1
2/*
3 * Copyright 2006 The Android Open Source Project
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9
10#ifndef SkTSearch_DEFINED
11#define SkTSearch_DEFINED
12
13#include "include/core/SkTypes.h"
14
15/**
16 * All of the SkTSearch variants want to return the index (0...N-1) of the
17 * found element, or the bit-not of where to insert the element.
18 *
19 * At a simple level, if the return value is negative, it was not found.
20 *
21 * For clients that want to insert the new element if it was not found, use
22 * the following logic:
23 *
24 * int index = SkTSearch(...);
25 * if (index >= 0) {
26 * // found at index
27 * } else {
28 * index = ~index; // now we are positive
29 * // insert at index
30 * }
31 */
32
33
34// The most general form of SkTSearch takes an array of T and a key of type K. A functor, less, is
35// used to perform comparisons. It has two function operators:
36// bool operator() (const T& t, const K& k)
37// bool operator() (const K& t, const T& k)
38template <typename T, typename K, typename LESS>
39int SkTSearch(const T base[], int count, const K& key, size_t elemSize, const LESS& less)
40{
41 SkASSERT(count >= 0);
42 if (count <= 0) {
43 return ~0;
44 }
45
46 SkASSERT(base != nullptr); // base may be nullptr if count is zero
47
48 int lo = 0;
49 int hi = count - 1;
50
51 while (lo < hi) {
52 int mid = lo + ((hi - lo) >> 1);
53 const T* elem = (const T*)((const char*)base + mid * elemSize);
54
55 if (less(*elem, key))
56 lo = mid + 1;
57 else
58 hi = mid;
59 }
60
61 const T* elem = (const T*)((const char*)base + hi * elemSize);
62 if (less(*elem, key)) {
63 hi += 1;
64 hi = ~hi;
65 } else if (less(key, *elem)) {
66 hi = ~hi;
67 }
68 return hi;
69}
70
71// Specialization for case when T==K and the caller wants to use a function rather than functor.
72template <typename T, bool (LESS)(const T&, const T&)>
73int SkTSearch(const T base[], int count, const T& target, size_t elemSize) {
74 return SkTSearch(base, count, target, elemSize,
75 [](const T& a, const T& b) { return LESS(a, b); });
76}
77
78// Specialization for T==K, compare using op <.
79template <typename T>
80int SkTSearch(const T base[], int count, const T& target, size_t elemSize) {
81 return SkTSearch(base, count, target, elemSize, [](const T& a, const T& b) { return a < b; });
82}
83
84// Specialization for case where domain is an array of T* and the key value is a T*, and you want
85// to compare the T objects, not the pointers.
86template <typename T, bool (LESS)(const T&, const T&)>
87int SkTSearch(T* base[], int count, T* target, size_t elemSize) {
88 return SkTSearch(base, count, target, elemSize,
89 [](const T* t, const T* k) { return LESS(*t, *k); });
90}
91
92int SkStrSearch(const char*const* base, int count, const char target[],
93 size_t target_len, size_t elemSize);
94int SkStrSearch(const char*const* base, int count, const char target[],
95 size_t elemSize);
96
97/** Like SkStrSearch, but treats target as if it were all lower-case. Assumes that
98 base points to a table of lower-case strings.
99*/
100int SkStrLCSearch(const char*const* base, int count, const char target[],
101 size_t target_len, size_t elemSize);
102int SkStrLCSearch(const char*const* base, int count, const char target[],
103 size_t elemSize);
104
105/** Helper class to convert a string to lower-case, but only modifying the ascii
106 characters. This makes the routine very fast and never changes the string
107 length, but it is not suitable for linguistic purposes. Normally this is
108 used for buiding and searching string tables.
109*/
110class SkAutoAsciiToLC {
111public:
112 SkAutoAsciiToLC(const char str[], size_t len = (size_t)-1);
113 ~SkAutoAsciiToLC();
114
115 const char* lc() const { return fLC; }
116 size_t length() const { return fLength; }
117
118private:
119 char* fLC; // points to either the heap or fStorage
120 size_t fLength;
121 enum {
122 STORAGE = 64
123 };
124 char fStorage[STORAGE+1];
125};
126
127// Helper when calling qsort with a compare proc that has typed its arguments
128#define SkCastForQSort(compare) reinterpret_cast<int (*)(const void*, const void*)>(compare)
129
130#endif
131