compress.zlib: changed to pure V RFC-compliant code

vlib/compress/deflate/deflate.v

@@ -26,6 +26,7 @@ pub fn compress(data []u8, format CompressParams) ![]u8 {
 	}
 }
 
+// compress_zlib compresses data into a zlib stream (RFC 1950).
 pub fn compress_zlib(data []u8) ![]u8 {
 	payload := deflate_compress_fixed(data)
 	cksum := adler32(data)
@@ -71,7 +72,9 @@ pub fn decompress(data []u8) ![]u8 {
 	return inflate(data)
 }
 
-fn decompress_zlib(data []u8) ![]u8 {
+// decompress_zlib decompresses a zlib stream (RFC 1950) and returns the
+// decompressed bytes in a new array.
+pub fn decompress_zlib(data []u8) ![]u8 {
 	if data.len < 6 {
 		return error('invalid zlib stream: too short')
 	}
@@ -93,7 +96,9 @@ fn decompress_zlib(data []u8) ![]u8 {
 	return decoded
 }
 
-fn decompress_gzip(data []u8) ![]u8 {
+// decompress_gzip decompresses a gzip stream (RFC 1952) and returns the
+// decompressed bytes in a new array.
+pub fn decompress_gzip(data []u8) ![]u8 {
 	if data.len < 18 {
 		return error('invalid gzip stream: too short')
 	}

vlib/compress/deflate/deflate_inflate.v

@@ -144,6 +144,9 @@ fn (mut r BitReader) huff_decode(t HuffTree) !u32 {
 		return error('inflate: invalid Huffman code')
 	}
 	len_ := int(entry & 0x1f)
+	if len_ > r.nbits {
+		return error('inflate: unexpected end of stream')
+	}
 	sym := entry >> 5
 	r.bits >>= u32(len_)
 	r.nbits -= len_

vlib/compress/deflate/deflate_test.v

@@ -61,3 +61,11 @@ fn test_corrupt_checksum_fails() {
 	}
 	assert false
 }
+
+fn test_truncated_zlib_payload_fails() {
+	decompress([u8(0x78), 0x9c, 0x03, 0x00, 0x00, 0x00, 0x01]) or {
+		assert err.msg().contains('unexpected end of stream')
+		return
+	}
+	assert false
+}

vlib/compress/zlib/README.md

@@ -1,17 +1,17 @@
 ## Description
 
-`compress.zlib` is a module that assists in the compression and
-decompression of binary data using `zlib` compression
+`compress.zlib` is a small wrapper around `compress.deflate` for working with zlib streams
+(RFC 1950).
 
 ## Examples
 
 ```v
 import compress.zlib
 
 fn main() {
-	uncompressed := 'Hello world!'
-	compressed := zlib.compress(uncompressed.bytes())!
-	decompressed := zlib.decompress(compressed)!
-	assert decompressed == uncompressed.bytes()
+	data := 'Hello world!'.bytes()
+	compressed := zlib.compress(data) or { panic(err) }
+	decompressed := zlib.decompress(compressed) or { panic(err) }
+	assert decompressed == data
 }
 ```

vlib/compress/zlib/interop/README.md

@@ -0,0 +1,16 @@
+# zlib interop checker
+This helper verifies interoperability between:
+- V module: `compress.zlib`
+- C helper linked with `libz`
+- Python stdlib: `zlib`
+It runs deterministic test vectors, compresses each vector with all three producers, then
+cross-decompresses every produced stream with all three consumers.
+A case passes only if every decompressed output is byte-identical to the original input.
+## Run
+```bash
+./vnew run vlib/compress/zlib/interop/zlib_interop.vsh
+```
+## Requirements
+- `python3` with the stdlib `zlib` module
+- a C compiler (`cc`, `gcc`, or `clang`)
+- `libz` development headers and linker support (`-lz`)

