Skip to content

Commit fc45e5b

Browse files
andrewrkandrewrk
authored
Merge pull request #19784 from tiehuis/simplify-hash-crc32
std.hash.crc: simplify api
2 parents 497f37c + 5f0ecaf commit fc45e5b

File tree

7 files changed

+65
-174
lines changed

7 files changed

+65
-174
lines changed

‎lib/std/debug.zig

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1150,7 +1150,7 @@ pub fn readElfDebugInfo(
11501150
};
11511151

11521152
const mapped_mem = try mapWholeFile(elf_file);
1153-
if (expected_crc) |crc| if (crc != std.hash.crc.Crc32SmallWithPoly(.IEEE).hash(mapped_mem)) return error.InvalidDebugInfo;
1153+
if (expected_crc) |crc| if (crc != std.hash.crc.Crc32.hash(mapped_mem)) return error.InvalidDebugInfo;
11541154

11551155
const hdr: *const elf.Ehdr = @ptrCast(&mapped_mem[0]);
11561156
if (!mem.eql(u8, hdr.e_ident[0..4], elf.MAGIC)) return error.InvalidElfMagic;

‎lib/std/hash/benchmark.zig

Lines changed: 2 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -56,12 +56,8 @@ const hashes = [_]Hash{
5656
.name = "adler32",
5757
},
5858
Hash{
59-
.ty = hash.crc.Crc32WithPoly(.IEEE),
60-
.name = "crc32-slicing-by-8",
61-
},
62-
Hash{
63-
.ty = hash.crc.Crc32SmallWithPoly(.IEEE),
64-
.name = "crc32-half-byte-lookup",
59+
.ty = hash.crc.Crc32,
60+
.name = "crc32",
6561
},
6662
Hash{
6763
.ty = hash.CityHash32,

‎lib/std/hash/crc.zig

Lines changed: 9 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,8 +7,7 @@ pub const Polynomial = impl.Polynomial;
77
pub const Crc32WithPoly = impl.Crc32WithPoly;
88
pub const Crc32SmallWithPoly = impl.Crc32SmallWithPoly;
99

10-
// IEEE is by far the most common CRC and so is aliased by default.
11-
pub const Crc32 = Crc32WithPoly(.IEEE);
10+
pub const Crc32 = Crc32IsoHdlc;
1211

1312
test {
1413
_ = @import("crc/test.zig");
@@ -822,6 +821,14 @@ pub const Crc32Jamcrc = Crc(u32, .{
822821
.xor_output = 0x00000000,
823822
});
824823

824+
pub const Crc32Koopman = Crc(u32, .{
825+
.polynomial = 0x741b8cd7,
826+
.initial = 0xffffffff,
827+
.reflect_input = true,
828+
.reflect_output = true,
829+
.xor_output = 0xffffffff,
830+
});
831+
825832
pub const Crc32Mef = Crc(u32, .{
826833
.polynomial = 0x741b8cd7,
827834
.initial = 0xffffffff,

‎lib/std/hash/crc/impl.zig

Lines changed: 6 additions & 135 deletions
Original file line numberDiff line numberDiff line change
@@ -1,11 +1,5 @@
11
// There is a generic CRC implementation "Crc()" which can be paramterized via
2-
// the Algorithm struct for a plethora of uses, along with two implementations
3-
// of CRC32 implemented with the following key characteristics:
4-
//
5-
// - Crc32WithPoly uses 8Kb of tables but is ~10x faster than the small method.
6-
//
7-
// - Crc32SmallWithPoly uses only 64 bytes of memory but is slower. Be aware that this is
8-
// still moderately fast just slow relative to the slicing approach.
2+
// the Algorithm struct for a plethora of uses.
93
//
104
// The primary interface for all of the standard CRC algorithms is the
115
// generated file "crc.zig", which uses the implementation code here to define
@@ -108,134 +102,11 @@ pub fn Crc(comptime W: type, comptime algorithm: Algorithm(W)) type {
108102
}
109103

110104
pub const Polynomial = enum(u32) {
111-
IEEE = 0xedb88320,
112-
Castagnoli = 0x82f63b78,
113-
Koopman = 0xeb31d82e,
105+
IEEE = @compileError("use Crc with algorithm .Crc32IsoHdlc"),
106+
Castagnoli = @compileError("use Crc with algorithm .Crc32Iscsi"),
107+
Koopman = @compileError("use Crc with algorithm .Crc32Koopman"),
114108
_,
115109
};
116110

