1 files changed, 261 insertions, 0 deletions
diff --git a/gfx/ots/src/variations.cc b/gfx/ots/src/variations.cc
new file mode 100644
index 000000000..cb7e5fb32
--- /dev/null
+++ b/gfx/ots/src/variations.cc
@@ -0,0 +1,261 @@
+// Copyright (c) 2018 The OTS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "layout.h"
+
+#include "fvar.h"
+
+// OpenType Variations Common Table Formats
+
+#define TABLE_NAME "Variations" // XXX: use individual table names
+
+namespace {
+
+bool ParseVariationRegionList(const ots::Font* font, const uint8_t* data, const size_t length,
+                              uint16_t* regionCount) {
+  ots::Buffer subtable(data, length);
+
+  uint16_t axisCount;
+
+  if (!subtable.ReadU16(&axisCount) ||
+      !subtable.ReadU16(regionCount)) {
+    return OTS_FAILURE_MSG("Failed to read variation region list header");
+  }
+
+  if (*regionCount == 0) {
+    return true;
+  }
+
+  const ots::OpenTypeFVAR* fvar =
+    static_cast<ots::OpenTypeFVAR*>(font->GetTypedTable(OTS_TAG_FVAR));
+  if (!fvar) {
+    return OTS_FAILURE_MSG("Required fvar table is missing");
+  }
+  if (axisCount != fvar->AxisCount()) {
+    return OTS_FAILURE_MSG("Axis count mismatch");
+  }
+
+  for (unsigned i = 0; i < *regionCount; i++) {
+    for (unsigned j = 0; j < axisCount; j++) {
+      int16_t startCoord, peakCoord, endCoord;
+      if (!subtable.ReadS16(&startCoord) ||
+          !subtable.ReadS16(&peakCoord) ||
+          !subtable.ReadS16(&endCoord)) {
+        return OTS_FAILURE_MSG("Failed to read region axis coordinates");
+      }
+      if (startCoord > peakCoord || peakCoord > endCoord) {
+        return OTS_FAILURE_MSG("Region axis coordinates out of order");
+      }
+      if (startCoord < -0x4000 || endCoord > 0x4000) {
+        return OTS_FAILURE_MSG("Region axis coordinate out of range");
+      }
+      if ((peakCoord < 0 && endCoord > 0) ||
+          (peakCoord > 0 && startCoord < 0)) {
+        return OTS_FAILURE_MSG("Invalid region axis coordinates");
+      }
+    }
+  }
+
+  return true;
+}
+
+bool
+ParseVariationDataSubtable(const ots::Font* font, const uint8_t* data, const size_t length,
+                           const uint16_t regionCount,
+                           uint16_t* regionIndexCount) {
+  ots::Buffer subtable(data, length);
+
+  uint16_t itemCount;
+  uint16_t shortDeltaCount;
+
+  if (!subtable.ReadU16(&itemCount) ||
+      !subtable.ReadU16(&shortDeltaCount) ||
+      !subtable.ReadU16(regionIndexCount)) {
+    return OTS_FAILURE_MSG("Failed to read variation data subtable header");
+  }
+
+  for (unsigned i = 0; i < *regionIndexCount; i++) {
+    uint16_t regionIndex;
+    if (!subtable.ReadU16(&regionIndex) || regionIndex >= regionCount) {
+      return OTS_FAILURE_MSG("Bad region index");
+    }
+  }
+
+  if (!subtable.Skip(size_t(itemCount) * (size_t(shortDeltaCount) + size_t(*regionIndexCount)))) {
+    return OTS_FAILURE_MSG("Failed to read delta data");
+  }
+
+  return true;
+}
+
+} // namespace
+
+namespace ots {
+
+bool
+ParseItemVariationStore(const Font* font,
+                        const uint8_t* data, const size_t length,
+                        std::vector<uint16_t>* regionIndexCounts) {
+  Buffer subtable(data, length);
+
+  uint16_t format;
+  uint32_t variationRegionListOffset;
+  uint16_t itemVariationDataCount;
+
+  if (!subtable.ReadU16(&format) ||
+      !subtable.ReadU32(&variationRegionListOffset) ||
+      !subtable.ReadU16(&itemVariationDataCount)) {
+    return OTS_FAILURE_MSG("Failed to read item variation store header");
+  }
+
+  if (format != 1) {
+    return OTS_FAILURE_MSG("Unknown item variation store format");
+  }
+
+  if (variationRegionListOffset < subtable.offset() + 4 * itemVariationDataCount ||
+      variationRegionListOffset > length) {
+    return OTS_FAILURE_MSG("Invalid variation region list offset");
+  }
+
+  uint16_t regionCount;
+  if (!ParseVariationRegionList(font,
+                                data + variationRegionListOffset,
+                                length - variationRegionListOffset,
+                                &regionCount)) {
+    return OTS_FAILURE_MSG("Failed to parse variation region list");
+  }
+
+  for (unsigned i = 0; i < itemVariationDataCount; i++) {