vlib/compress/zlib/interop/zlib_interop.vsh

@@ -0,0 +1,185 @@
+#!/usr/bin/env -S v
+
+import compress.zlib
+
+struct TestVector {
+	name string
+	data []u8
+}
+
+fn main() {
+	tmp_root := join_path(temp_dir(), 'v_zlib_interop_${getpid()}')
+	mkdir_all(tmp_root) or { panic(err) }
+	defer {
+		rmdir_all(tmp_root) or {}
+	}
+
+	c_bin := compile_c_helper(tmp_root) or {
+		eprintln('SKIP: ${err.msg()}')
+		exit(2)
+	}
+	py_script := join_path(@DIR, 'zlib_ref.py')
+	ensure_python(py_script) or {
+		eprintln('SKIP: ${err.msg()}')
+		exit(2)
+	}
+
+	vectors := make_test_vectors()
+	mut total_checks := 0
+	for i, vec in vectors {
+		total_checks += run_case(tmp_root, c_bin, py_script, i, vec) or {
+			eprintln('FAIL: ${vec.name}: ${err.msg()}')
+			exit(1)
+			0
+		}
+		println('ok ${i + 1}/${vectors.len}: ${vec.name} (${vec.data.len} bytes)')
+	}
+	println('PASS: ${vectors.len} vectors, ${total_checks} cross-checks')
+}
+
+fn compile_c_helper(tmp_root string) !string {
+	cc := choose_cc()
+	if cc == '' {
+		return error('no C compiler found (tried cc, gcc, clang)')
+	}
+	src := join_path(@DIR, 'zlib_ref.c')
+	bin := join_path(tmp_root, 'zlib_interop_ref')
+	must_succeed('${cc} -O2 ${shell_quote(src)} -lz -o ${shell_quote(bin)}',
+		'C zlib helper build failed')!
+	return bin
+}
+
+fn choose_cc() string {
+	for cc in ['cc', 'gcc', 'clang'] {
+		if execute('${cc} --version >/dev/null 2>&1').exit_code == 0 {
+			return cc
+		}
+	}
+	return ''
+}
+
+fn ensure_python(py_script string) ! {
+	must_succeed("python3 -c 'import zlib' >/dev/null 2>&1",
+		'python3 with zlib module is not available')!
+	if !exists(py_script) {
+		return error('missing Python helper: ${py_script}')
+	}
+}
+
+fn make_test_vectors() []TestVector {
+	mut vectors := []TestVector{}
+	vectors << TestVector{'empty', []u8{}}
+	vectors << TestVector{'ascii_text', 'The quick brown fox jumps over the lazy dog.\n'.repeat(64).bytes()}
+	vectors << TestVector{'repeated_byte', []u8{len: 10000, init: `A`}}
+	vectors << TestVector{'all_bytes_x4', all_bytes_repeated(4)}
+	vectors << TestVector{'lcg_64k', lcg_bytes(65536)}
+	return vectors
+}
+
+fn run_case(tmp_root string, c_bin string, py_script string, case_idx int, vec TestVector) !int {
+	case_dir := join_path(tmp_root, 'case_${case_idx:02}_${vec.name}')
+	mkdir_all(case_dir)!
+
+	v_z := zlib.compress(vec.data)!
+	c_z := c_compress(case_dir, c_bin, vec.data)!
+	py_z := py_compress(case_dir, py_script, vec.data)!
+
+	mut checks := 0
+	producers := {
+		'v':  v_z
+		'c':  c_z
+		'py': py_z
+	}
+	for producer, compressed in producers {
+		v_plain := zlib.decompress(compressed)!
+		assert_equal_bytes('v.decompress(${producer}.compress)', vec.data, v_plain)!
+		checks++
+
+		c_plain := c_decompress(case_dir, c_bin, producer, compressed)!
+		assert_equal_bytes('c.decompress(${producer}.compress)', vec.data, c_plain)!
+		checks++
+
+		py_plain := py_decompress(case_dir, py_script, producer, compressed)!
+		assert_equal_bytes('python.decompress(${producer}.compress)', vec.data, py_plain)!
+		checks++
+	}
+	return checks
+}
+
+fn c_compress(case_dir string, c_bin string, plain []u8) ![]u8 {
+	in_path := join_path(case_dir, 'plain.in')
+	out_path := join_path(case_dir, 'c.zlib')
+	write_file_array(in_path, plain)!
+	must_succeed('${shell_quote(c_bin)} compress ${shell_quote(in_path)} ${shell_quote(out_path)}',
+		'C zlib compression failed')!
+	return read_bytes(out_path)!
+}
+
+fn c_decompress(case_dir string, c_bin string, producer string, compressed []u8) ![]u8 {
+	in_path := join_path(case_dir, '${producer}.for_c.zlib')
+	out_path := join_path(case_dir, '${producer}.from_c.out')
+	write_file_array(in_path, compressed)!
+	must_succeed('${shell_quote(c_bin)} decompress ${shell_quote(in_path)} ${shell_quote(out_path)}',
+		'C zlib decompression failed')!
+	return read_bytes(out_path)!
+}
+
+fn py_compress(case_dir string, py_script string, plain []u8) ![]u8 {
+	in_path := join_path(case_dir, 'plain_py.in')
+	out_path := join_path(case_dir, 'py.zlib')
+	write_file_array(in_path, plain)!
+	must_succeed('python3 ${shell_quote(py_script)} compress ${shell_quote(in_path)} ${shell_quote(out_path)}',
+		'Python zlib compression failed')!
+	return read_bytes(out_path)!
+}
+
+fn py_decompress(case_dir string, py_script string, producer string, compressed []u8) ![]u8 {
+	in_path := join_path(case_dir, '${producer}.for_py.zlib')
+	out_path := join_path(case_dir, '${producer}.from_py.out')
+	write_file_array(in_path, compressed)!
+	must_succeed('python3 ${shell_quote(py_script)} decompress ${shell_quote(in_path)} ${shell_quote(out_path)}',
+		'Python zlib decompression failed')!
+	return read_bytes(out_path)!
+}
+
+fn all_bytes_repeated(times int) []u8 {
+	mut out := []u8{cap: 256 * times}
+	for _ in 0 .. times {
+		for i in 0 .. 256 {
+			out << u8(i)
+		}
+	}
+	return out
+}
+
+fn lcg_bytes(n int) []u8 {
+	mut out := []u8{len: n}
+	mut x := u32(0x12345678)
+	for i in 0 .. n {
+		x = x * u32(1664525) + u32(1013904223)
+		out[i] = u8((x >> 16) & u32(0xff))
+	}
+	return out
+}
+
+fn assert_equal_bytes(label string, expected []u8, got []u8) ! {
+	if expected.len != got.len {
+		return error('${label}: length mismatch expected=${expected.len} got=${got.len}')
+	}
+	for i in 0 .. expected.len {
+		if expected[i] != got[i] {
+			return error('${label}: byte mismatch at offset ${i}')
+		}
+	}
+}
+
+fn must_succeed(command string, context string) ! {
+	res := execute(command)
+	if res.exit_code != 0 {
+		return error('${context}\ncommand: ${command}\nexit_code: ${res.exit_code}\n${res.output}')
+	}
+}
+
+fn shell_quote(s string) string {
+	return "'${s.replace("'", "'\\''")}'"
+}