[Qemu-devel] [PATCH 07/10] io: add qio_channel_read/write_all

[Paolo Bonzini <pbonzini@redhat.com>]

It is pretty common to read a fixed-size buffer from a socket.  Add a
function that does this, either with multiple reads (on blocking sockets)
or by yielding if called from a coroutine.

Cc: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/io/channel.h | 36 ++++++++++++++++++++++++++++++++++-
 io/channel.c         | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/include/io/channel.h b/include/io/channel.h
index db9bb022a1..9cfb4d081f 100644
--- a/include/io/channel.h
+++ b/include/io/channel.h
@@ -299,7 +299,7 @@ ssize_t qio_channel_writev(QIOChannel *ioc,
                            Error **errp);
 
 /**
- * qio_channel_readv:
+ * qio_channel_read:
  * @ioc: the channel object
  * @buf: the memory region to read data into
  * @buflen: the length of @buf
@@ -315,6 +315,23 @@ ssize_t qio_channel_read(QIOChannel *ioc,
                          Error **errp);
 
 /**
+ * qio_channel_read_all:
+ * @ioc: the channel object
+ * @buf: the memory region to read data into
+ * @buflen: the number of bytes to @buf
+ * @errp: pointer to a NULL-initialized error object
+ *
+ * Reads @buflen bytes into @buf, possibly blocking or (if the
+ * channel is non-blocking) yielding from the current coroutine
+ * multiple times until the entire content is read.  Otherwise
+ * behaves as qio_channel_read().
+ */
+ssize_t coroutine_fn qio_channel_read_all(QIOChannel *ioc,
+                                          char *buf,
+                                          size_t buflen,
+                                          Error **errp);
+
+/**
  * qio_channel_write:
  * @ioc: the channel object
  * @buf: the memory regions to send data from
@@ -331,6 +348,23 @@ ssize_t qio_channel_write(QIOChannel *ioc,
                           Error **errp);
 
 /**
+ * qio_channel_write_all:
+ * @ioc: the channel object
+ * @buf: the memory region to write data into
+ * @buflen: the number of bytes to @buf
+ * @errp: pointer to a NULL-initialized error object
+ *
+ * Writes @buflen bytes from @buf, possibly blocking or (if the
+ * channel is non-blocking) yielding from the current coroutine
+ * multiple times until the entire content is written.  Otherwise
+ * behaves as qio_channel_write().
+ */
+ssize_t coroutine_fn qio_channel_write_all(QIOChannel *ioc,
+                                           const char *buf,
+                                           size_t buflen,
+                                           Error **errp);
+
+/**
  * qio_channel_set_blocking:
  * @ioc: the channel object
  * @enabled: the blocking flag state
diff --git a/io/channel.c b/io/channel.c
index 1cfb8b33a2..7ab3f4eede 100644
--- a/io/channel.c
+++ b/io/channel.c
@@ -113,6 +113,60 @@ ssize_t qio_channel_read(QIOChannel *ioc,
 }
 
 
+ssize_t qio_channel_read_all(QIOChannel *ioc,
+                             char *buf,
+                             size_t buflen,
+                             Error **errp)
+{
+    ssize_t total = 0;
+    while (buflen > 0) {
+        ssize_t n_read = qio_channel_read(ioc, buf, buflen, errp);
+
+        if (n_read == QIO_CHANNEL_ERR_BLOCK) {
+            assert(ioc->ctx);
+            qio_channel_yield(ioc, G_IO_IN);
+            continue;
+        }
+        if (n_read < 0) {
+            return n_read;
+        }
+
+        buf += n_read;
+        total += n_read;
+        buflen -= n_read;
+    }
+
+    return total;
+}
+
+
+ssize_t qio_channel_write_all(QIOChannel *ioc,
+                              const char *buf,
+                              size_t buflen,
+                              Error **errp)
+{
+    ssize_t total = 0;
+    while (buflen > 0) {
+        ssize_t n_written = qio_channel_write(ioc, buf, buflen, errp);
+
+        if (n_written == QIO_CHANNEL_ERR_BLOCK) {
+            assert(ioc->ctx);
+            qio_channel_yield(ioc, G_IO_OUT);
+            continue;
+        }
+        if (n_written < 0) {
+            return n_written;
+        }
+
+        buf += n_written;
+        total += n_written;
+        buflen -= n_written;
+    }
+
+    return total;
+}
+
+
 ssize_t qio_channel_write(QIOChannel *ioc,
                           const char *buf,
                           size_t buflen,
-- 
2.13.5