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std.compress.flate.Decompress: allow users to swap out Writer

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This commit is contained in:
Andrew Kelley 2025-07-31 17:31:54 -07:00
parent 2024abda6a
commit 6eac56caf7
1 changed files with 26 additions and 7 deletions
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33
lib/std/compress/flate/Decompress.zig
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@ -58,7 +58,7 @@ pub fn init(input: *Reader, container: Container, buffer: []u8) Decompress {
.reader = .{ .reader = .{
.vtable = &.{ .vtable = &.{
.stream = stream, .stream = stream,
.rebase = rebase, .rebase = rebaseFallible,
.discard = discard, .discard = discard,
.readVec = readVec, .readVec = readVec,
}, },
@ -78,12 +78,19 @@ pub fn init(input: *Reader, container: Container, buffer: []u8) Decompress {
}; };
} }
fn rebase(r: *Reader, capacity: usize) Reader.RebaseError!void { fn rebaseFallible(r: *Reader, capacity: usize) Reader.RebaseError!void {
const d: *Decompress = @alignCast(@fieldParentPtr("reader", r));
rebase(d, capacity);
}
fn rebase(d: *Decompress, capacity: usize) void {
const r = &d.reader;
assert(capacity <= r.buffer.len - flate.history_len); assert(capacity <= r.buffer.len - flate.history_len);
assert(r.end + capacity > r.buffer.len); assert(r.end + capacity > r.buffer.len);
const discard_n = r.end - flate.history_len; const discard_n = r.end - flate.history_len;
const keep = r.buffer[discard_n..r.end]; const keep = r.buffer[discard_n..r.end];
@memmove(r.buffer[0..keep.len], keep); @memmove(r.buffer[0..keep.len], keep);
assert(keep.len != 0);
r.end = keep.len; r.end = keep.len;
r.seek -= discard_n; r.seek -= discard_n;
} }
@ -101,6 +108,7 @@ fn discard(r: *Reader, limit: std.Io.Limit) Reader.Error!usize {
.end = r.end, .end = r.end,
}; };
defer { defer {
assert(writer.end != 0);
r.end = writer.end; r.end = writer.end;
r.seek = r.end; r.seek = r.end;
} }
@ -115,14 +123,20 @@ fn discard(r: *Reader, limit: std.Io.Limit) Reader.Error!usize {
fn readVec(r: *Reader, data: [][]u8) Reader.Error!usize { fn readVec(r: *Reader, data: [][]u8) Reader.Error!usize {
_ = data; _ = data;
assert(r.seek == r.end); const d: *Decompress = @alignCast(@fieldParentPtr("reader", r));
r.rebase(flate.history_len) catch unreachable; return streamIndirect(d);
}
fn streamIndirect(d: *Decompress) Reader.Error!usize {
const r = &d.reader;
if (r.end + flate.history_len > r.buffer.len) rebase(d, flate.history_len);
var writer: Writer = .{ var writer: Writer = .{
.buffer = r.buffer, .buffer = r.buffer,
.end = r.end, .end = r.end,
.vtable = &.{ .drain = Writer.fixedDrain }, .vtable = &.{ .drain = Writer.fixedDrain },
}; };
r.end += r.vtable.stream(r, &writer, .limited(writer.buffer.len - writer.end)) catch |err| switch (err) { defer r.end = writer.end;
_ = streamFallible(d, &writer, .limited(writer.buffer.len - writer.end)) catch |err| switch (err) {
error.WriteFailed => unreachable, error.WriteFailed => unreachable,
else => |e| return e, else => |e| return e,
}; };
@ -188,7 +202,12 @@ fn decodeSymbol(self: *Decompress, decoder: anytype) !Symbol {
pub fn stream(r: *Reader, w: *Writer, limit: std.Io.Limit) Reader.StreamError!usize { pub fn stream(r: *Reader, w: *Writer, limit: std.Io.Limit) Reader.StreamError!usize {
const d: *Decompress = @alignCast(@fieldParentPtr("reader", r)); const d: *Decompress = @alignCast(@fieldParentPtr("reader", r));
return readInner(d, w, limit) catch |err| switch (err) { if (w.end >= r.end) return streamFallible(d, w, limit);
return streamIndirect(d);
}
fn streamFallible(d: *Decompress, w: *Writer, limit: std.Io.Limit) Reader.StreamError!usize {
return streamInner(d, w, limit) catch |err| switch (err) {
error.EndOfStream => { error.EndOfStream => {
if (d.state == .end) { if (d.state == .end) {
return error.EndOfStream; return error.EndOfStream;
@ -207,7 +226,7 @@ pub fn stream(r: *Reader, w: *Writer, limit: std.Io.Limit) Reader.StreamError!us
}; };
} }
fn readInner(d: *Decompress, w: *Writer, limit: std.Io.Limit) (Error || Reader.StreamError)!usize { fn streamInner(d: *Decompress, w: *Writer, limit: std.Io.Limit) (Error || Reader.StreamError)!usize {
var remaining = @intFromEnum(limit); var remaining = @intFromEnum(limit);
const in = d.input; const in = d.input;
sw: switch (d.state) { sw: switch (d.state) {