node-fontnik/test/format/protobuf.js

'use strict';

var ieee754 = require('./ieee754.js');

module.exports = Protobuf;
function Protobuf(buf) {
    this.buf = buf;
    this.length = buf.length;
    this.pos = 0;
}

Protobuf.prototype.destroy = function() {
    this.buf = null;
};

Protobuf.prototype.readUInt32 = function() {
    var val = this.readUInt32LE(this.pos);
    this.pos += 4;
    return val;
};

Protobuf.prototype.readUInt64 = function() {
    var val = this.readUInt64LE(this.pos);
    this.pos += 8;
    return val;
};

Protobuf.prototype.readDouble = function() {
    var val = ieee754.readIEEE754(this.buf, this.pos, false, 52, 8);
    this.pos += 8;
    return val;
};

Protobuf.prototype.readVarint = function() {
    // TODO: bounds checking
    var pos = this.pos;
    if (this.buf[pos] <= 0x7f) {
        this.pos++;
        return this.buf[pos];
    } else if (this.buf[pos + 1] <= 0x7f) {
        this.pos += 2;
        return (this.buf[pos] & 0x7f) | (this.buf[pos + 1] << 7);
    } else if (this.buf[pos + 2] <= 0x7f) {
        this.pos += 3;
        return (this.buf[pos] & 0x7f) | (this.buf[pos + 1] & 0x7f) << 7 | (this.buf[pos + 2]) << 14;
    } else if (this.buf[pos + 3] <= 0x7f) {
        this.pos += 4;
        return (this.buf[pos] & 0x7f) | (this.buf[pos + 1] & 0x7f) << 7 | (this.buf[pos + 2] & 0x7f) << 14 | (this.buf[pos + 3]) << 21;
    } else if (this.buf[pos + 4] <= 0x7f) {
        this.pos += 5;
        return ((this.buf[pos] & 0x7f) | (this.buf[pos + 1] & 0x7f) << 7 | (this.buf[pos + 2] & 0x7f) << 14 | (this.buf[pos + 3]) << 21) + (this.buf[pos + 4] * 268435456);
    } else {
        this.skip(0);
        return 0;
        // throw new Error("TODO: Handle 6+ byte varints");
    }
};

Protobuf.prototype.readSVarint = function() {
    var num = this.readVarint();
    if (num > 2147483647) throw new Error('TODO: Handle numbers >= 2^30');
    // zigzag encoding
    return ((num >> 1) ^ -(num & 1));
};

Protobuf.prototype.readString = function() {
    var bytes = this.readVarint();
    // TODO: bounds checking
    var chr = String.fromCharCode;
    var b = this.buf;
    var p = this.pos;
    var end = this.pos + bytes;
    var str = '';
    while (p < end) {
        if (b[p] <= 0x7F) str += chr(b[p++]);
        else if (b[p] <= 0xBF) throw new Error('Invalid UTF-8 codepoint: ' + b[p]);
        else if (b[p] <= 0xDF) str += chr((b[p++] & 0x1F) << 6 | (b[p++] & 0x3F));
        else if (b[p] <= 0xEF) str += chr((b[p++] & 0x1F) << 12 | (b[p++] & 0x3F) << 6 | (b[p++] & 0x3F));
        else if (b[p] <= 0xF7) p += 4; // We can't handle these codepoints in JS, so skip.
        else if (b[p] <= 0xFB) p += 5;
        else if (b[p] <= 0xFD) p += 6;
        else throw new Error('Invalid UTF-8 codepoint: ' + b[p]);
    }
    this.pos += bytes;
    return str;
};

Protobuf.prototype.readBuffer = function() {
    var bytes = this.readVarint();
    var buffer = this.buf.subarray(this.pos, this.pos + bytes);
    this.pos += bytes;
    return buffer;
};

Protobuf.prototype.readPacked = function(type) {
    // TODO: bounds checking
    var bytes = this.readVarint();
    var end = this.pos + bytes;
    var array = [];
    while (this.pos < end) {
        array.push(this['read' + type]());
    }
    return array;
};

Protobuf.prototype.skip = function(val) {
    // TODO: bounds checking
    var type = val & 0x7;
    switch (type) {
        /* varint */ case 0: while (this.buf[this.pos++] > 0x7f); break;
        /* 64 bit */ case 1: this.pos += 8; break;
        /* length */ case 2: var bytes = this.readVarint(); this.pos += bytes; break;
        /* 32 bit */ case 5: this.pos += 4; break;
        default: throw new Error('Unimplemented type: ' + type);
    }
};