huwcampbell.com
Reactos
1//
2// lfind.cpp
3//
4// Copyright (c) Microsoft Corporation. All rights reserved.
5//
6// Defines _lfind(), which performs a linear search over an array.
7//
8#include <corecrt_internal.h>
9#include <search.h>
10
11#ifdef _M_CEE
12 #define __fileDECL __clrcall
13#else
14 #define __fileDECL __cdecl
15#endif
16
17
18
19#ifdef __USE_CONTEXT
20 #define __COMPARE(context, p1, p2) (*compare)(context, p1, p2)
21#else
22 #define __COMPARE(context, p1, p2) (*compare)(p1, p2)
23#endif
24
25// Performs a linear search over the array, looking for the value 'key' in an
26// array of 'num' elements of 'width' bytes in size. Returns a pointer to the
27// matching element if found. Otherwise, returns nullptr.
28//
29// Parameters:
30// * key: The key for which to search
31// * base: A pointer to the initial element of the array to be searched
32// * num: The number of elements in the array.
33// * width: The size of each element, in bytes.
34// * comp: Pointer to a function returning analog of strcmp for strings, but
35// supplied by the caller for comparing the array elements. It
36// accepts two pointers to elements; returns negative if 1 < 2;
37// zero if 1 == 2, and positive if 1 > 2.
38#ifndef _M_CEE
39extern "C"
40#endif
41#ifdef __USE_CONTEXT
42void* __fileDECL _lfind_s(
43 void const* const key,
44 void const* const base,
45 unsigned int* const num,
46 size_t const width,
47 int (__fileDECL* const compare)(void*, void const*, void const*),
48 void* const context
49 )
50#else // __USE_CONTEXT
51void* __fileDECL _lfind(
52 void const* const key,
53 void const* const base,
54 unsigned int* const num,
55 unsigned int const width,
56 int (__fileDECL* const compare)(void const*, void const*)
57 )
58#endif // __USE_CONTEXT
59{
60 _VALIDATE_RETURN(key != nullptr, EINVAL, nullptr);
61 _VALIDATE_RETURN(num != nullptr, EINVAL, nullptr);
62 _VALIDATE_RETURN(base != nullptr || *num == 0, EINVAL, nullptr);
63 _VALIDATE_RETURN(width > 0, EINVAL, nullptr);
64 _VALIDATE_RETURN(compare != nullptr, EINVAL, nullptr);
65
66 char const* const first = static_cast<char const*>(base);
67 char const* const last = first + *num * width;
68
69 for (char const* p = first; p != last; p += width)
70 {
71 if (__COMPARE(context, key, const_cast<char*>(p)) == 0)
72 {
73 return const_cast<char*>(p);
74 }
75 }
76
77 return nullptr;
78}
79
80#undef __COMPARE