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39
40#ifndef QPRIVATELINEARBUFFER_P_H
41#define QPRIVATELINEARBUFFER_P_H
42
43//
44// W A R N I N G
45// -------------
46//
47// This file is not part of the Qt API. It exists purely as an
48// implementation detail. This header file may change from version to
49// version without notice, or even be removed.
50//
51// We mean it.
52//
53
54// This is QIODevice's read buffer, optimised for read(), isEmpty() and getChar()
55class QPrivateLinearBuffer
56{
57public:
58 QPrivateLinearBuffer() : len(0), first(0), buf(0), capacity(0) {
59 }
60 ~QPrivateLinearBuffer() {
61 delete [] buf;
62 }
63 void clear() {
64 first = buf;
65 len = 0;
66 }
67 int size() const {
68 return len;
69 }
70 bool isEmpty() const {
71 return len == 0;
72 }
73 void skip(int n) {
74 if (n >= len) {
75 clear();
76 } else {
77 len -= n;
78 first += n;
79 }
80 }
81 int getChar() {
82 if (len == 0)
83 return -1;
84 int ch = uchar(*first);
85 len--;
86 first++;
87 return ch;
88 }
89 int read(char* target, int size) {
90 int r = qMin(a: size, b: len);
91 memcpy(dest: target, src: first, n: r);
92 len -= r;
93 first += r;
94 return r;
95 }
96 char* reserve(int size) {
97 makeSpace(required: size + len, where: freeSpaceAtEnd);
98 char* writePtr = first + len;
99 len += size;
100 return writePtr;
101 }
102 void chop(int size) {
103 if (size >= len) {
104 clear();
105 } else {
106 len -= size;
107 }
108 }
109 QByteArray readAll() {
110 char* f = first;
111 int l = len;
112 clear();
113 return QByteArray(f, l);
114 }
115 int readLine(char* target, int size) {
116 int r = qMin(a: size, b: len);
117 char* eol = static_cast<char*>(memchr(s: first, c: '\n', n: r));
118 if (eol)
119 r = 1+(eol-first);
120 memcpy(dest: target, src: first, n: r);
121 len -= r;
122 first += r;
123 return int(r);
124 }
125 bool canReadLine() const {
126 return memchr(s: first, c: '\n', n: len);
127 }
128 void ungetChar(char c) {
129 if (first == buf) {
130 // underflow, the existing valid data needs to move to the end of the (potentially bigger) buffer
131 makeSpace(required: len+1, where: freeSpaceAtStart);
132 }
133 first--;
134 len++;
135 *first = c;
136 }
137 void ungetBlock(const char* block, int size) {
138 if ((first - buf) < size) {
139 // underflow, the existing valid data needs to move to the end of the (potentially bigger) buffer
140 makeSpace(required: len + size, where: freeSpaceAtStart);
141 }
142 first -= size;
143 len += size;
144 memcpy(dest: first, src: block, n: size);
145 }
146
147private:
148 enum FreeSpacePos {freeSpaceAtStart, freeSpaceAtEnd};
149 void makeSpace(size_t required, FreeSpacePos where) {
150 size_t newCapacity = qMax(a: capacity, b: size_t(QPRIVATELINEARBUFFER_BUFFERSIZE));
151 while (newCapacity < required)
152 newCapacity *= 2;
153 const int moveOffset = (where == freeSpaceAtEnd) ? 0 : int(newCapacity) - len;
154 if (newCapacity > capacity) {
155 // allocate more space
156 char* newBuf = new char[newCapacity];
157 memmove(dest: newBuf + moveOffset, src: first, n: len);
158 delete [] buf;
159 buf = newBuf;
160 capacity = newCapacity;
161 } else {
162 // shift any existing data to make space
163 memmove(dest: buf + moveOffset, src: first, n: len);
164 }
165 first = buf + moveOffset;
166 }
167
168private:
169 // length of the unread data
170 int len;
171 // start of the unread data
172 char* first;
173 // the allocated buffer
174 char* buf;
175 // allocated buffer size
176 size_t capacity;
177};
178
179#endif // QPRIVATELINEARBUFFER_P_H
180

source code of qtconnectivity/src/bluetooth/qprivatelinearbuffer_p.h