// Copyright (c) 2009-2017 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 "loca.h"

#include "head.h"

#include "maxp.h"

// loca - Index to Location

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

namespace ots {

bool OpenTypeLOCA::Parse(const uint8_t *data, size_t length) {

  Buffer table(data, length);

  // We can't do anything useful in validating this data except to ensure that

  // the values are monotonically increasing.

  OpenTypeMAXP *maxp = static_cast<OpenTypeMAXP*>(

      GetFont()->GetTypedTable(OTS_TAG_MAXP));

  OpenTypeHEAD *head = static_cast<OpenTypeHEAD*>(

      GetFont()->GetTypedTable(OTS_TAG_HEAD));

  if (!maxp || !head) {

    return Error("Required maxp or head tables are missing");

  }

  const unsigned num_glyphs = maxp->num_glyphs;

  unsigned last_offset = 0;

  this->offsets.resize(num_glyphs + 1);

  // maxp->num_glyphs is uint16_t, thus the addition never overflows.

  if (head->index_to_loc_format == 0) {

    // Note that the <= here (and below) is correct. There is one more offset

    // than the number of glyphs in order to give the length of the final

    // glyph.

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

      uint16_t offset = 0;

      if (!table.ReadU16(&offset)) {

        return Error("Failed to read offset for glyph %d", i);

      }

      if (offset < last_offset) {

        return Error("Out of order offset %d < %d for glyph %d", offset, last_offset, i);

      }

      last_offset = offset;

      this->offsets[i] = offset * 2;

    }

  } else {

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

      uint32_t offset = 0;

      if (!table.ReadU32(&offset)) {

        return Error("Failed to read offset for glyph %d", i);

      }

      if (offset < last_offset) {

        return Error("Out of order offset %d < %d for glyph %d", offset, last_offset, i);

      }

      last_offset = offset;

      this->offsets[i] = offset;

    }

  }

  return true;

}

bool OpenTypeLOCA::Serialize(OTSStream *out) {

  OpenTypeHEAD *head = static_cast<OpenTypeHEAD*>(

      GetFont()->GetTypedTable(OTS_TAG_HEAD));

  if (!head) {

    return Error("Required head table is missing");

  }

  if (head->index_to_loc_format == 0) {

    for (unsigned i = 0; i < this->offsets.size(); ++i) {

      const uint16_t offset = static_cast<uint16_t>(this->offsets[i] >> 1);

      if ((offset != (this->offsets[i] >> 1)) ||

          !out->WriteU16(offset)) {

        return Error("Failed to write glyph offset for glyph %d", i);

      }

    }

  } else {

    for (unsigned i = 0; i < this->offsets.size(); ++i) {

      if (!out->WriteU32(this->offsets[i])) {

        return Error("Failed to write glyph offset for glyph %d", i);

      }

    }

  }

  return true;

}

}  // namespace ots