forked from
karlseguin.tngl.sh/buffer.zig
A poolable string builder (aka string buffer) for Zig
initial commit
Karl Seguin
(Jun 24, 2023, 5:54 PM +0800)
00835730
+851
+373
LICENSE
+373
LICENSE
···
1
+
Mozilla Public License Version 2.0
2
+
==================================
3
+
4
+
1. Definitions
5
+
--------------
6
+
7
+
1.1. "Contributor"
8
+
means each individual or legal entity that creates, contributes to
9
+
the creation of, or owns Covered Software.
10
+
11
+
1.2. "Contributor Version"
12
+
means the combination of the Contributions of others (if any) used
13
+
by a Contributor and that particular Contributor's Contribution.
14
+
15
+
1.3. "Contribution"
16
+
means Covered Software of a particular Contributor.
17
+
18
+
1.4. "Covered Software"
19
+
means Source Code Form to which the initial Contributor has attached
20
+
the notice in Exhibit A, the Executable Form of such Source Code
21
+
Form, and Modifications of such Source Code Form, in each case
22
+
including portions thereof.
23
+
24
+
1.5. "Incompatible With Secondary Licenses"
25
+
means
26
+
27
+
(a) that the initial Contributor has attached the notice described
28
+
in Exhibit B to the Covered Software; or
29
+
30
+
(b) that the Covered Software was made available under the terms of
31
+
version 1.1 or earlier of the License, but not also under the
32
+
terms of a Secondary License.
33
+
34
+
1.6. "Executable Form"
35
+
means any form of the work other than Source Code Form.
36
+
37
+
1.7. "Larger Work"
38
+
means a work that combines Covered Software with other material, in
39
+
a separate file or files, that is not Covered Software.
40
+
41
+
1.8. "License"
42
+
means this document.
43
+
44
+
1.9. "Licensable"
45
+
means having the right to grant, to the maximum extent possible,
46
+
whether at the time of the initial grant or subsequently, any and
47
+
all of the rights conveyed by this License.
48
+
49
+
1.10. "Modifications"
50
+
means any of the following:
51
+
52
+
(a) any file in Source Code Form that results from an addition to,
53
+
deletion from, or modification of the contents of Covered
54
+
Software; or
55
+
56
+
(b) any new file in Source Code Form that contains any Covered
57
+
Software.
58
+
59
+
1.11. "Patent Claims" of a Contributor
60
+
means any patent claim(s), including without limitation, method,
61
+
process, and apparatus claims, in any patent Licensable by such
62
+
Contributor that would be infringed, but for the grant of the
63
+
License, by the making, using, selling, offering for sale, having
64
+
made, import, or transfer of either its Contributions or its
65
+
Contributor Version.
66
+
67
+
1.12. "Secondary License"
68
+
means either the GNU General Public License, Version 2.0, the GNU
69
+
Lesser General Public License, Version 2.1, the GNU Affero General
70
+
Public License, Version 3.0, or any later versions of those
71
+
licenses.
72
+
73
+
1.13. "Source Code Form"
74
+
means the form of the work preferred for making modifications.
75
+
76
+
1.14. "You" (or "Your")
77
+
means an individual or a legal entity exercising rights under this
78
+
License. For legal entities, "You" includes any entity that
79
+
controls, is controlled by, or is under common control with You. For
80
+
purposes of this definition, "control" means (a) the power, direct
81
+
or indirect, to cause the direction or management of such entity,
82
+
whether by contract or otherwise, or (b) ownership of more than
83
+
fifty percent (50%) of the outstanding shares or beneficial
84
+
ownership of such entity.
85
+
86
+
2. License Grants and Conditions
87
+
--------------------------------
88
+
89
+
2.1. Grants
90
+
91
+
Each Contributor hereby grants You a world-wide, royalty-free,
92
+
non-exclusive license:
93
+
94
+
(a) under intellectual property rights (other than patent or trademark)
95
+
Licensable by such Contributor to use, reproduce, make available,
96
+
modify, display, perform, distribute, and otherwise exploit its
97
+
Contributions, either on an unmodified basis, with Modifications, or
98
+
as part of a Larger Work; and
99
+
100
+
(b) under Patent Claims of such Contributor to make, use, sell, offer
101
+
for sale, have made, import, and otherwise transfer either its
102
+
Contributions or its Contributor Version.
