1 files changed, 175 insertions, 0 deletions
diff --git a/kernel/file.c b/kernel/file.c
new file mode 100644
index 0000000..6f27f22
--- /dev/null
+++ b/kernel/file.c
@@ -0,0 +1,175 @@
+//
+// Support functions for system calls that involve file descriptors.
+//
+
+#include "types.h"
+#include "riscv.h"
+#include "defs.h"
+#include "param.h"
+#include "fs.h"
+#include "spinlock.h"
+#include "sleeplock.h"
+#include "file.h"
+#include "stat.h"
+#include "proc.h"
+
+struct devsw devsw[NDEV];
+struct {
+  struct spinlock lock;
+  struct file file[NFILE];
+} ftable;
+
+void
+fileinit(void)
+{
+  initlock(&ftable.lock, "ftable");
+}
+
+// Allocate a file structure.
+struct file*
+filealloc(void)
+{
+  struct file *f;
+
+  acquire(&ftable.lock);
+  for(f = ftable.file; f < ftable.file + NFILE; f++){
+    if(f->ref == 0){
+      f->ref = 1;
+      release(&ftable.lock);
+      return f;
+    }
+  }
+  release(&ftable.lock);
+  return 0;
+}
+
+// Increment ref count for file f.
+struct file*
+filedup(struct file *f)
+{
+  acquire(&ftable.lock);
+  if(f->ref < 1)
+    panic("filedup");
+  f->ref++;
+  release(&ftable.lock);
+  return f;
+}
+
+// Close file f.  (Decrement ref count, close when reaches 0.)
+void
+fileclose(struct file *f)
+{
+  struct file ff;
+
+  acquire(&ftable.lock);
+  if(f->ref < 1)
+    panic("fileclose");
+  if(--f->ref > 0){
+    release(&ftable.lock);
+    return;
+  }
+  ff = *f;
+  f->ref = 0;
+  f->type = FD_NONE;
+  release(&ftable.lock);
+
+  if(ff.type == FD_PIPE)
+    pipeclose(ff.pipe, ff.writable);
+  else if(ff.type == FD_INODE){
+    begin_op();
+    iput(ff.ip);
+    end_op();
+  }
+}
+
+// Get metadata about file f.
+// addr is a user virtual address, pointing to a struct stat.
+int
+filestat(struct file *f, uint64 addr)
+{
+  struct proc *p = myproc();
+  struct stat st;
+  
+  if(f->type == FD_INODE){
+    ilock(f->ip);
+    stati(f->ip, &st);
+    iunlock(f->ip);
+    if(copyout(p->pagetable, addr, (char *)&st, sizeof(st)) < 0)
+      return -1;
+    return 0;
+  }
+  return -1;
+}
+
+// Read from file f.
+// addr is a user virtual address.
+int
+fileread(struct file *f, uint64 addr, int n)
+{
+  int r = 0;
+
+  if(f->readable == 0)
+    return -1;
+
+  if(f->type == FD_PIPE){
+    r = piperead(f->pipe, addr, n);
+  } else if(f->type == FD_INODE){
+    ilock(f->ip);
+    if((r = readi(f->ip, 1, addr, f->off, n)) > 0)
+      f->off += r;
+    iunlock(f->ip);
+  } else {
+    panic("fileread");
+  }
+
+  return r;
+}
+
+//PAGEBREAK!
+// Write to file f.
+// addr is a user virtual address.
+int
+filewrite(struct file *f, uint64 addr, int n)
+{
+  int r, ret = 0;
+
+  if(f->writable == 0)
+    return -1;
+
+  if(f->type == FD_PIPE){
+    ret = pipewrite(f->pipe, addr, n);
+  } else if(f->type == FD_INODE){
+    // write a few blocks at a time to avoid exceeding
+    // the maximum log transaction size, including
+    // i-node, indirect block, allocation blocks,
+    // and 2 blocks of slop for non-aligned writes.
+    // this really belongs lower down, since writei()
+    // might be writing a device like the console.
+    int max = ((MAXOPBLOCKS-1-1-2) / 2) * 512;
+    int i = 0;
+    while(i < n){
+      int n1 = n - i;
+      if(n1 > max)
+        n1 = max;
+
+      begin_op();
+      ilock(f->ip);
+      if ((r = writei(f->ip, 1, addr + i, f->off, n1)) > 0)
+        f->off += r;
+      iunlock(f->ip);
+      end_op();
+
+      if(r < 0)
+        break;
+      if(r != n1)
+        panic("short filewrite");
+      i += r;
+    }
+    ret = (i == n ? n : -1);
+  } else {
+    panic("filewrite");
+  }
+
+  return ret;
+}
+