move io/Cursor-defs.h to io/Cursor.cpp

[folly.git] / folly / io / Cursor.cpp

diff --git a/folly/io/Cursor.cpp b/folly/io/Cursor.cpp
new file mode 100644 (file)
index 0000000..fe47840
--- /dev/null
+++ b/folly/io/Cursor.cpp
@@ -0,0 +1,70 @@
+/*
+ * Copyright 2016 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <folly/io/Cursor.h>
+
+#include <cstdio>
+#include <folly/ScopeGuard.h>
+
+namespace folly { namespace io {
+
+void Appender::printf(const char* fmt, ...) {
+  va_list ap;
+  va_start(ap, fmt);
+  vprintf(fmt, ap);
+  va_end(ap);
+}
+
+void Appender::vprintf(const char* fmt, va_list ap) {
+  // Make a copy of ap in case we need to retry.
+  // We use ap on the first attempt, so it always gets advanced
+  // passed the used arguments.  We'll only use apCopy if we need to retry.
+  va_list apCopy;
+  va_copy(apCopy, ap);
+  SCOPE_EXIT {
+    va_end(apCopy);
+  };
+
+  // First try writing into our available data space.
+  int ret = vsnprintf(reinterpret_cast<char*>(writableData()), length(),
+                      fmt, ap);
+  if (ret < 0) {
+    throw std::runtime_error("error formatting printf() data");
+  }
+  // vsnprintf() returns the number of characters that would be printed,
+  // not including the terminating nul.
+  if (size_t(ret) < length()) {
+    // All of the data was successfully written.
+    append(ret);
+    return;
+  }
+
+  // There wasn't enough room for the data.
+  // Allocate more room, and then retry.
+  ensure(ret + 1);
+  ret = vsnprintf(reinterpret_cast<char*>(writableData()), length(),
+                  fmt, apCopy);
+  if (ret < 0) {
+    throw std::runtime_error("error formatting printf() data");
+  }
+  if (size_t(ret) >= length()) {
+    // This shouldn't ever happen.
+    throw std::runtime_error("unexpectedly out of buffer space on second "
+                             "vsnprintf() attmept");
+  }
+  append(ret);
+}
+
+}}  // folly::io