From ffe929d8eab7bc9ac8ce716e210ea067d7d9c1c4 Mon Sep 17 00:00:00 2001
From: Tau <tau@nowhere>
Date: Thu, 8 Nov 2018 14:19:15 -0500
Subject: [PATCH] jvs/jvs-util.c: Add JVS dispatch helper

---
 jvs/jvs-util.c  | 109 ++++++++++++++++++++++++++++++++++++++++++++++++
 jvs/jvs-util.h  |  21 ++++++++++
 jvs/meson.build |   2 +
 3 files changed, 132 insertions(+)
 create mode 100644 jvs/jvs-util.c
 create mode 100644 jvs/jvs-util.h

diff --git a/jvs/jvs-util.c b/jvs/jvs-util.c
new file mode 100644
index 0000000..1bbe10e
--- /dev/null
+++ b/jvs/jvs-util.c
@@ -0,0 +1,109 @@
+#include <windows.h>
+
+#include <assert.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "hook/iobuf.h"
+
+#include "jvs/jvs-frame.h"
+#include "jvs/jvs-util.h"
+
+#include "util/dprintf.h"
+
+typedef HRESULT (*jvs_dispatch_fn_t)(
+        void *ctx,
+        struct const_iobuf *req,
+        struct iobuf *resp);
+
+void jvs_crack_request(
+        const void *bytes,
+        size_t nbytes,
+        struct iobuf *resp,
+        uint8_t jvs_addr,
+        jvs_dispatch_fn_t dispatch_fn,
+        void *dispatch_ctx)
+{
+    uint8_t req_bytes[128];
+    uint8_t resp_bytes[128];
+    struct iobuf decode;
+    struct iobuf encode;
+    struct const_iobuf segments;
+    HRESULT hr;
+
+    assert(bytes != NULL);
+    assert(resp != NULL);
+    assert(jvs_addr != 0x00 && (jvs_addr < 0x20 || jvs_addr == 0xFF));
+    assert(dispatch_fn != NULL);
+
+    decode.bytes = req_bytes;
+    decode.nbytes = sizeof(req_bytes);
+    decode.pos = 0;
+
+    hr = jvs_frame_decode(&decode, bytes, nbytes);
+
+    if (FAILED(hr)) {
+        return;
+    }
+
+#if 0
+    dprintf("Decoded request:\n");
+    dump_iobuf(&decode);
+#endif
+
+    if (req_bytes[0] != jvs_addr && req_bytes[0] != 0xFF) {
+        return;
+    }
+
+    iobuf_flip(&segments, &decode);
+    segments.pos = 2;
+
+    encode.bytes = resp_bytes;
+    encode.nbytes = sizeof(resp_bytes);
+    encode.pos = 3;
+
+    /* +1: Don't try to dispatch the trailing checksum byte */
+
+    hr = S_OK; /* I guess an empty request packet is technically valid? */
+
+    while (segments.pos + 1 < segments.nbytes) {
+        hr = dispatch_fn(dispatch_ctx, &segments, &encode);
+
+        if (FAILED(hr)) {
+            break;
+        }
+    }
+
+    if (FAILED(hr)) {
+        /* Send an error in the overall status byte */
+        encode.pos = 3;
+
+        resp_bytes[0] = 0x00;   /* Dest addr (master) */
+        resp_bytes[1] = 0x02;   /* Payload len: Status byte, checksum byte */
+
+        if (hr == HRESULT_FROM_WIN32(ERROR_INSUFFICIENT_BUFFER)) {
+            resp_bytes[2] = 0x04;   /* Status: "Overflow" */
+        } else {
+            resp_bytes[2] = 0x02;   /* Status: Encoutered unsupported command */
+        }
+    } else if (encode.pos == 3) {
+        /* Probably a reset, don't emit a response frame with empty payload */
+        return;
+    } else {
+        /* Send success response */
+        resp_bytes[0] = 0x00;   /* Dest addr (master) */
+        resp_bytes[1] = encode.pos - 2 + 1; /* -2 header +1 checksum */
+        resp_bytes[2] = 0x01;   /* Status: Success */
+    }
+
+#if 0
+    dprintf("Encoding response:\n");
+    dump_iobuf(&encode);
+#endif
+
+    hr = jvs_frame_encode(resp, encode.bytes, encode.pos);
+
+    if (FAILED(hr)) {
+        dprintf("JVS Node: Response encode error: %x\n", (int) hr);
+    }
+}
diff --git a/jvs/jvs-util.h b/jvs/jvs-util.h
new file mode 100644
index 0000000..e3fc4e5
--- /dev/null
+++ b/jvs/jvs-util.h
@@ -0,0 +1,21 @@
+#pragma once
+
+#include <windows.h>
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "hook/iobuf.h"
+
+typedef HRESULT (*jvs_dispatch_fn_t)(
+        void *ctx,
+        struct const_iobuf *req,
+        struct iobuf *resp);
+
+void jvs_crack_request(
+        const void *bytes,
+        size_t nbytes,
+        struct iobuf *resp,
+        uint8_t jvs_addr,
+        jvs_dispatch_fn_t dispatch_fn,
+        void *dispatch_ctx);
diff --git a/jvs/meson.build b/jvs/meson.build
index b08aba3..3c90966 100644
--- a/jvs/meson.build
+++ b/jvs/meson.build
@@ -11,5 +11,7 @@ jvs_lib = static_library(
         'jvs-bus.h',
         'jvs-frame.c',
         'jvs-frame.h',
+        'jvs-util.c',
+        'jvs-util.h',
     ],
 )