1 /**
2 Helper functions for working with $(I C strings).
3
4 This module is intended to provide fast, safe and garbage free
5 way to work with $(I C strings).
6
7 Copyright: Denis Shelomovskij 2013-2014
8
9 License: $(HTTP boost.org/LICENSE_1_0.txt, Boost License 1.0).
10
11 Authors: Denis Shelomovskij
12
13 Macros:
14 COREREF = $(HTTP dlang.org/phobos/core_$1.html#$2, `core.$1.$2`)
15 */
16 module my.cstring;
17
18 ///
19 @safe unittest {
20 version (Posix) {
21 import core.stdc.stdlib : free;
22 import core.sys.posix.stdlib : setenv;
23 import std.exception : enforce;
24
25 void setEnvironment(scope const(char)[] name, scope const(char)[] value) {
26 enforce(setenv(name.tempCString(), value.tempCString(), 1) != -1);
27 }
28 }
29
30 version (Windows) {
31 import core.sys.windows.winbase : SetEnvironmentVariableW;
32 import std.exception : enforce;
33
34 void setEnvironment(scope const(char)[] name, scope const(char)[] value) {
35 enforce(SetEnvironmentVariableW(name.tempCStringW(), value.tempCStringW()));
36 }
37 }
38 }
39
40 import std.range;
41 import std.traits;
42
43 /**
44 Creates temporary 0-terminated $(I C string) with copy of passed text.
45
46 Params:
47 To = character type of returned C string
48 str = string or input range to be converted
49
50 Returns:
51
52 The value returned is implicitly convertible to $(D const To*) and
53 has two properties: `ptr` to access $(I C string) as $(D const To*)
54 and `buffPtr` to access it as `To*`.
55
56 The value returned can be indexed by [] to access it as an array.
57
58 The temporary $(I C string) is valid unless returned object is destroyed.
59 Thus if returned object is assigned to a variable the temporary is
60 valid unless the variable goes out of scope. If returned object isn't
61 assigned to a variable it will be destroyed at the end of creating
62 primary expression.
63
64 Implementation_note:
65 For small strings tempCString will use stack allocated buffer,
66 for large strings (approximately 250 characters and more) it will
67 allocate temporary one using C's `malloc`.
68
69 Note:
70 This function is intended to be used in function call expression (like
71 `strlen(str.tempCString())`). Incorrect usage of this function may
72 lead to memory corruption.
73 See $(RED WARNING) in $(B Examples) section.
74 */
75
76 auto tempCString(To = char, From)(scope From str)
77 if (isSomeChar!To && (isInputRange!From || isSomeString!From)
78 && isSomeChar!(ElementEncodingType!From)) {
79 alias CF = Unqual!(ElementEncodingType!From);
80
81 auto res = TempCStringBuffer!To.trustedVoidInit(); // expensive to fill _buff[]
82
83 // Note: res._ptr can't point to res._buff as structs are movable.
84
85 // https://issues.dlang.org/show_bug.cgi?id=14980
86 static if (isSomeString!From) {
87 if (str is null) {
88 res._length = 0;
89 res._ptr = null;
90 return res;
91 }
92 }
93
94 // Use slice assignment if available.
95 static if (To.sizeof == CF.sizeof && is(typeof(res._buff[0 .. str.length] = str[]))) {
96 if (str.length < res._buff.length) {
97 res._buff[0 .. str.length] = str[];
98 res._buff[str.length] = 0;
99 res._ptr = res.useStack;
100 } else {
101 import my.internal.memory : enforceMalloc;
102
103 if (false) {
104 // This code is removed by the compiler but causes `@safe`ty
105 // to be inferred correctly.
106 CF[0] x;
107 x[] = str[0 .. 0];
108 }
109 res._ptr = () @trusted {
110 auto p = cast(CF*) enforceMalloc((str.length + 1) * CF.sizeof);
111 p[0 .. str.length] = str[];
112 p[str.length] = 0;
113 return cast(To*) p;
114 }();
115 }
116 res._length = str.length;
117 return res;
118 } else {
119 static assert(!(isSomeString!From && CF.sizeof == To.sizeof),
120 "Should be using slice assignment.");
121 To[] p = res._buff;
122 size_t i;
123
124 size_t strLength;
125 static if (hasLength!From) {
126 strLength = str.length;
127 }
128 import std.utf : byUTF;
129
130 static if (isSomeString!From)
131 auto r = cast(const(CF)[]) str; // because inout(CF) causes problems with byUTF
132 else
133 alias r = str;
134 To[] heapBuffer;
135 foreach (const c; byUTF!(Unqual!To)(r)) {
136 if (i + 1 == p.length) {
137 heapBuffer = trustedRealloc(p, strLength, heapBuffer is null);
138 p = heapBuffer;
139 }
140 p[i++] = c;
141 }
142 p[i] = 0;
143 res._length = i;
144 res._ptr = (heapBuffer is null ? res.useStack : &heapBuffer[0]);
145 return res;
146 }
147 }
148
149 ///
150 nothrow @nogc @system unittest {
151 import core.stdc..string;
152
153 string str = "abc";
154
155 // Intended usage
156 assert(strlen(str.tempCString()) == 3);
157
158 // Correct usage
159 auto tmp = str.tempCString();
160 assert(strlen(tmp) == 3); // or `tmp.ptr`, or `tmp.buffPtr`
161
162 // $(RED WARNING): $(RED Incorrect usage)
163 auto pInvalid1 = str.tempCString().ptr;
164 const char* pInvalid2 = str.tempCString();
165 // Both pointers refer to invalid memory here as
166 // returned values aren't assigned to a variable and
167 // both primary expressions are ended.
