std.tar: cleanups and fixes

tar.zig:
* convert V7Header, UstarHeader, StarHeader, GnuHeader to have fields of
  byte arrays instead of accessor methods.
* Header.getFormat() - optimize by using 64 bit compares rather than
  mem.eql().
* gnu_long{name,link} - allow for these to be longer than 512 bytes by
  using an internal heap.page_allocator backed arena in
  pipeToFileSystem().
* symlinks: cleanup logic and skip if wasi
* use std.os.toPosixPath() instead of custom one.

tests: minor cosmetic changes

Author: travisstaloch

Diff for: lib/std/compress/tar.zig

@@ -1,4 +1,4 @@
-test "std.tar" {
+test {
     _ = @import("tar/reader_test.zig");
     _ = @import("tar/test_decompress.zig");
 }

Diff for: lib/std/compress/tar/reader_test.zig

@@ -25,7 +25,7 @@ const TestCase = struct {
     skip: bool = false, // Wether to skip test case
 };
 
-test "tar validate testdata headers" {
+test "std.tar validate testdata headers" {
     // skip if wine and debug mode due to 'incorrect alignment'
     // TODO re-enable after https://github.com/ziglang/zig/issues/14036 is solved
     if (builtin.os.tag == .windows and builtin.mode == .Debug)
@@ -671,8 +671,9 @@ test "tar validate testdata headers" {
         var fbs = try test_common.decompressGz("testdata/" ++ test_case.file ++ ".gz", talloc);
         defer talloc.free(fbs.buffer);
         const reader = fbs.reader();
-        var buf: [tar.block_len * 4]u8 = undefined;
-        var iter = tar.headerIterator(reader, &buf);
+        var buf: [tar.block_len * 2]u8 = undefined;
+        var iter = tar.headerIterator(reader, &buf, talloc);
+        defer iter.deinit();
         for (test_case.headers, 0..) |header_, i| {
             // since we don't maintain a hash map of pax records, merge pax_recs
             // into this header record

Diff for: lib/std/compress/tar/test_decompress.zig

@@ -6,7 +6,7 @@ const talloc = testing.allocator;
 const builtin = @import("builtin");
 const test_common = @import("test_common.zig");
 
-test "tar decompress testdata" {
+test "std.tar decompress testdata" {
     // skip if wine and debug mode due to 'incorrect alignment'
     // TODO re-enable after https://github.com/ziglang/zig/issues/14036 is solved
     if (builtin.os.tag == .windows and builtin.mode == .Debug)
@@ -32,23 +32,17 @@ test "tar decompress testdata" {
         "gnu-multi-hdrs.tar",
     };
 
-    var cache_dir = testing.tmpDir(.{});
-    defer cache_dir.cleanup();
-
     inline for (test_files) |test_file| {
         var fbs = try test_common.decompressGz("testdata/" ++ test_file ++ ".gz", talloc);
         defer talloc.free(fbs.buffer);
-        {
-            var output_dir = try cache_dir.dir.makeOpenPath(test_file, .{});
-            defer output_dir.close();
-            try tar.pipeToFileSystem(output_dir, fbs.reader(), .{ .mode_mode = .ignore });
-        }
-        try cache_dir.dir.deleteTree(test_file);
+        try testDecompressTarToTmp(&fbs, .{ .mode_mode = .ignore });
         fbs.reset();
-        {
-            var output_dir = try cache_dir.dir.makeOpenPath(test_file, .{});
-            defer output_dir.close();
-            try tar.pipeToFileSystem(output_dir, fbs.reader(), .{ .mode_mode = .executable_bit_only });
-        }
+        try testDecompressTarToTmp(&fbs, .{ .mode_mode = .executable_bit_only });
     }
 }
+
+fn testDecompressTarToTmp(fbs: *std.io.FixedBufferStream([]u8), options: tar.Options) !void {
+    var tmpdir = testing.tmpDir(.{});
+    defer tmpdir.cleanup();
+    try tar.pipeToFileSystem(tmpdir.dir, fbs.reader(), options, talloc);
+}