From 45b44e9ccd08222560879086b7efacfd2f636c28 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Thu, 26 Feb 2026 11:23:32 +0300
Subject: [PATCH] archive: add tar library (fixes #1180)

---
 vlib/archive/tar/README.md     |  3 +-
 vlib/archive/tar/reader.v      | 13 +++++++-
 vlib/archive/tar/reader_test.v | 57 +++++++++++++++++++++++++++-------
 3 files changed, 59 insertions(+), 14 deletions(-)

diff --git a/vlib/archive/tar/README.md b/vlib/archive/tar/README.md
index 47b02679e..a6d8ce0bd 100644
--- a/vlib/archive/tar/README.md
+++ b/vlib/archive/tar/README.md
@@ -29,5 +29,6 @@ fn main() {
 	tar.read_tar_gz_file(path, reader)!
 }
 ```
-Look also in `examples` folder the `tar_gz_reader.v` program.
+For plain archives, use `tar.read_tar_file(path, reader)!`.
 
+Look also in `examples` folder the `tar_gz_reader.v` program.
diff --git a/vlib/archive/tar/reader.v b/vlib/archive/tar/reader.v
index 67b09939e..b541f4f85 100644
--- a/vlib/archive/tar/reader.v
+++ b/vlib/archive/tar/reader.v
@@ -3,11 +3,22 @@ module tar
 import compress.gzip
 import os
 
+// read_tar_file reads a given local .tar file and parses all blocks with a
+// given reader.
+pub fn read_tar_file(path string, reader Reader) ! {
+	all_blocks := os.read_bytes(path)!
+	read_tar_blocks(all_blocks, reader)!
+}
+
 // read_tar_gz_file decompresses a given local file and reads all the blocks
 // with a given reader.
 pub fn read_tar_gz_file(path string, reader Reader) ! {
 	tar_gz := os.read_bytes(path)!
 	all_blocks := gzip.decompress(tar_gz)!
+	read_tar_blocks(all_blocks, reader)!
+}
+
+fn read_tar_blocks(all_blocks []u8, reader Reader) ! {
 	mut untar := Untar{
 		reader: reader
 	}
@@ -251,7 +262,7 @@ fn (mut d ChunksReader) read_blocks(chunk []u8) ReadResult {
 			// after sending all complete blocks move the remaining not sent bytes
 			// to the start of the reused buffer to be prepended before next chunk
 			for i := cut; i < d.pending; i++ {
-				d.buffer[cut - 512] = d.buffer[i]
+				d.buffer[i - cut] = d.buffer[i]
 			}
 			d.pending -= cut
 			return .continue
diff --git a/vlib/archive/tar/reader_test.v b/vlib/archive/tar/reader_test.v
index 6be02a16b..3aa66f108 100644
--- a/vlib/archive/tar/reader_test.v
+++ b/vlib/archive/tar/reader_test.v
@@ -74,6 +74,49 @@ fn test_long_long_short() {
 	assert r1.texts[cat] == 'https://en.wikipedia.org/wiki/Cat'
 }
 
+@[heap]
+struct ChunksCollector {
+mut:
+	blocks [][]u8
+}
+
+fn test_chunks_reader_keeps_pending_bytes_between_chunks() {
+	mut collector := &ChunksCollector{}
+	read_block := fn [mut collector] (block []u8) !ReadResult {
+		collector.blocks << block.clone()
+		return .continue
+	}
+
+	mut block1 := []u8{len: 512}
+	mut block2 := []u8{len: 512}
+	for i in 0 .. 512 {
+		block1[i] = u8((i * 3) % 251)
+		block2[i] = u8((i * 7) % 251)
+	}
+
+	mut data := []u8{}
+	data << block1
+	data << block2
+
+	mut chunks := ChunksReader{
+		read_block_fn: read_block
+	}
+
+	assert chunks.read_blocks(data[..700]) == .continue
+	assert collector.blocks.len == 1
+	assert collector.blocks[0] == block1
+	assert chunks.pending == 188
+
+	assert chunks.read_blocks(data[700..900]) == .continue
+	assert collector.blocks.len == 1
+	assert chunks.pending == 388
+
+	assert chunks.read_blocks(data[900..]) == .continue
+	assert collector.blocks.len == 2
+	assert collector.blocks[1] == block2
+	assert chunks.pending == 0
+}
+
 struct TestReader {
 	debug bool
 mut:
@@ -92,11 +135,7 @@ fn new_test_reader(tar_file string, debug bool) !&TestReader {
 	mut reader := &TestReader{
 		debug: debug
 	}
-	mut untar := Untar{
-		reader: reader
-	}
-	all_blocks := os.read_bytes('${testdata}/${tar_file}')!
-	untar.read_all_blocks(all_blocks)!
+	read_tar_file('${testdata}/${tar_file}', reader)!
 	return reader
 }
 
@@ -105,13 +144,7 @@ fn new_test_reader_gz(tar_gz_file string, debug bool) !&TestReader {
 	mut reader := &TestReader{
 		debug: debug
 	}
-	mut untar := Untar{
-		reader: reader
-	}
-	mut decompressor := new_decompressor(untar)
-	tar_gz := os.read_bytes('${testdata}/${tar_gz_file}')!
-	decompressor.read_all(tar_gz)!
-
+	read_tar_gz_file('${testdata}/${tar_gz_file}', reader)!
 	return reader
 }
 
-- 
2.39.5