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 // Copyright (c) 2009 The Chromium 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 "kern.h"

 // kern - Kerning

 // http://www.microsoft.com/typography/otspec/kern.htm

 #define TABLE_NAME "kern"

 #define DROP_THIS_TABLE \

   do { \

     delete file->kern; \

     file->kern = 0; \

     OTS_FAILURE_MSG("Table discarded"); \

   } while (0)

 namespace ots {

 bool ots_kern_parse(OpenTypeFile *file, const uint8_t *data, size_t length) {

   Buffer table(data, length);

   OpenTypeKERN *kern = new OpenTypeKERN;

   file->kern = kern;

   uint16_t num_tables = 0;

   if (!table.ReadU16(&kern->version) ||

       !table.ReadU16(&num_tables)) {

     return OTS_FAILURE_MSG("Failed to read kern header");

   }

   if (kern->version > 0) {

     DROP_THIS_TABLE;

     return true;

   }

   if (num_tables == 0) {

     OTS_WARNING("num_tables is zero");

     DROP_THIS_TABLE;

     return true;

   }

   kern->subtables.reserve(num_tables);

   for (unsigned i = 0; i < num_tables; ++i) {

     OpenTypeKERNFormat0 subtable;

     uint16_t sub_length = 0;

     if (!table.ReadU16(&subtable.version) ||

         !table.ReadU16(&sub_length)) {

       return OTS_FAILURE_MSG("Failed to read kern subtable %d header", i);

     }

     if (subtable.version > 0) {

       OTS_WARNING("Bad subtable version: %d", subtable.version);

       continue;

     }

     const size_t current_offset = table.offset();

     if (current_offset - 4 + sub_length > length) {

       return OTS_FAILURE_MSG("Bad kern subtable %d offset %ld", i, current_offset);

     }

     if (!table.ReadU16(&subtable.coverage)) {

       return OTS_FAILURE_MSG("Cailed to read kern subtable %d coverage", i);

     }

     if (!(subtable.coverage & 0x1)) {

       OTS_WARNING(

           "We don't support vertical data as the renderer doesn't support it.");

       continue;

     }

     if (subtable.coverage & 0xF0) {

       OTS_WARNING("Reserved fields should zero-filled.");

       DROP_THIS_TABLE;

       return true;

     }

     const uint32_t format = (subtable.coverage & 0xFF00) >> 8;

     if (format != 0) {

       OTS_WARNING("Format %d is not supported.", format);

       continue;

     }

     // Parse the format 0 field.

     uint16_t num_pairs = 0;

     if (!table.ReadU16(&num_pairs) ||

         !table.ReadU16(&subtable.search_range) ||

         !table.ReadU16(&subtable.entry_selector) ||

         !table.ReadU16(&subtable.range_shift)) {

       return OTS_FAILURE_MSG("Failed to read kern subtable %d format 0 fields", i);

     }

     if (!num_pairs) {

       OTS_WARNING("Zero length subtable is found.");

       DROP_THIS_TABLE;

       return true;

     }

     // Sanity checks for search_range, entry_selector, and range_shift. See the

     // comment in ots.cc for details.

     const size_t kFormat0PairSize = 6;  // left, right, and value. 2 bytes each.

     if (num_pairs > (65536 / kFormat0PairSize)) {

       // Some fonts (e.g. calibri.ttf, pykes_peak_zero.ttf) have pairs >= 10923.

       OTS_WARNING("Too large subtable.");

       DROP_THIS_TABLE;

       return true;

     }

     unsigned max_pow2 = 0;

     while (1u << (max_pow2 + 1) <= num_pairs) {

       ++max_pow2;

     }

     const uint16_t expected_search_range = (1u << max_pow2) * kFormat0PairSize;

     if (subtable.search_range != expected_search_range) {

       OTS_WARNING("bad search range");

       subtable.search_range = expected_search_range;

     }

     if (subtable.entry_selector != max_pow2) {

       return OTS_FAILURE_MSG("Bad subtable %d entry selector %d", i, subtable.entry_selector);

     }

     const uint32_t expected_range_shift

         = kFormat0PairSize * num_pairs - subtable.search_range;

     if (subtable.range_shift != expected_range_shift) {

       OTS_WARNING("bad range shift");

       subtable.range_shift = expected_range_shift;

     }

     // Read kerning pairs.

     subtable.pairs.reserve(num_pairs);

     uint32_t last_pair = 0;

     for (unsigned j = 0; j < num_pairs; ++j) {

       OpenTypeKERNFormat0Pair kerning_pair;

       if (!table.ReadU16(&kerning_pair.left) ||

           !table.ReadU16(&kerning_pair.right) ||

           !table.ReadS16(&kerning_pair.value)) {

         return OTS_FAILURE_MSG("Failed to read subtable %d kerning pair %d", i, j);

       }

       const uint32_t current_pair

           = (kerning_pair.left << 16) + kerning_pair.right;

       if (j != 0 && current_pair <= last_pair) {

         OTS_WARNING("Kerning pairs are not sorted.");

         // Many free fonts don't follow this rule, so we don't call OTS_FAILURE

         // in order to support these fonts.

         DROP_THIS_TABLE;

         return true;

       }

       last_pair = current_pair;

       subtable.pairs.push_back(kerning_pair);

     }

     kern->subtables.push_back(subtable);

   }

   if (!kern->subtables.size()) {

     OTS_WARNING("All subtables are removed.");

     DROP_THIS_TABLE;

     return true;

   }

   return true;

 }

 bool ots_kern_should_serialise(OpenTypeFile *file) {

   if (!file->glyf) return false;  // this table is not for CFF fonts.

   return file->kern != NULL;

 }

 bool ots_kern_serialise(OTSStream *out, OpenTypeFile *file) {

   const OpenTypeKERN *kern = file->kern;

   if (!out->WriteU16(kern->version) ||

       !out->WriteU16(kern->subtables.size())) {

     return OTS_FAILURE_MSG("Can't write kern table header");

   }

   for (unsigned i = 0; i < kern->subtables.size(); ++i) {

     const uint16_t length = 14 + (6 * kern->subtables[i].pairs.size());

     if (!out->WriteU16(kern->subtables[i].version) ||

         !out->WriteU16(length) ||

         !out->WriteU16(kern->subtables[i].coverage) ||

         !out->WriteU16(kern->subtables[i].pairs.size()) ||

         !out->WriteU16(kern->subtables[i].search_range) ||

         !out->WriteU16(kern->subtables[i].entry_selector) ||

         !out->WriteU16(kern->subtables[i].range_shift)) {

       return OTS_FAILURE_MSG("Failed to write kern subtable %d", i);

     }

     for (unsigned j = 0; j < kern->subtables[i].pairs.size(); ++j) {

       if (!out->WriteU16(kern->subtables[i].pairs[j].left) ||

           !out->WriteU16(kern->subtables[i].pairs[j].right) ||

           !out->WriteS16(kern->subtables[i].pairs[j].value)) {

         return OTS_FAILURE_MSG("Failed to write kern pair %d for subtable %d", j, i);

       }

     }

   }

   return true;

 }

 void ots_kern_free(OpenTypeFile *file) {

   delete file->kern;

 }

 }  // namespace ots