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std.compress.flate.Decompress: add rebase impl

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This commit is contained in:
Andrew Kelley 2025-07-27 16:55:23 -07:00
parent fa410cc234
commit 88ca750209
1 changed files with 20 additions and 4 deletions
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24
lib/std/compress/flate/Decompress.zig
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@ -1,11 +1,13 @@
const std = @import("../../std.zig");
const assert = std.debug.assert;
const flate = std.compress.flate;
const Container = flate.Container;
const Token = @import("Token.zig");
const testing = std.testing;
const Decompress = @This();
const Writer = std.Io.Writer;
const Reader = std.Io.Reader;
const Container = flate.Container;
const Decompress = @This();
const Token = @import("Token.zig");
input: *Reader,
reader: Reader,
@ -54,7 +56,10 @@ pub fn init(input: *Reader, container: Container, buffer: []u8) Decompress {
.reader = .{
// TODO populate discard so that when an amount is discarded that
// includes an entire frame, skip decoding that frame.
.vtable = &.{ .stream = stream },
.vtable = &.{
.stream = stream,
.rebase = rebase,
},
.buffer = buffer,
.seek = 0,
.end = 0,
@ -69,6 +74,17 @@ pub fn init(input: *Reader, container: Container, buffer: []u8) Decompress {
};
}
fn rebase(r: *Reader, capacity: usize) Reader.RebaseError!void {
assert(capacity <= r.buffer.len - flate.history_len);
assert(r.end + capacity > r.buffer.len);
const buffered = r.buffer[0..r.end];
const discard = buffered.len - flate.history_len;
const keep = buffered[discard..];
@memmove(r.buffer[0..keep.len], keep);
r.end = keep.len;
r.seek -= discard;
}
fn decodeLength(self: *Decompress, code: u8) !u16 {
if (code > 28) return error.InvalidCode;
const ml = Token.matchLength(code);