103
+
104
+
2.2. Effective Date
105
+
106
+
The licenses granted in Section 2.1 with respect to any Contribution
107
+
become effective for each Contribution on the date the Contributor first
108
+
distributes such Contribution.
109
+
110
+
2.3. Limitations on Grant Scope
111
+
112
+
The licenses granted in this Section 2 are the only rights granted under
113
+
this License. No additional rights or licenses will be implied from the
114
+
distribution or licensing of Covered Software under this License.
115
+
Notwithstanding Section 2.1(b) above, no patent license is granted by a
116
+
Contributor:
117
+
118
+
(a) for any code that a Contributor has removed from Covered Software;
119
+
or
120
+
121
+
(b) for infringements caused by: (i) Your and any other third party's
122
+
modifications of Covered Software, or (ii) the combination of its
123
+
Contributions with other software (except as part of its Contributor
124
+
Version); or
125
+
126
+
(c) under Patent Claims infringed by Covered Software in the absence of
127
+
its Contributions.
128
+
129
+
This License does not grant any rights in the trademarks, service marks,
130
+
or logos of any Contributor (except as may be necessary to comply with
131
+
the notice requirements in Section 3.4).
132
+
133
+
2.4. Subsequent Licenses
134
+
135
+
No Contributor makes additional grants as a result of Your choice to
136
+
distribute the Covered Software under a subsequent version of this
137
+
License (see Section 10.2) or under the terms of a Secondary License (if
138
+
permitted under the terms of Section 3.3).
139
+
140
+
2.5. Representation
141
+
142
+
Each Contributor represents that the Contributor believes its
143
+
Contributions are its original creation(s) or it has sufficient rights
144
+
to grant the rights to its Contributions conveyed by this License.
145
+
146
+
2.6. Fair Use
147
+
148
+
This License is not intended to limit any rights You have under
149
+
applicable copyright doctrines of fair use, fair dealing, or other
150
+
equivalents.
151
+
152
+
2.7. Conditions
153
+
154
+
Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted
155
+
in Section 2.1.
156
+
157
+
3. Responsibilities
158
+
-------------------
159
+
160
+
3.1. Distribution of Source Form
161
+
162
+
All distribution of Covered Software in Source Code Form, including any
163
+
Modifications that You create or to which You contribute, must be under
164
+
the terms of this License. You must inform recipients that the Source
165
+
Code Form of the Covered Software is governed by the terms of this
166
+
License, and how they can obtain a copy of this License. You may not
167
+
attempt to alter or restrict the recipients' rights in the Source Code
168
+
Form.
169
+
170
+
3.2. Distribution of Executable Form
171
+
172
+
If You distribute Covered Software in Executable Form then:
173
+
174
+
(a) such Covered Software must also be made available in Source Code
175
+
Form, as described in Section 3.1, and You must inform recipients of
176
+
the Executable Form how they can obtain a copy of such Source Code
177
+
Form by reasonable means in a timely manner, at a charge no more
178
+
than the cost of distribution to the recipient; and
179
+
180
+
(b) You may distribute such Executable Form under the terms of this
181
+
License, or sublicense it under different terms, provided that the
182
+
license for the Executable Form does not attempt to limit or alter
183
+
the recipients' rights in the Source Code Form under this License.
184
+
185
+
3.3. Distribution of a Larger Work
186
+
187
+
You may create and distribute a Larger Work under terms of Your choice,
188
+
provided that You also comply with the requirements of this License for
189
+
the Covered Software. If the Larger Work is a combination of Covered
190
+
Software with a work governed by one or more Secondary Licenses, and the
191
+
Covered Software is not Incompatible With Secondary Licenses, this
192
+
License permits You to additionally distribute such Covered Software
193
+
under the terms of such Secondary License(s), so that the recipient of
194
+
the Larger Work may, at their option, further distribute the Covered
195
+
Software under the terms of either this License or such Secondary
196
+
License(s).
197
+
198
+
3.4. Notices
199
+
200
+
You may not remove or alter the substance of any license notices
201
+
(including copyright notices, patent notices, disclaimers of warranty,
202
+
or limitations of liability) contained within the Source Code Form of
203
+
the Covered Software, except that You may alter any license notices to
204
+
the extent required to remedy known factual inaccuracies.
