From 772feb6051978427ada1ebd8c5b3592bc737159f Mon Sep 17 00:00:00 2001
From: Gareth Sylvester-Bradley <garethsb@nvidia.com>
Date: Thu, 4 May 2023 22:10:42 +0100
Subject: [PATCH] Add nmos::parse_fmtp_channel_order

---
 Development/nmos/channels.cpp           | 48 +++++++++++++++++++++++++
 Development/nmos/channels.h             |  1 +
 Development/nmos/test/channels_test.cpp | 37 +++++++++++++++++++
 3 files changed, 86 insertions(+)

diff --git a/Development/nmos/channels.cpp b/Development/nmos/channels.cpp
index 611e22f3d..e9f596099 100644
--- a/Development/nmos/channels.cpp
+++ b/Development/nmos/channels.cpp
@@ -155,4 +155,52 @@ namespace nmos
 
         return channel_order.str();
     }
+
+    // See SMPTE ST 2110-30:2017 Section 6.2.2 Channel Order Convention
+    std::vector<nmos::channel_symbol> parse_fmtp_channel_order(const utility::string_t& channel_order)
+    {
+        std::vector<nmos::channel_symbol> channels;
+
+        const auto first = channel_order.data();
+        const auto last = first + channel_order.size();
+        auto it = first;
+
+        // check prefix
+
+        static const auto prefix = U("SMPTE2110.(");
+        auto pit = &prefix[0];
+        while (it != last && *pit != U('\0') && *it == *pit) ++it, ++pit;
+        if (*pit != U('\0')) return {};
+
+        // parse comma-separated channel group symbols
+
+        while (true)
+        {
+            const auto git = it;
+            while (it != last && *it != U(')') && *it != U(',')) ++it;
+            if (it == last) return {};
+
+            const channel_group_symbol symbol(utility::string_t(git, it));
+
+            // hm, does not handle 22.2 Surround ('222'), SDI audio group ('SGRP') or Undefined ('U01' to 'U64')
+            auto group = std::find_if(details::channel_groups.begin(), details::channel_groups.end(),
+                [&](const std::pair<std::vector<channel_symbol>, channel_group_symbol>& group)
+            {
+                return symbol == group.second;
+            });
+            if (details::channel_groups.end() == group) return {};
+            channels.insert(channels.end(), group->first.begin(), group->first.end());
+
+            if (*it == U(')')) break;
+            ++it;
+        }
+
+        // check suffix
+
+        if (it == last) return {};
+        ++it;
+        if (it != last) return {};
+
+        return channels;
+    }
 }
diff --git a/Development/nmos/channels.h b/Development/nmos/channels.h
index 77e12a945..df0522b12 100644
--- a/Development/nmos/channels.h
+++ b/Development/nmos/channels.h
@@ -113,6 +113,7 @@ namespace nmos
 
     // See SMPTE ST 2110-30:2017 Section 6.2.2 Channel Order Convention
     utility::string_t make_fmtp_channel_order(const std::vector<channel_symbol>& channels);
+    std::vector<nmos::channel_symbol> parse_fmtp_channel_order(const utility::string_t& channel_order);
 }
 
 #endif
diff --git a/Development/nmos/test/channels_test.cpp b/Development/nmos/test/channels_test.cpp
index 1868ee853..ce316e592 100644
--- a/Development/nmos/test/channels_test.cpp
+++ b/Development/nmos/test/channels_test.cpp
@@ -28,3 +28,40 @@ BST_TEST_CASE(testMakeFmtpChannelOrder)
     const std::vector<nmos::channel_symbol> example_3{ M1, M1, M1, M1, L, R, C, LFE };
     BST_REQUIRE_EQUAL(U("SMPTE2110.(M,M,M,M,ST,U02)"), nmos::make_fmtp_channel_order(example_3));
 }
+
+////////////////////////////////////////////////////////////////////////////////////////////
+BST_TEST_CASE(testParseFmtpChannelOrder)
+{
+    using namespace nmos::channel_symbols;
+
+    // two simple examples
+
+    const std::vector<nmos::channel_symbol> stereo{ L, R };
+    BST_REQUIRE_EQUAL(stereo, nmos::parse_fmtp_channel_order(U("SMPTE2110.(ST)")));
+
+    const std::vector<nmos::channel_symbol> dual_mono{ M1, M2 };
+    BST_REQUIRE_EQUAL(dual_mono, nmos::parse_fmtp_channel_order(U("SMPTE2110.(DM)")));
+
+    // two examples from ST 2110-30:2017 Section 6.2.2 Channel Order Convention
+
+    const std::vector<nmos::channel_symbol> example_1{ L, R, C, LFE, Ls, Rs, L, R };
+    BST_REQUIRE_EQUAL(example_1, nmos::parse_fmtp_channel_order(U("SMPTE2110.(51,ST)")));
+
+    //const std::vector<nmos::channel_symbol> example_2{ M1, M1, M1, M1, L, R, Undefined(1), Undefined(2) };
+    //BST_REQUIRE_EQUAL(example_2, nmos::parse_fmtp_channel_order(U("SMPTE2110.(M,M,M,M,ST,U02)")));
+
+    // bad examples
+
+    const std::vector<nmos::channel_symbol> empty;
+    BST_REQUIRE_EQUAL(empty, nmos::parse_fmtp_channel_order(U("SMPTE2110.(51,ST)BAD")));
+    BST_REQUIRE_EQUAL(empty, nmos::parse_fmtp_channel_order(U("SMPTE2110.(51,ST,)")));
+    BST_REQUIRE_EQUAL(empty, nmos::parse_fmtp_channel_order(U("SMPTE2110.(51,,ST)")));
+    BST_REQUIRE_EQUAL(empty, nmos::parse_fmtp_channel_order(U("SMPTE2110.(51,BAD)")));
+    BST_REQUIRE_EQUAL(empty, nmos::parse_fmtp_channel_order(U("SMPTE2110.(51,ST")));
+    BST_REQUIRE_EQUAL(empty, nmos::parse_fmtp_channel_order(U("SMPTE2110.(51,")));
+    BST_REQUIRE_EQUAL(empty, nmos::parse_fmtp_channel_order(U("SMPTE2110.(51")));
+    BST_REQUIRE_EQUAL(empty, nmos::parse_fmtp_channel_order(U("SMPTE2110.(")));
+    BST_REQUIRE_EQUAL(empty, nmos::parse_fmtp_channel_order(U("SMPTE2110.")));
+    BST_REQUIRE_EQUAL(empty, nmos::parse_fmtp_channel_order(U("BAD")));
+    BST_REQUIRE_EQUAL(empty, nmos::parse_fmtp_channel_order(U("")));
+}