168 }
169
170 @safe pure nothrow @nogc unittest {
171 static inout(C)[] arrayFor(C)(inout(C)* cstr) pure nothrow @nogc @trusted {
172 assert(cstr);
173 size_t length = 0;
174 while (cstr[length])
175 ++length;
176 return cstr[0 .. length];
177 }
178
179 assert(arrayFor("abc".tempCString()) == "abc");
180 assert(arrayFor("abc"d.tempCString().ptr) == "abc");
181 assert(arrayFor("abc".tempCString!wchar().buffPtr) == "abc"w);
182
183 import std.utf : byChar, byWchar;
184
185 char[300] abc = 'a';
186 assert(arrayFor(tempCString(abc[].byChar).buffPtr) == abc);
187 assert(arrayFor(tempCString(abc[].byWchar).buffPtr) == abc);
188 assert(tempCString(abc[].byChar)[] == abc);
189 }
190
191 // https://issues.dlang.org/show_bug.cgi?id=14980
192 pure nothrow @nogc @safe unittest {
193 const(char[]) str = null;
194 auto res = tempCString(str);
195 const char* ptr = res;
196 assert(ptr is null);
197 }
198
199 version (Windows) {
200 import core.sys.windows.winnt : WCHAR;
201
202 alias tempCStringW = tempCString!(WCHAR, const(char)[]);
203 }
204
205 private struct TempCStringBuffer(To = char) {
206 @trusted pure nothrow @nogc:
207
208 @disable this();
209 @disable this(this);
210 alias ptr this; /// implicitly covert to raw pointer
211
212 @property inout(To)* buffPtr() inout {
213 return _ptr == useStack ? _buff.ptr : _ptr;
214 }
215
216 @property const(To)* ptr() const {
217 return buffPtr;
218 }
219
220 const(To)[] opIndex() const pure {
221 return buffPtr[0 .. _length];
222 }
223
224 ~this() {
225 if (_ptr != useStack) {
226 import core.memory : pureFree;
227
228 pureFree(_ptr);
229 }
230 }
231
232 private:
233 enum To* useStack = () @trusted { return cast(To*) size_t.max; }();
234
235 To* _ptr;
236 size_t _length; // length of the string
237 version (StdUnittest) // the 'small string optimization'
238 {
239 // smaller size to trigger reallocations. Padding is to account for
240 // unittest/non-unittest cross-compilation (to avoid corruption)
241 To[16 / To.sizeof] _buff;
242 To[(256 - 16) / To.sizeof] _unittest_pad;
243 } else {
244 To[256 / To.sizeof] _buff; // production size
245 }
246
247 static TempCStringBuffer trustedVoidInit() {
248 TempCStringBuffer res = void;
249 return res;
250 }
251 }
252
253 private To[] trustedRealloc(To)(scope To[] buf, size_t strLength, bool bufIsOnStack) @trusted @nogc pure nothrow {
254 pragma(inline, false); // because it's rarely called
255
256 import my.internal.memory : enforceMalloc, enforceRealloc;
257
258 size_t newlen = buf.length * 3 / 2;
259
260 if (bufIsOnStack) {
261 if (newlen <= strLength)
262 newlen = strLength + 1; // +1 for terminating 0
263 auto ptr = cast(To*) enforceMalloc(newlen * To.sizeof);
264 ptr[0 .. buf.length] = buf[];
265 return ptr[0 .. newlen];
266 } else {
267 if (buf.length >= size_t.max / (2 * To.sizeof)) {
268 version (D_Exceptions) {
269 import core.exception : onOutOfMemoryError;
270
271 onOutOfMemoryError();
272 } else {
273 assert(0, "Memory allocation failed");
274 }
275 }
276 auto ptr = cast(To*) enforceRealloc(buf.ptr, newlen * To.sizeof);
277 return ptr[0 .. newlen];
278 }
279 }