std.tar: add writer (#19603)

Simplifies code in docs creation where we used `std.tar.output.Header`.
Writer uses that Header internally and provides higher level interface.
Updates checksum on write, handles long file names, allows setting mtime and file permission mode. Provides handy interface for passing `Dir.WalkerEntry`.

Author: ianic

lib/compiler/std-docs.zig

@@ -181,14 +181,16 @@ fn serveSourcesTar(request: *std.http.Server.Request, context: *Context) !void {
             },
         },
     });
-    const w = response.writer();
 
     var std_dir = try context.lib_dir.openDir("std", .{ .iterate = true });
     defer std_dir.close();
 
     var walker = try std_dir.walk(gpa);
     defer walker.deinit();
 
+    var archiver = std.tar.writer(response.writer());
+    archiver.prefix = "std";
+
     while (try walker.next()) |entry| {
         switch (entry.kind) {
             .file => {
@@ -199,47 +201,21 @@ fn serveSourcesTar(request: *std.http.Server.Request, context: *Context) !void {
             },
             else => continue,
         }
-
-        var file = try std_dir.openFile(entry.path, .{});
+        var file = try entry.dir.openFile(entry.basename, .{});
         defer file.close();
-
-        const stat = try file.stat();
-        const padding = p: {
-            const remainder = stat.size % 512;
-            break :p if (remainder > 0) 512 - remainder else 0;
-        };
-
-        var file_header = std.tar.output.Header.init();
-        file_header.typeflag = .regular;
-        try file_header.setPath("std", entry.path);
-        try file_header.setSize(stat.size);
-        try file_header.updateChecksum();
-        try w.writeAll(std.mem.asBytes(&file_header));
-        try w.writeFile(file);
-        try w.writeByteNTimes(0, padding);
+        try archiver.writeFile(entry.path, file);
     }
 
     {
         // Since this command is JIT compiled, the builtin module available in
         // this source file corresponds to the user's host system.
         const builtin_zig = @embedFile("builtin");
-
-        var file_header = std.tar.output.Header.init();
-        file_header.typeflag = .regular;
-        try file_header.setPath("builtin", "builtin.zig");
-        try file_header.setSize(builtin_zig.len);
-        try file_header.updateChecksum();
-        try w.writeAll(std.mem.asBytes(&file_header));
-        try w.writeAll(builtin_zig);
-        const padding = p: {
-            const remainder = builtin_zig.len % 512;
-            break :p if (remainder > 0) 512 - remainder else 0;
-        };
-        try w.writeByteNTimes(0, padding);
+        archiver.prefix = "builtin";
+        try archiver.writeFileBytes("builtin.zig", builtin_zig, .{});
     }
 
     // intentionally omitting the pointless trailer
-    //try w.writeByteNTimes(0, 512 * 2);
+    //try archiver.finish();
     try response.end();
 }
 

lib/std/Build/Fuzz/WebServer.zig

@@ -456,7 +456,6 @@ fn serveSourcesTar(ws: *WebServer, request: *std.http.Server.Request) !void {
             },
         },
     });
-    const w = response.writer();
 
     const DedupeTable = std.ArrayHashMapUnmanaged(Build.Cache.Path, void, Build.Cache.Path.TableAdapter, false);
     var dedupe_table: DedupeTable = .{};
@@ -490,40 +489,21 @@ fn serveSourcesTar(ws: *WebServer, request: *std.http.Server.Request) !void {
 
     var cwd_cache: ?[]const u8 = null;
 
+    var archiver = std.tar.writer(response.writer());
+
     for (deduped_paths) |joined_path| {
         var file = joined_path.root_dir.handle.openFile(joined_path.sub_path, .{}) catch |err| {
             log.err("failed to open {}: {s}", .{ joined_path, @errorName(err) });
             continue;
         };
         defer file.close();
 
-        const stat = file.stat() catch |err| {
-            log.err("failed to stat {}: {s}", .{ joined_path, @errorName(err) });
-            continue;
-        };
-        if (stat.kind != .file)
-            continue;
-
-        const padding = p: {
-            const remainder = stat.size % 512;
-            break :p if (remainder > 0) 512 - remainder else 0;
-        };
-
-        var file_header = std.tar.output.Header.init();
-        file_header.typeflag = .regular;
-        try file_header.setPath(
-            joined_path.root_dir.path orelse try memoizedCwd(arena, &cwd_cache),
-            joined_path.sub_path,
-        );
-        try file_header.setSize(stat.size);
-        try file_header.updateChecksum();
-        try w.writeAll(std.mem.asBytes(&file_header));
-        try w.writeFile(file);
-        try w.writeByteNTimes(0, padding);
+        archiver.prefix = joined_path.root_dir.path orelse try memoizedCwd(arena, &cwd_cache);
+        try archiver.writeFile(joined_path.sub_path, file);
     }
 
     // intentionally omitting the pointless trailer
-    //try w.writeByteNTimes(0, 512 * 2);
+    //try archiver.finish();
     try response.end();
 }
 

lib/std/tar.zig

@@ -19,7 +19,7 @@ const std = @import("std");
 const assert = std.debug.assert;
 const testing = std.testing;
 
-pub const output = @import("tar/output.zig");
+pub const writer = @import("tar/writer.zig").writer;
 
 /// Provide this to receive detailed error messages.
 /// When this is provided, some errors which would otherwise be returned
@@ -355,13 +355,13 @@ pub fn Iterator(comptime ReaderType: type) type {
             }
 
             // Writes file content to writer.
-            pub fn writeAll(self: File, writer: anytype) !void {
+            pub fn writeAll(self: File, out_writer: anytype) !void {
                 var buffer: [4096]u8 = undefined;
 
                 while (self.unread_bytes.* > 0) {
                     const buf = buffer[0..@min(buffer.len, self.unread_bytes.*)];
                     try self.parent_reader.readNoEof(buf);
-                    try writer.writeAll(buf);
+                    try out_writer.writeAll(buf);
                     self.unread_bytes.* -= buf.len;
                 }
             }