authorgravatar for andrew@ziglang.orgAndrew Kelley <andrew@ziglang.org> 2025-05-06 20:25:55-07:00
committergravatar for andrew@ziglang.orgAndrew Kelley <andrew@ziglang.org> 2025-07-01 16:35:29-07:00
log110af768bbd80c602ad3314091d6a392ee2fd341
tree8e599377274250c6a61c1e09e15a88d2e00e4050
parente76afef8477ae6f1df7c8132342aa6ddea51d4fb

remove std.io.BitWriter

4 files changed, 8 insertions(+), 196 deletions(-)

lib/std/io.zig-4
......@@ -19,9 +19,6 @@ pub const AllocatingWriter = @import("io/AllocatingWriter.zig");
1919pub const MultiWriter = @import("io/multi_writer.zig").MultiWriter;
2020pub const multiWriter = @import("io/multi_writer.zig").multiWriter;
2121
22pub const BitWriter = @import("io/bit_writer.zig").BitWriter;
23pub const bitWriter = @import("io/bit_writer.zig").bitWriter;
24
2522pub const ChangeDetectionStream = @import("io/change_detection_stream.zig").ChangeDetectionStream;
2623pub const changeDetectionStream = @import("io/change_detection_stream.zig").changeDetectionStream;
2724
......@@ -434,7 +431,6 @@ pub fn PollFiles(comptime StreamEnum: type) type {
434431
435432test {
436433 _ = AllocatingWriter;
437 _ = BitWriter;
438434 _ = BufferedReader;
439435 _ = BufferedWriter;
440436 _ = Reader;
lib/std/io/BufferedReader.zig+8
......@@ -1160,3 +1160,11 @@ test readSliceShort {
11601160test readVec {
11611161 return error.Unimplemented;
11621162}
1163
1164test "expected error.EndOfStream" {
1165 // Unit test inspired by https://github.com/ziglang/zig/issues/17733
1166 var br: std.io.BufferedReader = undefined;
1167 br.initFixed("");
1168 try std.testing.expectError(error.EndOfStream, br.readEnum(enum(u8) { a, b }, .little));
1169 try std.testing.expectError(error.EndOfStream, br.isBytes("foo"));
1170}
lib/std/io/bit_writer.zig deleted-179
......@@ -1,179 +0,0 @@
1const std = @import("../std.zig");
2
3//General note on endianess:
4//Big endian is packed starting in the most significant part of the byte and subsequent
5// bytes contain less significant bits. Thus we write out bits from the high end
6// of our input first.
7//Little endian is packed starting in the least significant part of the byte and
8// subsequent bytes contain more significant bits. Thus we write out bits from
9// the low end of our input first.
10//Regardless of endianess, within any given byte the bits are always in most
11// to least significant order.
12//Also regardless of endianess, the buffer always aligns bits to the low end
13// of the byte.
14
15/// Creates a bit writer which allows for writing bits to an underlying standard writer
16pub fn BitWriter(comptime endian: std.builtin.Endian, comptime Writer: type) type {
17 return struct {
18 writer: Writer,
19 bits: u8 = 0,
20 count: u4 = 0,
21
22 const low_bit_mask = [9]u8{
23 0b00000000,
24 0b00000001,
25 0b00000011,
26 0b00000111,
27 0b00001111,
28 0b00011111,
29 0b00111111,
30 0b01111111,
31 0b11111111,
32 };
33
34 /// Write the specified number of bits to the writer from the least significant bits of
35 /// the specified value. Bits will only be written to the writer when there
36 /// are enough to fill a byte.
37 pub fn writeBits(self: *@This(), value: anytype, num: u16) !void {
38 const T = @TypeOf(value);
39 const UT = std.meta.Int(.unsigned, @bitSizeOf(T));
40 const U = if (@bitSizeOf(T) < 8) u8 else UT; //<u8 is a pain to work with
41
42 var in: U = @as(UT, @bitCast(value));
43 var in_count: u16 = num;
44
45 if (self.count > 0) {
46 //if we can't fill the buffer, add what we have
47 const bits_free = 8 - self.count;
48 if (num < bits_free) {
49 self.addBits(@truncate(in), @intCast(num));
50 return;
51 }
52
53 //finish filling the buffer and flush it
54 if (num == bits_free) {
55 self.addBits(@truncate(in), @intCast(num));
56 return self.flushBits();
57 }
58
59 switch (endian) {
60 .big => {
61 const bits = in >> @intCast(in_count - bits_free);
62 self.addBits(@truncate(bits), bits_free);
63 },
64 .little => {
65 self.addBits(@truncate(in), bits_free);
66 in >>= @intCast(bits_free);
67 },
68 }
69 in_count -= bits_free;
