infinite loop

[weoil]

jsgif/gif.js

Line 52 in 8f57a8d

var lzwDecode = function(minCodeSize, data) {

I encountered an infinite loop issue while using the library. The problematic image is shown below. After making the following changes, the issue was resolved:

var lzwDecode = function (minCodeSize, data) {
        var pos = 0;
        var readCode = function (size) {
            var code = 0;
            for (var i = 0; i < size; i++) {
                if (pos >= data.length * 8) {
                    return null; // 返回 null 以指示读取超出范围
                }
                if (data.charCodeAt(pos >> 3) & (1 << (pos & 7))) {
                    code |= 1 << i;
                }
                pos++;
            }
            return code;
        };
    
        var output = [];
        var clearCode = 1 << minCodeSize;
        var eoiCode = clearCode + 1;
        var codeSize = minCodeSize + 1;
        var dict = [];
    
        var clear = function () {
            dict = [];
            codeSize = minCodeSize + 1;
            for (var i = 0; i < clearCode; i++) {
                dict[i] = [i];
            }
            dict[clearCode] = [];
            dict[eoiCode] = null;
        };
    
        var code;
        var last;
    
        while (true) {
            last = code;
            code = readCode(codeSize);
    
            // 检查 code 是否为 null
            if (code === null) {
                break; // 退出循环
            }
    
            if (code === clearCode) {
                clear();
                continue;
            }
            if (code === eoiCode) break;
    
            if (code < dict.length) {
                if (last !== clearCode) {
                    dict.push(dict[last].concat(dict[code][0]));
                }
            } else {
                if (code !== dict.length) throw new Error('Invalid LZW code.');
                dict.push(dict[last].concat(dict[last][0]));
            }
            output.push.apply(output, dict[code]);
    
            if (dict.length === (1 << codeSize) && codeSize < 12) {
                codeSize++;
            }
        }
    
        return output;
    };