lib/mmap: library to do memory allocation with anonymous memory maps

lib/mmap/mmap_unix.go

@@ -0,0 +1,33 @@
+// Package mmap implements a large block memory allocator using
+// anonymous memory maps.
+
+// +build !plan9,!windows
+
+package mmap
+
+import (
+	"github.com/pkg/errors"
+	"golang.org/x/sys/unix"
+)
+
+// Alloc allocates size bytes and returns a slice containing them.  If
+// the allocation fails it will return with an error.  This is best
+// used for allocations which are a multiple of the PageSize.
+func Alloc(size int) ([]byte, error) {
+	mem, err := unix.Mmap(-1, 0, size, unix.PROT_READ|unix.PROT_WRITE, unix.MAP_PRIVATE|unix.MAP_ANON)
+	if err != nil {
+		return nil, errors.Wrap(err, "mmap: failed to allocate memory for buffer")
+	}
+	return mem, nil
+}
+
+// Free frees buffers allocated by Alloc.  Note it should be passed
+// the same slice (not a derived slice) that Alloc returned.  If the
+// free fails it will return with an error.
+func Free(mem []byte) error {
+	err := unix.Munmap(mem)
+	if err != nil {
+		return errors.Wrap(err, "mmap: failed to unmap memory")
+	}
+	return nil
+}