From 05badf19300e2970cdeb914a62b2c2b424fe7711 Mon Sep 17 00:00:00 2001
From: Lukas Larsson <lukas@erlang.org>
Date: Fri, 20 May 2016 17:45:56 +0200
Subject: erts: Split large binaries into multiple iovec

On windows the max size of an iov element is long, i.e. 4GB
so in order to write larger binaries to file we split the
binary into smaller 2GB chunks so that the write is possible.
---
 erts/emulator/beam/io.c | 59 ++++++++++++++++++++++++++++++++-----------------
 1 file changed, 39 insertions(+), 20 deletions(-)

(limited to 'erts/emulator/beam')

diff --git a/erts/emulator/beam/io.c b/erts/emulator/beam/io.c
index 0377f6cb5e..01df5476db 100644
--- a/erts/emulator/beam/io.c
+++ b/erts/emulator/beam/io.c
@@ -938,18 +938,32 @@ int erts_port_handle_xports(Port *prt)
 **        -2 on type error
 */
 
-#define SET_VEC(iov, bv, bin, ptr, len, vlen) do {	\
-   (iov)->iov_base = (ptr);				\
-   (iov)->iov_len = (len);				\
-   if (sizeof((iov)->iov_len) < sizeof(len)				\
-       /* Check if (len) overflowed (iov)->iov_len */                   \
-       && (iov)->iov_len != (len)) {		                        \
-       goto L_overflow;							\
-   }									\
-   *(bv)++ = (bin);					\
-   (iov)++;						\
-   (vlen)++;						\
-} while(0)
+#ifdef DEBUG
+#define MAX_SYSIOVEC_IOVLEN (1ull << (32 - 1))
+#else
+#define MAX_SYSIOVEC_IOVLEN (1ull << (sizeof(((SysIOVec*)0)->iov_len) * 8 - 1))
+#endif
+
+static ERTS_INLINE void
+io_list_to_vec_set_vec(SysIOVec **iov, ErlDrvBinary ***binv,
+                        ErlDrvBinary *bin, byte *ptr, Uint len,
+                        int *vlen)
+{
+    while (len > MAX_SYSIOVEC_IOVLEN) {
+        (*iov)->iov_base = ptr;
+        (*iov)->iov_len = MAX_SYSIOVEC_IOVLEN;
+        ptr += MAX_SYSIOVEC_IOVLEN;
+        len -= MAX_SYSIOVEC_IOVLEN;
+        (*iov)++;
+        (*vlen)++;
+        *(*binv)++ = bin;
+    }
+    (*iov)->iov_base = ptr;
+    (*iov)->iov_len = len;
+    *(*binv)++ = bin;
+    (*iov)++;
+    (*vlen)++;
+}
 
 static int
 io_list_to_vec(Eterm obj,	/* io-list */
@@ -960,11 +974,11 @@ io_list_to_vec(Eterm obj,	/* io-list */
 {
     DECLARE_ESTACK(s);
     Eterm* objp;
-    char *buf  = cbin->orig_bytes;
+    byte *buf  = (byte*)cbin->orig_bytes;
     Uint len = cbin->orig_size;
     Uint csize  = 0;
     int vlen   = 0;
-    char* cptr = buf;
+    byte* cptr = buf;
 
     goto L_jump_start;  /* avoid push */
 
@@ -1032,15 +1046,17 @@ io_list_to_vec(Eterm obj,	/* io-list */
 		    len -= size;
 		} else {
 		    if (csize != 0) {
-			SET_VEC(iov, binv, cbin, cptr, csize, vlen);
+                        io_list_to_vec_set_vec(&iov, &binv, cbin,
+                                               cptr, csize, &vlen);
 			cptr = buf;
 			csize = 0;
 		    }
 		    if (pb->flags) {
 			erts_emasculate_writable_binary(pb);
 		    }
-		    SET_VEC(iov, binv, Binary2ErlDrvBinary(pb->val),
-			    pb->bytes+offset, size, vlen);
+                    io_list_to_vec_set_vec(
+                        &iov, &binv, Binary2ErlDrvBinary(pb->val),
+                        pb->bytes+offset, size, &vlen);
 		}
 	    } else {
 		ErlHeapBin* hb = (ErlHeapBin *) bptr;
@@ -1060,7 +1076,7 @@ io_list_to_vec(Eterm obj,	/* io-list */
     }
 
     if (csize != 0) {
-	SET_VEC(iov, binv, cbin, cptr, csize, vlen);
+        io_list_to_vec_set_vec(&iov, &binv, cbin, cptr, csize, &vlen);
     }
 
     DESTROY_ESTACK(s);
@@ -1086,10 +1102,13 @@ do {									\
     if (_bitsize != 0) goto L_type_error;				\
     if (thing_subtag(*binary_val(_real)) == REFC_BINARY_SUBTAG &&	\
 	_bitoffs == 0) {						\
-	b_size += _size;						\
+	b_size += _size;                                                \
         if (b_size < _size) goto L_overflow_error;			\
 	in_clist = 0;							\
-	v_size++;							\
+        v_size++;                                                       \
+        /* If iov_len is smaller then Uint we split the binary into*/   \
+        /* multiple smaller (2GB) elements in the iolist.*/             \
+	v_size += _size / MAX_SYSIOVEC_IOVLEN;                          \
         if (_size >= ERL_SMALL_IO_BIN_LIMIT) {				\
             p_in_clist = 0;						\
             p_v_size++;							\
-- 
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