file descriptors

pipes

1 files changed, 80 insertions, 0 deletions

diff --git a/fd.c b/fd.c
new file mode 100644
index 0000000..0546cef
--- /dev/null
+++ b/fd.c
@@ -0,0 +1,80 @@
+#include "types.h"
+#include "param.h"
+#include "x86.h"
+#include "mmu.h"
+#include "proc.h"
+#include "defs.h"
+#include "fd.h"
+
+struct fd fds[NFD];
+
+/*
+ * allocate a file descriptor number for curproc.
+ */
+int
+fd_ualloc()
+{
+  int fd;
+  struct proc *p = curproc[cpu()];
+  for(fd = 0; fd < NOFILE; fd++)
+    if(p->fds[fd] == 0)
+      return fd;
+  return -1;
+}
+
+struct fd *
+fd_alloc()
+{
+  int i;
+
+  for(i = 0; i < NFD; i++){
+    if(fds[i].type == FD_CLOSED){
+      fds[i].type = FD_NONE;
+      fds[i].count = 1;
+      return fds + i;
+    }
+  }
+  return 0;
+}
+
+void
+fd_close(struct fd *fd)
+{
+  if(fd->type == FD_CLOSED || fd->count <= 0)
+    panic("fd_close");
+  fd->count -= 1;
+  if(fd->count == 0){
+    if(fd->type == FD_PIPE)
+      pipe_close(fd->pipe, fd->writeable);
+    fd->type = FD_CLOSED;
+  }
+}
+
+/*
+ * addr is a kernel address, pointing into some process's p->mem.
+ */
+int
+fd_write(struct fd *fd, char *addr, int n)
+{
+  if(fd->writeable == 0)
+    return -1;
+  if(fd->type == FD_PIPE){
+    return pipe_write(fd->pipe, addr, n);
+  } else {
+    panic("fd_write");
+    return -1;
+  }
+}
+
+int
+fd_read(struct fd *fd, char *addr, int n)
+{
+  if(fd->readable == 0)
+    return -1;
+  if(fd->type == FD_PIPE){
+    return pipe_read(fd->pipe, addr, n);
+  } else {
+    panic("fd_read");
+    return -1;
+  }
+}