file descriptors

pipes

1 files changed, 100 insertions, 0 deletions

diff --git a/pipe.c b/pipe.c
new file mode 100644
index 0000000..9a81e0b
--- /dev/null
+++ b/pipe.c
@@ -0,0 +1,100 @@
+#include "types.h"
+#include "param.h"
+#include "x86.h"
+#include "mmu.h"
+#include "proc.h"
+#include "defs.h"
+#include "fd.h"
+
+#define PIPESIZE 512
+
+struct pipe {
+  int readopen; // read fd is still open
+  int writeopen; // write fd is still open
+  int writep; // next index to write
+  int readp;  // next index to read
+  char data[PIPESIZE];
+};
+
+int
+pipe_alloc(struct fd **fd1, struct fd **fd2)
+{
+  *fd1 = *fd2 = 0;
+  struct pipe *p = 0;
+
+  if((*fd1 = fd_alloc()) == 0)
+    goto oops;
+  if((*fd2 = fd_alloc()) == 0)
+    goto oops;
+  if((p = (struct pipe *) kalloc(PAGE)) == 0)
+    goto oops;
+  (*fd1)->type = FD_PIPE;
+  (*fd1)->readable = 1;
+  (*fd1)->writeable = 0;
+  (*fd1)->pipe = p;
+  (*fd2)->type = FD_PIPE;
+  (*fd2)->readable = 0;
+  (*fd2)->writeable = 1;
+  (*fd2)->pipe = p;
+  return 0;
+ oops:
+  if(p)
+    kfree((char *) p, PAGE);
+  if(*fd1){
+    (*fd1)->type = FD_NONE;
+    fd_close(*fd1);
+  }
+  if(*fd2){
+    (*fd2)->type = FD_NONE;
+    fd_close(*fd2);
+  }
+  return -1;
+}
+
+void
+pipe_close(struct pipe *p, int writeable)
+{
+  if(writeable)
+    p->writeopen = 0;
+  else
+    p->readopen = 0;
+  if(p->readopen == 0 && p->writeopen == 0)
+    kfree((char *) p, PAGE);
+}
+
+int
+pipe_write(struct pipe *p, char *addr, int n)
+{
+  int i;
+
+  for(i = 0; i < n; i++){
+    while(((p->writep + 1) % PIPESIZE) == p->readp){
+      if(p->readopen == 0)
+        return -1;
+      sleep(&p->writep);
+    }
+    p->data[p->writep] = addr[i];
+    p->writep = (p->writep + 1) % PIPESIZE;
+  }
+  return i;
+}
+
+int
+pipe_read(struct pipe *p, char *addr, int n)
+{
+  int i;
+
+  while(p->readp == p->writep){
+    if(p->writeopen == 0)
+      return 0;
+    sleep(&p->readp);
+  }
+
+  for(i = 0; i < n; i++){
+    if(p->readp == p->writep)
+      break;
+    addr[i] = p->data[p->readp];
+    p->readp = (p->readp + 1) % PIPESIZE;
+  }
+  return i;
+}