fonteditor-core/src/ttf/reader.js

fonts (ttf, woff, woff2, eot, svg, otf) parse, write, transform, glyph adjust.

/**
 * @file 数据读取器
 * @author mengke01(kekee000@gmail.com)
 *
 * thanks to：
 * ynakajima/ttf.js
 * https://github.com/ynakajima/ttf.js
 */

import {curry} from '../common/lang';
import error from './error';

// 检查数组支持情况
if (typeof ArrayBuffer === 'undefined' || typeof DataView === 'undefined') {
    throw new Error('not support ArrayBuffer and DataView');
}

// 数据类型
const dataType = {
    Int8: 1,
    Int16: 2,
    Int32: 4,
    Uint8: 1,
    Uint16: 2,
    Uint32: 4,
    Float32: 4,
    Float64: 8
};

export default class Reader {

    /**
     * 读取器
     *
     * @constructor
     * @param {Array.<byte>} buffer 缓冲数组
     * @param {number} offset 起始偏移
     * @param {number} length 数组长度
     * @param {boolean} littleEndian 是否小尾
     */
    constructor(buffer, offset, length, littleEndian) {

        const bufferLength = buffer.byteLength || buffer.length;

        this.offset = offset || 0;
        this.length = length || (bufferLength - this.offset);
        this.littleEndian = littleEndian || false;

        this.view = new DataView(buffer, this.offset, this.length);
    }

    /**
     * 读取指定的数据类型
     *
     * @param {string} type 数据类型
     * @param {number=} offset 位移
     * @param {boolean=} littleEndian 是否小尾
     * @return {number} 返回值
     */
    read(type, offset, littleEndian) {

        // 使用当前位移
        if (undefined === offset) {
            offset = this.offset;
        }

        // 使用小尾
        if (undefined === littleEndian) {
            littleEndian = this.littleEndian;
        }

        // 扩展方法
        if (undefined === dataType[type]) {
            return this['read' + type](offset, littleEndian);
        }

        const size = dataType[type];
        this.offset = offset + size;
        return this.view['get' + type](offset, littleEndian);
    }

    /**
     * 获取指定的字节数组
     *
     * @param {number} offset 偏移
     * @param {number} length 字节长度
     * @return {Array} 字节数组
     */
    readBytes(offset, length = null) {

        if (length == null) {
            length = offset;
            offset = this.offset;
        }

        if (length < 0 || offset + length > this.length) {
            error.raise(10001, this.length, offset + length);
        }

        const buffer = [];
        for (let i = 0; i < length; ++i) {
            buffer.push(this.view.getUint8(offset + i));
        }

        this.offset = offset + length;
        return buffer;
    }

    /**
     * 读取一个string
     *
     * @param {number} offset 偏移
     * @param {number} length 长度
     * @return {string} 字符串
     */
    readString(offset, length = null) {

        if (length == null) {
            length = offset;
            offset = this.offset;
        }

        if (length < 0 || offset + length > this.length) {
            error.raise(10001, this.length, offset + length);
        }

        let value = '';
        for (let i = 0; i < length; ++i) {
            const c = this.readUint8(offset + i);
            value += String.fromCharCode(c);
        }

        this.offset = offset + length;

        return value;
    }

    /**
     * 读取一个字符
     *
     * @param {number} offset 偏移
     * @return {string} 字符串
     */
    readChar(offset) {
        return this.readString(offset, 1);
    }

    /**
     * 读取一个uint24整形
     *
     * @param {number} offset 偏移
     * @return {number}
     */
    readUint24(offset) {
        const [i, j, k] = this.readBytes(offset || this.offset, 3);
        return (i << 16) + (j << 8) + k;
    }

    /**
     * 读取fixed类型
     *
     * @param {number} offset 偏移
     * @return {number} float
     */
    readFixed(offset) {
        if (undefined === offset) {
            offset = this.offset;
        }
        const val = this.readInt32(offset, false) / 65536.0;
        return Math.ceil(val * 100000) / 100000;
    }

    /**
     * 读取长日期
     *
     * @param {number} offset 偏移
     * @return {Date} Date对象
     */
    readLongDateTime(offset) {
        if (undefined === offset) {
            offset = this.offset;
        }

        // new Date(1970, 1, 1).getTime() - new Date(1904, 1, 1).getTime();
        const delta = -2077545600000;
        const time = this.readUint32(offset + 4, false);
        const date = new Date();
        date.setTime(time * 1000 + delta);
        return date;
    }

    /**
     * 跳转到指定偏移
     *
     * @param {number} offset 偏移
     * @return {Object} this
     */
    seek(offset) {
        if (undefined === offset) {
            this.offset = 0;
        }

        if (offset < 0 || offset > this.length) {
            error.raise(10001, this.length, offset);
        }

        this.offset = offset;

        return this;
    }

    /**
     * 注销
     */
    dispose() {
        delete this.view;
    }
}

// 直接支持的数据类型
Object.keys(dataType).forEach((type) => {
    Reader.prototype['read' + type] = curry(Reader.prototype.read, type);
});