c_minilib_sip_codec

c_minilib_sip_codec is a lightweight, modular C library for parsing, decoding, and generating SIP messages. Designed for embedded systems and minimalist runtimes, it offers structured access to SIP fields, extensible encoding/decoding logic, and clean memory handling.

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✨ Features

• Full SIP Message Lifecycle: Supports parsing and generating SIP requests/responses.
• Structured Field Access: Direct access to decoded fields like From, To, CSeq, Via, Call-ID, etc.
• Custom Header Support: Arbitrary headers preserved and handled generically.
• Macro-Free C API: Explicit, predictable interface—ideal for embedded or static analysis-sensitive environments.
• Modular Design: Header-based decoder/encoder dispatch for easy extension.
• Comprehensive Tests: Full test coverage with Unity.
• Safe Buffer Management: Internal dynamic buffer management to avoid overflows.

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📥 Example Usage

generate.c

#include <c_minilib_sip_codec.h>
#include <stdio.h>

int main(void) {
  struct cmsc_SipMessage *msg = NULL;
  const char *buf = NULL;
  uint32_t len = 0;

  cmsc_init();
  cmsc_sipmsg_create_with_buf(&msg);

  cmsc_sipmsg_insert_request_line(
      strlen("SIP/2.0"), "SIP/2.0",
      strlen("sip:bob@example.com"), "sip:bob@example.com",
      strlen("INVITE"), "INVITE", msg);

  cmsc_sipmsg_insert_from(strlen("<sip:alice@example.com>"),
                          "<sip:alice@example.com>", strlen("123"), "123", msg);

  cmsc_sipmsg_insert_to(strlen("<sip:bob@example.com>"),
                        "<sip:bob@example.com>", strlen("456"), "456", msg);

  cmsc_generate_sip(msg, &len, &buf);
  fwrite(buf, 1, len, stdout);

  free((void *)buf);
  cmsc_sipmsg_destroy_with_buf(&msg);
  cmsc_destroy();
  return 0;
}

parse.c

#include <c_minilib_sip_codec.h>
#include <stdio.h>

int main(void) {
  cmsc_init();
  struct cmsc_SipMessage *msg = NULL;

  const char *raw_msg = "INVITE sip:bob@example.com SIP/2.0\r\n"
                        "From: <sip:alice@example.com>;tag=123\r\n"
                        "To: <sip:bob@example.com>;tag=456\r\n"
                        "Call-ID: abc123\r\n"
                        "CSeq: 1 INVITE\r\n\r\n";

  cmsc_parse_sip(strlen(raw_msg), raw_msg, &msg);

  struct cmsc_String from = cmsc_bs_msg_to_string(&msg->from.uri, msg);
  printf("From URI: %.*s\n", from.len, from.buf);

  cmsc_sipmsg_destroy(&msg);
  cmsc_destroy();
  return 0;
}

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⚙️ Build Instructions

Using Meson:

meson setup build
meson compile -C build

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✅ Run Tests

meson test -C build

Includes test coverage for:

• Parsing requests and responses
• Header decoding (To, From, Via, etc.)
• Buffer overflows
• SIP generation and reconstruction

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🛠️ Development Tools

Automated using Invoke:

inv install     # Install dependencies
inv build       # Build with Meson
inv test        # Run all tests
inv lint        # Run clang-tidy checks
inv format      # Apply clang-format
inv clean       # Clean build artifacts

Supports --debug and --backtrace build flags.

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🧠 SIP Decoding Logic

Decoding is modular:

• Recognized headers are parsed and attached directly to cmsc_SipMessage.
• Remaining headers are preserved as generic key/value pairs.
• Structured access through buffer-backed string views.
• Includes iterator-based parsing for arguments like branch, ttl, received.

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🖋️ Example Outputs

Example-generated and parsed messages are available in the example/ directory:

• generate.c: Creates a SIP request and writes it to a file named message.sip.
• parse.c: Loads the message.sip file, parses it using cmsc_parse_sip(), and prints key fields such as From, To, Call-ID, CSeq, and message body to stdout.

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📄 License

MIT License. See LICENSE for full details.