+    uint32_t offset;
+    if (!subtable.ReadU32(&offset)) {
+      return OTS_FAILURE_MSG("Failed to read variation data subtable offset");
+    }
+    if (offset >= length) {
+      return OTS_FAILURE_MSG("Bad offset to variation data subtable");
+    }
+    uint16_t regionIndexCount = 0;
+    if (!ParseVariationDataSubtable(font, data + offset, length - offset,
+                                    regionCount,
+                                    &regionIndexCount)) {
+      return OTS_FAILURE_MSG("Failed to parse variation data subtable");
+    }
+    if (regionIndexCounts) {
+      regionIndexCounts->push_back(regionIndexCount);
+    }
+  }
+
+  return true;
+}
+
+bool ParseDeltaSetIndexMap(const Font* font, const uint8_t* data, const size_t length) {
+  Buffer subtable(data, length);
+
+  uint16_t entryFormat;
+  uint16_t mapCount;
+
+  if (!subtable.ReadU16(&entryFormat) ||
+      !subtable.ReadU16(&mapCount)) {
+    return OTS_FAILURE_MSG("Failed to read delta set index map header");
+  }
+
+  const uint16_t MAP_ENTRY_SIZE_MASK = 0x0030;
+
+  const uint16_t entrySize = (((entryFormat & MAP_ENTRY_SIZE_MASK) >> 4) + 1);
+  if (!subtable.Skip(entrySize * mapCount)) {
+    return OTS_FAILURE_MSG("Failed to read delta set index map data");
+  }
+
+  return true;
+}
+
+bool ParseVariationData(const Font* font, const uint8_t* data, size_t length,
+                        size_t axisCount, size_t sharedTupleCount) {
+  Buffer subtable(data, length);
+
+  uint16_t tupleVariationCount;
+  uint16_t dataOffset;
+  if (!subtable.ReadU16(&tupleVariationCount) ||
+      !subtable.ReadU16(&dataOffset)) {
+    return OTS_FAILURE_MSG("Failed to read variation data header");
+  }
+
+  if (dataOffset > length) {
+    return OTS_FAILURE_MSG("Invalid serialized data offset");
+  }
+
+  tupleVariationCount &= 0x0FFF; // mask off flags
+
+  const uint16_t EMBEDDED_PEAK_TUPLE = 0x8000;
+  const uint16_t INTERMEDIATE_REGION = 0x4000;
+  const uint16_t TUPLE_INDEX_MASK    = 0x0FFF;
+
+  for (unsigned i = 0; i < tupleVariationCount; i++) {
+    uint16_t variationDataSize;
+    uint16_t tupleIndex;
+
+    if (!subtable.ReadU16(&variationDataSize) ||
+        !subtable.ReadU16(&tupleIndex)) {
+      return OTS_FAILURE_MSG("Failed to read tuple variation header");
+    }
+
+    if (tupleIndex & EMBEDDED_PEAK_TUPLE) {
+      for (unsigned axis = 0; axis < axisCount; axis++) {
+        int16_t coordinate;
+        if (!subtable.ReadS16(&coordinate)) {
+          return OTS_FAILURE_MSG("Failed to read tuple coordinate");
+        }
+        if (coordinate < -0x4000 || coordinate > 0x4000) {
+          return OTS_FAILURE_MSG("Invalid tuple coordinate");
+        }
+      }
+    }
+
+    if (tupleIndex & INTERMEDIATE_REGION) {
+      std::vector<int16_t> startTuple(axisCount);
+      for (unsigned axis = 0; axis < axisCount; axis++) {
+        int16_t coordinate;
+        if (!subtable.ReadS16(&coordinate)) {
+          return OTS_FAILURE_MSG("Failed to read tuple coordinate");
+        }
+        if (coordinate < -0x4000 || coordinate > 0x4000) {
+          return OTS_FAILURE_MSG("Invalid tuple coordinate");
+        }
+        startTuple.push_back(coordinate);
+      }
+
+      std::vector<int16_t> endTuple(axisCount);
+      for (unsigned axis = 0; axis < axisCount; axis++) {
+        int16_t coordinate;
+        if (!subtable.ReadS16(&coordinate)) {
+          return OTS_FAILURE_MSG("Failed to read tuple coordinate");
+        }
+        if (coordinate < -0x4000 || coordinate > 0x4000) {
+          return OTS_FAILURE_MSG("Invalid tuple coordinate");
+        }
+        endTuple.push_back(coordinate);
+      }
+
+      for (unsigned axis = 0; axis < axisCount; axis++) {
+        if (startTuple[axis] > endTuple[axis]) {
+          return OTS_FAILURE_MSG("Invalid intermediate range");
+        }
+      }
+    }
+
+    if (!(tupleIndex & EMBEDDED_PEAK_TUPLE)) {
+      tupleIndex &= TUPLE_INDEX_MASK;
+      if (tupleIndex >= sharedTupleCount) {
+        return OTS_FAILURE_MSG("Tuple index out of range");
+      }
+    }
+  }
+
+  // TODO: we don't attempt to interpret the serialized data block
+
+  return true;
+}
+
+} // namespace ots
+
+#undef TABLE_NAME