From 859771b3160dcfa3d3a26aa84fa2edfa09fc09ca Mon Sep 17 00:00:00 2001
From: Michael Santos <michael.santos@gmail.com>
Date: Sat, 26 Apr 2014 17:23:30 +0000
Subject: [PATCH] Add lseek(2)

---
 README.md               |  7 +++++++
 c_src/alcove.h          |  5 +++++
 c_src/alcove_call.proto |  1 +
 c_src/alcove_file.c     | 45 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 58 insertions(+)

diff --git a/README.md b/README.md
index 018c370..59d98ab 100644
--- a/README.md
+++ b/README.md
@@ -582,6 +582,13 @@ probably confuse the process.
 
         kill(2) : terminate a process
 
+    lseek(Drv, FD, Offset, Whence) -> ok | {error, posix()}
+    lseek(Drv, Pids, FD, Offset, Whence) -> ok | {error, posix()}
+
+        Types   Offset = Whence = integer()
+
+        lseek(2) : set file offset for read/write
+
     mkdir(Drv, Path, Mode) -> ok | {error, posix()}
     mkdir(Drv, Pids, Path, Mode) -> ok | {error, posix()}
 
diff --git a/c_src/alcove.h b/c_src/alcove.h
index 1e178ea..e348336 100644
--- a/c_src/alcove.h
+++ b/c_src/alcove.h
@@ -69,6 +69,11 @@
         ? ERL_INT_UVALUE(x) \
         : ERL_LL_UVALUE(x))
 
+#define ALCOVE_LL_VALUE(x) \
+    ((ERL_IS_INTEGER(x)) \
+        ? ERL_INT_VALUE(x) \
+        : ERL_LL_VALUE(x))
+
 #define ALCOVE_SETOPT(x,k,v) \
     (x)->opt = (v) ? (x)->opt | (k) : (x)->opt & ~(k)
 
diff --git a/c_src/alcove_call.proto b/c_src/alcove_call.proto
index 80b353a..1798d80 100644
--- a/c_src/alcove_call.proto
+++ b/c_src/alcove_call.proto
@@ -21,6 +21,7 @@ getpid/0
 getrlimit/1
 getuid/0
 kill/2
+lseek/3
 mkdir/2
 mount/5
 mount_define/1
diff --git a/c_src/alcove_file.c b/c_src/alcove_file.c
index fa9e104..d83f8f7 100644
--- a/c_src/alcove_file.c
+++ b/c_src/alcove_file.c
@@ -115,6 +115,51 @@ BADARG:
     return erl_mk_atom("badarg");
 }
 
+/*
+ * lseek(2)
+ *
+ */
+    ETERM *
+alcove_lseek(alcove_state_t *ap, ETERM *arg)
+{
+    ETERM *hd = NULL;
+    int fd = 0;
+    off_t offset = 0;
+    int whence = 0;
+
+    /* fd */
+    arg = alcove_list_head(&hd, arg);
+    if (!hd || !ERL_IS_INTEGER(hd))
+        goto BADARG;
+
+    fd = ERL_INT_VALUE(hd);
+
+    /* offset */
+    arg = alcove_list_head(&hd, arg);
+    if (!hd || !ALCOVE_IS_LONGLONG(hd))
+        goto BADARG;
+
+    offset = ALCOVE_LL_VALUE(hd);
+
+    /* whence */
+    arg = alcove_list_head(&hd, arg);
+    if (!hd || !ERL_IS_INTEGER(hd))
+        goto BADARG;
+
+    offset = ERL_INT_VALUE(hd);
+
+    /* stdin, stdout, stderr, ctl are reserved */
+    if (fd < 4)
+        return alcove_errno(EBADF);
+
+    return (lseek(fd, offset, whence) == -1)
+        ? alcove_errno(errno)
+        : erl_mk_atom("ok");
+
+BADARG:
+    return erl_mk_atom("badarg");
+}
+
 /*
  * read(2)
  *