1 files changed, 111 insertions, 0 deletions
diff --git a/Src/nsmkv/Lacing.cpp b/Src/nsmkv/Lacing.cpp
new file mode 100644
index 00000000..3341a522
--- /dev/null
+++ b/Src/nsmkv/Lacing.cpp
@@ -0,0 +1,111 @@
+#include "Lacing.h"
+#include "Cluster.h"
+#include "vint.h"
+
+
+
+bool nsmkv::Lacing::GetState(uint8_t flags, const uint8_t *data, size_t data_len, nsmkv::LacingState *state)
+{
+	// TODO: error check by making sure data_len doesn't go below 0
+	switch(flags & BlockBinary::LACE_MASK)
+	{
+	case BlockBinary::NO_LACING:
+		state->laces = 1;
+		state->positions[0] = 0;
+		state->sizes[0] = data_len;
+#ifdef WA_VALIDATE
+		printf("        Lacing = NO_LACING\n");
+#endif
+		return true;
+	case BlockBinary::EBML_LACING:
+		{
+			uint16_t number_of_frames = state->laces = *data++ + 1;
+			uint64_t delta = vint_get_number_bytes(data[0]);
+			state->sizes[0] = vint_read_ptr_len((uint8_t)delta, data);
+			delta++;
+			state->positions[0] = 1;
+			state->positions[1] = 1+state->sizes[0];
+			for (uint16_t i=1;i<number_of_frames-1;i++)
+			{
+				uint8_t this_len = vint_get_number_bytes(data[delta]);
+				state->sizes[i] = vsint_read_ptr_len(this_len, data+delta);
+				state->sizes[i] += state->sizes[i-1];
+				state->positions[i+1] = state->positions[i] + state->sizes[i];
+				delta+=this_len + 1;
+			}
+			state->sizes[number_of_frames-1] = data_len - state->positions[number_of_frames-1] - delta;
+
+			for (uint16_t i=0;i<number_of_frames;i++)
+			{
+				state->positions[i] += delta;
+			}
+#ifdef WA_VALIDATE
+			printf("        Lacing = EBML_LACING\n");
+#endif
+		}
+		return true;
+	case BlockBinary::XIPH_LACING:
+		{
+			const uint8_t *orig_data = data;
+			uint16_t number_of_frames=state->laces = *data++ + 1;
+			for (uint16_t i=0;i!=number_of_frames-1;i++)
+			{
+				size_t frame_len = 0;
+				do
+				{
+					frame_len += *data;
+				} while (data && *data++ == 255);
+				state->sizes[i] = frame_len;
+			}
+			uint64_t delta = data - orig_data;
+			uint64_t last_position = delta;
+			uint64_t last_size = 0;
+			for (uint16_t i=0;i!=number_of_frames;i++)
+			{
+				state->positions[i] = last_position + last_size;
+				last_position = state->positions[i];
+				last_size = state->sizes[i];
+			}
+			state->sizes[number_of_frames-1] = data_len - state->positions[number_of_frames-1];
+#ifdef WA_VALIDATE
+			printf("        Lacing = XIPH LACING\n");
+#endif
+		}
+		return true;
+	case BlockBinary::FIXED_LACING:
+		{
+			uint16_t number_of_frames=state->laces=data[0]+1;
+			uint32_t size_per_frame = (uint32_t)(data_len-1) / number_of_frames;
+			for (uint16_t i=0;i<number_of_frames;i++)
+			{
+				state->positions[i] = (uint64_t)(1 + size_per_frame*i);
+				state->sizes[i] = size_per_frame;
+			}
+#ifdef WA_VALIDATE
+			printf("        Lacing = FIXED LACING\n");
+#endif
+		}
+		return true;
+
+	default:
+		return false;
+	}
+}
+
+bool nsmkv::Lacing::GetFrame(uint16_t frame_number, const uint8_t *data, size_t data_len, const uint8_t **frame, size_t *frame_len, const LacingState *state)
+{
+	if (frame_number >= state->laces)
+		return false;
+
+	const uint8_t *lace = data + state->positions[frame_number];
+	size_t lace_len = (size_t)state->sizes[frame_number];
+	if (lace < data  // if the lace starts before our data
+		|| (state->positions[frame_number] + lace_len) > data_len) // or extends out past our data
+	{
+		return false;
+	}
+
+	*frame = lace;
+	*frame_len = lace_len;
+	return true;
+}