From 9d96c3eb02121156002e75fd516b47dcb4cc59cb Mon Sep 17 00:00:00 2001
From: Simon Tatham <anakin@pobox.com>
Date: Fri, 18 May 2018 07:22:57 +0100
Subject: [PATCH] bufchain: new combined fetch + consume functions.

bufchain_fetch_consume is a one-stop function that moves a given
number of bytes out of the head of a bufchain into an output buffer,
removing them from the bufchain in the process.

That function will fail an assertion (just like bufchain_fetch) if the
bufchain doesn't actually _have_ at least that many bytes to read, so
I also provide bufchain_try_fetch_consume which will return a success
or failure status.

Nothing uses these functions yet, but they will.
---
 misc.c | 16 ++++++++++++++++
 misc.h |  2 ++
 2 files changed, 18 insertions(+)

diff --git a/misc.c b/misc.c
index fb32da5d..08198004 100644
--- a/misc.c
+++ b/misc.c
@@ -751,6 +751,22 @@ void bufchain_fetch(bufchain *ch, void *data, int len)
     }
 }
 
+void bufchain_fetch_consume(bufchain *ch, void *data, int len)
+{
+    bufchain_fetch(ch, data, len);
+    bufchain_consume(ch, len);
+}
+
+int bufchain_try_fetch_consume(bufchain *ch, void *data, int len)
+{
+    if (ch->buffersize >= len) {
+        bufchain_fetch_consume(ch, data, len);
+        return TRUE;
+    } else {
+        return FALSE;
+    }
+}
+
 /* ----------------------------------------------------------------------
  * My own versions of malloc, realloc and free. Because I want
  * malloc and realloc to bomb out and exit the program if they run
diff --git a/misc.h b/misc.h
index 32e7bc32..d2efdca7 100644
--- a/misc.h
+++ b/misc.h
@@ -82,6 +82,8 @@ void bufchain_add(bufchain *ch, const void *data, int len);
 void bufchain_prefix(bufchain *ch, void **data, int *len);
 void bufchain_consume(bufchain *ch, int len);
 void bufchain_fetch(bufchain *ch, void *data, int len);
+void bufchain_fetch_consume(bufchain *ch, void *data, int len);
+int bufchain_try_fetch_consume(bufchain *ch, void *data, int len);
 
 int validate_manual_hostkey(char *key);