From 8a042a220d825a248ff3ab663023d4bcb1ba2d32 Mon Sep 17 00:00:00 2001
From: Jeremy Soller <jeremy@system76.com>
Date: Sun, 25 Nov 2018 14:34:18 -0700
Subject: [PATCH] Implement pread, add more poll constants

---
 src/header/poll/mod.rs   |  4 ++++
 src/header/unistd/mod.rs | 20 ++++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/src/header/poll/mod.rs b/src/header/poll/mod.rs
index fab03b382d..47c2b655ef 100644
--- a/src/header/poll/mod.rs
+++ b/src/header/poll/mod.rs
@@ -6,6 +6,10 @@ use platform::{Pal, Sys};
 pub const POLLIN: c_short = 0x001;
 pub const POLLPRI: c_short = 0x002;
 pub const POLLOUT: c_short = 0x004;
+pub const POLLERR: c_short = 0x008;
+pub const POLLHUP: c_short = 0x010;
+pub const POLLNVAL: c_short = 0x020;
+
 
 pub type nfds_t = c_ulong;
 
diff --git a/src/header/unistd/mod.rs b/src/header/unistd/mod.rs
index 3cf2e16bd3..4573d4d854 100644
--- a/src/header/unistd/mod.rs
+++ b/src/header/unistd/mod.rs
@@ -387,9 +387,25 @@ pub unsafe extern "C" fn pipe(fildes: *mut c_int) -> c_int {
     Sys::pipe(slice::from_raw_parts_mut(fildes, 2))
 }
 
-// #[no_mangle]
+#[no_mangle]
 pub extern "C" fn pread(fildes: c_int, buf: *mut c_void, nbyte: size_t, offset: off_t) -> ssize_t {
-    unimplemented!();
+    //TODO: better pread using system calls
+
+    let previous = lseek(fildes, offset, SEEK_SET);
+    if previous == -1 {
+        return -1;
+    }
+
+    let res = read(fildes, buf, nbyte);
+    if res < 0 {
+        return res;
+    }
+
+    if lseek(fildes, previous, SEEK_SET) == -1 {
+        return -1;
+    }
+
+    res
 }
 
 // #[no_mangle]