135 lines
5.1 KiB
TypeScript
135 lines
5.1 KiB
TypeScript
import inflate from './tiny-inflate'
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// Shift size for getting the index-1 table offset.
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const SHIFT_1 = 6 + 5;
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// Shift size for getting the index-2 table offset.
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const SHIFT_2 = 5;
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// Difference between the two shift sizes,
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// for getting an index-1 offset from an index-2 offset. 6=11-5
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const SHIFT_1_2 = SHIFT_1 - SHIFT_2;
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// Number of index-1 entries for the BMP. 32=0x20
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// This part of the index-1 table is omitted from the serialized form.
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const OMITTED_BMP_INDEX_1_LENGTH = 0x10000 >> SHIFT_1;
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// Number of entries in an index-2 block. 64=0x40
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const INDEX_2_BLOCK_LENGTH = 1 << SHIFT_1_2;
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// Mask for getting the lower bits for the in-index-2-block offset. */
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const INDEX_2_MASK = INDEX_2_BLOCK_LENGTH - 1;
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// Shift size for shifting left the index array values.
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// Increases possible data size with 16-bit index values at the cost
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// of compactability.
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// This requires data blocks to be aligned by DATA_GRANULARITY.
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const INDEX_SHIFT = 2;
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// Number of entries in a data block. 32=0x20
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const DATA_BLOCK_LENGTH = 1 << SHIFT_2;
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// Mask for getting the lower bits for the in-data-block offset.
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const DATA_MASK = DATA_BLOCK_LENGTH - 1;
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// The part of the index-2 table for U+D800..U+DBFF stores values for
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// lead surrogate code _units_ not code _points_.
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// Values for lead surrogate code _points_ are indexed with this portion of the table.
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// Length=32=0x20=0x400>>SHIFT_2. (There are 1024=0x400 lead surrogates.)
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const LSCP_INDEX_2_OFFSET = 0x10000 >> SHIFT_2;
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const LSCP_INDEX_2_LENGTH = 0x400 >> SHIFT_2;
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// Count the lengths of both BMP pieces. 2080=0x820
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const INDEX_2_BMP_LENGTH = LSCP_INDEX_2_OFFSET + LSCP_INDEX_2_LENGTH;
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// The 2-byte UTF-8 version of the index-2 table follows at offset 2080=0x820.
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// Length 32=0x20 for lead bytes C0..DF, regardless of SHIFT_2.
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const UTF8_2B_INDEX_2_OFFSET = INDEX_2_BMP_LENGTH;
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const UTF8_2B_INDEX_2_LENGTH = 0x800 >> 6; // U+0800 is the first code point after 2-byte UTF-8
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// The index-1 table, only used for supplementary code points, at offset 2112=0x840.
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// Variable length, for code points up to highStart, where the last single-value range starts.
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// Maximum length 512=0x200=0x100000>>SHIFT_1.
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// (For 0x100000 supplementary code points U+10000..U+10ffff.)
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//
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// The part of the index-2 table for supplementary code points starts
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// after this index-1 table.
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//
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// Both the index-1 table and the following part of the index-2 table
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// are omitted completely if there is only BMP data.
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const INDEX_1_OFFSET = UTF8_2B_INDEX_2_OFFSET + UTF8_2B_INDEX_2_LENGTH;
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// The alignment size of a data block. Also the granularity for compaction.
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const DATA_GRANULARITY = 1 << INDEX_SHIFT;
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const isBigEndian = (new Uint8Array(new Uint32Array([0x12345678]).buffer)[0] === 0x12);
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class UnicodeTrie {
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private data: Uint32Array;
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private highStart: number;
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private errorValue: number;
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constructor(data: Uint8Array) {
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// read binary format
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const view = new DataView(data.buffer);
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this.highStart = view.getUint32(0, true);
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this.errorValue = view.getUint32(4, true);
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let uncompressedLength = view.getUint32(8, true);
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data = data.subarray(12);
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// double inflate the actual trie data
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data = inflate(data, new Uint8Array(uncompressedLength));
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data = inflate(data, new Uint8Array(uncompressedLength));
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if (isBigEndian) {
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// swap bytes from little-endian
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const len = data.length;
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for (let i = 0; i < len; i += 4) {
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// Exchange data[i] and data[i + 3]:
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let x = data[i]; data[i] = data[i+3]; data[i+3] = x;
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// Exchange data[i + 1] and data[i + 2]:
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let y = data[i+1]; data[i+1] = data[i+2]; data[i+2] = y;
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}
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}
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this.data = new Uint32Array(data.buffer);
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}
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get(codePoint: number): number {
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let index;
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if ((codePoint < 0) || (codePoint > 0x10ffff)) {
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return this.errorValue;
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}
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if ((codePoint < 0xd800) || ((codePoint > 0xdbff) && (codePoint <= 0xffff))) {
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// Ordinary BMP code point, excluding leading surrogates.
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// BMP uses a single level lookup. BMP index starts at offset 0 in the index.
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// data is stored in the index array itself.
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index = (this.data[codePoint >> SHIFT_2] << INDEX_SHIFT) + (codePoint & DATA_MASK);
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return this.data[index];
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}
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if (codePoint <= 0xffff) {
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// Lead Surrogate Code Point. A Separate index section is stored for
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// lead surrogate code units and code points.
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// The main index has the code unit data.
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// For this function, we need the code point data.
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index = (this.data[LSCP_INDEX_2_OFFSET + ((codePoint - 0xd800) >> SHIFT_2)] << INDEX_SHIFT) + (codePoint & DATA_MASK);
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return this.data[index];
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}
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if (codePoint < this.highStart) {
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// Supplemental code point, use two-level lookup.
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index = this.data[(INDEX_1_OFFSET - OMITTED_BMP_INDEX_1_LENGTH) + (codePoint >> SHIFT_1)];
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index = this.data[index + ((codePoint >> SHIFT_2) & INDEX_2_MASK)];
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index = (index << INDEX_SHIFT) + (codePoint & DATA_MASK);
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return this.data[index];
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}
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return this.data[this.data.length - DATA_GRANULARITY];
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}
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}
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export default UnicodeTrie
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