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// Copyright 2014 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// This is part of java port of project hosted at https://github.com/google/woff2
package com.itextpdf.io.font.woff2;

import static com.itextpdf.io.font.woff2.JavaUnsignedUtil.asU8;
import static com.itextpdf.io.font.woff2.JavaUnsignedUtil.compareAsUnsigned;

// Common definition for WOFF2 encoding/decoding
// Helpers common across multiple parts of woff2
class Woff2Common {
    public static final int kWoff2Signature = 0x774f4632;  // "wOF2"

    // Leave the first byte open to store flag_byte
    public static final int kWoff2FlagsTransform = 1 << 8;

    // TrueType Collection ID string: 'ttcf'
    public static final int kTtcFontFlavor = 0x74746366;

    public static final int kSfntHeaderSize = 12;
    public static final int kSfntEntrySize = 16;

    public static class Point {
        public int x;
        public int y;
        public boolean on_curve;

        public Point(int x, int y, boolean on_curve) {
            this.x = x;
            this.y = y;
            this.on_curve = on_curve;
        }
    }

    public static class Table implements Comparable {
        public int tag;
        public int flags;
        public int src_offset;
        public int src_length;

        public int transform_length;

        public int dst_offset;
        public int dst_length;

        @Override
        public int compareTo(Table o) {
            return compareAsUnsigned(tag, o.tag);
        }
    }

    // Size of the collection header. 0 if version indicates this isn't a
    // collection. Ref http://www.microsoft.com/typography/otspec/otff.htm,
    // True Type Collections
    public static int collectionHeaderSize(int header_version, int num_fonts) {
        int size = 0;
        if (header_version == 0x00020000) {
            size += 12;  // ulDsig{Tag,Length,Offset}
        }
        if (header_version == 0x00010000 || header_version == 0x00020000) {
            size += 12   // TTCTag, Version, numFonts
                    + 4 * num_fonts;  // OffsetTable[numFonts]
        }
        return size;
    }

    // Compute checksum over size bytes of buf
    public static int computeULongSum(byte[] buf, int offset, int size) {
        int checksum = 0;
        int aligned_size = (size & ~3);
        for (int i = 0; i < aligned_size; i += 4) {
            checksum += (asU8(buf[offset + i]) << 24) | (asU8(buf[offset + i + 1]) << 16) |
                    (asU8(buf[offset + i + 2]) << 8) | asU8(buf[offset + i + 3]);
        }

        // treat size not aligned on 4 as if it were padded to 4 with 0's
        if (size != aligned_size) {
            int v = 0;
            for (int i = aligned_size; i < size; ++i) {
                v |= asU8(buf[offset + i]) << (24 - 8 * (i & 3));
            }
            checksum += v;
        }

        return checksum;
    }
}




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