]

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Print Str$("Len=%i\twith MasmBasic Len\n", Len(edi))

change this line the value of edi?
I don't use masm, therefore I can't test it.

[dedndave]

in most cases....
EAX, ECX, EDX are volatile
EBX, EBP, ESI, EDI are preserved

[MichaelW]

And of course, StringCbLengthA reports "The operation completed successfully"...

In my test it failed.

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#include <windows.h>
#include <stdio.h>
#include <conio.h>
#define STRSAFE_LIB
#include <strsafe.h>
int main (void)
{
    int res;
    size_t slen;
    char *p = VirtualAlloc(0,4096,MEM_COMMIT,PAGE_READWRITE);
    FILE *stream = fopen( "\\masm32\\include\\windows.inc", "r");
    printf("read: %d\n",fread(p,1,4096,stream));

    res = StringCbLength(p,4096,&slen);
    switch(res)
    {
        case S_OK:
            printf("S_OK\n");
            break;
        case STRSAFE_E_INSUFFICIENT_BUFFER:
            printf("STRSAFE_E_INSUFFICIENT_BUFFER\n");
            break;
        case STRSAFE_E_INVALID_PARAMETER:
            printf("STRSAFE_E_INVALID_PARAMETER\n");
            break;
        case STRSAFE_E_END_OF_FILE:
            printf("STRSAFE_E_END_OF_FILE\n");
            break;
    }
    printf("length: %d\n\n",slen);

    // For StringCbLength the cbMax parameter must specify the maximum
    // number of bytes allowed, including the null terminator, so to
    // correct this problem overwrite the last byte with a null.

    p[4095] = 0;

    res = StringCbLength(p,4096,&slen);
    switch(res)
    {
        case S_OK:
            printf("S_OK\n");
            break;
        case STRSAFE_E_INSUFFICIENT_BUFFER:
            printf("STRSAFE_E_INSUFFICIENT_BUFFER\n");
            break;
        case STRSAFE_E_INVALID_PARAMETER:
            printf("STRSAFE_E_INVALID_PARAMETER\n");
            break;
        case STRSAFE_E_END_OF_FILE:
            printf("STRSAFE_E_END_OF_FILE\n");
            break;
    }
    printf("length: %d\n\n",slen);

    fclose(stream);

    getch();
    return 0;
}


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read: 4096
STRSAFE_E_INVALID_PARAMETER
length: 0

S_OK
length: 4095


[jj2007]

And of course, StringCbLengthA reports "The operation completed successfully"...

In my test it failed.

I am wrong and you are right, Michael. While GetLastError reports "The operation completed successfully", StringCbLengthA returns indeed STRSAFE_E_INVALID_PARAMETER (80070057h).

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Print Str$("Len=%i\twith MasmBasic Len\n", Len(edi))

change this line the value of edi?

As Dave already wrote, edi is one of the non-volatile registers. See "register gets trashed".
In this specific case, only eax and edx get changed, because all MasmBasic macros preserve ecx.