117-
// slicing-by-8 crc32 implementation.
118-
pub fn Crc32WithPoly(comptime poly: Polynomial) type {
119-
return struct {
120-
const Self = @This();
121-
const lookup_tables = block: {
122-
@setEvalBranchQuota(20000);
123-
var tables: [8][256]u32 = undefined;
124-
125-
for (&tables[0], 0..) |*e, i| {
126-
var crc = @as(u32, @intCast(i));
127-
var j: usize = 0;
128-
while (j < 8) : (j += 1) {
129-
if (crc & 1 == 1) {
130-
crc = (crc >> 1) ^ @intFromEnum(poly);
131-
} else {
132-
crc = (crc >> 1);
133-
}
134-
}
135-
e.* = crc;
136-
}
137-
138-
var i: usize = 0;
139-
while (i < 256) : (i += 1) {
140-
var crc = tables[0][i];
141-
var j: usize = 1;
142-
while (j < 8) : (j += 1) {
143-
const index: u8 = @truncate(crc);
144-
crc = tables[0][index] ^ (crc >> 8);
145-
tables[j][i] = crc;
146-
}
147-
}
148-
149-
break :block tables;
150-
};
151-
152-
crc: u32,
153-
154-
pub fn init() Self {
155-
return Self{ .crc = 0xffffffff };
156-
}
157-
158-
pub fn update(self: *Self, input: []const u8) void {
159-
var i: usize = 0;
160-
while (i + 8 <= input.len) : (i += 8) {
161-
const p = input[i..][0..8];
162-
163-
// Unrolling this way gives ~50Mb/s increase
164-
self.crc ^= std.mem.readInt(u32, p[0..4], .little);
165-
166-
self.crc =
167-
lookup_tables[0][p[7]] ^
168-
lookup_tables[1][p[6]] ^
169-
lookup_tables[2][p[5]] ^
170-
lookup_tables[3][p[4]] ^
171-
lookup_tables[4][@as(u8, @truncate(self.crc >> 24))] ^
172-
lookup_tables[5][@as(u8, @truncate(self.crc >> 16))] ^
173-
lookup_tables[6][@as(u8, @truncate(self.crc >> 8))] ^
174-
lookup_tables[7][@as(u8, @truncate(self.crc >> 0))];
175-
}
176-
177-
while (i < input.len) : (i += 1) {
178-
const index = @as(u8, @truncate(self.crc)) ^ input[i];
179-
self.crc = (self.crc >> 8) ^ lookup_tables[0][index];
180-
}
181-
}
182-
183-
pub fn final(self: *Self) u32 {
184-
return ~self.crc;
185-
}
186-
187-
pub fn hash(input: []const u8) u32 {
188-
var c = Self.init();
189-
c.update(input);
190-
return c.final();
191-
}
192-
};
193-
}
194-
195-
// half-byte lookup table implementation.
196-
pub fn Crc32SmallWithPoly(comptime poly: Polynomial) type {
197-
return struct {
198-
const Self = @This();
199-
const lookup_table = block: {
200-
var table: [16]u32 = undefined;
201-
202-
for (&table, 0..) |*e, i| {
203-
var crc = @as(u32, @intCast(i * 16));
204-
var j: usize = 0;
205-
while (j < 8) : (j += 1) {
206-
if (crc & 1 == 1) {
207-
crc = (crc >> 1) ^ @intFromEnum(poly);
208-
} else {
209-
crc = (crc >> 1);
210-
}
211-
}
212-
e.* = crc;
213-
}
214-
215-
break :block table;
216-
};
217-
218-
crc: u32,
219-
220-
pub fn init() Self {
221-
return Self{ .crc = 0xffffffff };
222-
}
223-
224-
pub fn update(self: *Self, input: []const u8) void {
225-
for (input) |b| {
226-
self.crc = lookup_table[@as(u4, @truncate(self.crc ^ (b >> 0)))] ^ (self.crc >> 4);
227-
self.crc = lookup_table[@as(u4, @truncate(self.crc ^ (b >> 4)))] ^ (self.crc >> 4);
228-
}
229-
}
230-
231-
pub fn final(self: *Self) u32 {
232-
return ~self.crc;
233-
}
234-
235-
pub fn hash(input: []const u8) u32 {
236-
var c = Self.init();
237-
c.update(input);
238-
return c.final();
239-
}
240-
};
241-
}
111+
pub const Crc32WithPoly = @compileError("use Crc instead");
112+
pub const Crc32SmallWithPoly = @compileError("use Crc instead");

