mmfl

minimalist message framing library

overview

prefixed length generic stream protocol format like netstrings

design highlights

• implemented as macros
• no need to link to anything
• few lines only
• no heap usage
• user provided buffers
• buffer must be large enough to hold the largest message
• one memmove per message
• every read-like i/o supported
• intuitive API
• message start detection
• payload ASCII printable only (isprint())

format

messages on wire

\n11 hello world\n2 ok
msg1            msg2

format: \n len <space> message

usage

RB_INIT(rb, buf, size, fd)

Initializes the message reader.

• Parameters:
  • rb: Pointer to an rb_t struct (reader state).
  • buf: Buffer for storing incoming bytes.
  • size: Size of buf. One byte is internally reserved, so actual usable size is size - 1.
  • fd: File descriptor or opaque user context passed to your read function.

Example:

char buffer[128];
rb_t reader;
RB_INIT(&reader, buffer, sizeof(buffer), fd);

RB_READMSG(rb, msg_ptr, msg_len, read_func)

Reads and decodes the next complete message from the stream.

• Parameters:

  • rb: Pointer to the initialized rb_t struct.
  • msg_ptr: Output pointer to the start of the message (within rb->buf).
  • msg_len: Output variable, will contain the length of the message.
  • read_func: A function with signature int (*)(int fd, void *buf, int len) for reading data from the stream (e.g., read() or your own source).

  Returns: 0 when a complete message is available. 1 when more data is needed (incomplete message). -1 on error (e.g., malformed header or read failure).

Example:

char *msg;
int len;
int rc = RB_READMSG(&reader, msg, len, my_read_func);
if (rc == 0) {
    // msg points to message content of length len
}

generating

use printf