205
+
206
+
3.5. Application of Additional Terms
207
+
208
+
You may choose to offer, and to charge a fee for, warranty, support,
209
+
indemnity or liability obligations to one or more recipients of Covered
210
+
Software. However, You may do so only on Your own behalf, and not on
211
+
behalf of any Contributor. You must make it absolutely clear that any
212
+
such warranty, support, indemnity, or liability obligation is offered by
213
+
You alone, and You hereby agree to indemnify every Contributor for any
214
+
liability incurred by such Contributor as a result of warranty, support,
215
+
indemnity or liability terms You offer. You may include additional
216
+
disclaimers of warranty and limitations of liability specific to any
217
+
jurisdiction.
218
+
219
+
4. Inability to Comply Due to Statute or Regulation
220
+
---------------------------------------------------
221
+
222
+
If it is impossible for You to comply with any of the terms of this
223
+
License with respect to some or all of the Covered Software due to
224
+
statute, judicial order, or regulation then You must: (a) comply with
225
+
the terms of this License to the maximum extent possible; and (b)
226
+
describe the limitations and the code they affect. Such description must
227
+
be placed in a text file included with all distributions of the Covered
228
+
Software under this License. Except to the extent prohibited by statute
229
+
or regulation, such description must be sufficiently detailed for a
230
+
recipient of ordinary skill to be able to understand it.
231
+
232
+
5. Termination
233
+
--------------
234
+
235
+
5.1. The rights granted under this License will terminate automatically
236
+
if You fail to comply with any of its terms. However, if You become
237
+
compliant, then the rights granted under this License from a particular
238
+
Contributor are reinstated (a) provisionally, unless and until such
239
+
Contributor explicitly and finally terminates Your grants, and (b) on an
240
+
ongoing basis, if such Contributor fails to notify You of the
241
+
non-compliance by some reasonable means prior to 60 days after You have
242
+
come back into compliance. Moreover, Your grants from a particular
243
+
Contributor are reinstated on an ongoing basis if such Contributor
244
+
notifies You of the non-compliance by some reasonable means, this is the
245
+
first time You have received notice of non-compliance with this License
246
+
from such Contributor, and You become compliant prior to 30 days after
247
+
Your receipt of the notice.
248
+
249
+
5.2. If You initiate litigation against any entity by asserting a patent
250
+
infringement claim (excluding declaratory judgment actions,
251
+
counter-claims, and cross-claims) alleging that a Contributor Version
252
+
directly or indirectly infringes any patent, then the rights granted to
253
+
You by any and all Contributors for the Covered Software under Section
254
+
2.1 of this License shall terminate.
255
+
256
+
5.3. In the event of termination under Sections 5.1 or 5.2 above, all
257
+
end user license agreements (excluding distributors and resellers) which
258
+
have been validly granted by You or Your distributors under this License
259
+
prior to termination shall survive termination.
260
+
261
+
************************************************************************
262
+
* *
263
+
* 6. Disclaimer of Warranty *
264
+
* ------------------------- *
265
+
* *
266
+
* Covered Software is provided under this License on an "as is" *
267
+
* basis, without warranty of any kind, either expressed, implied, or *
268
+
* statutory, including, without limitation, warranties that the *
269
+
* Covered Software is free of defects, merchantable, fit for a *
270
+
* particular purpose or non-infringing. The entire risk as to the *
271
+
* quality and performance of the Covered Software is with You. *
272
+
* Should any Covered Software prove defective in any respect, You *
273
+
* (not any Contributor) assume the cost of any necessary servicing, *
274
+
* repair, or correction. This disclaimer of warranty constitutes an *
275
+
* essential part of this License. No use of any Covered Software is *
276
+
* authorized under this License except under this disclaimer. *
277
+
* *
278
+
************************************************************************
279
+
280
+
************************************************************************
281
+
* *
282
+
* 7. Limitation of Liability *
283
+
* -------------------------- *
284
+
* *
285
+
* Under no circumstances and under no legal theory, whether tort *
286
+
* (including negligence), contract, or otherwise, shall any *
287
+
* Contributor, or anyone who distributes Covered Software as *
288
+
* permitted above, be liable to You for any direct, indirect, *
289
+
* special, incidental, or consequential damages of any character *
290
+
* including, without limitation, damages for lost profits, loss of *
291
+
* goodwill, work stoppage, computer failure or malfunction, or any *
292
+
* and all other commercial damages or losses, even if such party *
293
+
* shall have been informed of the possibility of such damages. This *
294
+
* limitation of liability shall not apply to liability for death or *
295
+
* personal injury resulting from such party's negligence to the *
296
+
* extent applicable law prohibits such limitation. Some *
297
+
* jurisdictions do not allow the exclusion or limitation of *
298
+
* incidental or consequential damages, so this exclusion and *
299
+
* limitation may not apply to You. *
300
+
* *
301
+
************************************************************************
302
+
303
+
8. Litigation
304
+
-------------
305
+
306
+
Any litigation relating to this License may be brought only in the
307
+
courts of a jurisdiction where the defendant maintains its principal
308
+
place of business and such litigation shall be governed by laws of that
309
+
jurisdiction, without reference to its conflict-of-law provisions.
