net: extend Sock with methods for robust send & read until terminator

Introduce two high level, convenience methods in the `Sock` class:

* `SendComplete()`: keep trying to send the specified data until either
  successfully sent all of it, timeout or interrupted.

* `RecvUntilTerminator()`: read until a terminator is encountered (never
  after it), timeout or interrupted.

These will be convenient in the I2P SAM implementation.

`SendComplete()` can also be used in the SOCKS5 implementation instead
of calling `send()` directly.

1 files changed, 29 insertions, 0 deletions

diff --git a/src/util/sock.h b/src/util/sock.h
index 2d9cac14af..209d30def4 100644
--- a/src/util/sock.h
+++ b/src/util/sock.h
@@ -6,6 +6,7 @@
 #define BITCOIN_UTIL_SOCK_H
 
 #include <compat.h>
+#include <threadinterrupt.h>
 #include <util/time.h>
 
 #include <chrono>
@@ -114,6 +115,34 @@ public:
                       Event requested,
                       Event* occurred = nullptr) const;
 
+    /* Higher level, convenience, methods. These may throw. */
+
+    /**
+     * Send the given data, retrying on transient errors.
+     * @param[in] data Data to send.
+     * @param[in] timeout Timeout for the entire operation.
+     * @param[in] interrupt If this is signaled then the operation is canceled.
+     * @throws std::runtime_error if the operation cannot be completed. In this case only some of
+     * the data will be written to the socket.
+     */
+    virtual void SendComplete(const std::string& data,
+                              std::chrono::milliseconds timeout,
+                              CThreadInterrupt& interrupt) const;
+
+    /**
+     * Read from socket until a terminator character is encountered. Will never consume bytes past
+     * the terminator from the socket.
+     * @param[in] terminator Character up to which to read from the socket.
+     * @param[in] timeout Timeout for the entire operation.
+     * @param[in] interrupt If this is signaled then the operation is canceled.
+     * @return The data that has been read, without the terminating character.
+     * @throws std::runtime_error if the operation cannot be completed. In this case some bytes may
+     * have been consumed from the socket.
+     */
+    virtual std::string RecvUntilTerminator(uint8_t terminator,
+                                            std::chrono::milliseconds timeout,
+                                            CThreadInterrupt& interrupt) const;
+
 private:
     /**
      * Contained socket. `INVALID_SOCKET` designates the object is empty.