file::pread

f7766586 · Silas Boyd-Wickizer · 0b6ffac6 · f7766586 · f7766586 · f7766586
--- a/include/file.hh
+++ b/include/file.hh
@@ -13,6 +13,7 @@ struct file : public referenced {
  file *dup();
  int stat(struct stat*);
  int read(char *addr, int n);
+  ssize_t pread(char *addr, size_t n, off_t offset);
  int write(char *addr, int n);
  enum { FD_NONE, FD_PIPE, FD_INODE, FD_SOCKET } type;  

--- a/kernel/file.cc
+++ b/kernel/file.cc
@@ -80,6 +80,21 @@ file::read(char *addr, int n)
  panic("fileread");
 }
+ssize_t
+file::pread(char *addr, size_t n, off_t off)
+{
+  if(type == file::FD_INODE){
+    int r;
+    ilock(ip, 0);
+    if(ip->type == 0)
+      panic("file::pread");
+    r = readi(ip, addr, off, n);
+    iunlock(ip);
+    return r;
+  }
+  return -1;
+}
 int
 file::write(char *addr, int n)
 {

--- a/kernel/sysfile.cc
+++ b/kernel/sysfile.cc
@@ -57,7 +57,6 @@ sys_pread(int fd, void *ubuf, size_t count, off_t offset)
 {
  sref<file> f;
  uptr i = (uptr)ubuf;
-  int r;
  if (!getfile(fd, &f))
    return -1;
@@ -65,16 +64,8 @@ sys_pread(int fd, void *ubuf, size_t count, off_t offset)
  for(uptr va = PGROUNDDOWN(i); va < i+count; va = va + PGSIZE)
    if(pagefault(myproc()->vmap, va, 0) < 0)
      return -1;
-  if(f->type == file::FD_INODE){
+  return f->pread((char*)ubuf, count, offset);
-    ilock(f->ip, 0);
-    if(f->ip->type == 0)
-      panic("fileread");
-    r = readi(f->ip, (char*)ubuf, offset, count);
-    iunlock(f->ip);
-    return r;
-  }
-  return -1;
 }
 long