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std.compress.flate.Decompress: don't compute checksums

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These have no business being in-bound; simply provide the expected
values to user code for maximum flexibility.
This commit is contained in:
Andrew Kelley 2025-07-28 18:00:20 -07:00
parent 5f571f53d6
commit ac4fbb427b
2 changed files with 37 additions and 14 deletions
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23
lib/std/compress/flate.zig
View File

@ -148,6 +148,29 @@ pub const Container = enum {
}
}
};
pub const Metadata = union(Container) {
raw: void,
gzip: struct {
crc: u32 = 0,
count: u32 = 0,
},
zlib: struct {
adler: u32 = 0,
},
pub fn init(containter: Container) Metadata {
return switch (containter) {
.gzip => .{ .gzip = .{} },
.zlib => .{ .zlib = .{} },
.raw => .raw,
};
}
pub fn container(m: Metadata) Container {
return m;
}
};
};
test {

28
lib/std/compress/flate/Decompress.zig
View File

@ -15,8 +15,7 @@ remaining_bits: std.math.Log2Int(usize),
reader: Reader,
/// Hashes, produces checksum, of uncompressed data for gzip/zlib footer.
hasher: Container.Hasher,
container_metadata: Container.Metadata,
lit_dec: LiteralDecoder,
dst_dec: DistanceDecoder,
@ -71,7 +70,7 @@ pub fn init(input: *Reader, container: Container, buffer: []u8) Decompress {
.input = input,
.next_bits = 0,
.remaining_bits = 0,
.hasher = .init(container),
.container_metadata = .init(container),
.lit_dec = .{},
.dst_dec = .{},
.final_block = false,
@ -169,7 +168,7 @@ fn readInner(d: *Decompress, w: *Writer, limit: std.Io.Limit) (Error || Reader.S
var remaining = @intFromEnum(limit);
const in = d.input;
sw: switch (d.state) {
.protocol_header => switch (d.hasher.container()) {
.protocol_header => switch (d.container_metadata.container()) {
.gzip => {
const Header = extern struct {
magic: u16 align(1),
@ -258,7 +257,7 @@ fn readInner(d: *Decompress, w: *Writer, limit: std.Io.Limit) (Error || Reader.S
try d.lit_dec.generate(dec_lens[0..hlit]);
// distance code lengths to distance decoder
try d.dst_dec.generate(dec_lens[hlit .. hlit + hdist]);
try d.dst_dec.generate(dec_lens[hlit..][0..hdist]);
continue :sw .dynamic_block;
},
@ -332,14 +331,17 @@ fn readInner(d: *Decompress, w: *Writer, limit: std.Io.Limit) (Error || Reader.S
},
.protocol_footer => {
d.alignBitsToByte();
switch (d.hasher) {
switch (d.container_metadata) {
.gzip => |*gzip| {
if (try in.takeInt(u32, .little) != gzip.crc.final()) return error.WrongGzipChecksum;
if (try in.takeInt(u32, .little) != gzip.count) return error.WrongGzipSize;
gzip.* = .{
.crc = try in.takeInt(u32, .little),
.count = try in.takeInt(u32, .little),
};
},
.zlib => |*zlib| {
const chksum: u32 = @byteSwap(zlib.adler);
if (try in.takeInt(u32, .big) != chksum) return error.WrongZlibChecksum;
zlib.* = .{
.adler = try in.takeInt(u32, .little),
};
},
.raw => {},
}
@ -868,8 +870,7 @@ fn testBasicCase(in: []const u8, out: []const u8) !void {
defer aw.deinit();
var decompress: Decompress = .init(&reader, .raw, &.{});
const r = &decompress.reader;
_ = try r.streamRemaining(&aw.writer);
_ = try decompress.reader.streamRemaining(&aw.writer);
try testing.expectEqualStrings(out, aw.getWritten());
}
@ -917,8 +918,7 @@ fn testGzipDecompress(in: []const u8, out: []const u8) !void {
defer aw.deinit();
var decompress: Decompress = .init(&reader, .gzip, &.{});
const r = &decompress.reader;
_ = try r.streamRemaining(&aw.writer);
_ = try decompress.reader.streamRemaining(&aw.writer);
try testing.expectEqualStrings(out, aw.getWritten());
}