feat: added memory mapped file reader

1 files changed, 42 insertions, 0 deletions

diff --git a/sys/libn/mmap.c b/sys/libn/mmap.c
new file mode 100644
index 0000000..d8b2a61
--- /dev/null
+++ b/sys/libn/mmap.c
@@ -0,0 +1,42 @@
+#include <u.h>
+#include <libn.h>
+
+#include <sys/mman.h>
+
+mmap·Reader
+mmap·open(byte *filename)
+{
+    int     fd;
+    int    err;
+    void  *buf;
+    Stream  *s;
+    io·Stat st;
+
+    s   = io·open(filename, "r");
+    fd  = io·fd(s);
+    err = io·stat(s, &st);
+    if (err) {
+        errorf("file stat: error code %d", err);
+        goto ERROR;
+    }
+    buf = mmap(nil, st.st_size, PROT_READ, MAP_SHARED, fd, 0);
+    if (!buf) {
+        errorf("mmap: failed");
+        goto ERROR;
+    }
+    // NOTE: posix systems require that reference kept to mmap file after fd is closed
+    io·close(s);
+    return (mmap·Reader){.len=st.st_size, .buf=buf};
+
+ERROR:
+    io·close(s);
+    return (mmap·Reader){ 0 };
+}
+
+error
+mmap·close(mmap·Reader rdr)
+{
+    munmap(rdr.buf, rdr.len);
+
+    return 0;
+}