RtlStringLengthWorkerA - NtDoc

#ifndef _NTSTRSAFE_H_INCLUDED_

// prototypes for the worker functions

NTSTRSAFEWORKERDDI
RtlStringLengthWorkerA(
    _In_reads_or_z_(cchMax) STRSAFE_PCNZCH psz,
    _In_ _In_range_(<=, NTSTRSAFE_MAX_CCH) size_t cchMax,
    _Out_opt_ _Deref_out_range_(<, cchMax) _Deref_out_range_(<=, _String_length_(psz)) size_t* pcchLength);

#endif
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#ifndef _NTSTRSAFE_H_INCLUDED_
// Below here are the worker functions that actually do the work
#if defined(NTSTRSAFE_LIB_IMPL) || !defined(NTSTRSAFE_LIB)

NTSTRSAFEWORKERDDI
    RtlStringLengthWorkerA(
            _In_reads_or_z_(cchMax) STRSAFE_PCNZCH psz,
            _In_ _In_range_(<=, NTSTRSAFE_MAX_CCH) size_t cchMax,
            _Out_opt_ _Deref_out_range_(<, cchMax) _Deref_out_range_(<=, _String_length_(psz)) size_t* pcchLength)
{
    NTSTATUS status = STATUS_SUCCESS;
    size_t cchOriginalMax = cchMax;

    while (cchMax && (*psz != '\0'))
    {
        psz++;
        cchMax--;
    }

    if (cchMax == 0)
    {
        // the string is longer than cchMax
        status = STATUS_INVALID_PARAMETER;
    }

    if (pcchLength)
    {
        if (NT_SUCCESS(status))
        {
            *pcchLength = cchOriginalMax - cchMax;
        }
        else
        {
            *pcchLength = 0;
        }
    }

    return status;
}

#endif
#endif
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#ifndef _NTSTRSAFE_H_INCLUDED_
// Do not call these functions, they are worker functions for internal use within this file
#ifdef DEPRECATE_SUPPORTED
// ...
#else

#define RtlStringLengthWorkerA             RtlStringLengthWorkerA_instead_use_StringCchLengthA_or_StringCbLengthA

#endif
#endif
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