‎lib/std/hash/crc/test.zig

Lines changed: 28 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -5,22 +5,25 @@ const testing = std.testing;
55
const verify = @import("../verify.zig");
66
const crc = @import("../crc.zig");
77

8-
test "crc32 ieee" {
9-
inline for ([2]type{ crc.Crc32WithPoly(.IEEE), crc.Crc32SmallWithPoly(.IEEE) }) |ieee| {
10-
try testing.expect(ieee.hash("") == 0x00000000);
11-
try testing.expect(ieee.hash("a") == 0xe8b7be43);
12-
try testing.expect(ieee.hash("abc") == 0x352441c2);
13-
try verify.iterativeApi(ieee);
14-
}
8+
test "crc32 ieee regression" {
9+
const crc32 = crc.Crc32IsoHdlc;
10+
try testing.expectEqual(crc32.hash(""), 0x00000000);
11+
try testing.expectEqual(crc32.hash("a"), 0xe8b7be43);
12+
try testing.expectEqual(crc32.hash("abc"), 0x352441c2);
1513
}
1614

17-
test "crc32 castagnoli" {
18-
inline for ([2]type{ crc.Crc32WithPoly(.Castagnoli), crc.Crc32SmallWithPoly(.Castagnoli) }) |casta| {
19-
try testing.expect(casta.hash("") == 0x00000000);
20-
try testing.expect(casta.hash("a") == 0xc1d04330);
21-
try testing.expect(casta.hash("abc") == 0x364b3fb7);
22-
try verify.iterativeApi(casta);
23-
}
15+
test "crc32 castagnoli regression" {
16+
const crc32 = crc.Crc32Iscsi;
17+
try testing.expectEqual(crc32.hash(""), 0x00000000);
18+
try testing.expectEqual(crc32.hash("a"), 0xc1d04330);
19+
try testing.expectEqual(crc32.hash("abc"), 0x364b3fb7);
20+
}
21+
22+
test "crc32 koopman regression" {
23+
const crc32 = crc.Crc32Koopman;
24+
try testing.expectEqual(crc32.hash(""), 0x00000000);
25+
try testing.expectEqual(crc32.hash("a"), 0x0da2aa8a);
26+
try testing.expectEqual(crc32.hash("abc"), 0xba2322ac);
2427
}
2528

2629
test "CRC-3/GSM" {
@@ -1134,6 +1137,17 @@ test "CRC-32/JAMCRC" {
11341137
try testing.expectEqual(@as(u32, 0x340bc6d9), c.final());
11351138
}
11361139

1140+
test "CRC-32/KOOPMAN" {
1141+
const Crc32Koopman = crc.Crc32Koopman;
1142+
1143+
try testing.expectEqual(@as(u32, 0x2d3dd0ae), Crc32Koopman.hash("123456789"));
1144+
1145+
var c = Crc32Koopman.init();
1146+
c.update("1234");
1147+
c.update("56789");
1148+
try testing.expectEqual(@as(u32, 0x2d3dd0ae), c.final());
1149+
}
1150+
11371151
test "CRC-32/MEF" {
11381152
const Crc32Mef = crc.Crc32Mef;
11391153