310
+
Nothing in this Section shall prevent a party's ability to bring
311
+
cross-claims or counter-claims.
312
+
313
+
9. Miscellaneous
314
+
----------------
315
+
316
+
This License represents the complete agreement concerning the subject
317
+
matter hereof. If any provision of this License is held to be
318
+
unenforceable, such provision shall be reformed only to the extent
319
+
necessary to make it enforceable. Any law or regulation which provides
320
+
that the language of a contract shall be construed against the drafter
321
+
shall not be used to construe this License against a Contributor.
322
+
323
+
10. Versions of the License
324
+
---------------------------
325
+
326
+
10.1. New Versions
327
+
328
+
Mozilla Foundation is the license steward. Except as provided in Section
329
+
10.3, no one other than the license steward has the right to modify or
330
+
publish new versions of this License. Each version will be given a
331
+
distinguishing version number.
332
+
333
+
10.2. Effect of New Versions
334
+
335
+
You may distribute the Covered Software under the terms of the version
336
+
of the License under which You originally received the Covered Software,
337
+
or under the terms of any subsequent version published by the license
338
+
steward.
339
+
340
+
10.3. Modified Versions
341
+
342
+
If you create software not governed by this License, and you want to
343
+
create a new license for such software, you may create and use a
344
+
modified version of this License if you rename the license and remove
345
+
any references to the name of the license steward (except to note that
346
+
such modified license differs from this License).
347
+
348
+
10.4. Distributing Source Code Form that is Incompatible With Secondary
349
+
Licenses
350
+
351
+
If You choose to distribute Source Code Form that is Incompatible With
352
+
Secondary Licenses under the terms of this version of the License, the
353
+
notice described in Exhibit B of this License must be attached.
354
+
355
+
Exhibit A - Source Code Form License Notice
356
+
-------------------------------------------
357
+
358
+
This Source Code Form is subject to the terms of the Mozilla Public
359
+
License, v. 2.0. If a copy of the MPL was not distributed with this
360
+
file, You can obtain one at http://mozilla.org/MPL/2.0/.
361
+
362
+
If it is not possible or desirable to put the notice in a particular
363
+
file, then You may include the notice in a location (such as a LICENSE
364
+
file in a relevant directory) where a recipient would be likely to look
365
+
for such a notice.
366
+
367
+
You may add additional accurate notices of copyright ownership.
368
+
369
+
Exhibit B - "Incompatible With Secondary Licenses" Notice
370
+
---------------------------------------------------------
371
+
372
+
This Source Code Form is "Incompatible With Secondary Licenses", as
373
+
defined by the Mozilla Public License, v. 2.0.
+21
build.zig
+21
build.zig
···
1
+
const std = @import("std");
2
+
3
+
pub fn build(b: *std.Build) !void {
4
+
const target = b.standardTargetOptions(.{});
5
+
const optimize = b.standardOptimizeOption(.{});
6
+
7
+
_ = b.addModule("string_builder", .{
8
+
.source_file = .{ .path = "src/string_builder.zig" },
9
+
});
10
+
11
+
const lib_test = b.addTest(.{
12
+
.root_source_file = .{ .path = "src/string_builder.zig" },
13
+
.target = target,
14
+
.optimize = optimize,
15
+
});
16
+
const run_test = b.addRunArtifact(lib_test);
17
+
run_test.has_side_effects = true;
18
+
19
+
const test_step = b.step("test", "Run tests");
20
+
test_step.dependOn(&run_test.step);
21
+
}
+40
readme.md
+40
readme.md
···
1
+
# StringBuilder For Zig
2
+
3
+
Behaves a lot like a `std.ArrayList(u8)` but with a cleaner interface and pooling capabilities.
