srctree

Igor Anić parent 71128160 f2508abf
flate: use 4 bytes lookahead for zlib

That ensures no bytes are left in the BitReader buffer after we reachend of the stream.

inline split

lib/std/compress/flate.zig added: 31, removed: 14, total 17

@@ -13,7 +13,7 @@ pub fn decompress(reader: anytype, writer: anytype) !void {

/// Decompressor type

pub fn Decompressor(comptime ReaderType: type) type {

return inflate.Inflate(.raw, ReaderType);

return inflate.Decompressor(.raw, ReaderType);

}

/// Create Decompressor which will read compressed data from reader.

lib/std/compress/flate/container.zig added: 31, removed: 14, total 17

@@ -154,6 +154,7 @@ pub const Container = enum {

pub fn parseFooter(comptime wrap: Container, hasher: *Hasher(wrap), reader: anytype) !void {

switch (wrap) {

.gzip => {

try reader.fill(0);

if (try reader.read(u32) != hasher.chksum()) return error.WrongGzipChecksum;

if (try reader.read(u32) != hasher.bytesRead()) return error.WrongGzipSize;

lib/std/compress/flate/inflate.zig added: 31, removed: 14, total 17

@@ -3,7 +3,7 @@ const assert = std.debug.assert;

const testing = std.testing;

const hfd = @import("huffman_decoder.zig");

const BitReader = @import("bit_reader.zig").BitReader64;

const BitReader = @import("bit_reader.zig").BitReader;

const CircularBuffer = @import("CircularBuffer.zig");

const Container = @import("container.zig").Container;

const Token = @import("Token.zig");

@@ -17,8 +17,16 @@ pub fn decompress(comptime container: Container, reader: anytype, writer: anytyp

}

/// Inflate decompressor for the reader type.

pub fn decompressor(comptime container: Container, reader: anytype) Inflate(container, @TypeOf(reader)) {

return Inflate(container, @TypeOf(reader)).init(reader);

pub fn decompressor(comptime container: Container, reader: anytype) Decompressor(container, @TypeOf(reader)) {

return Decompressor(container, @TypeOf(reader)).init(reader);

}

pub fn Decompressor(comptime container: Container, comptime ReaderType: type) type {

// zlib has 4 bytes footer, lookahead of 4 bytes ensures that we will not overshoot.

// gzip has 8 bytes footer so we will not overshoot even with 8 bytes of lookahead.

// For raw deflate there is always possibility of overshot so we use 8 bytes lookahead.

const lookahead: type = if (container == .zlib) u32 else u64;

return Inflate(container, lookahead, ReaderType);

}

/// Inflate decompresses deflate bit stream. Reads compressed data from reader

@@ -40,9 +48,12 @@ pub fn decompressor(comptime container: Container, reader: anytype) Inflate(cont

/// * 64K for history (CircularBuffer)

/// * ~10K huffman decoders (Literal and DistanceDecoder)

///

pub fn Inflate(comptime container: Container, comptime ReaderType: type) type {

pub fn Inflate(comptime container: Container, comptime LookaheadType: type, comptime ReaderType: type) type {

assert(LookaheadType == u32 or LookaheadType == u64);

const BitReaderType = BitReader(LookaheadType, ReaderType);

return struct {

const BitReaderType = BitReader(ReaderType);

//const BitReaderType = BitReader(ReaderType);

const F = BitReaderType.flag;

bits: BitReaderType = .{},

@@ -219,9 +230,14 @@ pub fn Inflate(comptime container: Container, comptime ReaderType: type) type {

switch (sym.kind) {

.literal => self.hist.write(sym.symbol),

.match => { // Decode match backreference <length, distance>

try self.bits.fill(5 + 15 + 13); // so we can use buffered reads

// fill so we can use buffered reads

if (LookaheadType == u32)

try self.bits.fill(5 + 15)

else

try self.bits.fill(5 + 15 + 13);

const length = try self.decodeLength(sym.symbol);

const dsm = try self.decodeSymbol(&self.dst_dec);

if (LookaheadType == u32) try self.bits.fill(13);

const distance = try self.decodeDistance(dsm.symbol);

try self.hist.writeMatch(length, distance);

lib/std/compress/gzip.zig added: 31, removed: 14, total 17

@@ -8,7 +8,7 @@ pub fn decompress(reader: anytype, writer: anytype) !void {

/// Decompressor type

pub fn Decompressor(comptime ReaderType: type) type {

return inflate.Inflate(.gzip, ReaderType);

return inflate.Decompressor(.gzip, ReaderType);

}

/// Create Decompressor which will read compressed data from reader.

lib/std/compress/zlib.zig added: 31, removed: 14, total 17

@@ -8,7 +8,7 @@ pub fn decompress(reader: anytype, writer: anytype) !void {

/// Decompressor type

pub fn Decompressor(comptime ReaderType: type) type {

return inflate.Inflate(.zlib, ReaderType);

return inflate.Decompressor(.zlib, ReaderType);

}

/// Create Decompressor which will read compressed data from reader.