From 30e8b23e52a9ee5b5735d0179dd572656feeaa6b Mon Sep 17 00:00:00 2001
From: Martin Mares <mj@ucw.cz>
Date: Sun, 19 Oct 2003 16:47:06 +0000
Subject: [PATCH] Added fastbuf backend for reading from file descriptors with
 a given limit. (Very useful for communication over sockets.)

---
 lib/fastbuf.h  |  4 +++
 lib/fb-limfd.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)
 create mode 100644 lib/fb-limfd.c

diff --git a/lib/fastbuf.h b/lib/fastbuf.h
index e08e16a1..8699fe40 100644
--- a/lib/fastbuf.h
+++ b/lib/fastbuf.h
@@ -82,6 +82,10 @@ struct fastbuf *fbmem_clone_read(struct fastbuf *);	/* Create reading fastbuf */
 
 struct fastbuf *bopen_mm(byte *name, uns mode);
 
+/* FastI on file descriptors with limit */
+
+struct fastbuf *bopen_limited_fd(int fd, uns bufsize, uns limit);
+
 /* Configuring stream parameters */
 
 int bconfig(struct fastbuf *f, uns type, int data);
diff --git a/lib/fb-limfd.c b/lib/fb-limfd.c
new file mode 100644
index 00000000..c1b6cb2c
--- /dev/null
+++ b/lib/fb-limfd.c
@@ -0,0 +1,74 @@
+/*
+ *	Sherlock Library -- Fast Buffered Input on Limited File Descriptors
+ *
+ *	(c) 2003 Martin Mares <mj@ucw.cz>
+ *
+ *	This software may be freely distributed and used according to the terms
+ *	of the GNU Lesser General Public License.
+ */
+
+#include "lib/lib.h"
+#include "lib/fastbuf.h"
+
+#include <stdlib.h>
+#include <unistd.h>
+
+struct fb_limfd {
+  struct fastbuf fb;
+  int fd;				/* File descriptor */
+  int limit;
+};
+#define FB_LIMFD(f) ((struct fb_limfd *)(f)->is_fastbuf)
+
+static int
+bfl_refill(struct fastbuf *f)
+{
+  int max = MIN(FB_LIMFD(f)->limit - f->pos, f->bufend - f->buffer);
+  int l = read(FB_LIMFD(f)->fd, f->buffer, max);
+  if (l < 0)
+    die("Error reading %s: %m", f->name);
+  f->bptr = f->buffer;
+  f->bstop = f->buffer + l;
+  f->pos += l;
+  return l;
+}
+
+static void
+bfl_close(struct fastbuf *f)
+{
+  xfree(f);
+}
+
+struct fastbuf *
+bopen_limited_fd(int fd, uns buflen, uns limit)
+{
+  struct fb_limfd *F = xmalloc(sizeof(struct fb_limfd) + buflen);
+  struct fastbuf *f = &F->fb;
+
+  bzero(F, sizeof(*F));
+  f->buffer = (char *)(F+1);
+  f->bptr = f->bstop = f->buffer;
+  f->bufend = f->buffer + buflen;
+  f->name = "limited-fd";
+  F->fd = fd;
+  F->limit = limit;
+  f->refill = bfl_refill;
+  f->close = bfl_close;
+  return f;
+}
+
+#ifdef TEST
+
+int main(int argc, char **argv)
+{
+  struct fastbuf *f = bopen_limited_fd(0, 3, 13);
+  struct fastbuf *o = bfdopen_shared(1, 16);
+  int c;
+  while ((c = bgetc(f)) >= 0)
+    bputc(o, c);
+  bclose(o);
+  bclose(f);
+  return 0;
+}
+
+#endif
-- 
2.39.2