Remove the nested read loops in FastCGIConn, hide complexity inside StreamBuffer

stream_buffer.cpp

@@ -0,0 +1,26 @@
+#include "stream_buffer.h"
+
+StreamBuffer::StreamBuffer(int sock, size_t size)
+		: Buffer(size),
+		  sock_(sock) {}
+
+bool StreamBuffer::BufferAtLeast(size_t len) {
+	CHECK_LE(start_ + len, size_);
+
+	while (ReadMaxLen() < len) {
+		auto read_len = read(sock_, WritePtr(), WriteMaxLen());
+		PCHECK(read_len >= 0);
+		if (read_len == 0) {
+			return false;
+		}
+		Wrote(read_len);
+	}
+	return true;
+}
+
+const char *StreamBuffer::Read(size_t len) {
+	if (!BufferAtLeast(len)) {
+		return nullptr;
+	}
+	return Buffer::Read(len);
+}