Fix libsndfile build and add CI

.github/workflows/build.yml

@@ -102,6 +102,49 @@ jobs:
         name: Linux tarball
         path: ${{runner.workspace}}/build/${{env.install_name}}.tar.gz
 
+  build_with_libsndfile:
+    runs-on: ubuntu-18.04
+    steps:
+    - name: Set install name
+      run: |
+        echo "install_ref=${GITHUB_REF##*/}" >> "$GITHUB_ENV"
+        echo "install_name=sfizz-${GITHUB_REF##*/}-linux" >> "$GITHUB_ENV"
+    - uses: actions/checkout@v2
+      with:
+        submodules: recursive
+    - name: Set up dependencies
+      run: |
+        sudo apt-get update && \
+        sudo apt-get install \
+          ninja-build \
+          libsndfile1-dev
+    - name: Create Build Environment
+      shell: bash
+      working-directory: ${{runner.workspace}}
+      run: cmake -E make_directory build
+    - name: Configure CMake
+      shell: bash
+      working-directory: ${{runner.workspace}}/build
+      run: |
+        cmake "$GITHUB_WORKSPACE" -G Ninja \
+          -DCMAKE_BUILD_TYPE="$BUILD_TYPE" \
+          -DSFIZZ_JACK=OFF \
+          -DSFIZZ_VST=OFF \
+          -DSFIZZ_LV2_UI=OFF \
+          -DSFIZZ_PUREDATA=OFF \
+          -DSFIZZ_USE_SNDFILE=ON \
+          -DSFIZZ_TESTS=ON \
+          -DSFIZZ_SHARED=OFF \
+          -DSFIZZ_STATIC_DEPENDENCIES=OFF \
+          -DSFIZZ_LV2=OFF
+    - name: Build tests
+      shell: bash
+      working-directory: ${{runner.workspace}}/build
+      run: cmake --build . --config "$BUILD_TYPE" -j 2 --target sfizz_tests
+    - name: Run tests
+      shell: bash
+      run: ${{runner.workspace}}/build/tests/sfizz_tests
+
   build_for_macos:
     runs-on: macos-11
     steps:

external/st_audiofile/src/st_audiofile_sndfile.c

@@ -17,8 +17,92 @@
 struct st_audio_file {
     SNDFILE* snd;
     SF_INFO info;
+    // Virtual IO data
+    const void* data;
+    sf_count_t offset;
+    sf_count_t size;
 };
 
+static sf_count_t sndfile_vio_get_filelen(void *user_data)
+{
+	const struct st_audio_file* af = user_data;
+	return af->size;
+}
+
+static sf_count_t sndfile_vio_seek(sf_count_t offset, int whence, void *user_data)
+{
+	struct st_audio_file* af = user_data;
+
+    sf_count_t new_offset = af->offset;
+	switch(whence) {
+        case SEEK_SET:
+            new_offset = offset;
+            break;
+        case SEEK_CUR:
+            new_offset += offset;
+            break;
+        case SEEK_END:
+            new_offset = af->size + offset;
+            break;
+	}
+
+	if( ( new_offset >= 0 ) && ( new_offset < af->size ) ) {
+		af->offset = new_offset;
+	} else {
+		return 1;
+	}
+
+	return 0;
+}
+
+static sf_count_t sndfile_vio_read(void *ptr, sf_count_t count, void *user_data)
+{
+	struct st_audio_file* af = user_data;
+    sf_count_t remaining = af->size - af->offset;
+    sf_count_t to_read = remaining > count ? count : remaining;
+    memcpy(ptr, af->data + af->offset, to_read);
+    af->offset += to_read;
+	return to_read;
+}
+
+static sf_count_t sndfile_vio_write(const void *ptr, sf_count_t count, void *user_data)
+{
+	(void)ptr;
+	(void)count;
+	(void)user_data;
+	return -1;
+}
+
+static sf_count_t sndfile_vio_tell(void *user_data)
+{
+	const struct st_audio_file* af = user_data;
+	return af->offset;
+}
+
+
+st_audio_file* st_open_memory(const void* memory, size_t length)
+{
+    st_audio_file* af = (st_audio_file*)malloc(sizeof(st_audio_file));
+    if (!af)
+        return NULL;
+
+    memset(&af->info, 0, sizeof(SF_INFO));
+    af->data = memory;
+    af->size = length;
+    af->offset = 0;
+
+    SF_VIRTUAL_IO virtual_io = {
+        .get_filelen = sndfile_vio_get_filelen,
+        .seek = sndfile_vio_seek,
+        .read = sndfile_vio_read,
+        .write = sndfile_vio_write,
+        .tell = sndfile_vio_tell
+    };
+
+    af->snd = sf_open_virtual(&virtual_io, SFM_READ, &af->info, af);
+    return af;
+}
+
 st_audio_file* st_open_file(const char* filename)
 {
     st_audio_file* af = (st_audio_file*)malloc(sizeof(st_audio_file));

src/sfizz/AudioReader.cpp

@@ -68,9 +68,9 @@ bool BasicSndfileReader::getWavetableInfo(WavetableInfo& wt)
 
 bool BasicSndfileReader::getInstrumentInfo(InstrumentInfo& instrument)
 {
-#if defined(SFIZZ_USE_SNDFILE)
+#if 0 // Our metadata reader is more general, e.g. for FLAC
     SNDFILE* sndfile = reinterpret_cast<SNDFILE*>(handle_.get_sndfile_handle());
-    SF_INSTRUMENT* sfins = instrument;
+    SF_INSTRUMENT* sfins = &instrument;
     if (sf_command(sndfile, SFC_GET_INSTRUMENT, sfins, sizeof(SF_INSTRUMENT)) == SF_TRUE)
         return true;
 #else