4
+
5
+
```zig
6
+
const StringBuilder = @import("string_builder").StringBuilder;
7
+
8
+
// Starts off with a static buffer of 100 bytes
9
+
// If you go over this, memory will be dynamically allocated
10
+
// It's like calling ensureTotalCapacity on an ArrrayList, but
11
+
// those 100 bytes (aka the static portion of the buffer) are
12
+
// re-used when pooling is used
13
+
14
+
var sb = try new StringBuilder(allocator, 100);
15
+
16
+
try sb.writeByte('o');
17
+
try sb.write('ver 9000!1');
18
+
sb.truncate(1);
19
+
20
+
sb.len(); // 10
21
+
sb.string(); // "over 9000!"
22
+
```
23
+
24
+
You can call `sb.writer()` to get an `std.io.Writer`.
25
+
```
26
+
27
+
## Pooling
28
+
29
+
```zig
30
+
const Pool = @import("string_builder").Pool;
31
+
32
+
33
+
// Creates pool of 100 StringBuilders, each configured with a static buffer
34
+
// of 10000 bytes
35
+
var pool = try Pool.init(allocator, 100, 10000);
36
+
var sb = try pool.acquire();
37
+
defer pool.release(sb);
38
+
```
39
+
40
+
The `Pool` is thread-safe. The `StringBuilder` is not thread safe.
+138
src/pool.zig
+138
src/pool.zig
···
1
+
const std = @import("std");
2
+
const builtin = @import("builtin");
3
+
4
+
const StringBuilder = @import("string_builder.zig").StringBuilder;
5
+
6
+
const Mutex = std.Thread.Mutex;
7
+
const Allocator = std.mem.Allocator;
8
+
9
+
pub const Pool = struct {
10
+
mutex: Mutex,
11
+
available: usize,
12
+
allocator: Allocator,
13
+
builder_size: usize,
14
+
builders: []*StringBuilder,
15
+
16
+
pub fn init(allocator: Allocator, pool_size: u16, builder_size: usize) !Pool {
17
+
const builders = try allocator.alloc(*StringBuilder, pool_size);
18
+
19
+
for (0..pool_size) |i| {
20
+
var sb = try allocator.create(StringBuilder);
21
+
sb.* = try StringBuilder.init(allocator, builder_size);
22
+
builders[i] = sb;
23
+
}
24
+
25
+
return Pool{
26
+
.mutex = Mutex{},
27
+
.builders = builders,
28
+
.allocator = allocator,
29
+
.available = pool_size,
30
+
.builder_size = builder_size
31
+
};
32
+
}
33
+
34
+
pub fn deinit(self: *Pool) void {
35
+
const allocator = self.allocator;
36
+
for (self.builders) |sb| {
37
+
sb.deinit();
38
+
allocator.destroy(sb);
39
+
}
40
+
allocator.free(self.builders);
41
+
}
42
+
43
+
pub fn acquire(self: *Pool) !*StringBuilder {
44
+
self.mutex.lock();
45
+
46
+
const builders = self.builders;
47
+
const available = self.available;
48
+
if (available == 0) {
49
+
// dont hold the lock over factory
50
+
self.mutex.unlock();
51
+
const allocator = self.allocator;
52
+
53
+
const sb = try allocator.create(StringBuilder);
54
+
sb.* = try StringBuilder.init(allocator, self.builder_size);
55
+
if (comptime builtin.is_test) sb.buf[0] = 0;
56
+
return sb;
57
+
}
58
+
const index = available - 1;
59
+
const sb = builders[index];
60
+
self.available = index;
61
+
self.mutex.unlock();
62
+
return sb;
63
+
}
64
+
65
+
pub fn release(self: *Pool, sb: *StringBuilder) void {
66
+
sb.reset();
67
+
self.mutex.lock();
68
+
69
+
var builders = self.builders;
70
+
const available = self.available;
71
+
if (available == builders.len) {
72
+
self.mutex.unlock();
73
+
const allocator = self.allocator;
74
+
sb.deinit();
75
+
allocator.destroy(sb);
76
+
return;
77
+
}
78
+
builders[available] = sb;
79
+
self.available = available + 1;
80
+
self.mutex.unlock();
81
+
}
82
+
};
83
+
84
+
const t = @import("t.zig");
85
+
test "pool: acquire and release" {
86
+
var p = try Pool.init(t.allocator, 2, 100);
87
+
defer p.deinit();
88
