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std.compress.flate.Decompress: be in indirect or direct mode

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depending on whether buffered
This commit is contained in:
Andrew Kelley
2025-07-31 18:05:22 -07:00
parent 6eac56caf7
commit a7808892f7
1 changed files with 30 additions and 17 deletions
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47
lib/std/compress/flate/Decompress.zig
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@@ -53,15 +53,24 @@ pub const Error = Container.Error || error{
EndOfStream,
};
const direct_vtable: Reader.VTable = .{
.stream = streamDirect,
.rebase = rebaseFallible,
.discard = discard,
.readVec = readVec,
};
const indirect_vtable: Reader.VTable = .{
.stream = streamIndirect,
.rebase = rebaseFallible,
.discard = discard,
.readVec = readVec,
};
pub fn init(input: *Reader, container: Container, buffer: []u8) Decompress {
return .{
.reader = .{
.vtable = &.{
.stream = stream,
.rebase = rebaseFallible,
.discard = discard,
.readVec = readVec,
},
.vtable = if (buffer.len == 0) &direct_vtable else &indirect_vtable,
.buffer = buffer,
.seek = 0,
.end = 0,
@@ -79,12 +88,10 @@ pub fn init(input: *Reader, container: Container, buffer: []u8) Decompress {
}
fn rebaseFallible(r: *Reader, capacity: usize) Reader.RebaseError!void {
const d: *Decompress = @alignCast(@fieldParentPtr("reader", r));
rebase(d, capacity);
rebase(r, capacity);
}
fn rebase(d: *Decompress, capacity: usize) void {
const r = &d.reader;
fn rebase(r: *Reader, capacity: usize) void {
assert(capacity <= r.buffer.len - flate.history_len);
assert(r.end + capacity > r.buffer.len);
const discard_n = r.end - flate.history_len;
@@ -98,7 +105,7 @@ fn rebase(d: *Decompress, capacity: usize) void {
/// This could be improved so that when an amount is discarded that includes an
/// entire frame, skip decoding that frame.
fn discard(r: *Reader, limit: std.Io.Limit) Reader.Error!usize {
r.rebase(flate.history_len) catch unreachable;
if (r.end + flate.history_len > r.buffer.len) rebase(r, flate.history_len);
var writer: Writer = .{
.vtable = &.{
.drain = std.Io.Writer.Discarding.drain,
@@ -124,12 +131,12 @@ fn discard(r: *Reader, limit: std.Io.Limit) Reader.Error!usize {
fn readVec(r: *Reader, data: [][]u8) Reader.Error!usize {
_ = data;
const d: *Decompress = @alignCast(@fieldParentPtr("reader", r));
return streamIndirect(d);
return streamIndirectInner(d);
}
fn streamIndirect(d: *Decompress) Reader.Error!usize {
fn streamIndirectInner(d: *Decompress) Reader.Error!usize {
const r = &d.reader;
if (r.end + flate.history_len > r.buffer.len) rebase(d, flate.history_len);
if (r.end + flate.history_len > r.buffer.len) rebase(r, flate.history_len);
var writer: Writer = .{
.buffer = r.buffer,
.end = r.end,
@@ -200,10 +207,16 @@ fn decodeSymbol(self: *Decompress, decoder: anytype) !Symbol {
return sym;
}
pub fn stream(r: *Reader, w: *Writer, limit: std.Io.Limit) Reader.StreamError!usize {
fn streamDirect(r: *Reader, w: *Writer, limit: std.Io.Limit) Reader.StreamError!usize {
const d: *Decompress = @alignCast(@fieldParentPtr("reader", r));
if (w.end >= r.end) return streamFallible(d, w, limit);
return streamIndirect(d);
return streamFallible(d, w, limit);
}
fn streamIndirect(r: *Reader, w: *Writer, limit: std.Io.Limit) Reader.StreamError!usize {
const d: *Decompress = @alignCast(@fieldParentPtr("reader", r));
_ = limit;
_ = w;
return streamIndirectInner(d);
}
fn streamFallible(d: *Decompress, w: *Writer, limit: std.Io.Limit) Reader.StreamError!usize {