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std.fs: extract AtomicFile to separate file

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This commit is contained in:
Andrew Kelley 2023-11-22 13:54:16 -07:00
parent c95e2e65fa
commit e00e9c0fbf
3 changed files with 86 additions and 80 deletions
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1
CMakeLists.txt
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@ -247,6 +247,7 @@ set(ZIG_STAGE2_SOURCES
"${CMAKE_SOURCE_DIR}/lib/std/fmt/errol/lookup.zig"
"${CMAKE_SOURCE_DIR}/lib/std/fmt/parse_float.zig"
"${CMAKE_SOURCE_DIR}/lib/std/fs.zig"
"${CMAKE_SOURCE_DIR}/lib/std/fs/AtomicFile.zig"
"${CMAKE_SOURCE_DIR}/lib/std/fs/Dir.zig"
"${CMAKE_SOURCE_DIR}/lib/std/fs/file.zig"
"${CMAKE_SOURCE_DIR}/lib/std/fs/get_app_data_dir.zig"

81
lib/std/fs.zig
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@ -7,11 +7,11 @@ const base64 = std.base64;
const crypto = std.crypto;
const Allocator = std.mem.Allocator;
const assert = std.debug.assert;
const math = std.math;
const is_darwin = builtin.os.tag.isDarwin();
pub const Dir = @import("fs/Dir.zig");
pub const AtomicFile = @import("fs/AtomicFile.zig");
pub const has_executable_bit = switch (builtin.os.tag) {
.windows, .wasi => false,
@ -150,85 +150,6 @@ pub fn copyFileAbsolute(
return Dir.copyFile(my_cwd, source_path, my_cwd, dest_path, args);
}
pub const AtomicFile = struct {
file: File,
// TODO either replace this with rand_buf or use []u16 on Windows
tmp_path_buf: [TMP_PATH_LEN:0]u8,
dest_basename: []const u8,
file_open: bool,
file_exists: bool,
close_dir_on_deinit: bool,
dir: Dir,
pub const InitError = File.OpenError;
const RANDOM_BYTES = 12;
const TMP_PATH_LEN = base64_encoder.calcSize(RANDOM_BYTES);
/// Note that the `Dir.atomicFile` API may be more handy than this lower-level function.
pub fn init(
dest_basename: []const u8,
mode: File.Mode,
dir: Dir,
close_dir_on_deinit: bool,
) InitError!AtomicFile {
var rand_buf: [RANDOM_BYTES]u8 = undefined;
var tmp_path_buf: [TMP_PATH_LEN:0]u8 = undefined;
while (true) {
crypto.random.bytes(rand_buf[0..]);
const tmp_path = base64_encoder.encode(&tmp_path_buf, &rand_buf);
tmp_path_buf[tmp_path.len] = 0;
const file = dir.createFile(
tmp_path,
.{ .mode = mode, .exclusive = true },
) catch |err| switch (err) {
error.PathAlreadyExists => continue,
else => |e| return e,
};
return AtomicFile{
.file = file,
.tmp_path_buf = tmp_path_buf,
.dest_basename = dest_basename,
.file_open = true,
.file_exists = true,
.close_dir_on_deinit = close_dir_on_deinit,
.dir = dir,
};
}
}
/// Always call deinit, even after a successful finish().
pub fn deinit(self: *AtomicFile) void {
if (self.file_open) {
self.file.close();
self.file_open = false;
}
if (self.file_exists) {
self.dir.deleteFile(&self.tmp_path_buf) catch {};
self.file_exists = false;
}
if (self.close_dir_on_deinit) {
self.dir.close();
}
self.* = undefined;
}
pub const FinishError = std.os.RenameError;
pub fn finish(self: *AtomicFile) FinishError!void {
assert(self.file_exists);
if (self.file_open) {
self.file.close();
self.file_open = false;
}
try os.renameat(self.dir.fd, self.tmp_path_buf[0..], self.dir.fd, self.dest_basename);
self.file_exists = false;
}
};
/// Create a new directory, based on an absolute path.
/// Asserts that the path is absolute. See `Dir.makeDir` for a function that operates
/// on both absolute and relative paths.

84
lib/std/fs/AtomicFile.zig Normal file
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@ -0,0 +1,84 @@
file: File,
// TODO either replace this with rand_buf or use []u16 on Windows
tmp_path_buf: [TMP_PATH_LEN:0]u8,
dest_basename: []const u8,
file_open: bool,
file_exists: bool,
close_dir_on_deinit: bool,
dir: Dir,
pub const InitError = File.OpenError;
const RANDOM_BYTES = 12;
const TMP_PATH_LEN = fs.base64_encoder.calcSize(RANDOM_BYTES);
/// Note that the `Dir.atomicFile` API may be more handy than this lower-level function.
pub fn init(
dest_basename: []const u8,
mode: File.Mode,
dir: Dir,
close_dir_on_deinit: bool,
) InitError!AtomicFile {
var rand_buf: [RANDOM_BYTES]u8 = undefined;
var tmp_path_buf: [TMP_PATH_LEN:0]u8 = undefined;
while (true) {
std.crypto.random.bytes(rand_buf[0..]);
const tmp_path = fs.base64_encoder.encode(&tmp_path_buf, &rand_buf);
tmp_path_buf[tmp_path.len] = 0;
const file = dir.createFile(
tmp_path,
.{ .mode = mode, .exclusive = true },
) catch |err| switch (err) {
error.PathAlreadyExists => continue,
else => |e| return e,
};
return AtomicFile{
.file = file,
.tmp_path_buf = tmp_path_buf,
.dest_basename = dest_basename,
.file_open = true,
.file_exists = true,
.close_dir_on_deinit = close_dir_on_deinit,
.dir = dir,
};
}
}
/// Always call deinit, even after a successful finish().
pub fn deinit(self: *AtomicFile) void {
if (self.file_open) {
self.file.close();
self.file_open = false;
}
if (self.file_exists) {
self.dir.deleteFile(&self.tmp_path_buf) catch {};
self.file_exists = false;
}
if (self.close_dir_on_deinit) {
self.dir.close();
}
self.* = undefined;
}
pub const FinishError = posix.RenameError;
pub fn finish(self: *AtomicFile) FinishError!void {
assert(self.file_exists);
if (self.file_open) {
self.file.close();
self.file_open = false;
}
try posix.renameat(self.dir.fd, self.tmp_path_buf[0..], self.dir.fd, self.dest_basename);
self.file_exists = false;
}
const AtomicFile = @This();
const std = @import("../std.zig");
const File = std.fs.File;
const Dir = std.fs.Dir;
const fs = std.fs;
const assert = std.debug.assert;
const posix = std.os;