+
89
+
var sb1a = p.acquire() catch unreachable;
90
+
var sb2a = p.acquire() catch unreachable;
91
+
var sb3a = p.acquire() catch unreachable; // this should be dynamically generated
92
+
93
+
try t.expectEqual(false, sb1a == sb2a);
94
+
try t.expectEqual(false, sb2a == sb3a);
95
+
96
+
p.release(sb1a);
97
+
98
+
var sb1b = p.acquire() catch unreachable;
99
+
try t.expectEqual(true, sb1a == sb1b);
100
+
101
+
p.release(sb3a);
102
+
p.release(sb2a);
103
+
p.release(sb1b);
104
+
}
105
+
106
+
test "pool: threadsafety" {
107
+
var p = try Pool.init(t.allocator, 4, 20);
108
+
defer p.deinit();
109
+
110
+
// initialize this to 0 since we're asserting that it's 0
111
+
for (p.builders) |sb| {
112
+
sb.buf[0] = 0;
113
+
}
114
+
115
+
const t1 = try std.Thread.spawn(.{}, testPool, .{&p});
116
+
const t2 = try std.Thread.spawn(.{}, testPool, .{&p});
117
+
const t3 = try std.Thread.spawn(.{}, testPool, .{&p});
118
+
const t4 = try std.Thread.spawn(.{}, testPool, .{&p});
119
+
const t5 = try std.Thread.spawn(.{}, testPool, .{&p});
120
+
121
+
t1.join(); t2.join(); t3.join(); t4.join(); t5.join();
122
+
}
123
+
124
+
fn testPool(p: *Pool) void {
125
+
var r = t.getRandom();
126
+
const random = r.random();
127
+
128
+
for (0..5000) |_| {
129
+
var sb = p.acquire() catch unreachable;
130
+
// no other thread should have set this to 255
131
+
std.debug.assert(sb.buf[0] == 0);
132
+
133
+
sb.buf[0] = 255;
134
+
std.time.sleep(random.uintAtMost(u32, 100000));
135
+
sb.buf[0] = 0;
136
+
p.release(sb);
137
+
}
138
+
}
+258
src/string_builder.zig
+258
src/string_builder.zig
···
1
+
const std = @import("std");
2
+
3
+
const Allocator = std.mem.Allocator;
4
+
pub const Pool = @import("pool.zig").Pool;
5
+
6
+
pub const StringBuilder = struct {
7
+
allocator: Allocator,
8
+
9
+
// where in buf we currently are
10
+
pos: usize,
11
+
12
+
// fixed size, created on startup
13
+
static: []u8,
14
+
15
+
// created when we try to write more than static.len
16
+
dynamic: ?[]u8,
17
+
18
+
// points to either static or dynamic,
19
+
buf: []u8,
20
+
21
+
pub fn init(allocator: Allocator, size: usize) !StringBuilder {
22
+
const static = try allocator.alloc(u8, size);
23
+
return .{
24
+
.pos = 0,
25
+
.dynamic = null,
26
+
.buf = static,
27
+
.static = static,
28
+
.allocator = allocator,
29
+
};
30
+
}
31
+
32
+
pub fn deinit(self: StringBuilder) void {
33
+
const allocator = self.allocator;
34
+
allocator.free(self.static);
35
+
if (self.dynamic) |dyn| {
36
+
allocator.free(dyn);
37
+
}
38
+
}
39
+
40
+
pub fn reset(self: *StringBuilder) void {
41
+
self.pos = 0;
42
+
if (self.dynamic) |dyn| {
43
+
self.allocator.free(dyn);
44
+
self.dynamic = null;
45
+
self.buf = self.static;
46
+
}
47
+
}
48
+
49
+
pub fn len(self: StringBuilder) usize {
50
+
return self.pos;
51
+
}
52
+
53
+
pub fn string(self: StringBuilder) []const u8 {
54
+
return self.buf[0..self.pos];
55
+
}
56
+
57
+
pub fn truncate(self: *StringBuilder, n: usize) void {
58
+
const pos = self.pos;
59
+
if (n >= pos) {
60
+
self.pos = 0;
61
+
return;
62
+
}
63
+
self.pos = pos - n;
64
+
}
65
+
66
+
pub fn writeByte(self: *StringBuilder, b: u8) !void {
67
+
try self.ensureUnusedCapacity(1);
68
+
self.writeByteAssumeCapacity(b);
69
+
}
70
+
71
+
pub fn writeByteAssumeCapacity(self: *StringBuilder, b: u8) void {
72
+
const pos = self.pos;
73
+
self.buf[pos] = b;
74
+
self.pos = pos + 1;
75
+
}
76
+
77
+
pub fn writeByteNTimes(self: *StringBuilder, b: u8, n: usize) !void {
78
+
