breaking: std.os read/write functions + sendfile

 * rework os.sendfile and add macosx support, and a fallback
   implementation for any OS.
 * fix sendto compile error
 * std.os write functions support partial writes. closes #3443.
 * std.os pread / pwrite functions can now return `error.Unseekable`.
 * std.fs.File read/write functions now have readAll/writeAll variants
   which loop to complete operations even when partial reads/writes
   happen.
 * Audit std.os read/write functions with respect to Linux returning
   EINVAL for lengths greater than 0x7fff0000.
 * std.os read/write shim functions do not unnecessarily loop. Since
   partial reads/writes are part of the API, the caller will be forced
   to loop anyway, and so that would just be code bloat.
 * Improve doc comments
 * Add a non-trivial test for std.os.sendfile
 * Fix std.os.pread on 32 bit Linux
 * Add missing SYS_sendfile bit on aarch64

1 files changed, 28 insertions, 5 deletions

diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
index 95b1018a6b..c2fc06bc9b 100644
--- a/lib/std/os/linux.zig
+++ b/lib/std/os/linux.zig
@@ -316,8 +316,19 @@ pub fn symlinkat(existing: [*:0]const u8, newfd: i32, newpath: [*:0]const u8) us
     return syscall3(SYS_symlinkat, @ptrToInt(existing), @bitCast(usize, @as(isize, newfd)), @ptrToInt(newpath));
 }
 
-pub fn pread(fd: i32, buf: [*]u8, count: usize, offset: usize) usize {
-    return syscall4(SYS_pread, @bitCast(usize, @as(isize, fd)), @ptrToInt(buf), count, offset);
+pub fn pread(fd: i32, buf: [*]u8, count: usize, offset: u64) usize {
+    if (@hasDecl(@This(), "SYS_pread64")) {
+        return syscall5(
+            SYS_pread64,
+            @bitCast(usize, @as(isize, fd)),
+            @ptrToInt(buf),
+            count,
+            @truncate(usize, offset),
+            @truncate(usize, offset >> 32),
+        );
+    } else {
+        return syscall4(SYS_pread, @bitCast(usize, @as(isize, fd)), @ptrToInt(buf), count, offset);
+    }
 }
 
 pub fn access(path: [*:0]const u8, mode: u32) usize {
@@ -846,11 +857,23 @@ pub fn sendto(fd: i32, buf: [*]const u8, len: usize, flags: u32, addr: ?*const s
     return syscall6(SYS_sendto, @bitCast(usize, @as(isize, fd)), @ptrToInt(buf), len, flags, @ptrToInt(addr), @intCast(usize, alen));
 }
 
-pub fn sendfile(outfd: i32, infd: i32, offset: ?*u64, count: usize) usize {
+pub fn sendfile(outfd: i32, infd: i32, offset: ?*i64, count: usize) usize {
     if (@hasDecl(@This(), "SYS_sendfile64")) {
-        return syscall4(SYS_sendfile64, @bitCast(usize, @as(isize, outfd)), @bitCast(usize, @as(isize, infd)), @ptrToInt(offset), count);
+        return syscall4(
+            SYS_sendfile64,
+            @bitCast(usize, @as(isize, outfd)),
+            @bitCast(usize, @as(isize, infd)),
+            @ptrToInt(offset),
+            count,
+        );
     } else {
-        return syscall4(SYS_sendfile, @bitCast(usize, @as(isize, outfd)), @bitCast(usize, @as(isize, infd)), @ptrToInt(offset), count);
+        return syscall4(
+            SYS_sendfile,
+            @bitCast(usize, @as(isize, outfd)),
+            @bitCast(usize, @as(isize, infd)),
+            @ptrToInt(offset),
+            count,
+        );
     }
 }