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std.os: (p)writev should perform partial writes if iov.len > IOV_MAX

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Co-authored-by: Veikka Tuominen <git@vexu.eu>
This commit is contained in:
daurnimator 2021-08-23 05:22:53 +10:00 committed by GitHub
parent 62e3d67605
commit 72c4b80d31
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GPG Key ID: 4AEE18F83AFDEB23
7 changed files with 26 additions and 4 deletions
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8
lib/std/os.zig
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@ -787,7 +787,7 @@ pub fn write(fd: fd_t, bytes: []const u8) WriteError!usize {
/// On Windows, if the application has a global event loop enabled, I/O Completion Ports are
/// used to perform the I/O. `error.WouldBlock` is not possible on Windows.
///
/// If `iov.len` is larger than will fit in a `u31`, a partial write will occur.
/// If `iov.len` is larger than `IOV_MAX`, a partial write will occur.
pub fn writev(fd: fd_t, iov: []const iovec_const) WriteError!usize {
if (std.Target.current.os.tag == .windows) {
// TODO improve this to use WriteFileScatter
@ -816,7 +816,7 @@ pub fn writev(fd: fd_t, iov: []const iovec_const) WriteError!usize {
}
}
const iov_count = math.cast(u31, iov.len) catch math.maxInt(u31);
const iov_count = if (iov.len > IOV_MAX) IOV_MAX else @intCast(u31, iov.len);
while (true) {
const rc = system.writev(fd, iov.ptr, iov_count);
switch (errno(rc)) {
@ -954,7 +954,7 @@ pub fn pwrite(fd: fd_t, bytes: []const u8, offset: u64) PWriteError!usize {
/// * Darwin
/// * Windows
///
/// If `iov.len` is larger than will fit in a `u31`, a partial write will occur.
/// If `iov.len` is larger than `IOV_MAX`, a partial write will occur.
pub fn pwritev(fd: fd_t, iov: []const iovec_const, offset: u64) PWriteError!usize {
const have_pwrite_but_not_pwritev = switch (std.Target.current.os.tag) {
.windows, .macos, .ios, .watchos, .tvos, .haiku => true,
@ -997,7 +997,7 @@ pub fn pwritev(fd: fd_t, iov: []const iovec_const, offset: u64) PWriteError!usiz
else
system.pwritev;
const iov_count = math.cast(u31, iov.len) catch math.maxInt(u31);
const iov_count = if (iov.len > IOV_MAX) IOV_MAX else @intCast(u31, iov.len);
const ioffset = @bitCast(i64, offset); // the OS treats this as unsigned
while (true) {
const rc = pwritev_sym(fd, iov.ptr, iov_count, ioffset);

1
lib/std/os/bits/darwin.zig
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@ -235,6 +235,7 @@ pub const host_t = mach_port_t;
pub const CALENDAR_CLOCK = 1;
pub const PATH_MAX = 1024;
pub const IOV_MAX = 16;
pub const STDIN_FILENO = 0;
pub const STDOUT_FILENO = 1;

1
lib/std/os/bits/dragonfly.zig
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@ -168,6 +168,7 @@ pub const SA_NOCLDWAIT = 0x0020;
pub const SA_SIGINFO = 0x0040;
pub const PATH_MAX = 1024;
pub const IOV_MAX = KERN_IOV_MAX;
pub const ino_t = c_ulong;

2
lib/std/os/bits/freebsd.zig
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@ -238,8 +238,10 @@ pub const CTL_DEBUG = 5;
pub const KERN_PROC = 14; // struct: process entries
pub const KERN_PROC_PATHNAME = 12; // path to executable
pub const KERN_IOV_MAX = 35;
pub const PATH_MAX = 1024;
pub const IOV_MAX = KERN_IOV_MAX;
pub const STDIN_FILENO = 0;
pub const STDOUT_FILENO = 1;

2
lib/std/os/bits/netbsd.zig
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@ -405,8 +405,10 @@ pub const CTL_DEBUG = 5;
pub const KERN_PROC_ARGS = 48; // struct: process argv/env
pub const KERN_PROC_PATHNAME = 5; // path to executable
pub const KERN_IOV_MAX = 38;
pub const PATH_MAX = 1024;
pub const IOV_MAX = KERN_IOV_MAX;
pub const STDIN_FILENO = 0;
pub const STDOUT_FILENO = 1;

2
lib/std/os/bits/wasi.zig
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@ -76,6 +76,8 @@ pub const kernel_stat = struct {
}
};
pub const IOV_MAX = 1024;
pub const AT_REMOVEDIR: u32 = 0x4;
pub const AT_FDCWD: fd_t = -2;

14
lib/std/os/test.zig
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@ -786,3 +786,17 @@ test "dup & dup2" {
var buf: [7]u8 = undefined;
try testing.expectEqualStrings("dupdup2", buf[0..try file.readAll(&buf)]);
}
test "writev longer than IOV_MAX" {
if (native_os == .windows or native_os == .wasi) return error.SkipZigTest;
var tmp = tmpDir(.{});
defer tmp.cleanup();
var file = try tmp.dir.createFile("pwritev", .{});
defer file.close();
const iovecs = [_]os.iovec_const{.{ .iov_base = "a", .iov_len = 1 }} ** (os.IOV_MAX + 1);
const amt = try file.writev(&iovecs);
try testing.expectEqual(@as(usize, os.IOV_MAX), amt);
}