try self.ensureUnusedCapacity(n);
79
+
const pos = self.pos;
80
+
const buf = self.buf;
81
+
for (0..n) |offset| {
82
+
buf[pos+offset] = b;
83
+
}
84
+
self.pos = pos + n;
85
+
}
86
+
87
+
pub fn write(self: *StringBuilder, data: []const u8) !void {
88
+
try self.ensureUnusedCapacity(data.len);
89
+
return self.writeAssumeCapacity(data);
90
+
}
91
+
92
+
pub fn writeAssumeCapacity(self: *StringBuilder, data: []const u8) void {
93
+
const pos = self.pos;
94
+
const end_pos = pos + data.len;
95
+
std.mem.copyForwards(u8, self.buf[pos..end_pos], data);
96
+
self.pos = end_pos;
97
+
}
98
+
99
+
pub fn ensureUnusedCapacity(self: *StringBuilder, n: usize) !void {
100
+
return self.ensureTotalCapacity(self.pos + n);
101
+
}
102
+
103
+
pub fn ensureTotalCapacity(self: *StringBuilder, required_capacity: usize) !void {
104
+
const buf = self.buf;
105
+
if (required_capacity <= buf.len) {
106
+
return;
107
+
}
108
+
109
+
// from std.ArrayList
110
+
var new_capacity = self.buf.len;
111
+
while (true) {
112
+
new_capacity +|= new_capacity / 2 + 8;
113
+
if (new_capacity >= required_capacity) break;
114
+
}
115
+
116
+
const allocator = self.allocator;
117
+
if (buf.ptr == self.static.ptr or !allocator.resize(buf, new_capacity)) {
118
+
const new_buffer = try allocator.alloc(u8, new_capacity);
119
+
std.mem.copyForwards(u8, new_buffer[0..buf.len], buf);
120
+
121
+
if (self.dynamic) |dyn| {
122
+
allocator.free(dyn);
123
+
}
124
+
125
+
self.buf = new_buffer;
126
+
self.dynamic = new_buffer;
127
+
} else {
128
+
const new_buffer = buf.ptr[0..new_capacity];
129
+
self.buf = new_buffer;
130
+
self.dynamic = new_buffer;
131
+
}
132
+
}
133
+
134
+
pub fn writer(self: *StringBuilder) Writer.IOWriter {
135
+
return .{.context = Writer.init(self)};
136
+
}
137
+
138
+
pub const Writer = struct {
139
+
sb: *StringBuilder,
140
+
141
+
pub const Error = Allocator.Error;
142
+
pub const IOWriter = std.io.Writer(Writer, error{OutOfMemory}, Writer.write);
143
+
144
+
fn init(sb: *StringBuilder) Writer {
145
+
return .{.sb = sb};
146
+
}
147
+
148
+
pub fn write(self: Writer, data: []const u8) Allocator.Error!usize {
149
+
try self.sb.write(data);
150
+
return data.len;
151
+
}
152
+
};
153
+
};
154
+
155
+
const t = @import("t.zig");
156
+
test {
157
+
std.testing.refAllDecls(@This());
158
+
}
159
+
160
+
test "growth" {
161
+
var sb = try StringBuilder.init(t.allocator, 10);
162
+
defer sb.deinit();
163
+
164
+
// we reset at the end of the loop, and things should work the exact same
165
+
// after a reset
166
+
for (0..5) |_| {
167
+
try t.expectEqual(0, sb.len());
168
+
try sb.writeByte('o');
169
+
try t.expectEqual(1, sb.len());
170
+
try t.expectString("o", sb.string());
171
+
try t.expectEqual(true, sb.dynamic == null);
172
+
173
+
// stays in static
174
+
try sb.write("ver 9000!");
175
+
try t.expectEqual(10, sb.len());
176
+
try t.expectString("over 9000!", sb.string());
177
+
try t.expectEqual(true, sb.dynamic == null);
178
+
179
+
// grows into dynamic
180
+
try sb.write("!!!");
181
+
try t.expectEqual(13, sb.len());
182
+
try t.expectString("over 9000!!!!", sb.string());
183
+
try t.expectEqual(false, sb.dynamic == null);
184
+
185
+
186
+
try sb.write("If you were to run this code, you'd almost certainly see a segmentation fault (aka, segfault). We create a Response which involves creating an ArenaAllocator and from that, an Allocator. This allocator is then used to format our string. For the purpose of this example, we create a 2nd response and immediately free it. We need this for the same reason that warning1 in our first example printed an almost ok value: we want to re-initialize the memory in our init function stack.");