‎tools/crc/catalog.txt

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -100,6 +100,7 @@ width=32 poly=0x04c11db7 init=0x00000000 refin=false refout=false xorout=0x
100100
width=32 poly=0x1edc6f41 init=0xffffffff refin=true refout=true xorout=0xffffffff check=0xe3069283 residue=0xb798b438 name="CRC-32/ISCSI"
101101
width=32 poly=0x04c11db7 init=0xffffffff refin=true refout=true xorout=0xffffffff check=0xcbf43926 residue=0xdebb20e3 name="CRC-32/ISO-HDLC"
102102
width=32 poly=0x04c11db7 init=0xffffffff refin=true refout=true xorout=0x00000000 check=0x340bc6d9 residue=0x00000000 name="CRC-32/JAMCRC"
103+
width=32 poly=0x741b8cd7 init=0xffffffff refin=true refout=true xorout=0xffffffff check=0x2d3dd0ae residue=0x00000000 name="CRC-32/KOOPMAN"
103104
width=32 poly=0x741b8cd7 init=0xffffffff refin=true refout=true xorout=0x00000000 check=0xd2c22f51 residue=0x00000000 name="CRC-32/MEF"
104105
width=32 poly=0x04c11db7 init=0xffffffff refin=false refout=false xorout=0x00000000 check=0x0376e6e7 residue=0x00000000 name="CRC-32/MPEG-2"
105106
width=32 poly=0x000000af init=0x00000000 refin=false refout=false xorout=0x00000000 check=0xbd0be338 residue=0x00000000 name="CRC-32/XFER"

‎tools/update_crc_catalog.zig

Lines changed: 18 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -48,8 +48,7 @@ pub fn main() anyerror!void {
4848
\\pub const Crc32WithPoly = impl.Crc32WithPoly;
4949
\\pub const Crc32SmallWithPoly = impl.Crc32SmallWithPoly;
5050
\\
51-
\\// IEEE is by far the most common CRC and so is aliased by default.
52-
\\pub const Crc32 = Crc32WithPoly(.IEEE);
51+
\\pub const Crc32 = Crc32IsoHdlc;
5352
\\
5453
\\test {
5554
\\ _ = @import("crc/test.zig");
@@ -72,22 +71,25 @@ pub fn main() anyerror!void {
7271
\\const verify = @import("../verify.zig");
7372
\\const crc = @import("../crc.zig");
7473
\\
75-
\\test "crc32 ieee" {
76-
\\ inline for ([2]type{ crc.Crc32WithPoly(.IEEE), crc.Crc32SmallWithPoly(.IEEE) }) |ieee| {
77-
\\ try testing.expect(ieee.hash("") == 0x00000000);
78-
\\ try testing.expect(ieee.hash("a") == 0xe8b7be43);
79-
\\ try testing.expect(ieee.hash("abc") == 0x352441c2);
80-
\\ try verify.iterativeApi(ieee);
81-
\\ }
74+
\\test "crc32 ieee regression" {
75+
\\ const crc32 = crc.Crc32IsoHdlc;
76+
\\ try testing.expectEqual(crc32.hash(""), 0x00000000);
77+
\\ try testing.expectEqual(crc32.hash("a"), 0xe8b7be43);
78+
\\ try testing.expectEqual(crc32.hash("abc"), 0x352441c2);
8279
\\}
8380
\\
84-
\\test "crc32 castagnoli" {
85-
\\ inline for ([2]type{ crc.Crc32WithPoly(.Castagnoli), crc.Crc32SmallWithPoly(.Castagnoli) }) |casta| {
86-
\\ try testing.expect(casta.hash("") == 0x00000000);
87-
\\ try testing.expect(casta.hash("a") == 0xc1d04330);
88-
\\ try testing.expect(casta.hash("abc") == 0x364b3fb7);
89-
\\ try verify.iterativeApi(casta);
90-
\\ }
81+
\\test "crc32 castagnoli regression" {
82+
\\ const crc32 = crc.Crc32Iscsi;
83+
\\ try testing.expectEqual(crc32.hash(""), 0x00000000);
84+
\\ try testing.expectEqual(crc32.hash("a"), 0xc1d04330);
85+
\\ try testing.expectEqual(crc32.hash("abc"), 0x364b3fb7);
86+
\\}
87+
\\
88+
\\test "crc32 koopman regression" {
89+
\\ const crc32 = crc.Koopman;
90+
\\ try testing.expectEqual(crc32.hash(""), 0x00000000);
91+
\\ try testing.expectEqual(crc32.hash("a"), 0x0da2aa8a);
92+
\\ try testing.expectEqual(crc32.hash("abc"), 0xba2322ac);
9193
\\}
9294
\\
9395
);

0 commit comments

Comments
 (0)