70 try self.flushBits();
71 }
72
73 //write full bytes while we can
74 const full_bytes_left = in_count / 8;
75 for (0..full_bytes_left) |_| {
76 switch (endian) {
77 .big => {
78 const bits = in >> @intCast(in_count - 8);
79 try self.writer.writeByte(@truncate(bits));
80 },
81 .little => {
82 try self.writer.writeByte(@truncate(in));
83 if (U == u8) in = 0 else in >>= 8;
84 },
85 }
86 in_count -= 8;
87 }
88
89 //save the remaining bits in the buffer
90 self.addBits(@truncate(in), @intCast(in_count));
91 }
92
93 //convenience funciton for adding bits to the buffer
94 //in the appropriate position based on endianess
95 fn addBits(self: *@This(), bits: u8, num: u4) void {
96 if (num == 8) self.bits = bits else switch (endian) {
97 .big => {
98 self.bits <<= @intCast(num);
99 self.bits |= bits & low_bit_mask[num];
100 },
101 .little => {
102 const pos = bits << @intCast(self.count);
103 self.bits |= pos;
104 },
105 }
106 self.count += num;
107 }
108
109 /// Flush any remaining bits to the writer, filling
110 /// unused bits with 0s.
111 pub fn flushBits(self: *@This()) !void {
112 if (self.count == 0) return;
113 if (endian == .big) self.bits <<= @intCast(8 - self.count);
114 try self.writer.writeByte(self.bits);
115 self.bits = 0;
116 self.count = 0;
117 }
118 };
119}
120
121pub fn bitWriter(comptime endian: std.builtin.Endian, writer: anytype) BitWriter(endian, @TypeOf(writer)) {
122 return .{ .writer = writer };
123}
124
125///////////////////////////////
126
127test "api coverage" {
128 var mem_be = [_]u8{0} ** 2;
129 var mem_le = [_]u8{0} ** 2;
130
131 var mem_out_be = std.io.fixedBufferStream(&mem_be);
132 var bit_stream_be = bitWriter(.big, mem_out_be.writer());
133
134 const testing = std.testing;
135
136 try bit_stream_be.writeBits(@as(u2, 1), 1);
137 try bit_stream_be.writeBits(@as(u5, 2), 2);
138 try bit_stream_be.writeBits(@as(u128, 3), 3);
139 try bit_stream_be.writeBits(@as(u8, 4), 4);
140 try bit_stream_be.writeBits(@as(u9, 5), 5);
141 try bit_stream_be.writeBits(@as(u1, 1), 1);
142
143 try testing.expect(mem_be[0] == 0b11001101 and mem_be[1] == 0b00001011);
144
145 mem_out_be.pos = 0;
146
147 try bit_stream_be.writeBits(@as(u15, 0b110011010000101), 15);
148 try bit_stream_be.flushBits();
149 try testing.expect(mem_be[0] == 0b11001101 and mem_be[1] == 0b00001010);
150
151 mem_out_be.pos = 0;
152 try bit_stream_be.writeBits(@as(u32, 0b110011010000101), 16);
153 try testing.expect(mem_be[0] == 0b01100110 and mem_be[1] == 0b10000101);
154
155 try bit_stream_be.writeBits(@as(u0, 0), 0);
156
157 var mem_out_le = std.io.fixedBufferStream(&mem_le);
158 var bit_stream_le = bitWriter(.little, mem_out_le.writer());
159
160 try bit_stream_le.writeBits(@as(u2, 1), 1);
161 try bit_stream_le.writeBits(@as(u5, 2), 2);
162 try bit_stream_le.writeBits(@as(u128, 3), 3);
163 try bit_stream_le.writeBits(@as(u8, 4), 4);
164 try bit_stream_le.writeBits(@as(u9, 5), 5);
165 try bit_stream_le.writeBits(@as(u1, 1), 1);
166
167 try testing.expect(mem_le[0] == 0b00011101 and mem_le[1] == 0b10010101);
168
169 mem_out_le.pos = 0;
170 try bit_stream_le.writeBits(@as(u15, 0b110011010000101), 15);
171 try bit_stream_le.flushBits();
172 try testing.expect(mem_le[0] == 0b10000101 and mem_le[1] == 0b01100110);
173
174 mem_out_le.pos = 0;
175 try bit_stream_le.writeBits(@as(u32, 0b1100110100001011), 16);
176 try testing.expect(mem_le[0] == 0b00001011 and mem_le[1] == 0b11001101);
177
178 try bit_stream_le.writeBits(@as(u0, 0), 0);
179}
lib/std/io/test.zig-13
......@@ -167,16 +167,3 @@ test "updateTimes" {
167167 try expect(stat_new.atime < stat_old.atime);
168168 try expect(stat_new.mtime < stat_old.mtime);
169169}
170
171test "GenericReader methods can return error.EndOfStream" {
172 // https://github.com/ziglang/zig/issues/17733
173 var fbs = std.io.fixedBufferStream("");
174 try std.testing.expectError(
175 error.EndOfStream,
176 fbs.reader().readEnum(enum(u8) { a, b }, .little),
177 );
178 try std.testing.expectError(
179 error.EndOfStream,
180 fbs.reader().isBytes("foo"),
181 );
182}