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Properly fix zstd streaming decompression

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I had a feeling my last workaround wasn't correct, turns out my basic
assumption about ZSTD_decompressStream() was wrong: rather than
guaranteeing some output when there's enough input, it always guarantees
to consume input when there's space in the output.

Fixed the code and adjusted the buffers again.
This commit is contained in:
Yorhel 2024-11-14 09:59:45 +01:00
parent 4bd6e3daba
commit 7ed209a8e5
1 changed files with 15 additions and 21 deletions
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36
src/json_import.zig
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@ -13,9 +13,8 @@ const c = @import("c.zig").c;
const ZstdReader = struct {
ctx: ?*c.ZSTD_DStream,
in: c.ZSTD_inBuffer,
// Assumption: ZSTD_decompressStream() can always output uncompressed data
// as long as half of this buffer is filled.
inbuf: [c.ZSTD_BLOCKSIZE_MAX * 2 + 1024]u8, // This twice ZSTD_DStreamInSize() + a little bit extra
lastret: usize = 0,
inbuf: [c.ZSTD_BLOCKSIZE_MAX + 16]u8, // This ZSTD_DStreamInSize() + a little bit extra
fn create(head: []const u8) *ZstdReader {
const r = main.allocator.create(ZstdReader) catch unreachable;
@ -39,26 +38,21 @@ const ZstdReader = struct {
}
fn read(r: *ZstdReader, f: std.fs.File, out: []u8) !usize {
while (r.in.size - r.in.pos < r.inbuf.len / 2) {
if (r.in.pos > 0) {
std.mem.copyForwards(u8, &r.inbuf, r.inbuf[r.in.pos..][0..r.in.size - r.in.pos]);
r.in.size -= r.in.pos;
while (true) {
if (r.in.size == r.in.pos) {
r.in.pos = 0;
r.in.size = try f.read(&r.inbuf);
if (r.in.size == 0) {
if (r.lastret == 0) return 0;
return error.ZstdDecompressError; // Early EOF
}
}
const rd = try f.read(r.inbuf[r.in.size..]);
r.in.size += rd;
if (rd == 0) break;
var arg = c.ZSTD_outBuffer{ .dst = out.ptr, .size = out.len, .pos = 0 };
r.lastret = c.ZSTD_decompressStream(r.ctx, &arg, &r.in);
if (c.ZSTD_isError(r.lastret) != 0) return error.ZstdDecompressError;
if (arg.pos > 0) return arg.pos;
}
var arg = c.ZSTD_outBuffer{
.dst = out.ptr,
.size = out.len,
.pos = 0,
};
const v = c.ZSTD_decompressStream(r.ctx, &arg, &r.in);
if (c.ZSTD_isError(v) != 0) return error.ZstdDecompressError;
// No output implies that the input buffer has been fully consumed.
if (arg.pos == 0 and r.in.pos != r.in.size) return error.ZstdDecompressError;
return arg.pos;
}
};
@ -75,7 +69,7 @@ const Parser = struct {
rdsize: usize = 0,
byte: u64 = 1,
line: u64 = 1,
buf: [16*1024]u8 = undefined,
buf: [129*1024]u8 = undefined,
fn die(p: *Parser, str: []const u8) noreturn {
ui.die("Error importing file on line {}:{}: {s}.\n", .{ p.line, p.byte, str });