187
+
try t.expectEqual(492, sb.len());
188
+
try t.expectString("over 9000!!!!If you were to run this code, you'd almost certainly see a segmentation fault (aka, segfault). We create a Response which involves creating an ArenaAllocator and from that, an Allocator. This allocator is then used to format our string. For the purpose of this example, we create a 2nd response and immediately free it. We need this for the same reason that warning1 in our first example printed an almost ok value: we want to re-initialize the memory in our init function stack.", sb.string());
189
+
190
+
sb.reset();
191
+
}
192
+
}
193
+
194
+
test "truncate" {
195
+
var sb = try StringBuilder.init(t.allocator, 10);
196
+
defer sb.deinit();
197
+
198
+
sb.truncate(100);
199
+
try t.expectEqual(0, sb.len());
200
+
201
+
try sb.write("hello world!1");
202
+
203
+
sb.truncate(0);
204
+
try t.expectEqual(13, sb.len());
205
+
try t.expectString("hello world!1", sb.string());
206
+
207
+
sb.truncate(1);
208
+
try t.expectEqual(12, sb.len());
209
+
try t.expectString("hello world!", sb.string());
210
+
211
+
sb.truncate(5);
212
+
try t.expectEqual(7, sb.len());
213
+
try t.expectString("hello w", sb.string());
214
+
}
215
+
216
+
test "fuzz" {
217
+
var control = std.ArrayList(u8).init(t.allocator);
218
+
defer control.deinit();
219
+
220
+
var r = t.getRandom();
221
+
const random = r.random();
222
+
223
+
var arena = std.heap.ArenaAllocator.init(t.allocator);
224
+
defer arena.deinit();
225
+
226
+
const aa = arena.allocator();
227
+
228
+
for (1..100) |_| {
229
+
var sb = try StringBuilder.init(t.allocator, random.uintAtMost(u16, 1000) + 1);
230
+
defer sb.deinit();
231
+
232
+
for (1..100) |_| {
233
+
const input = testString(aa, random);
234
+
try sb.write(input);
235
+
try control.appendSlice(input);
236
+
try t.expectString(control.items, sb.string());
237
+
}
238
+
sb.reset();
239
+
control.clearRetainingCapacity();
240
+
_ = arena.reset(.free_all);
241
+
}
242
+
}
243
+
244
+
test "writer" {
245
+
var sb = try StringBuilder.init(t.allocator, 10);
246
+
defer sb.deinit();
247
+
248
+
try std.json.stringify(.{.over = 9000, .spice = "must flow", .ok = true}, .{}, sb.writer());
249
+
try t.expectString("{\"over\":9000,\"spice\":\"must flow\",\"ok\":true}", sb.string());
250
+
}
251
+
252
+
fn testString(allocator: Allocator, random: std.rand.Random) []const u8 {
253
+
var s = allocator.alloc(u8, random.uintAtMost(u8, 100) + 1) catch unreachable;
254
+
for (0..s.len) |i| {
255
+
s[i] = random.uintAtMost(u8, 90) + 32;
256
+
}
257
+
return s;
258
+
}
+16
src/t.zig
+16
src/t.zig
···
1
+
const std = @import("std");
2
+
pub const allocator = std.testing.allocator;
3
+
4
+
// std.testing.expectEqual won't coerce expected to actual, which is a problem
5
+
// when expected is frequently a comptime.
6
+
// https://github.com/ziglang/zig/issues/4437
7
+
pub fn expectEqual(expected: anytype, actual: anytype) !void {
8
+
try std.testing.expectEqual(@as(@TypeOf(actual), expected), actual);
9
+
}
10
+
pub const expectString = std.testing.expectEqualStrings;
11
+
12
+
pub fn getRandom() std.rand.DefaultPrng {
13
+
var seed: u64 = undefined;
14
+
std.os.getrandom(std.mem.asBytes(&seed)) catch unreachable;
15
+
return std.rand.DefaultPrng.init(seed);
16
+
}